Fluid Waste Disposal (Environmental Science, Engineering and Technology)

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ENVIRONMENTAL SCIENCE, ENGINEERING AND TECHNOLOGY SERIES

FLUID WASTE DISPOSAL No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.


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FLUID WASTE DISPOSAL

KAY W. CANTON EDITOR

Nova Science Publishers, Inc. New York

Copyright © 2010 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers‘ use of, or reliance upon, this material. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Fluid waste disposal / editor, Kay W. Canton. p. cm. Includes index. ISBN 978-1-61122-590-7 (eBook) 1. Sewage disposal. I. Canton, Kay W. TD741.F55 2009 628.3--dc22

Published by Nova Science Publishers, Inc.  New York

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CONTENTS Preface Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

ix Treatment of Wastewater by Electrocoagulation Method and the Effect of Low Cost Supporting Electrolytes Lazare Etiégni, K. Senelwa, B. K. Balozi, K. Ofosu-Asiedu, A. Yitambé, D. O. Oricho and B. O. Orori

1

Application of Sulphate-Reducing Bacteria in Biological Treatment Wastewaters Dorota Wolicka

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Utilization of Water and Wastewater Sludge for Production of Lightweight-Stabilized Ceramsite Zou Jinlong, Yu Xiujuan, Dai Ying and Xu Guoren

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Modelling and Observation of Produced Formation Water (PFW) at Sea D. Cianelli, L. Manfra, E. Zambianchi, C. Maggi and A. M. Cicero Disposal of Sulfur Dioxide Generated in Industries Using Eco-Friendly Biotechnological Process – A Review A. Gangagni Rao and P.N. Sarma Novel Biological Nitrogen-Removal Processes: Applications and Perspectives J.L. Campos, J.R. Vázquez-Padín, M. Figueroa, C. Fajardo, A. Mosquera-Corral and R. Méndez Application of Microbial Melanoidin-Decomposing Activity (MDA) for Treatment of Molasses Wastewater Suntud Sirianuntapiboon and Sadahiro Ohmomo Wastewaters from Olive Oil Industry: Characterization and Treatment L. Nieto Martínez, Gassan Hodaifa,M. Eugenia Martínez and Sebastián Sánchez

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viii Chapter 9

Chapter 10

Chapter 11

Contents Usability of Boron Doped Diamond Electrodes in the Field of Waste Water Treatment and Tap Water Disinfection Hannes Menapace, Stefan Weiß, Markus Fellerer, Martin Treschnitzer and Josef Adam Utilization of Biosolids as Fertilization Agents on Agricultural Land: Do the Obvious Benefits of Recycling Organic Matter and Nutrients Outweigh the Potential Risks? Veronica Arthurson Integrated Approach for Domestic Wastewater Treatment in Decentralized Sectors Rani Devi and R. P. Dahiya

Chapter 12

Biodegradation Characteristics of Wastewaters Fatos Germirli Babuna and Derin Orhon

Chapter 13

Batch Treatment of a Coffee Factory Effluent for Colour Removal Using a Combination of Electro-Coagulation and Different Supporting Electrolytes L. Etiégni, D. O. Oricho, K. Senelwa B. O. Orori, B. K. Balozi, K. Ofosu-Asiedu and A. Yitambé

Chapter 14

Water as a Scarce Resource: Potential for Future Conflicts M. A. Babu

Chapter 15

Recycling Wastewater After Hemodialysis: An Environmental and Cost Benefits Analysis for Alternative Water Sources in Arid Regions Faissal Tarrass, Meryem Benjelloun and Omar Benjelloun

Chapter 16

Chapter 17

Index

Pb (II) Ions Removal by Dried Rhizopus Oligosporus Biomass Produced from Food Processing Wastewater H. Duygu Ozsoy and J. Hans van Leeuwen Control of Plasticizers in Drinking Water, Effluents and Surface Waters Rosa Mosteo, Judith Sarasa, M. Peña Ormad and Jose Luis Ovelleiro

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249 265

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PREFACE Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations. In the most common usage, it refers to the municipal wastewater that contains a broad spectrum of contaminants resulting from the mixing of wastewaters from different sources. With the dwindling available water resources in the world coupled with high population growth, pressure is being exerted on water and wastewater plant managers the world over to find cost-effective methods to treat a wide range of wastewater pollutants in a diverse range of situations. This new and important book gathers the latest research from around the globe on fluid waste disposal with a focus on such topics as: wastewaters from the olive industry, application of sulphate-reducing bacteria in biological treatment wastewaters, electrocoagulation treatment method, usability of boron doped diamond electrodes in wastewater treatment and others. Chapter 1 - Coagulation and flocculation are traditional methods of treating of polluted water. Electrocoagulation (EC) presents a robust novel and innovative alternative in which a sacrificial metal anode doses water electrochemically. This has the major advantage of providing active cations required for coagulation, without necessarily increasing the salinity of the water. Electrocoagulation is a complex process with a multitude of mechanisms operating synergistically to remove pollutants from water. A wide variety of opinions exist in the literature for key mechanisms and reactor configurations. A lack of a systematic approach has resulted in a myriad of designs for electrocoagulation reactors without due consideration of the complexity of the system. A systematic, holistic approach is required to understand electrocoagulation and its controlling parameters (pH, temperature, conductivity, current density). This will enable a priori prediction of the treatment of various pollutant types. Electrocoagulation involves applying a current across electrodes in water. This results in the dissolution of the anode (either aluminum or iron). These ions then form hydroxides which complex with and/or absorb contaminants and precipitate out. The precipitate with the contaminants can then be removed from the water by settling and decantation or filtration. EC has the potential to be applied in many other areas besides the textile and semiconductor industry. It has been successfully tested in the pulp and paper industry, as well as tea and coffee processing. However over electrical potential within electrodes during electrocoagulation normally causes extra voltage, which wastes energy. There have been attempts to reduce this extra voltage which, in these days of World energy crisis, will render

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the electrocoagulation process uneconomical. The inclusion of supporting electrolyte such as NaCl achieves this. One of the methods pioneered by researchers at Moi University in Kenya is the use of wood ash leachate as supporting electrolyte which in some cases could reduce energy consumption by as much as 80%. Other supporting electrolytes tested are ash from bagasse and from coffee husks. These supporting electrolytes are relatively inexpensive, but they all generally result in large amount of coagulated sludge. Other supporting electrolytes such phosphate rock are less effective than wood ash, but they yield almost 50% less sludge after electrocoagulation. Most of the supporting electrolytes have an added advantage of reducing other wastewater pollution parameters such as BOD, COD, TSS, TS, turbidity, pH and color. Because of the inherent benefits of these low cost supporting electrolytes, electrochemical methods could be a credible alternative to more traditional wastewater treatment approaches. Chapter 3 - Disposal of wastewater treatment sludge (WWTS) and drinking-water treatment sludge (DWTS) is one of the most important environmental issues nowadays. Traditional options for WWTS and DWTS management, such as landfilling, incineration, etc., are no longer acceptable because they can cause many environmental problems. Conversion of WWTS and DWTS into useful resources or materials is of great interest and must be intensely investigated. To attain this goal, WWTS and DWTS were used as components for making ceramsite. Part I: SiO2 and Al2O3 were the major acidic oxides in WWTS and DWTS, so their effect on characteristics of ceramsite was investigated. Results show that WWTS and DWTS can be utilized as resources for producing ceramsite with optimal contents of SiO2 and Al2O3 ranging from 14–26% and 22.5–45%, respectively. Bloating and crystallization in ceramsite above 900 ℃ are caused by the oxidation and volatilization of inorganic substances. Higher strength ceramsite with less Na-Ca feldspars and amorphous silica and more densified surfaces can be obtained at 18%≤Al2O3≤26% and 30%≤SiO2≤45%. Part II: Fe2O3 and CaO were the major basic oxides, so their effect on characteristics of ceramsite was also investigated. The optimal contents of Fe2O3 and CaO are in the range of 5%–8% and 2.75%–7%, respectively. Higher strength ceramsite with more complex crystalline phases and fewer pores can be obtained at 6%≤Fe2O3≤8%. Lower strength ceramsite with more pores and amorphous phases can be obtained at 5%≤CaO≤7%, which implies that excessive Ca2+ exceeds the needed ions for producing electrical neutrality of silicate networks. Part III: To investigate stabilization of heavy metals in ceramsite, leaching tests were conducted to find out the effect of sintering temperature, pH, and oxidative condition. Results show that sintering exhibits good binding capacity for Cd, Cr, Cu, and Pb and leaching contents of heavy metals will not change above 1000 ℃. Main compounds of heavy metals are crocoite, chrome oxide, cadmium silicate, and copper oxide, which prove that stronger chemical bonds are formed between these heavy metals and the components. Leaching contents of heavy metals decrease as pH increases and increase as H2O2 concentration increases. Leaching results indicate that even subjected to rigorous leaching conditions, the crystalline structures still exhibit good chemically binding capacity for heavy metals and it is environmentally safe to use ceramsite in civil and construction fields. It is concluded from the 3 parts that utilization of WWTS and DWTS can produce high performance ceramsite, in accordance with the concept of sustainable development. Chapter 4 - Through the last decades, the ever increasing energetic demands have been accomplished by exploiting new natural reservoirs, including offshore oil and gas deposits located in marine coastal areas. During the extraction and production phases, large amounts of

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water are brought to the surface along with the hydrocarbons. These waters include the ‗formation water‘, that lies underneath the hydrocarbon layer, and ‗additional water‘ usually injected into the reservoirs to help force the oil to the surface. Both formation and injected waters, named ―produced formation waters‖ (PFWs), are separated from the hydrocarbons onboard offshore platforms and then disposed into the marine environment through ocean diffusers. PFWs contain several contaminants and represent one of the main sources of marine environment pollution associated with oil and gas production. This makes the study of PFW fate of paramount importance for a proper management of environmental resources as well as for planning and optimizing the discharge and monitoring procedures. In the first part of this chapter we provide a detailed description of the chemical characteristics of PFWs and their potential toxic effects and review the mixing processes governing their dispersion in the marine environment. In the second part of the work we briefly review past efforts in observing and modelling PFW spreading in the ocean. Finally, we propose a multidisciplinary approach, integrating in situ observations and numerical modelling, to assess dispersion of PFWs in space and time. As a case study we will refer to the results of a previous study conducted in the Northern Adriatic Sea, a sub-basin of the Mediterranean Sea, where a number of offshore natural gas (CH4) extraction platforms are currently active. Chapter 5 - Sulfur dioxide (SO2) is a known pollutant and responsible for various ill effects on living and non-living organisms. SO2 emissions can be reduced by using nonconventional energy sources or using conventional fuels containing less sulfur. However, under the present circumstances SO2 emissions cannot be completely avoided due to the reasons of rapid industrialization. Various technologies are available for the removal of SO2 from flue and waste gases. Most of these technologies fall under the category of physical, chemical or thermal. All these technologies generate secondary pollutants ending up in disposal problems and also cost prohibitive. Biotechnology offers relatively cheaper solutions for the conventional problems. Due to this reason, biotechnology is making in roads into the conventional treatment processes in all the fields. Over the last decade, efforts have been made to develop biotechnological alternatives to conventional physicochemical processes for the removal of SO2 from flue gases known as Biological flue gas desulphurization (BIOFGD).SO2 from flue gas can be absorbed in a suitable organic media. In the aqueous phase SO2 would be converted to sulfite and some part may again be converted to sulfate due to the presence of dissolved oxygen. Therefore, the aqueous phase will be having both sulfate and sulfite, which can be reduced to sulfide using Sulfate Reducing Bacteria (SRB) under anaerobic conditions. The sulfide formed in the anaerobic reactor could be converted to elemental sulfur using Sulfur Oxidizing Bacteria (SOB) under partial microbial aerobic conditions. The elemental sulfur can be used either as a soil conditioner or raw material for industrial applications. Therefore, BIO-FGD process could be an environmentally benign and economically viable alternative for the disposal of SO2 emitted from the industries especially from power plants and refineries. The present article reviews the state of art of BIO-FGD process. Chapter 6 - Since the requirement for nutrient removal is becoming increasingly stringent, a high efficiency of nitrogen removal is necessary to achieve a low total nitrogen concentration in the effluent. Biological nitrification and denitrification processes are generally employed to remove nitrogen from wastewater. Unfortunately, these processes are

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not suitable to treat wastewater with a low COD/N ratio because it involves the addition of an external organic carbon source and, therefore, an increase of the operational costs. Several alternative processes for nitrogen removal can be applied in order to reduce partially (―nitrite route‖) or totally (anammox, autotrophic denitrification) the organic matter required. Such processes suppose not only an economical way to treat these wastewaters but they are also more environmentally friendly technologies (lower production of CO2, N2O and sludge; lower energy consumption). Up to now, they were basically applied to the return sludge line of municipal wastewater treatment plants (WWTPs). However, these processes could even be implemented in the actual WWTPs in order to achieve more compact and energy efficient systems. Their potential advantages can make them also feasible technologies to treat polluted ground water or to remove nitrogen compounds from recirculating aquaculture systems. Chapter 7 - This review will discuss the melanoidin-decomposing activity (MDA) among microorganisms. The focus will be on the potential use of the microbial-MDA to treat the wastewater discharged from factories using molasses as the raw material (molasses wastewater: MWW) because molasses is one of the most useful raw materials in various types of industries, such as the fermentation and animal feed industries. However, the wastewater discharged from factories using molasses contains a large amount of dark brown pigment, melanoidin pigment: MP, which is poorly decomposed and/or decolorized by normal biological treatment processes, such as the activated sludge or anaerobic treatment systems (anaerobic pond or anaerobic contact digester), because, the microorganisms in those wastewater treatment systems showed very poor MDA. The distribution of MDA among microorganisms and the mechanism of decomposing activities, in particular, were reviewed. Also, the application of the isolated strains having the MDA to treat molasses wastewater in the wastewater treatment plant was tested. Chapter 8 - Countries in the Mediterranean basin are among the main producers of olive oil. The elaboration of olive-oil is typically carried out by small companies in small facilities. The olive-oil plants produce high and variable amounts of residual waters of olives and oliveoil washing (OMW) that has a great impact in the environment. According to the procedure used different types of OMW with different chemical oxygen demand can be generated, the OMW from the three phase process (COD = 150 g O2 L-1) and the OMW from olives washing (COD = 0.8-4.5 g O2 L-1) and olive oil washing (COD = 1.1- 6 g O2 L-1) in the two-phase process. The uncontrolled disposal of OMW is a serious environmental problem, due to its high organic load, and because of its high content of microbial growth-inhibiting compounds, such as phenolic compounds. The improper disposal of OMW to the environment or to domestic wastewater treatment plants is prohibited due to its toxicity to microorganisms, and also because of its potential threat to surface and groundwater. These waters normally are stored in great rafts of accumulation for their evaporation during the summer. This solution among others until the moment dose not represent a definitive solution for this problem, especially as the administrations more and more demanding the preparation of this spill and the constructive quality of the rafts. Today, effective technologies have been proposed such as the chemical oxidation process using ferric chloride catalyst for the activation of H2O2 as a treatment of OMW produced from two-phase process. In the previous works the authors have described the experimental results on laboratory-scale. These results have been taken to pilotindustrial scale, making the chemical oxidation in the optimum conditions of operations: [H2O2] = 5% (w/v), using a ferric chloride catalyst with a relation of [FeCl3]/[H2O2] = 0.25

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(w/w), at OMW pH and environmental temperature. The final average value of COD obtained next to 370 mg L-1 (%CODremoval = 86.2%), and the water obtained can be destined to irrigation or disposed directly to the municipal wastewater system for their tertiary treatment. OMW from three-phase process does not allow direct chemical and biological purification for its content in phenolic compounds and generally used natural and forced evaporation process. Another way of using is the application of OMW nutrients to the growth of microorganisms such as microalgae. Chapter 9 - Over the past few years one main focus on the research efforts at the Institute for Sustainable Waste Management and Technology (IAE) has been on possible applications for reactors with boron doped diamond electrodes (BDD) in the field of (waste) water treatment. This article deals with the technical construction of the electrodes used (continuous reactor with a different number of plate electrodes), which were produced by a spin-off of the institute. The electrodes consist of conductible industrial diamond particles (< 250 µm), which are mechanically implanted on a fluoride plastic substrate. These electrodes showed a high mechanical and chemical stability in different test runs. At the institute, treatment methods for micro pollutants (e.g. pharmaceuticals and complexing agents) were developed with electrochemical oxidation by BDD. In this case test runs were made on laboratory scale and technical scale treatment units and elimination rates up to 99 % were achieved. In this project the analytic is partly provided by the ―Umweltbundesamt GmbH‖ (UBA), one of the project partners. This agency has been a project partner in different studies about pharmaceuticals in the ecosystem. These techniques could also be used for the waste water treatment of alpine cabins. Pilot projects have been set up. On the basis of these results a follow-up project was launched last October, in which an alternative treatment process for oilin-water emulsions and mixtures was developed by the usage of electrochemical oxidation with BDD. A third possible application is the disinfection of drinking water from contaminated ground and spring water. In this process oxidation agents like ozone or OH radicals produced in situ by the BDD reactor from the treated water are used to eliminate bacterial contaminants (for example e. coli) in the water. Chapter 10 - Treatment of wastewater, commonly performed at municipal sewage plants, generates sanitized water and sewage sludge. Anaerobic degradation of sewage sludge results in the production of different gases, including the economically valuable methane, and digested residue (biosolids) with potential value as a crop fertilizer. Traditionally, digested sewage sludge is disposed either into water, onto or into the earth or into the air. However, alternative exploitation of digested sewage sludge in agriculture has several advantages over commercial fertilizers, including environmental aspects benefiting agricultural sustainability and increased crop yield. Additionally, residue utilization is nearly always a cheaper option than disposal costs. Biosolids obtained from the treatment of municipal sewage sludge consist of a mixture of organic and mineral compounds that significantly affect soil microbial communities and their biogeochemical activities when applied as a crop fertilizer. The microorganisms influence soil quality through nutrient cycling, decomposition of organic matter and maintenance of soil structure, in turn, affecting agricultural and environmental quality, and subsequently, plant and animal health. Moreover, both soil and residue normally contain considerable quantities of microorganisms, including both beneficial and potentially human pathogenic species that may be supported by the new conditions in the soil. Thus, soil amended with biosolids may

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present a modified microbial community composition after some time and, hence, a modified ecosystem function. At the end of the present chapter, we discuss whether the potential risks of recycling biosolids to agricultural cropland are acceptable for consumers, producers and scientific expertise, in view of the resulting alterations in soil microbial diversity, activity and accompanying functions. Furthermore, optimal ways of managing the recycling process to achieve the most favourable balance of benefits and risks for the community are highlighted. Chapter 11 - The purpose of the present study was to design an integrated wastewater treatment system for a nalla (riverlet) flowing through Indian Institute of Technology Delhi (IITD), India, besides its cost estimation and comparison with the conventional wastewater treatment system. The design parameters for integrated aeration-cum-adsorption tank were worked out for 240 m3 / d flow rate of the wastewater. The important parameters used for the design included initial COD and BOD concentration in the influent, treatment time, adsorbent dose, pH, adsorbent particle size and the desired COD and BOD in the effluent after treatment as prescribed by Central Pollution Control Board, (CPCB) Delhi, India. All the design parameters of this system were similar to those of conventional system except for the replacement of aeration tank in conventional system by the aeration-cum-adsorption tank. The concentration of COD and BOD of the treated effluent by the integrated system were well within the permissible limits of CPCB standards (for COD it is 100 ppm and for BOD of 30 ppm) to discharge in the canal for irrigation purpose. It was worth mentioning here that the adsorbents used in the present study were based on discarded materials which were available free of cost. Of course, the cost of their transportation and processing should have been taken into account. The total cost estimated for the conventional system and the adsorption based system would be Rs. 198,312 and Rs. 141,275 respectively (including civil work, machinery, labour, adsorbent and miscellaneous). The cost difference for the two systems would be approximately Rs 57,037. This design of integrated system has resulted into saving of cost by 28 % over the conventional system. Thus, it is a good approach for saving of conventional energy in addition to saving the cost of treatment and can be applicable for any country for decentralized sector. Moreover, it is an open ended research and we can recommend more research by changing the adsorbents types and operating parameters to improve the model. Chapter 12 - The objective of this chapter is to put forward an overview of biodegradation characteristics of wastewaters by emphasizing the significance of COD fractionation. Recalcitrant COD fractions of effluents can be used as a tool to evaluate whether discharge standards can be met with a prescribed biological treatment. Moreover, the appropriate type of biological treatment applicable to the wastewater under investigation can be addressed and the performance of an existing biological treatment system can be appraised with reference to inert COD fractions. Besides recalcitrant COD fractions of segregated industrial effluent streams can be regarded as an essential input of a sound industrial wastewater management strategy adopting minimization at source philosophy. Last but not least, data on COD fractions can be used as a solid source of information for modelling studies that define the design and performance of biological treatment systems. In this context, COD fractionation data on a wide spectrum of activities ranging from various industrial sectors to hotels is presented. Segregated industrial wastewater streams together

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with domestic sewage and end-of-pipe industrial effluents are evaluated in terms of their biodegradation characteristics. Chapter 13 - In the present study, two types of colour removal systems were tested on effluent samples collected from a coffee pulping factory which discharged on average 15 m3 of wastewater daily with a colour index of about 2500 OH that was too high for direct discharge into a river in Kenya. The two colour removal systems used were: (i) electrolysis combined with wood ash or coffee husks leachate and (ii) electrolysis combined with phosphate rock solutions at a rate of 0.5 g/l to 4g/l. Phosphate rock is often used as agricultural liming agent. The surface area of the electrodes was set at close to 75 m2/m3 of effluent with a current density of 1,200 mA/m2. The experiments were laid out in a stratified random sampling design and the data were analysed using the Statistical Package for Social Scientists (SPSS) computer programme version 10.0. Electrolysis combined with phosphate rock (ELPHOS) proved to be the best process in terms of power consumption (68% reduction) compared with the 57% reduction by electrolysis combined with wood ash (ELCAS) and the 58% reduction by electrolysis combined with coffee husks ash (ELCHAS). Besides the 100% colour removal, ELPHOS also reduced other effluent physico-chemical parameters such as BOD, COD, TSS and TS by 79%, 80%, 69%, and 88% respectively. The analysis of ELPHOS treated wastewater showed that the mill could discharge an effluent that meets local discharge standards for colour requirements. It is recommended that recycling of the treated water by ELPHOS back to the factory for cleaning and washing purposes be considered since the quality meets the requirement for uses of fresh water for cleaning purposes. Furthermore, calculation of power consumption based on a scale-up batch reactor of 15 m3 proved less expensive to treat the factory effluent than a set of 12 one 100-L reactors similar to the one used in the field. Chapter 14 - The major aim of this paper is to review the major problems of water resources in the developing countries. It is based on problems related to population growth and pollution and how these are more likely to lead to future conflicts. We know that fresh water is only 3 % of the total global water and 78% of this is in glaciers. This makes it a scarce and precious resource which must be sustainably managed. The paper also analyses some of the already existing and potential conflicts based on water resources. It reviews the potential threats to Ugandan water resources and problems which are most likely to occur as a result of these threats. Factors hindering treatment of wastewater as a remedy to pollution in developing countries have also been discussed. The methodology used in this paper is based on literature review of the most current issues that affect water resources world-wide. The review is limited to scientific facts and no political factors affecting water resources have been included. It has been found that although Uganda is endowed with 66km2/year of renewable water resources, population increase, deforestation, degradation of wetlands and pollution are major threats to its water resources. Problems associated with water quality and quantities are more likely to result into internal conflicts which are bound to spread beyond Ugandan borders. Chapter 15 - Water is a vital aspect of hemodialysis. During the procedure, large volumes of water are used to prepare dialysate and to clean and reprocess machines. This paper evaluates the technical and economical feasibility of recycling hemodialysis wastewater for irrigation uses, such as watering gardens and landscape plantings. Water characteristics, possible recycling methods, and the production costs of treated water are discussed in terms of the quality of the generated wastewater. A cost-benefit analysis is also performed through

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comparison of intended cost with that of seawater desalination, which is widely used in irrigation. Chapter 16 - Heavy metal pollution is a serious problem in many developed and developing countries. Lead had been recognized as a particularly toxic metal and comes into water bodies mainly from metallurgical, battery, metal plating, mining and alloy industries. In order to minimize the impacts of this metal on human health, animals and the environment, lead-contaminated water and wastewater need to be treated before discharge to water bodies. This chapter concerns an investigation of potential usage of corn-processing wastewater as a new alternative low-cost substrate to produce biosorbent and evaluate this biosorbent to remove Pb(II) ions from aqueous solutions. For this aim, Rhizopus oligosporus cultivated on corn-processing wastewater and dried biomass of these fungi was used as an adsorbent. The adsorption experiments were conducted in a batch process and the effects of contact time (148 hours), initial pH (2-7), initial metal ion concentration (20-100 mg L-1) and adsorbent dosage (0.5-5 g L-1) on the adsorption were investigated. Pb (II) ion concentrations before and after adsorption were measured using Inductively Coupled Plasma-Mass Spectrometry. Maximum adsorption capacity was achieved at pH 5.0. The isothermal data of dried fungal biomass could be described well by the Langmuir equation and monolayer capacity had a mean value of 59.88 mg g-1. The pseudo-second order reaction model provided the best description of the data with a correlation coefficient 0.99 for different initial metal concentrations. This result indicates that chemical sorption might be the basic mechanism for this adsorption process and Fourier Transform Infrared Spectroscopy analyses showed that amide I and hydroxyl groups play an important role in binding Pb (II). Because of the high activation capacity of adsorbent and low cost of process dried R. oligosporus biomass presents a good potential as an alternative material for removal of Pb (II) ions from the aqueous solutions. Chapter 17 - The main objective of this research work is to determine the presence of di(2-ethylhexyl) phthalate, di(2-ethylhexyl) adipate and diisodecyl phthalate, in different water samples (drinking waters, effluents and surface waters). Different analytical methods were studied in order to know the best methodology for the quantification of these compounds. Solid-liquid and liquid-liquid extraction were investigated and finally the liquidliquid extraction and analysis by gas chromatography followed by mass spectroscopy was chosen because of offering the highest recovery rate. In the whole of this research study, the control of background pollution by reagents and material was extremely important. The problem of background pollution is more serious in the trace analysis of phthalates and adipates as a consequence of their presence in almost all equipment and reagents used in the laboratory. Respect to the control of the selected plasticizers in the different water samples, bis (2ethylhexyl) phthalate and bis (2-ethylhexyl) adipate were detected in drinking water, effluents and surface waters. On the other hand, diisodecyl phthalate was not detected in any sample.

In: Fluid Waste Disposal Editor: Kay W. Canton, pp. 1-48

ISBN: 978-1-60741-915-0 © 2010 Nova Science Publishers, Inc.

Chapter 1

TREATMENT OF WASTEWATER BY ELECTROCOAGULATION METHOD AND THE EFFECT OF LOW COST SUPPORTING ELECTROLYTES Lazare Etiégni1*, K. Senelwa1, B. K. Balozi1, K. Ofosu-Asiedu2, A. Yitambé3, D. O. Oricho1, and B. O. Orori1 1

Moi University, Department of Forestry & Wood Science, P. O. Box 1125 Eldoret, Kenya. 2 J.I.C., Dept. of Chem. Eng. Box 10099, Jubail Industrial City-31961, Kingdom of Saudi Arabia. 3 Kenyatta University, Department of Public Health P.O Box 43844-00100 Nairobi, Kenya

ABSTRACT Coagulation and flocculation are traditional methods of treating of polluted water. Electrocoagulation (EC) presents a robust novel and innovative alternative in which a sacrificial metal anode doses water electrochemically. This has the major advantage of providing active cations required for coagulation, without necessarily increasing the salinity of the water. Electrocoagulation is a complex process with a multitude of mechanisms operating synergistically to remove pollutants from water. A wide variety of opinions exist in the literature for key mechanisms and reactor configurations. A lack of a systematic approach has resulted in a myriad of designs for electrocoagulation reactors without due consideration of the complexity of the system. A systematic, holistic approach is required to understand electrocoagulation and its controlling parameters (pH, temperature, conductivity, current density). This will enable a priori prediction of the treatment of various pollutant types. Electrocoagulation involves applying a current across electrodes in water. This results in the dissolution of the anode (either aluminum or iron). These ions then form hydroxides which complex with and/or absorb contaminants and precipitate out. The precipitate with the contaminants can then be *

Corresponding author: E-mail: [email protected]

2

Lazare Etiégni, K. Senelwa, B. K. Balozi et al. removed from the water by settling and decantation or filtration. EC has the potential to be applied in many other areas besides the textile and semiconductor industry. It has been successfully tested in the pulp and paper industry, as well as tea and coffee processing. However over electrical potential within electrodes during electrocoagulation normally causes extra voltage, which wastes energy. There have been attempts to reduce this extra voltage which, in these days of World energy crisis, will render the electrocoagulation process uneconomical. The inclusion of supporting electrolyte such as NaCl achieves this. One of the methods pioneered by researchers at Moi University in Kenya is the use of wood ash leachate as supporting electrolyte which in some cases could reduce energy consumption by as much as 80%. Other supporting electrolytes tested are ash from bagasse and from coffee husks. These supporting electrolytes are relatively inexpensive, but they all generally result in large amount of coagulated sludge. Other supporting electrolytes such phosphate rock are less effective than wood ash, but they yield almost 50% less sludge after electrocoagulation. Most of the supporting electrolytes have an added advantage of reducing other wastewater pollution parameters such as BOD, COD, TSS, TS, turbidity, pH and color. Because of the inherent benefits of these low cost supporting electrolytes, electro-chemical methods could be a credible alternative to more traditional wastewater treatment approaches.

INTRODUCTION With the dwindling availability of water resources in the World coupled with high population growth, pressure is being exerted on water and wastewater plant managers the world over to find cost-effective methods to treat a wide range of wastewater pollutants in a diverse range of situations. Traditionally coagulation, flocculation and lagooning have been used as chemical and biological processes with varying degrees of success to treat polluted waters. However a more cost-effective and proven method to clean an ever widening range of water pollutants, on-site, and with minimum additives, is required for sustainable water and wastewater management. Electrocoagulation treatment of water seems to fit this description. Colloidal dispersions in water or wastewater often referred to as sols consist of discrete particles held in suspension by their extreme small size (1-200 nm), state of hydration (chemical combination with water), and surface electric charge. The chemistry of coagulation and flocculation is primarily based on the electrical properties of the particles. Like charges repel each other while opposite charges attract. Particles finer than 0.1 µm (1x10-7 m) in water or wastewater remain continuously in motion due to electrostatic charges (often negative) which cause them to repel each other. There are two types of colloids - hydrophilic and hydrophobic. Hydrophilic are readily dispersed in water and their stability depends on the affinity for water rather than the slight negative charge they possess. Hydrophobic colloids on the other hand have no affinity for water and their stability depends on the charge they possess, usually positive. The electrostatic repulsion between the colloidal particles leads to a stable sol. The surface or primary charge of colloidal particles comes from charged groups within the particles or the adsorption of charged particles. The sign and magnitude of the surface charge depends on the character of colloids, the pH (the lower the pH the more positive the charge becomes), the ionic strength and the characteristics of the water or wastewater. The surface of the colloid has a certain δ-potential (zeta potential) which is the magnitude of the charge at the surface of shear. The δ-potential is derived from the diffused double-layer

Treatment of Wastewater by Electrocoagulation Method…

3

theory applied to hydrophobic colloids (Figure 1), and can be estimated using Smoluchowski‘s (1872-1917) electrokinetic mobility equation:

δε μ=

--------------------------------- (1) (1)

ε where μ = the electrophoretic mobility δ = zeta potential ε = the electric permittivity ε = the viscosity of the water or wastewater

Zeta potential can also be calculated using the following relationship for electrostatic force

4πqd δ=

--------------------------- (2) D

(2)

q = charge per unit area d = thickness of the layer surrounding the shear surface through which the charge is effective π = pi (= 3.142857) D = dielectric constant of the liquid + + + + +

+

+

+ +

Stern layer

+ +

+

+

+ +

Surface shear

+

+

+ +

+

+ +

Particle + +

+

+

+

Bulk of solution n

+ + + +

+

+

+

+ +

+ + +

+ +

Zeta potential +

Fixed layer of ions

Figure 1. Diffused double layer.

Electric potential surrounding particle Diffusion layer of counterions

4

Lazare Etiégni, K. Senelwa, B. K. Balozi et al.

The diffused double layer (Figure 1) consists of two parts: an inner region, also referred to as Stern layer, which includes ions bound relatively strongly to the surface (including specifically adsorbed ions) and an outer, diffuse or movable region in which the ion distribution is determined by a balance of electrostatic forces and random thermal motion. The potential in this region, therefore, decays as the distance from the surface increases until, at sufficient distance, it reaches the bulk solution value, conventionally taken to be zero. The repulsive force of the charged double layer scatters particles thus preventing agglomeration. Particles with high zeta potential have a very stable sol. The zeta potential is the overall charge a particle acquires in a specific medium. In other words, it is a measure of the magnitude of electrical charge surrounding the colloidal particles. The magnitude of the zeta potential gives an indication of the potential stability of the colloidal system. Zeta potential can be equated to the amount of repulsive force which keeps the particles in suspension. If the zeta potential is large, then more coagulants will be needed to destabilize colloidal particles. If all the particles have a large negative or positive zeta potential they will repel each other and there is dispersion stability. When particles have low zeta potential values, there is no force to prevent the particles coming together and there is dispersion instability. A dividing line between stable and unsable aqueous dispersions is generally taken at either +30 or -30mV.

FACTORS AFFECTING ZETA POTENTIAL There are several factors that can affect zeta potential

1. pH In aqueous media, the pH of a sample is one of the most important factors that affect its zeta potential. A zeta potential value on its own without defining the solution conditions is virtually meaningless. A zeta potential versus pH curve will be higher or positive at low pH and lower or negative at high pH. There may be a point where the plot passes through zero zeta potential. This point is called the isoelectric point and is very important from a practical consideration. It is normally the point where the colloidal system is least stable.

2. Conductivity The thickness of the double layer (κ-1) depends upon the concentration of ions in solution and can be calculated from the ionic strength of the medium. The higher the ionic strength, the more compressed the double layer becomes. The valence of the ions will also influence double layer thickness. A trivalent ion such as Al3+ will compress the double layer to a greater extent in comparison to a monovalent ion such as Na+. Inorganic ions can interact with charged surfaces in one of two distinct ways (i) non-specific ion adsorption where they have no effect on the isoelectric point and (ii) specific ion adsorption, which will lead to a


5

change in the value of the isoelectric point. The specific adsorption of ions onto a particle surface, even at low concentrations, can have a dramatic effect on the zeta potential of the particle dispersion. In some cases, specific ion adsorption can lead to charge reversal of the surface.

3. Concentration of a Formulation Component The effect of the concentration of a formulation component on the zeta potential can give information to assist in formulating a product to give maximum stability. The influence of known contaminants on the zeta potential of a sample can be a powerful tool in formulating the product to resist flocculation for example.

COAGULATION Schulze, in 1882, first showed that colloidal systems could be destabilized by the addition of ions having a charge opposite to that of the colloid (Benefield et al., 1982). Coagulation in water or wastewater chemistry is a process in which a chemical referred to as a coagulant is added to destabilize dispersed colloidal particles so that they agglomerate. Coagulation experiments using natural products such as Moringa oleifera have also been tried with varying degrees of success (Kasser et al., 1990; Ogutveren et al., 1994; Ndabigengesere et al., 1995; Mohammed, 2001; Bhuptawat and Chaudhari, 2003). The objectives of coagulation are to (i) destabilize suspended and colloidal particles to enhance their removal through sedimentation and filtration and (ii) to precipitate dissolved maters i.e. PO43-, color, natural organic matter (NOM). Coagulation process may require several reaction steps: (i) hydrolysis of multivalent metal ions; (ii) adsorption of hydrolysis species at the solid-solution interface for the destabilization of colloidal particle (reduction of zeta potential); (iii) aggregation of destabilized particles by interparticle bridging; (iv) aggregation of destabilized particles by particle transport and van der Waals‘ forces; (v) ―aging‖ of flocs formed in the process; and (vi) precipitation of metal hydroxides (Stumm and O‘Melia, 1968).

ELECTROCOAGULATION Electrocoagulation is a process that applies a current across electrodes through a liquid, using a variety of anode and cathode geometries, including plates, balls fluidized bed spheres, wire mesh, plates (either aluminum or iron), rods, and tubes. This results in the dissolution of the anode (Equation 3 & 12). These ions then form hydroxides which complex with and/or absorb contaminants and precipitate from water or wastewater. They are subsequently removed by surface complexation and electrostatic attraction according to the following equations:

6


WITH IRON ELECTRODES In acidic medium, Fe(s) → Fe2+(aq) + 2e-

(Equation 3)

4Fe2+(aq) + 10 H2O(l) + O2 (g) → 4 Fe (OH)3(s) + 8H+ (aq)

(Equation 4)

Cathode:

2H+ (aq) + 2e- → H2 (g)

(Equation 5)

Overall:

4 Fe(s) + 10 H2O(l) + O2 (g) → 4Fe(OH)2(s) + 4H2 (g)

(Equation 6)

Anode:

In alkaline medium, Anode:

Fe(s)

Fe2+ (aq) + 2e-

Fe2+(aq) + 2OH-(aq) 2H2O(l) + 2e-

Cathode: Overall:

Fe (s) + 2H2O(l) Floc + H2 (g)

(Equation 7)

Fe(OH)2(s)

(Equation 8)

H2(g) + 2OH-(aq)

(Equation 9)

Fe(OH)2(s) + H2(g) Floats

(Equation 10) (Equation 11)

WITH ALUMINUM ELECTRODES In acidic medium Anode:

Al (s) 2Al3+ (aq) + 4H2O(l) + O2 (g)

Cathode:

2H+ (aq) + 2eOverall: 2Al(s) + 4H2O(l) + O2 (g)

Al3+ + 3e-

(Equation 12)

2Al(OH)3(s) + 2H+ (aq) (Equation 13) H2 (g)

(Equation 14)

2Al(OH)3(s) + 2H2(g)(Equation 15)

In alkaline medium Anode:

Al (s) Al3+ (aq) + 3OH- (aq)

Cathode: Overall:

2H2O(l) + 2e2Al(s) + 3H2O(l)

Al3+ + 3e-

(Equation 16)

Al(OH)3(s)

(Equation 17)

H2(g) + 2OH-(aq)

(Equation 18)

Al(OH)3 + 3/2H2 (g)

(Equation 19)


7

The cation hydrolyses in water to form a hydroxide. The following equations (20 to 23) are an illustration of this phenomenon in the case of aluminum: pH

Al3+ + H2O AlOH2+ + H2O Al(OH)2+ + H2O Al(OH)30 + H2O

AlOH2+ + H+ Al(OH)2+ + H+ Al(OH)30 + H+ Al(OH)4- + H+

(Equation 20) (Equation 21) (Equation 22) (Equation 23)

ELECTROCOAGULATION MECHANISMS The electrocoagulation overall mechanism is a combination of mechanisms that operate concurrently or in series but synergistically. The main mechanism may vary throughout the dynamic process as the reaction progresses, and will almost certainly shift with changes in operating and environmental parameters and pollutant types. Highly charged cations destabilize any colloidal particles by the formation of polyvalent polyhydroxide complexes. These complexes have high adsorption properties, forming aggregates with pollutants. The pollutants presumably act as a ligand to bind with iron or aluminum ions resulting in the formation of amorphous polymeric complexes (hydroxo-complexes). These compounds with a large specific surface area are very active and able to coagulate and adsorb pollutants soon after their in situ generation (Rajeshwar and Ibanez 1997; Scott, 2001). Besides the generation of polyvalent cations described above, electrocoagulation includes also the production of electrolysis gases that are hydrogen and oxygen (Equation 5, 6, 9, 10, 14, 15 & 19). Evolution of hydrogen gas aids in mixing and flocculation. Once the floc is generated, the electrolytic gas binds to and creates a buoyant force on the floc leading to its flotation and ultimately to the removal of the pollutant as a floc - foam layer at the liquid surface (Equation 11). Other flocs that are heavier settle at the bottom of the reactor. There are many ways in which species can interact in solution: 1. Migration to an oppositely charged electrode (electrophoresis) and aggregation due to charge neutralization. 2. The cation or hydroxyl ion (OH-) forms a precipitate with the pollutant. 3. The metallic cation interacts with OH- to form a hydroxide, which has high adsorption properties thus bonding to the pollutant (bridge coagulation). 4. The hydroxides form larger lattice-like structures that sweep through the water (sweep coagulation). 5. Oxidation of pollutants to less toxic species. 6. Removal by electroflotation and adhesion to bubbles (Figure 2). Electrocoagulation process has been around for some time. The process was proposed before the turn of the last century with Vik et al. (1984) describing a treatment plant in London built in 1889 (for the treatment of sewage by mixing with seawater and electrolyzing). In 1909, Harries (cited in Vik et al., 1984) in the United States, received a patent for wastewater treatment by electrolysis with sacrificial aluminum and iron anodes. Matteson and Dobson (1995) described a device of the 1940‘s, the ―Electronic Coagulator‖

8


which electrochemically dissolved aluminum (from the anode) into solution, reacting this with the hydroxyl ion (from the cathode) to form aluminum hydroxide. The hydroxide flocculates and coagulates the suspended solids purifying the water. A similar process was used in Britain in 1956 for which iron electrodes were used to treat river water (Matteson and Dobson, 1995). Because of its capability to remove several types of water pollutants, the recent thirty years have seen an explosion of journal article reports on electrocoagulation methods probably due to new and more stringent environmental regulations on a wide range of water and wastewater pollutants. This has further translated into a number of electrocoagulation devices, designed to purify water or wastewater, being put on the market.

REACTIONS WITHIN THE ELECTROCOAGULATION REACTOR Several distinct electrochemical reactions are produced independently within the electrocoagulation reactor. They are as follows: Emulsion breaking, resulting from the oxygen and hydrogen ions that bond into the water receptor sites creating a water insoluble complex that separate water from pollutants. Seeding, resulting from the anode reduction of metal ions that become new centers for larger, stable, insoluble complexes that precipitate as complex metal ions. Bleaching by the oxygen ions produced in the reaction chamber oxidizing pollutants such as dyes, cyanides, biohazards, chlorolignins from pulp and paper mill effluent. DC power supply

Coagulation & Flocculation

Cathode

Anode

Flocs

H2

Sediments Figure 2. Electrocoagulation process interactions (Hydrogen discharge at the cathode generates gas micro-bubbles that cause the floatation of flocs and the increase of pH).


9

Electron flooding of the water that eliminates the polar effect of the water complex, allowing colloidal materials to precipitate. The increase of electrons creates an osmotic pressure that ruptures bacteria, cysts, and viruses. Oxidation reduction reactions that are forced to their natural end point within the reactor which speeds up the natural process. Electrocoagulation induced pH swings toward neutral although this will not always be the case and will depend on the type of electrolyte used.

TYPE OF ELECTRODES Electrode material can subtancially affect the performance of an electrocoagulation reactor. The heart of EC is the dimensionally stable oxygen evolution anode which is usually expensive. The anode material determines the cation introduced into solution. Several researchers have studied the choice of electrode material with a variety of theories as to the preference of a particular material. The most common electrodes were aluminum or iron plates as described by Vik et al. (1984) and Novikova and Shkorbatova (1982). Do and Chen (1994) have compared the performance of iron and aluminum electrodes for removing color from dye-containing solutions. Their conclusion was that the optimal electrocoagulation conditions varied with the choice of iron or aluminum electrodes, which in turn was determined by initial pollutant concentration and pollutant type.

STIRRING RATE Bazrafshan et al. (2008), while comparing chromium removal efficiency with iron and aluminum electrodes, showed that removal efficiency of chromium with aluminum electrodes was lower than chromium removal efficiency with iron electrodes. Metal consumption equally was much lower with aluminum than with iron electrodes. Conversely, power consumption was lower with aluminum than with iron electrodes for the same concentration of pollutant. However, as the chromium concentration in the solution increased to 500.0 mg/L , the consumption of the electrode reduced, but efficient chromium removal occurred due to the large amount of flocs formation that helped sweep away chromium. For example, iron electrode consumption for the initial concentration of 5.0 mg/l and voltage of 40 V was 9.01 g while for an initial concentration of 500.0 mg/L it was 7.70 g (Bazrafshan et al., 2008). The highest efficiency of chromium removal (for both iron and aluminum electrodes) was measured in acidic medium (pH = 3) for an initial chromium concentration of 500.0 mg/L and at lower concentrations, the removal efficiency was almost complete at all pH values. At high chromium concentration, however, the complete removal would have required longer time i.e. higher power consumption. Some researchers have investigated the relationship between ―size‖ of the cation introduced and removal efficiency of organic waste (Baklan and Kolesnikova, 1996; Vlyssides et al., 1997). The size of the cation produced (10-30μm for Fe3+ compared to 0.05-1 μm for Al3+) was suggested to contribute to the higher efficiency of iron electrodes. Their conclusion was based on a single experiment, however, using chemical absorption of oxygen

10


as the only measure. Hulser et al. (1996) observed that electrocoagulation is strongly enhanced at aluminum surfaces in comparison to steel. This is attributed to a higher efficiency due to the in situ formation of dispersed aluminum-hydroxide complexes through hydrolysis of the aluminate ion, which does not occur with steel electrodes. Tsai et al. (1997) employed Fe and Al anodes to simultaneously utilize electrocoagulation, responsible for removal of high molecules, and oxidation during treatment of a raw leachate. Iron anodes provided better COD removal at low applied voltages than did aluminum (Englehardt et al., 2006). As a general statement the efficiency of aluminum or iron electrodes will depend on the specific type of pollutant and also on the different set of operating parameters (Kobya et al., 2003).

ELECTRODE PASSIVATION One of the greatest operational issues with electrocoagulation is electrode passivation. The passivation of electrodes is of concern for the longevity of the process. Passivation of aluminum electrodes has been widely reported in the literature (Nikolaev et al., 1982; Osipenko and Pogorelyi, 1977). The latter also observed that during electrocoagulation with iron electrodes, deposits of calcium carbonate and magnesium hydroxide were formed at the cathode and an oxide layer was formed at the anode. Nikolaev et al. (1982) investigated various methods of preventing electrode passivation and suggested the following options for its control: Changing polarity of the electrode; Hydromechanical cleaning; Introducing inhibiting agents; Mechanical cleaning of the electrodes. According to these researchers, the most efficient and reliable method of electrode maintenance was to periodically mechanically clean the electrodes or wash the electrodes with 8% sulfuric acid between runs in batch which for large-scale, continuous processes is a challenging issue. Corrosion promoters such as Cl - ions have been found to induce thinning of passive layer, enhance dissolution and promote depassivation (spontaneous depassivation). Other types of electrodes with a wide range of materials have been tested for electrocoagulation process. These materials include: Graphite, Platinum oxide, Iridium oxide, lead oxide, tin oxide, boron doped diamond (BDD). Graphite electrodes are deemed to be cheap but unstable and for most part ineffective (Barisa et al., 2009). They become easily fouled during the electrocoagulation process and this reduces their effectiveness. Platinum and Iridium oxide electrodes are too expensive and ineffective. Electrodes made of lead oxide (PbO 2) and tin oxide (SnO 2) are easy to manufacture but they are highly unstable. Boron doped diamonds are materials suitable for use as anodes in the electrocoagulation of organic compounds. Due to their very high resistance to deactivation via fouling and extreme electrochemical stability they show no significant corrosion even under high current densities. They have good chemical, mechanical and


11

thermal resistance and a wide electrochemical potential window in aqueous solutions. Above all they can provide very high current efficiencies. Diamond coated electrodes have been investigated worldwide over the past number of years with notable results (Fryda et al., 2003). It is possible to vary electrical properties of diamond from semiconductor (very wide band gap) to close to metallically conductive by varying the boron doping level (1019-1021 cm-3). The most important electrochemical properties of BDD electrodes are their very high corrosion stability in electrochemical applications and their extremely high overvoltage for water electrolysis (Fryda et al., 1999). This large working potential window in aqueous electrolytes provides the possibility of producing strong oxidizing solutions with extremely high efficiency. As reported by Michaud and Comninellis (2000), compared to other electrode materials, BDD electrodes produce hydroxyl radicals on their surface with higher current efficiency. These hydroxyl radicals completely mineralize organic impurities in water or wastewater, such as oil, cooling fluid, toxic compounds (Tennakone et al., 1995). As diamond electrodes are both stable as anodes and cathodes, it is possible to reverse polarity in order to prevent calcium build-up on the electrode surface. Through the use of diamond electrodes, it is possible to obtain an electrochemical process which, without the addition of further chemicals, results in an environmentally friendly and relatively maintenance-free method for the treatment of waste water. Nonetheless, despite the promising results with respect to effectiveness and energy efficiency which have been demonstrated for wastewater treatment, electrosynthesis and electroplating, BDD electrodes remain extremely expensive. A new anode coated IrOx−Sb2O5−SnO2 onto titanium has also been proposed (Xueming et al., 2002). Accelerated life test showed that the electrochemical stability of the Ti/IrOx−Sb2O5−SnO2 anode containing only 2.5 mol % of IrO x nominally in the activated coating was even higher than that of the conventional Ti/IrO x anode. Its service life for electroflotation application is predicted to be about 20 years. Voltametric investigation demonstrated that the Ti/IrO x−Sb2O5−SnO2 anode could provide fast electron transfer. The present anode had a fork-like design and arranged in an interlocking manner with the cathode with a similar shape. Such an innovation in electrode configuration and arrangement is claimed to allow bubbles produced at both electrodes to be dispersed into wastewater flow quickly and, therefore, enhances the effective contact between bubbles and particles, favorable for high flotation efficiency. In addition, the novel electrode system reduces the interelectrode gap to 2 mm, a spacing that is technically difficult for a conventional electrode system (Xueming et al., 2002). This small gap results in a significant energy saving. Easy maintenance is another advantage of this novel electrode system.

AREAS OF APPLICATION OF ELECTROCOAGULATION According to Can et al. (2006), electrocoagulation has been proposed in recent years as an effective method to treat various wastewaters such as: landfill leachate, restaurant wastewater, saline wastewater, tar sand, paper mill effluent, coffee factory effluent, tea factory effluent, oil shale wastewater, urban wastewater, laundry wastewater, nitrate and

12


arsenic bearing wastewater, and chemical mechanical polishing wastewater. The electrocoagulation process can successfully remove a wide range of pollutants in a much shorter time than conventional treatment methods (Ogutveren et al., 1994; Kongsricharoern and Polprasert, 1995, ). They include: removal of metals, oil, BOD, TSS, TDS, FOG, color etc., from wastewater before final disposal, thus reducing or eliminating discharge surcharges; reconditioning antifreeze by removing oil, dirt, and metals; reconditioning brine chiller water by removing bacteria and fat; pretreatment before membrane technologies such as reverse osmosis, ultrafiltration and nanofiltration; preconditioning boiler makeup water by removing silica, hardness, TSS; reconditioning boiler blow down by removing dissolved solids eliminating the need for boiler chemical treatment; recycling water, allowing closed loop systems; harvesting protein, fat and fiber from food processor waste streams; de-watering sewage sludge and stabilizing heavy metals in sewage, lowering freight and allowing sludge to be land applied; conditioning and polishing drinking water; removing chlorine and bacteria before water discharge or reuse (Cenkin and Belevstev ,1985; Biswas and Lazarescu,1991; Browning,1996; Adhoum et al., 2004).

COLOR Color is found mostly in surface waters, although some groundwater inside deep wells may also contain color that is noticeable (APHA-AWWA, 1992; AWWA, 1999). Many domestic and industrial wastewaters are rarely colorless and the color levels depend on the industrial process and the age of the wastewater i.e. the travel time in the collection and treatment system (Kim et al., 2005). The pulping and bleaching of wood for example generally produce large amounts of wastewaters that contain lignin derivatives and other dissolved wood by-products. Lignin derivatives which are usually brownish in color remain resistant to biological degradation during wastewater treatment. The brownish color of a pulp and paper mill effluent is mainly attributed to products of lignin polymerization formed during pulping and bleaching operations. These chromophoric groups are mainly quinonic types with conjugated double bonds originating from pulping processes (Luner et al., 1970). When disposed of into natural watercourses, they add color which persists for great distance. Additionally, colored effluents from pulp and paper mills for example result in reduced photosynthetic activity, increased long term BOD, increased water treatment cost for users downstream, and increased toxicity (Springer et al., 1995). Several studies have been carried out to determine the effectiveness of EC in color removal. In general, the findings indicate that EC is more cost effective than normal or conventional coagulation. Moreover, other wastewater pollution parameters are reduced (Orori et al., 2005; Kashefialasl et al., 2006, Oricho et al., 2008). Electrocoagulation combined with wood ash or bagasse ash has also been applied on tea factory effluent. In one study by Maghanga (2008) on tea factory effluent, the treated effluent COD, BOD and electrical conductivity were reduced by 96.6%, 42.4%, and 20.9% respectively. Supporting electrolytes from wood ash, phosphate rock and bagasse ash further reduced power consumption by between 64% and 16%, confirming the effectiveness of this process.


13

ADVANTAGES OF ELECTROCOAGULATION (EC) Electrocoagulation has several advantages that are as follows: EC produces effluent with less total dissolved solids (TDS) content compared to chemical treatments. If this water is reused, the low TDS level contributes to a lower water recovery cost. EC requires simple equipment and is easy to operate with sufficient operational latitude to handle most problems encountered during its running. Wastewater treated by EC can give palatable, clear, colorless and odorless water. Sludge formed by EC tends to be readily settable and easy to de-water, because it is composed of mainly metallic oxides/hydroxides. Flocs formed by EC are similar to chemical floc, except that EC floc tends to be much larger, contains less bound water, is acid-resistant and more stable, and therefore, can be separated faster by filtration. The EC process can remove the smallest colloidal particles, because the applied electric field sets them in faster motion, thereby facilitating their agglomeration and subsequent coagulation. The EC process often avoids uses of chemicals and so there may be no problem of neutralizing excess chemicals and no possibility of secondary pollution caused by chemical substances added at high concentration as when chemical coagulation of wastewater is used alone. The gas bubbles produced during electrolysis can carry the pollutant to the top of the solution where it can be more easily concentrated, collected and removed. The electrolytic processes in the EC cell are controlled electrically and with no moving parts, thus requiring less maintenance.

DISADVANTAGES OF ELECTROCOAGULATION (EC) High capital cost has often been cited as one of the major disadvantages of EC although labour requirement may also be high when running an EC batch reactor. Higher voltages and thus high specific energy consumption are also seen as a big disadvantage of the system. The final deficiency of this process relates to the fact that an EC reactor is an electrochemical cell whose performance is directly related to the operational state of its electrodes. As mentioned earlier, they vary widely in design and mode of operation- from simple vertical plate arrangements to packed-bed style reactors containing various metallic packings, and in material used (Ogutveren et al., 1992; Barkley et al., 1993). Potential for electrode passivation, thus slow reaction rates is another draw back because passivation impedes dissolution which normally provides the coagulants in situ. Electrode passivation, specifically of aluminum electrodes, has been widely observed and acknowledged as detrimental to reactor performance (Osipenko and Pogorelyi, 1977; Novikova and Shkorbatova, 1982). This formation of an inhibiting layer, usually an oxide, on the electrode surface prevents metal dissolution and electron transfer, thereby limiting coagulant addition to the solution. Over time, the thickness of this layer increases, reducing the efficacy of the electrocoagulation

14


process as a whole. The use of new materials, different electrode types and arrangements (Pretorius et al., 1991; Mameri et al., 1998) and more sophisticated reactor operational strategies (such as periodic polarity reversal of the electrodes mentioned above) have led to significant reductions in the impact of passivation. The issue, however, is still seen as a serious potential limitation for applications where a low-cost, low maintenance water treatment facility is required.

DESIGN OF ELECTROCOAGULATION UNITS The inherent complexity of the electrocoagulation reactions makes it difficult to model and control this process. Adequate scale-up parameters, a systematic approach to the optimization and a priori prediction for the performance of the electrocoagulation reactor are yet to be established. A literature survey reveals that previously each ―new‖ system has been considered separately on an individual basis. The key driver for the development of any particular application of this process has generally been the removal of a specific pollutant i.e. color, heavy metal, COD, tannin etc. There has been little or no attempt to provide a holistic approach to electrocoagulation. Consequently, despite more than a century‘s worth of applications, many of them deemed successful, the science and engineering behind EC reactor design is still largely empirical and heuristic. It has failed to take full advantage of the potential success and incorporation in the understanding behind the science of electrocoagulation. A literature review indicates that EC reactors can be configured as batch or continuous and that the majority of reactors reported so far fall in the latter category with continuous feed and outflow operating under pseudo-steady state. Electrocoagulation systems require amperage to treat the water. The amount of amperage drawn is dependent upon the conductivity of the water or wastewater. If the water is not conductive then no amperage will be used. The system should be designed with adequate wiring and electrical capacity to deliver adequate amperage if needed by a particular water stream.

PHYSICAL DESIGN ISSUES There has been a range of laboratory, pilot and industrial scale electrocoagulation units produced. The designs range from fully integrated units to ‗stand alone‘ reactors. The electrocoagulation process has been combined with many units including microfiltration, dissolved air flotation (DAF), sand filtration and electroflotation. Obviously, pre- and postwater treatment impacts significantly on the performance of the electrocoagulation reactor. The design of the electrocoagulation process influences its operation and efficiency (Holt et al., 2005). The design phase should consider the following physical factors: Continuous versus batch operation Reactor geometry Reactor scale-up Current density


15

GEOMETRY Geometry of the reactor affects operational parameters including bubble path, flotation effectiveness, floc formation, fluid flow regime and mixing/settling characteristics. From the literature, the most common approach involves plate electrodes (aluminum or iron) and continuous operation. Water is dosed with dissolved metal ions as it passes through the electrocoagulation cell. A downstream unit is often required to separate pollutant and water.

SCALE-UP ISSUES One of the cornerstones of chemical engineering is to establish key scale-up parameters to define the relationships between laboratory and full-scale equipment. The surface area to volume ratio (S/V) is a significant scale-up parameter. Electrode area influences current density, position and rate of cation dosing, as well as bubble production and bubble path length. Mameri et al. (1998) reported that as the S/V ratio increases the optimal current density decreases. However, the S/V ratio was not widely reported. Some of the values reported are listed in Table 1 below: The values reported here seem empirical with no specific criteria for their choice. A more rigorous and consistent approach is clearly required to establish a set of design characteristics for Electrocoagulation reactors. The prime differentiator between pollutant removal by settling or flotation would seem to be the current density employed in the reactor. A low current produces a low bubble density, leading to a low upward momentum flux—conditions that encourage sedimentation over flotation (Holt et al., 2002). As the current is increased, so does the bubble density resulting in a greater upwards momentum flux and thus more likely removal by flotation. Other researchers such as Zolotukhin (1989) scaled up an electrocoagulation-flotation system from laboratory to industrial scale. The following dimensionless scale-up parameters have been chosen to ensure correct sizing and proportioning of the reactors: Reynolds number – indication of the fluid flow regime; Froude number – indication of buoyancy; Weber criteria – indication of the surface tension; Gas saturation similarity; Geometric similarity. Table 1. S/V values reported in the literature. Reference (Author) Amosov et al. Osipenko and Pogorelyi Novikova and Shkorbatova Orori et al. Oricho et al. Maghanga

Year 1976 1977 1982 2005 2008 2008

S/V (m2/m3) 30.8 18.8 42.5 80.0 75.5 18.2

16


Horizontal Flow

Vertical flow

Figure 3. Types of electrodes set-up during EC.

Electrodes during EC can be set up as parallel vertical or horizontal sheets as can be seen in Figure 3. The turbulence generated by the gases at the anode and cathode can be used in both types of flow. However, vertical flow allows for more improved separation by electroflotation as compared with horizontal flow.

FACTORS AFFECTING ELECTROCOAGULATION PROCESSES Several studies have shown that electrocoagulation is quite complex and may be affected by several operating parameters such as pollutant concentrations, initial pH, electrical potential voltage, COD, turbidity, pollutant type and concentration, bubble size and position, floc stability and agglomerate, size and type of supporting electrolyte. The complexity and number of possible interactions are highlighted in Figure 2.

EFFECT OF PH ON ELECTROCOAGULATION Optimal pH reported for electrocoagulation reactions varies significantly. These discrepancies probably derive from the complex and variability of wastewater composition, and the different operating conditions used in the electrocoagulation studies. It has been established that pH has a considerable effect on the efficiency of the electrocoagulation process (Springer et al., 1995, Chen et al., 2000, Li et al. 2001). The wastewater pH determines the speciation of metal ions and influences the state of other species in solution and the solubility of products formed. The pH of the medium also changes during electrocoagulation process, as observed by other investigators. This change depends on the type of electrode material and initial pH and alkalinity. In a study by Bazrafshan et al. (2008) on the removal of Chromium VI from synthetic chromium solutions by electrocoagulation


17

using aluminum electrode, it was observed that there was an increased in the solution pH for an initial pH of less than 7. The increase was ascribed to hydrogen evolution at the cathodes contrary to Chen et al. (2000) assertion that the pH increase is due to the release of CO2 from wastewater owing to H2 bubble disturbance. At low pH, wastewater is over saturated with CO2 which can be released during H2 evolution, causing a pH increase. In addition, if the initial pH is acidic, reactions would shift towards a pH increase (Bazrafshan et al. 2008). During the same experiment, in alkaline medium (pH > 8), the final pH did not vary considerably but a slight drop was recorded. This result concurs with previous published works and suggests that electrocoagulation can act as a pH buffer (Gao et al.,2005). In the same study of chromium removal by electrocoagulation carried out over a wide range of Cr concentrations, it was also observed that the influent pH did not significantly affect the removal efficiencies of Cr VI. This means that for practical applications, pH adjustment before treatment is not required. In another study by Springer et al. (1995) on the effect of pH on the color removal reaction by electrocoagulation, it was found that higher pH slowed the electrocoagulation reaction, thereby increasing power consumption. In a separate study on color removal from a pulp and paper mill effluent, Orori (2003) found that decreasing the original effluent pH led to a significant reduction in power consumption during electrocoagulation combined with wood ash leachate. Lowering pH from 12.0 to pH 10.0 significantly (P 0.05) reduced power consumption by between 20 to 21% during electrochemical removal of a paper mill effluent color. It was postulated that decreasing the original effluent pH increased ionisation of wastewater, which increased the rate of iron (II) ions production at the anode and hydrogen at the cathode. Consequently, decreasing pH led to increased production of positively charged iron (II) ions, which attracted the negatively colored flocci (Springer et al., 1995). Thus increased production rate of these ions led to an increase in the rate of color removal at lower pH than at higher pH. Therefore lower pH facilitated color removal and lowered electrical power consumption. Li et al. (2001) reported that COD removal was at least 20% higher at pH 4.0 than at pH 8.0 after a 4-hour electrolysis. Vlyssides et al. (2003) found that pH was the most significant operational parameter in electrolyzing leachate, compared to Clconcentration, temperature, applied voltage, SO42- concentration and leachate input rate. Lower pH favored COD removal and saved energy consumption within the range pH 5.5 – 7.5. The disagreement in these investigations suggests further work, perhaps in terms of the mechanisms by which pH affects COD removal in leachate electrolysis. Theoretically, it can be stated that acidic conditions decrease the concentrations of CO32and HCO3- , both well-known scavengers of OH radical generated at the anodes (Li et al., 2001), while alkaline conditions promote the Cl-→Cl2→ClO-→Cl- redox cycle. Therefore, low pH may enhance direct oxidation, while high pH may enhance indirect oxidation (Wang et al., 2001). Thus, solution pH influences the overall efficiency and effectiveness of electrocoagulation. An optimal pH seems to exist for a given pollutant, with optimal pH values ranging from 6.5 to 7.5 (Holt et al.,2002). Kashefialasl et al. (2006) showed that the maximum efficiency of color removal during the treatment of dye solution containing colored index acid yellow 36 by electrocoagulation using iron electrodes was observed at pH range 7–9 as expected considering the nature of the reaction between ferrous and hydroxide ions. When the pH of solution was lower than 6, Fe(OH)3 was in soluble form (Fe+3) and when it was higher than 9, Fe(OH)3 was in soluble form {Fe(OH)4-} and because Fe(OH)3 played a major role in removing color, when pH of

18


solution was 8, color removal was the highest. The dye solution with different initial concentrations in the range of 20-60 mg/l was treated by EC at optimized current density and time. In contrast, other investigators have found that pH variation does not considerably alter COD removal in leachate electrolysis. Chiang et al. (1995a) have reported that the pH effect on chlorine/hypochlorite production efficiency was insignificant over the range pH 4-10 during an electrolysis experiment in saline water conducted to help elucidate the mechanism of electrolyzing leachate. Cossu et al. (1998) found that a pseudo-first-order rate constant for COD reduction in real leachate increased only slightly at pH 3, compared with pH 8.3. Also, Wang et al. (2001) have reported that at pH 8.9 and 10, COD removal was approximately 4% higher than at pH 7.5, not a very significant effect.

EFFECT OF CURRENT DENSITY ON ELECTROCOAGULATION Current density (i) is the current delivered to the electrode divided by the active area of the electrode. Varying the current easily controls this parameter. Current density determines both the rate of electrochemical metal dosing to the water and the electrolytic bubble density production. Current densities ranging from 10 to 2000 A/m2 have been reported (Holt et al., 2005). The majority of the sources used for this write-up report a current density in the range 10 – 150 A/m2. Different current densities are desirable in different situations. Current densities reported for electrochemical oxidation of leachate ranged from 5 to 540 mA/cm2 (Englehardt et al., 2006). It is reported that at least 5 mA/cm2 is required to achieve effective oxidation of organics in leachate. Table 2. Percent of chromium removal during electrocoagulation process using aluminum electrodes (Initial concentration = 50 mg l−1). T = 60 min 98.62 98.74 98.88 98.40 98.44 98.72 92.00 97.64 98.34

T = 40 min 94.78 95.64 95.80 89.76 91.72 95.72 90.80 92.18 92.58

Source: Bazrafshan et al. 2008, with permission

T = 20 min 83.76 85.64 88.98 82.76 83.14 83.46 64.60 77.00 81.80

Voltage (V) 20 30 40 20 30 40 20 30 40

pH 3

7

10

High current densities are desirable for separation processes involving flotation cells or large settling tanks, while small current densities are appropriate for electro-coagulators that are integrated with conventional sand and coal filters. A systematic analysis will be required to define and refine the relationship between current density and desired separation effects. Current density (current per unit area of electrode) in an electrochemical process indicates gross reaction rate. For example under weaker oxidative conditions, leachate may darken and


19

brown precipitates may form at the anode (Cossu et al., 1998; Li et al., 2001). Increasing current density improves COD and NH3-N treatment efficiencies at the same charge loading. Bazrafshan et al. (2008) showed that increasing electrocoagulation voltage increased the removal efficiency of Chromium, which was also helped by higher pHs as can be seen in Tables 1 and 2. Chiang et al. (1995b) reported that during electrolytic treatment of leachate, COD removal at 25 mA/cm2 was approximately 50% higher than that observed at 6.25 mA/cm2, for the same charge loading (1.178 x 105 Coulombs/L). This is probably due to the fact that increasing current density during electrolysis enhances chlorine generation, which may have been responsible for subsequent removal of pollutants (Costaz et al., 1983; Chiang et al., 1995a). Li et al., (2001) have shown that the effect of current density on treatment was not evident between 30 and 120 mA/cm2 at a low Cl- concentration (1650 mg/L), but became noticeable when Cl- concentration reached the 5000 mg/L level. Table 3. Percent of chromium removal during electrocoagulation process using aluminum Electrodes (Initial concentration = 500 mg l−1). T = 60 min 25.60 35.80 83.00 20.40 24.60 80.80 23.00 26.80 52.00

T = 40 min 22.0 27.00 71.20 19.60 20.40 64.60 13.80 22.00 41.20

Source: Bazrafshan et al. 2008, with permission.

T = 20 min 21.80 24.80 51.80 13.60 17.80 41.00 8.80 12.80 32.00

Voltage, (V) 20 30 40 20 30 40 20 30 40

pH 3

7

10

Figure 4. Effect of current density on the efficiency of color removal from a solution with concentration of the dye = 50 ppm (Source: Kashefialasl, et al., 2006 with permission).

20


This result corroborates the importance of indirect oxidation during the electrolytic treatment of leachate. In addition, Moraes et al. (2005) reported that color removal from leachate strongly depended upon current density. Color removal efficiency at 116 mA/cm2 was five times higher than that at 13 mA/cm2, after 180 minutes of electrochemical treatment. In the treatment of dye solution containing colored index acid yellow 36 by electrocoagulation using iron electrodes Kashefialasl et al. (2006) showed that as current density increased so did color removal from the dye solution up to a certain maximum as shown in Figure 4. During electrocoagulation, electrical current not only determines the coagulant dosage rate but also the bubble production rate and size and the floc growth, which can influence the treatment efficiency by electrocoagulation (Letterman et al., 1999; Holt et al., 2002). This is ascribed to the fact that at higher voltage the amount of anode material oxidized increases, resulting in a greater amount of precipitate for the removal of pollutants. In addition, it has been demonstrated that bubble density increases and their size decreases with increasing current density resulting in a greater upwards flux and a faster removal of pollutants and sludge flotation (Khosla et al., 1991). As the current decreased, the time needed to achieve similar efficiencies increases. This expected behavior is explained by the fact that the treatment efficiency is mainly affected by charge loading (Q = It), as reported by Chen et al. (2000). However, the cost of the process is determined by the consumption of the sacrificial electrode and the electrical energy. It has also been established that for a given time, the removal efficiency increased significantly with increase of current density. The highest electrical potential normally produces the quickest treatment.

EFFECT OF THE CONCENTRATION OF POLLUTANTS Several investigations have shown that the initial concentration of pollutants has a bearing on the efficiency of the electrocoagulation process (Orori, 2003, Etiegni et al., 2007, Mahvi and Bazrafshan, 2007). A set of experiments was performed with different initial concentrations of chromium to determine the time required for its removal under various conditions of electrocoagulation process (Bazrafshan et al. 2008). SPP1

Power Consumption (MWh))

45

SPP2

40 SPP3

35

SPP4

30

SPP5

25 20 15 10 5 0 15

20

25

30

35

40

45

o

Temperature ( C)

Figure 5. Effect of temperature on power consumption by ELCAS at five sampling points along a pulp and paper Mill effluent treatment system (Source: Orori, 2003 with permission).


21

The results obtained at different electrical potentials showed that initial concentration of chromium may have an effect on the efficiency of its removal and for higher concentration of chromium, higher electrical potential or more reaction time is needed. On the other hand, if the initial concentration increases, the time required should increase too. It is clear from Tables 1 & 2 that at higher concentrations, longer time is needed for removal of chromium, but higher initial concentrations of chromium were reduced significantly in relatively less time compared to lower concentrations. The time taken for its reduction thus increases with the increase in concentration. This can be explained by the theory of dilute solution. In dilute solution, formation of the diffusion layer at the vicinity of the electrode slows the reaction rate, but in concentrated solution the diffusion layer has no effect on the rate of diffusion or migration of metal ions to the electrode surface (Chaudhary et al., 2003). Chromium removal with respect to time by electrocoagulation process at different pH levels is shown in Tables 1 & 2.

EFFECT OF DISTANCE BETWEEN THE ELECTRODES

Metal removal (%)

Numerous research work have been conducted on the effect of electrode distance on the removal of wastewater contaminants by EC (Springer et al., 1995; Ecobar et al.,2006). For some researchers, the electrode gap did not seem to have an impact on the electrocoagulation process although at the narrowest of gap, the clogging of electrodes appeared to reduce the rate of reaction (Springer et al., 1995).

Distance between the electrodes (cm) Source: Escobar et al., 2006, with permission Figure 6. Effect of electrode gap on the removal of (A) Cu, (B) Pb and (C) Cd Current density=36 Am2, Electrolysis time =10 min, Conductivity = 900 mS/cm.

22


EFFECT OF GAP BETWEEN ELECTRODES Escobar et al. (2006) while studying the optimization of the electrocoagulation process for the removal of copper, lead and cadmium in natural waters and simulated wastewater found that increasing the gap between the electrodes reduced metal removal due to a decrease in current flow and coagulant generation (Figure 6). An optimal distance of 2.0 cm for removal of lead and 2.5 cm for removal of cadmium and copper was identified for subsequent experiments. It will appear that each solution has an optimum electrode gap that should be determined experimentally before the EC can be optimized. In general, small gap results in a significant energy saving but makes it difficult to clean the electrode surface in conventional EC

EFFECT OF TURBIDITY In order to study the effect of turbidity (10, 50 and 200 NTU) on removal efficiency of cadmium a set of experiments was performed with different initial concentrations of cadmium (5, 50 and 500 mg l-1). The results obtained at optimum condition (pH=10, time reaction = 60 min and voltage = 40 V) showed that the removal efficiency for various concentrations of cadmium was fairly unchanged and hence electrocoagulation process can be applied efficiently for cadmium removal in the presence of turbidity (Mahvi and Bazrafshan, 2007).

EFFECT OF TEMPERATURE Raising temperature during electrocoagulation increases the rate of reaction (Shenz et al., 2006). Springer et al. (1995) showed that the time required for color removal reaction through electrocoagulation to reach 0.2 Absorbance Units (AU) was cut approximately by half by increasing temperatures from 23oC to 80oC (12 min vs 7 min). Orori (2003) studied the effect of temperature on color removal by electrocoagulation combined with wood ash leachate (ELCAS) and the results are shown in Figure 5. It was found that at 40oC color removal consumed less than 50% the electric power used at 20oC by ELCAS treatment. This was attributed to fast movement of electrons at higher temperatures compared to low temperatures.

EFFECT OF SUPPORTING ELECTROLYTES The underlying principle of EC (Figure 2) is the generation of cations by the dissolution of sacrificial anodes that induce flocculation of the dispersed pollutants contained by the zeta potential reduction system (Calvo et al., 2003; Mollah et al., 2004). During EC processes, high energy can be consumed leading to longer and slower reaction rates. For the EC to be effective, various types of electrodes and configurations have been tested. Several studies have also been conducted to determine the impact of certain additives such as supporting electrolytes during EC (Eichhorn et al.,1996). A supporting electrolyte (SE) is used to increase conductivity in the majority of all electroanalytical or electrosynthetic experiments


23

such as electrocoagulation in aqueous and non-aqueous solutions (Lund et al., 1991; Fry, 1996). While a large number of experiments have been performed with electrodes under conditions where no SE was deliberately added, it is increasingly common practice to operate an EC in the presence of a certain amount of ions such as chloride or ammonium or salts such as NaCl, Na2SO4 and NaNO3 (Lopes et al., 2004; Orori et al., 2005; Shenz et al., 2006; Englehardt et al., 2006; Uğurlu, 2006; Oricho et al., 2008; Yildiz et al. 2008). Some of the electrolytes used in past experiments are shown in Table 4 and their respective effects on effluent color removal. Hu et al., (2003) carried out an experiment on defluoridation by EC and studied the effect of coexisting anions. The results showed that the type of dominant anion had a direct impact on the EC defluoridation reaction. Defluoridation efficiency was nearly 100% and most of the fluoride removal reaction occurred on the surface of the anode in the solution without the coexisting anions, due to the electro-condensation effect. In the solutions with co-existing anions, most of the defluoridation took place in the bulk solution. The residual fluoride concentration was a function of the total mass of Al3+ liberated. It was found that sulfate ions inhibited the localized corrosion of aluminum electrodes, leading to lower defluoridation process because of lower current efficiency. However the presence of chloride or nitrate ions prevented the inhibition of sulfate ions, and the chloride ions were more efficient. Different corrosion types occurred in different anion-containing solutions and the form of corrosion affected the kinetic over-potential of the EC reaction. When the concentration of NaCl salt or any other supporting electrolyte in solution increases, solution conductivity increases. Consequently, with respect to the solution voltage if any SE is added: V = EC - EA- δA- δC - IRcell - IRcircuit

(24)

where: EC EA δA δC IRcell IRcircuit

= Electrical potential difference at the cathode = Electrical potential difference at the anode = Zeta potential at the anode = Zeta potential at the cathode = voltage-drop across the cell = voltage-drop across the circuit

the necessary voltage for access to a certain current density will reduce, and the consumed electrical energy will be decreased (Kashefialasl et al., 2006). Excess SE affects the current in the bulk of the solution, which is maintained mostly by the ions of the SE, and migration effects on charged substrates can be neglected. The SE can also have some affects on the double layer reducing the Zeta potential of the substrate ions and helping their agglomeration or coagulation. Orori et al. (2005) showed that when the volume of wood ash leachate increased during color removal from a pulp and paper mill effluent, the power consumption reduced considerably by almost 80%. Similar results were also obtained by Etiégni et al. (2007) and Oricho et al. (2008).

24

Lazare Etiégni, K. Senelwa, B. K. Balozi et al. Table 4. Effect of the electrolyte concentration on the efficiency of color removal. Type of Electrolyte *NaCl *BaCl2 *KCl *NaBr *KI *Na2SO3 *Na2CO3 **Wood ash leachate ***Phosphate rock ****Bagasse ash leachate *****NH4NO3 *****Na2SO4 **Alum **Ca(OH)2

Applied voltage (v) 2.9 5.1 2.7 4.2 5.3 3.8 4.2 23 23 24 3.9 3.5 23 23

Conductivity (μS/cm) 19.13 9.67 18.75 11.77 9.18 13.8 15.8 4823.12 1150-1730 310

Color removal (%) 83 77 80 80 79 76 76 100 100 100

3456.23 3358.34

100 94 100 100

*Source: Kashefialasl et al., 2006: (Current density =127.8A/m2, Time of electrolyses =6min) **Source: Orori , 2003 (Current density= 250 A/m2, Time of electrolysis= 150 s) ***Source: Etiégni et al., 2007: (Current density = 222.2 A/m2, Time of electrolysis = 55 s) **** Source: Maghanga, 2008: (Current density = 55 A/m2, Time of electrolysis = 4 min) ***** Source: Lopes et al., 2004: (Current density = 2 mA/cm2, Time of electrolysis = 70-96 hrs)

30

Power (Whr)

25

OSA

NSA

OSC

NSC

OSR

NSR

20 15 10 5

0 0

1000

2000

3000

4000

5000

Electrolyte Dosage (g/m3 )

Source: Etiégni et al., 2009 Figure 7. Effect of electrolyte volume on the power consumption.

It appears that leachates from wood ash contain a wide range of ions or supporting electrolytes that may be helping or assisting the electrocoagulation reaction (Figure 7). Chou et al. (2009) studied the effect of NaCl concentration on the removal efficiency of indium


25

(III). They showed that there was an increase removal efficiency up to 83% when NaCl (used as supporting electrolyte) concentration was 8 g/l. The concentration of supporting electrolyte was adjusted to the desired levels by adding a suitable amount of NaCl to the synthetic wastewater. Increasing the concentration of the supporting electrolyte from 0 to 200ppm led to an increase in indium (III) ion removal efficiency, whereas with the concentration of the supporting electrolyte increasing, the specific energy consumption decreased by almost 80%. When the concentration of the supporting electrolyte increased, the solution ohmic resistance decreased, so the current required to reach the optimum applied voltage diminished, decreasing the consumed energy (Chou et al. (2009). Although some SEs are available commercially, they can be extracted from material otherwise considered as waste. Several research papers have been recently published on the use of leachate from ash emanating from wood, coffee husk or bagasse as supporting electrolyte (Orori et al., 2005; Etiégni et al., 2007, Oricho et al., 2008).

OPERATING COST ANALYSIS OF ELECTROCOAGULATION PROCESSES Several studies have been carried out on the operating cost of electrochemically treated wastewater (Bayramoglu et al., 2004; Can et al., 2006; Bayramoglu et al., 2007). In a study by Bayramoglu et al. (2004) for the treatment of textile wastewater by EC using aluminum and iron electrode materials, the effect of wastewater characteristics and operational variables on the technical performances of COD and turbidity removal efficiencies as well as on the EC operating cost were determined.. Only direct costs such as material (electrodes and chemical reagents) and energy costs were considered for the calculation of the operating cost. Other cost items such as labor, maintenance and solid/liquid separation costs, depreciation of fixed investment such as rectifier and electro-coagulators were not taken into account. This simplified cost equation was used to evaluate the effect of various process variables on the operating cost: Operating cost + aCenergy + bCelectrode

(25)

where Cenergy and Celectrode, were consumption of energy and electrode material per kg of COD removed, which are normally obtained experimentally. Unit prices, a and b, determined for a specific market are as follows: a= electrical energy price and b= electrode material price for aluminum or for iron. Using equation 6, Bayramoglu et al. (2004) found that for iron electrode, the operating cost decreased initially with pH until pH = 5, where it remained constant up to pH=7, beyond which it increased (Figure 8). For aluminum electrodes, the EC cost increased with initial pH.

26


Operating cost $/kg of COD

Figure 8 shows the effect of initial pH on the EC operating cost.

Initial pH Source: Bayramoglu et al. (2004) with permission Figure 8. Effect of initial pH on EC cost.

EFFECT OF CONNECTION MODES ON EC OPERATING COST When cells are set-up in an electrocoagulation process, one can choose from different modes or connections depending on the required voltage, the expected output and the overall efficiency of the EC system. Kobya et al. (2007) studied the effect of wastewater pH, current density and operating parameters for two sacrificial electrode materials, Fe and Al, and three electrode connection modes - namely monopolar-parallel (MP-P), monopolar-serial (MP-S) and bipolar-serial (BP-S) on the EC operating cost. The highest consumption of electrode material occurred with bipolar series mode (BP-S); approximately 0.27 kgm−3 for Fe electrode and between 0.18–0.23 kgm−3 for Al electrode. Monopolar parallel (MP-P) mode showed the lowest electrode consumption for both electrode Fe and Al materials: 0.12 kgm−3 for Al electrode and 0.16 kgm−3 for Fe electrode (Kobya et al., 2007). When the consumption of energy was compared for the three modes, as seen in Figure 10, only a minor change was observed with pH for all of the systems using Fe or Al electrodes. MP-S and BP-S modes exhibited high consumptions of energy because of the serial connection that required higher potential. When MP-P mode was used, it consumed the lowest energy or approximately 0.63 kWhm−3 and 0.7 kWhm−3 for Fe and Al electrode respectively. The effect of the initial pH on amount of sludge production is depicted in Figure 12. Sludge amounts vary from 0.65 to 1.0 kgm−3 for Fe electrode and from 0.9 to 1.3 kgm−3 for Al electrode (Kobya et al., 2007). In general, more sludge was produced with BP-S mode than with MP-P mode because of high electrode material consumed leading to high power consumption and higher electro-coagulant produced in situ. MP-P mode for both


27

electrode materials was therefore economically more feasible owing to its low electrical energy consumptions and amount of sludge produced (Figure 12).

EFFECT OF ELECTRICAL CONDUCTIVITY OF EC COST Bayramoglu et al. (2004) studied the impact of electrical conductivity on the operating cost of a dye wastewater treatment system using two sets of electrodes (Figure 11). For both electrode materials, operating cost decreased with increasing conductivity and the decrease was almost similar for iron and aluminum electrodes with only a slight difference at 3500 μS/cm for aluminum electrode. For aluminum, the percentage of the electrode consumption cost with respect to the total cost was nearly constant as 76%. For iron, on the other hand, this ratio increases from 33 to 58%, with increasing conductivity from 1000 to 4000 μS /cm. The decrease in operating cost was probably due to a decrease in solution ohmic resistance. As SE increased, lower current required to reach the optimum applied voltage leading to the overall decreased of consumed energy (Chou et al. (2009).

Figure 9. Different types of electrode connection modes: a-Monopolar parallel (MP-P), b-Monopolar Serial (MP-S), c-Bipolar parallel (BP-P) modes. (Source : Kobya et al., 2007, with permission).

EFFECT OF RETENTION TIME ON EC COST Kobya et al. (2006) studied the effect of detention time during the treatment of potato chips manufacturing wastewater by electrocoagulation. They found that both energy and electrode consumption increased with retention time. Retention time is therefore likely to affect the operating cost of EC.

EFFECT OF CURRENT DENSITY ON EC COST In a study aimed at determining the impact of current density on operating cost of EC Kobya et al. (2007) showed that, in the case of iron, current density did not have a substantive impact on the performances of MP-P and MP-S modes; COD removal reached a maximum of

28


67% with MP-P mode for a current density of 50Am−2. However, for aluminum electrode, the effect of the current density was more pronounced on COD removal, especially for MP-P mode and that lower current densities were more favourable. For example a 30Am−2 was preferred with MP-S mode.

Source: Kobya et al. (2003) with permission Figure 10. Effect of initial pH on energy consumption.

EFFECT OF POLYELECTROLYTE AND SE ON THE EC OPERATING COST As a general rule, EC operating cost has been found to reduce with the addition of polyelectrolyte up to an optimum concentration beyond which it usually rises, although this will also depend on the type of polyelectrolyte. Can et al. (2006) showed alum and polyaluminum chloride (PAC) increased operating EC operating cost when their concentration increased (Figure 13). However, Orori et al. (2005) found that increasing the concentration of wood ash leachate reduced power consumption and reduced operating cost, although the cost of electrode replacement and sludge removal was not included in the overall operating cost calculations.

Operating cost $/kg COD


Conductivity, μS/cm Source: Bayramoglu et al. (2004) with permission. Figure 11. Effect of wastewater conductivity on EC cost.

Source: Bayramoglu et al. (2007) with permission

Figure 12. Effect of initial pH on sludge formation

29


Operating cost ($/kg COD)

30

Polyelectrolyte dosage (kg/m3) Source: Can et al. (2006) with permission Figure 13. Effect of polyelectrolyte addition on EC operating cost.

WOOD ASH LEACHATE USED AS A SUPPORTING ELECTROLYTE What Is Wood Ash? Wood ash is the residue powder left after the combustion of wood. The main producers of wood ash are wood industries, power plants, homesteads especially in Third World countries. Large amount of this residue are produced every day. Typically 6-10 percent of burned wood results in ash. Wood ash is commonly disposed of in landfills or agricultural lands, but with rising disposal costs ecologically friendly alternatives are becoming more attractive. These alternatives will be based on the ash composition. It has been demonstrated that wood ash composition is a function of the wood combustion temperature as can be seen in Table 5 (Etiégni and Campbell, 1991). Wood combustion produces a highly alkaline ash that can be used to neutralize acidic effluent. As can be seen in Table 5 below Ca, K, Mg, Mn, Fe and Na are important elements found in wood ash. Misra et al., (1993) analyzed samples of wood ash using Inductively Coupled Plasma Emission Spectrometer (ICPES) and X-ray diffraction (XRD) to identify the minerals present in wood ash. A list of the compounds identified in ash is shown below in Table 6. The low temperature ash at 600oC showed strong peaks corresponding to calcium carbonate. Pine and aspen ash contained relatively higher amounts of potassium compared to poplar ash and showed strong peaks corresponding to K2Ca(CO3)2. Pine ash contained calcium manganese oxide, Aspen ash had sulfates of calcium and potassium, and poplar ash, silicates of K, Mg, and Ca. At higher temperatures (1000oC) where most industrial wood-fired boilers operate, with the dissociation of carbonates, XRD patterns showed predominant presence of calcium and magnesium oxides. In addition, pine ash which contains more


31

manganese showed the presence of calcium manganese oxide and manganese oxide. Similarly, poplar, being richer in sodium, displayed weak peaks corresponding to sodium calcium silicate. It appears that when the ash is left standing in air, calcium oxide reacts with atmospheric water vapor to form calcium hydroxide. However calcium hydroxide is unstable at temperatures over 600oC. Table 6 also indicates that small amounts of potassium may be present as K2SO4 as the peaks corresponding to this compound become distinct at higher temperatures. Low temperature ash produced from the wood waste appears to contain predominantly calcium carbonate while at high temperatures the content changes to predominantly calcium oxide. What this Table shows is the close relationship of ash composition with combustion temperature. Many of these elements, when in solution, will behave as counter-ions. Wood ash leachate added to wastewater does the following: it hydrolyzes hydroxo-metallic positively charged ions are added to the wastewater medium the solution ionic strength is increased the solution electrical conductivity increases the positive hydroxo-metallic ions are adsorbed on the negative charge of the colloids surface, reducing the zeta potential to destabilization point the electrostatic distance between colloid particles is reduced and the energy barrier is overcome to allow agglomeration the presence of non-hydrolyzing counter-ions (Na+, Ca2+, Mg 2+) leads to the compression of the double layer (Figure 1) which leads to the reduction of the Zeta potential to van der Waals levels. with wood leachate, Al3+ and Fe2+ are also added and help neutralize the solution charge. They form precipitates that catch colloids in the flocs. these destabilized colloids and hydroxo-metallic complex by van der Waals forces lead to adsorption and flocculation.

Important Consideration of Wood Ash Leachate as Supporting Electrolyte One of the most important factors that need to be considered when using wood ash leachate as supporting electrolyte is the time required to allow leaching to take place and the ash to water ratio for leaching. In an experiment conducted on wood ash leaching, Etiégni and Campbell (1991) found that the total dissolved solids (TDS), K, Na, and Mg concentration increased linearly as the ash to water ratio increased (Figure 14). However, the percentage of ash dissolving did not change significantly, as approximately 10% of the ash dissolved at 50 g/L and 9% at 390 g/L.

32

Lazare Etiégni, K. Senelwa, B. K. Balozi et al. Table 5. Chemical composition of wood ash samples produced at different combustion temperatures given as the concentration in μg/g. (Source: Etiégni & Campbell, 1991). Element Aluminum Antimony Arsenic Barium Beryllium Bismuth Cadmium Calcium Cerium Chromium Cobalt Copper Iron Lanthanum Lead Lithium Magnesium Manganese Molybdenum Nickel Phosphorus Potassium Selenium Silicon Sodium Titanium Vanadium Ytterbium Zinc Zirconium Carbonate

Temperature (oC) 538 649 10,415 12,825 264 142 20: Removal by nitrogen assimilation by heterotrophic bacteria. 20>COD/N>5: Removal by assimilation, nitrification and denitrification. COD/N 5: Removal by partial nitrification-denitrification or partial nitrificationanammox.

2.1. Nitrification-Denitrification The combination of nitrification-denitrification processes is generally applied to remove nitrogen from municipal wastewater and most industrial wastewaters. Nitrification is a twostep process: ammonia is firstly oxidized into nitrite and then nitrite into nitrate (Equations 1 and 2). These steps are carried out by autotrophic ammonia- and nitrite-oxidizing bacteria, respectively (Khin and Annachhatre, 2004). NO2- + H2O + 2 H+

NH4+ + 1.5 O2

NO2- + 0.5 O2

[1]

NO3-

[2]

During denitrification both nitrate and nitrite are reduced to nitrogen gas under anoxic conditions, organic matter being used as electron donor (Equation 3). This process is carried out by denitrifying bacteria.

m Deco

n io Ni

De

ni

Vegetal protein

at

N org

tio n

Fix

NO2-

ica

ing feed

o ec

on ati Chemical industry

m

D

tio

N2

Atmospheric N2 Nitrogen

fic

n

si po

im

Assim il

ation

Figure 1. Nitrogen cycle.

on

al Anim

s As

tio

ati

n

ila

ox

Animal protein

mm

Urine Urea

N org

a An

s

i lis

o dr Hy

fic

Faecal matter

Fixation

o

NH+4+

NH4 Ammonium

ion posit

ri Nit

m Am

n

ic nif

tri f

o ati

8HCO3- + 6H2O + 2CO2 + 4N2

tr i

8NO3- + 5CH3COOH

NO3-

[3]

158

J.L. Campos, J.R. Vázquez-Padín, M. Figueroa et al. Predenitrification Wastewater COD NH4+

N2

O2

NH4+ Denitrification

Nitrification

Effluent

COD

NO3-

Postdenitrification Wastewater COD NH4+

N2

O2 NO3Nitrification

Denitrification

Effluent

COD

Figure 2. Schematic representation of predenitrifying and postdenitrifying configurations.

Integration of both nitrification and denitrification also allows reducing the amount of chemicals needed to control pH during the treatment since alkalinity generated during denitrification compensates for the pH decrease due to nitrification. Nitrification occurs under aerobic conditions while anoxic conditions are necessary for denitrification. This implies the use of two different tanks which can be provided in two possible configurations (Figure 2): a) Predenitrifying configuration—wastewater is fed into the denitrifying reactor and later nitrification is carried out. A stream from the aerobic tank containing nitrate and/or nitrite is recirculated to the first unit to carry out denitrification. Therefore, nitrogen removal efficiency depends on the recycling ratio; b) Postdenitrification configuration—wastewater is fed into the nitrifying unit and its effluent enters into the denitrifying reactor. This configuration is very simple, easy to control and no recycling is needed. Nevertheless, organic matter is oxidized in the aerobic unit and an external carbon source must be added for denitrification which increases the operational costs. This configuration is only used when the COD/N ratio of wastewater is low. In the predenitrification configuration, the organic matter coming from the denitrification unit causes the proliferation of heterotrophic bacteria in the aerobic unit. These microorganisms compete with nitrifying bacteria for oxygen and its concentration must be maintained at levels around 1–2 mg O2/L to avoid the failure of the nitrification process. On the other hand, the concentration of nitrifiers in the aerobic tank is low due to their slow growth rate and, therefore, the required volume of the aerobic unit is high. The use of carrier material in this unit would increase the concentration of nitrifiers and, then, decrease the required volume [Pegasus system (Tanaka et al., 1996)].

2.2. Partial Nitrification Nitrification and denitrification processes are suitable to remove ammonia from wastewater when its COD/N ratio is high but operational costs increase when no organic matter is available (for example effluents from sludge digesters, landfill leachates, effluents from anaerobic digesters of fish canneries…).

Novel Biological Nitrogen-Removal Processes: Applications and Perspectives

159

To treat such effluents a postdenitrification configuration should be used, being necessary the addition of an external carbon source (methanol, acetic acid…) to complete denitrification. In those cases, partial oxidation of ammonia into nitrite would suppose a decrease of both oxygen and organic matter requirements of 25% and 40%, respectively, and only 60% of sludge is generated compared to the full oxidation into nitrate (Van Kempen et al., 2001) (Figure 3). Under normal operational conditions of municipal wastewater treatment plants (pH= 6.58.5; T= 10-20 ºC; dissolved oxygen= 1-2 mg O2/L; low ammonia concentrations), no nitrite production is observed. Since the nitrification process consists on two serial reactions, nitrite accumulation will occur when the rate of ammonia oxidation is higher than that of nitrite oxidation. To achieve this aim, factors affecting to both reactions must be changed in such a way that the growth rate of ammonia-oxidizers is more enhanced than that of nitrite-oxidizers. Both rates depend on temperature, dissolved oxygen and free ammonia concentrations (Park and Bae, 2009) (Equation 4): max

(T)

O2

[4]

S

KO2 O2 K S (1 NH3 ) S KINH3

where μmax is the maximum growth rate (d-1), O2 the dissolved oxygen concentration (mg O2/L), KO2 the oxygen affinity constant (mg O2/L), S the substrate concentration (NH4+ for ammonia-oxidizers and NO2- for nitrite-oxidizers) (mg N/L), KS the substrate affinity constant (mg N/L), NH3 the free ammonia concentration which inhibits both ammonia- and nitrite oxidizers (mg N/L) and KINH3 the free ammonia inhibition constant (mg N/L). 1 mol Nitrate (NO3-)

40%Organic matter

Nitrifiers

Heterotrophs

Aerobic-Nitrification

Anoxic-denitrification

25% O2 1 mol Nitrite (NO2-)

1 mol Nitrite (NO2-)

60% Organic matter

75% O2 1 mol Ammonia (NH4+)

Nitrification-denitrification 4.6 g O2/g NH4+-N oxidized 7.5 g DQO/g NO3--N reduced

½ mol Nitrogen Gas (N2)

Partial nitrification-denitrification Advantages; 25% Reduction of O2 demand 40% Reduction of required organic matter 40% Reduction of biomass generated

Figure 3. Conventional nitrification-denitrification process compared to partial nitrificationdenitrification process.

160

J.L. Campos, J.R. Vázquez-Padín, M. Figueroa et al. Table 1. Kinetic parameters of ammonia- and nitrite oxidizers (Wiesmann, 1994). Parameter KO2 (mg O2/L) KINH3 (mg N/L) Ea (kJ/mol)

Ammoniaoxidizers 0.3 116

Nitrite-oxidizers

68

44

1.1 0.52

Table 1 shows the values of the different kinetic parameters. Since the oxygen affinity constant of nitrite-oxidizers is higher than that of ammonia-oxidizers, a decrease of the dissolved oxygen in the reactor would exert a higher effect on the former one. Therefore, nitrite generation would be favoured at low dissolved oxygen concentrations (Figure 4a). However, this operational strategy implies also the decrease of the ammonia-oxidizers activity and a control system for oxygen is required when the influent characteristics are not constant. It is also known that ammonia oxidation is inhibited by higher free ammonia concentrations than nitrite oxidation. Therefore, partial nitrification could be achieved by maintaining free ammonia levels in the reactor which only causes the inhibition of nitriteoxidizers (Figure 4b). Albeit, the maintaining of a certain concentration of free ammonia in the system means that the effluent does not fulfil the disposal requirements. Another disadvantage of this strategy is the possible adaptation of nitrite-oxidizers to free ammonia and the restoration of their activity. Since the activation energy of ammonia oxidation is higher than that of nitrite oxidation, an increase of temperature will cause a higher effect on the first step. In practise, the ammonia oxidation rate is higher than the nitrite oxidation rate at temperatures higher than 30 ºC (Figure 4c). From an economic point of view, this strategy would be only feasible when effluents have already such temperature, for example effluents of anaerobic digesters.

2.3. Anammox Process Anammox process (Anaerobic Ammonium Oxidation) was discovered around 15 years ago in the Technical University of Delft (The Netherlands) during the operation of a denitrifying pilot plant treating wastewater of a yeast company. This process is carried out by a group of autotrophic bacteria capable of oxidizing ammonia into nitrogen gas using nitrite as electron donor. Neither oxygen nor organic matter are needed in this process (Equation 5): NH4+ + 1.32 NO2- + 0.066 HCO3- + 0.13 H+ 1.02 N2 + 0.26 NO3- + 0.066 CH2O0.5N0.15 + 2 H2O

[5]

These bacteria belong to the phylum Planctomycetes and their yield coefficient is low (Y= 0.038 g VSS/g NH4+-N). This low sludge production reduces the management costs but makes the start-up of anammox reactors quite long. For this reason, systems with high biomass retention capacity must be used. Another characteristic of these microorganisms is


161

the decrease of their activity in the presence of oxygen, nitrite or organic matter (DapenaMora et al., 2004; 2007). Growth rate (d -1)

1

A

ammonia oxidizers

0.8 0.6 0.4

nitrite oxidizers

0.2 0 0

1

2

3

4

O2 [mg/L]

Growth rate (d -1)

1.2

B

ammonia oxidizers

1 0.8 0.6 0.4

nitrite oxidizers

0.2 0 0

0.2

0.4

0.6

0.8

1

NH3 [mg N/L]

Growth rate (d -1)

3

C

2.5

ammonia oxidizers

2 1.5 1

nitrite oxidizers

0.5 0 10

15

20

25

30

35

40

T [ºC]

Figure 4. Possible strategies to carry out partial nitrification by changing dissolved oxygen concentration (A), free ammonia concentration (B) and temperature (C).

To apply the anammox process, the effluent should contain suitable concentrations of both ammonia and nitrite. Ammonia is generally present in wastewater but nitrite is not and has therefore to be generated by the oxidation of 50% of the ammonia. During partial nitrification, organic matter is also oxidized which prevents its possible negative effects on the anammox reactor. The combination of anammox and partial nitrification to treat wastewaters with high nitrogen content and without organic matter gives some advantages compared to the conventional nitrification-denitrification process (Figure 5): 1) The oxygen

162

J.L. Campos, J.R. Vázquez-Padín, M. Figueroa et al.

requirements are 60% lower; 2) No organic matter must be added; and 3) Sludge production is 85% lower (Fux and Siegrist, 2004). Nitrification/denitrification

Partial nitrification/anammox

1 mol NH4+ CO2

1 mol NH4+ CO2

1.9 mol O2 (100%) 3.4 g CODbiomass 1 mol NO357 g COD

17 g CODbiomass 0.5 mol N2 + 20 g CODbiomass

0.4 mol O2 (40%) 1.6 g CODbiomass 0.55 mol NO2-

0.45 mol NH4+

CO2

1.5 g CODbiomass 0.45 mol N2 + 0.1 mol NO3-+ 3 g CODbiomass

Figure 5. Comparison between nitrification-denitrification and partial nitrification-anammox processes to treat wastewaters with low COD/N ratios (Adapted from Fux and Siegrist, 2004).

2.4. CANON Process Under limiting oxygen conditions (lower than 0.5% of air saturation) a mixed culture of both ammonia-oxidizers and anammox bacteria can be obtained. This culture converts ammonia directly into nitrogen gas with nitrite as intermediate product. Nitrifiers consume oxygen and generate both nitrite and an anoxic environment for anammox microorganisms. Then, ammonia can be removed in a single unit under autotrophic conditions. Different acronyms were used to define this process: OLAND (Oxygen-Limited Aerobic Nitrification and Denitrification) (Windey et al., 2005), aerobic deammonification (Wett, 2006) and CANON (Completely Autotrophic Nitrogen removal Over Nitrite) (Sliekers et al., 2002; 2003). The two former names are based on the idea that the own ammonia-oxidizers carried out the denitrification process. However, nowadays, it was demonstrated that anammox bacteria are responsible of the denitrification process, the last acronym being the most suitable to define the process. Two possible strategies to start-up a CANON system are possible: 1) to inoculate an anammox reactor with nitrifying biomass and to supply air to maintain microaerobic conditions or 2) to operate a nitrifying reactor under oxygen limited conditions to obtain the desired ammonia to nitrite molar ratio inside the system and then to inoculate anammox biomass (Pynaert et al., 2004; Gong et al., 2007). The second strategy seems to be more suitable because an important decrease of the anammox activity is observed when the first strategy is applied (Sliekers et al., 2002; 2003; Liu et al., 2008). Moreover, only a few amount of anammox biomass is necessary to start-up the CANON process with this second strategy (Vázquez-Padín et al., 2009a; 2009b).


163

2.5. Autotrophic Denitrification Sulfur compounds can be present in wastewaters together with carbon and nitrogen compounds and the interactions between the biological cycles of the three elements can be used to remove them (Figure 6). The biological interaction between sulfur and nitrogen cycles is given by autotrophic denitrification which consists on the reduction of nitrogen oxides (NO3- and/or NO2-) into nitrogen gas by using reduced sulfur compounds as electron donors (S2O3-2, Sº and/or H2S) (Equations 6, 7 and 8). The end product is sulfate which is less harmful than nitrate, especially when the effluent is disposed in a marine environment. 5 S2O3-2 + 8 NO3- + H2O 5 S-2 + 8 NO3- + 8 H+ 5 S° + 6 NO3- + 2 H2O

10 SO4-2 + 4 N2 + 2 H+

[6]

5 SO4-2 + 4 N2 + 4 H2O

[7]

5 SO4-2 + 3 N2 + 4 H+

[8]

Autotrophic denitrification presents the following advantages compared to heterotrophic denitrification: a) No carbon source is required; b) Elemental sulfur can be used as an economical electron source; c) The sludge production is lower (Campos et al., 2008). The main autotrophic denitrifying bacteria belong to the Thiobacillus denitrificans and Thiomicrospira denitrificans genus. These microorganisms are mainly mesophilic with an optimum temperature of 25-35 °C while their optimum pH is 7-8. Contrary to heterotrophic denitrification, this process requires a source of alkalinity (HCO3-, CaCO3) to neutralize the protons produced (Fajardo et al., 2008).

Figure 6. Biological interactions between carbon, nitrogen and sulfur cycles.

164


Figure 7. Configuration of a WWTP with sludge treatment.

These bacteria can also use oxygen as electron acceptor to oxidize sulfur compounds. The end product is sulfate under high dissolved oxygen levels while, at low oxygen concentrations ( 0.1 mg O2/L), only a partial oxidation into S° occurs (Equations 9 and 10). If the aim of the treatment is to remove nitrate, the presence of oxygen must be avoided since the microorganims will preferentially use it as electron acceptor. 2HS- + 0.5O2 2HS- + 4O2

S°

+ H2O

[9]

2SO4-2 + 2H+

[10]

3. NITROGEN REMOVAL TECHNOLOGIES BABE, SHARON and partial nitrification-anammox technologies, which will be described in the following sections, have already been applied at industrial scale to treat sludge digesters effluents of municipal WWTPs (Figure 7). Nitrogen concentration of these effluents ranges between 300 and 1,700 mg N/L and contributes to 15-20% of the total inlet nitrogen load of the WWTP although its flow rate is only about 1% (van Loosdrecht and Salem, 2006). As this stream is previously treated by the anaerobic digester, it contains a low amount of organic matter and its temperature is around 30 °C. On the other hand, its HCO3/NH4+ ratio is 1, that is, the available alkalinity only allows nitrifying 50% of ammonia.

3.1. BABE (Bio Augmentation Batch Enhance) Bioaugmentation of nitrifying bacteria in the flocculent sludge could reduce the required volume of the aerobic tank. This may be achieved by promoting nitrification of the sludge digester effluent with biomass coming from the return sludge stream. Only part of this stream


165

should be applied to the effluent in order to maintain its temperature around 20-30 °C. This process has been successfully applied at industrial scale and was named BABE (Salem et al., 2002a; Berends et al., 2005). Another advantage of its application is the increase of the denitrification capacity of the WWTP since part of the volume of the aerobic tank is not required and can be operated under anoxic conditions. The BABE process is operated with denitrification in order to control pH. In this aspect, the sludge supplied to the process allows minimizing the amount of external organic matter added. Under anoxic conditions, the electrons needed to reduce nitrate are given by endogenous respiration of sludge. The BABE process can be carried out in a system with one or two units. The system with one only unit is operated in cycles. Firstly, the reject water and sludge are fed to the system to nitrify under aerobic conditions. During a second stage, denitrification occurs and sludge partially settles. At the end of this stage, the liquid fraction and the non settled sludge are fed to the main stream of the WWTP. The two reactors configuration consists of an anoxic reactor following by an aerobic tank (Figure 8). In the anoxic tank, the supernatant of the sludge digester is mixed with the sludge which also acts as carbon source and even external organic matter could be added if necessary. A recirculation between both units is maintained in order to supply nitrate to the anoxic tank. The BABE process with a single unit has been tested at industrial scale in the WWTP of Garmerwolde (The Netherlands) with a capacity of 300,000 inhabitants-equivalent (Salem et al., 2004). The implementation of this process allowed improving ammonia concentration in the effluent from 13.3 to 5.2 mg NH4+-N/L. In order to upgrade the WWTP of Walcheren to fulfil disposal requirements ( 10 mg N/L) (140,000 inhabitants-equivalent, The Netherlands) two alternatives were evaluated: An increase of both anoxic and aerobic tanks and the implementation of the BABE technology. The second option allowed reducing 50% of the required area and supposed saving costs of 115,000 Euros/year (Salem et al., 2002b) (Table 2). This technology has also been implemented in the WWTP of Hertogenbosch (350,000 inhabitants-equivalent, The Netherlands).

Figure 8. Configuration of the two units BABE process.

166


Table 2. Comparison of the upgrading of the WWTP of Walcheren (The Netherlands) by the conventional procedure and by bioaugmentation in order to fulfil disposal requirements ( 10 mg N/L) (Salem et al., 2002b). Item

Upgrading by the conventional method

Aerobic tank Anoxic tank BABE system Total increase

Upgrading by the implementation of the BABE process Increase (%) (Additional volume required/initial volume) 88 22 1,300 370 0 14 225

75

3.2. SHARON (Single-Reactor System for High Activity Ammonia Removal Over Nitrite) The SHARON process takes advantage of the higher growth rate of ammonia-oxidizers compared to nitrite-oxidizers at high temperatures (Hellinga et al., 1998; van Dongen et al., 2001; Mosquera-Corral et al., 2005). This process is carried out in a conventional CSTR with suspended biomass, without sludge retention which operates at elevated temperatures (30–40 °C) and at a HRT of 1 day to promote the wash-out of nitrite-oxidizers while ammoniaoxidizers are retained (Figure 9). This process is combined with denitrification, by adding methanol, to control the pH and to remove the nitrite generated. Both nitrification and denitrification can take place in the same unit with an intermittent aeration or in two different units. Table 3. SHARON reactors in operation (van Loosdrecht and Salem, 2006). Plant

Capacity (inhab-eq)

Utrecht Rotterdam Zwolle Beverwijk Garmerwolde Den Haag New York

400,000 470,000 150,000 320,000 300,000 1.100,000 3.000,000

Nitrogen load (kg N/d) 900 830 540 1.200 700 1.200 5.500

Year of start-up 1997 1999 2000 2004 2004 2005 2007


167

Figure 9. One single unit SHARON process.

The SHARON process was developed in 1997 and the first plant at full scale was built the same year. Nowadays, full-scale sludge liquor treatment with partial nitrification/denitrification in SHARON reactors has already been introduced in 7 WWTPs (van Loosdrecht and Salem, 2006) (Table 3). Economic balances demonstrated the cost savings using the combined SHARON-denitrification processes to treat reject water in comparison to physicochemical processes or conventional nitrification-denitrification processes (Table 4). The costs distribution of this treatment are: 47% installation costs, 15% energy costs, 4% maintenance, 8% working costs, 18% methanol and 7% management of sludge produced. Table 4. Estimation of costs for nitrogen removal in the sludge line for a WWTP of 500,000 inhabitants-equivalent (van Kempen et al., 2001).

Physico-chemical process Stripping with air Stripping with steam Precipitation Nitrification/denitrificatio n Membrane reactor Airlift reactor SHARON/denitrification

Chemical sludge

Biologica l sludge

Energy requiremen t

Cost (Euro/kg N)

Yes Yes Yes

No No No

Normal High Low

6.0 8.0 6.0

No No No

Yes Low Low

High Normal Normal

2.8 5.7 1.5

168


3.3. SHARON-Anammox The combination of partial nitrification and anammox processes allow minimizing oxygen and organic matter requirements during the sludge liquor treatment. This technology can be applied in systems of one and two units. In the two-units configuration, a SHARON reactor is used to nitrify only 50% of ammonia by controlling both dissolved oxygen concentration and pH. Later, anammox process is carried out in UASB (Upflow Anaerobic Sludge Blanket) o IC (Internal Circulation) reactor similar to those used during anaerobic treatment at high loading rates (Figure 10). Activated sludge reactor Anoxic

Aerobic

Effluent

Influent

Sludge return SHARON reactor

Secondary settler Thickening tank

Anammox reactor

Water line Sludge line

Sludge digester Dehyrated sludge

Dehydration system

Figure 10. SHARON-Anammox process.

In the one-unit system, partial nitrification and anammox processes are simultaneously carried out under microaerobic conditions. For this propose systems with flocculent ammonia-oxidizing and anammox granular biomasses can be used. Another option is the utilization of granular biomass where ammonia-oxidizing bacteria grow in the outer layers consuming oxygen and generating nitrite and, therefore, suitable conditions are promoted in the inner layers to develop the anammox process (Figure 11). Under a practical point of view, systems of one unit are preferred because higher removal rates can be achieved (smaller reactors) and their N2O emissions are low although systems with two units are more flexible and stable against influent fluctuations (Kampschreur et al., 2008).


169

PARTIAL + NITRIFICATION NH4 O2

ANÓXICA AEROBIC NO2-

ANOXIC N2 + NO3-

NO2NH4+

ANAMMOX

Figure 11. Simultaneous partial nitrification and anammox processes in granular systems.

Up to now, there are 4 anammox plants operating at full scale (Abma et al., 2007), three of them in The Netherlands and one in Japan (Table 5). All of them have reached their design capacity treating wastewater from different origins which indicates the wide applicability of the process. It is important to point out that the length of the first reactor (72 m3) start-up was 3 years while the fourth plant was started up in 2 months (Van der Star et al., 2007). This fact was mainly due to a higher knowledge about anammox process and a greater availability of inoculum. Table 5. Full-scale anammox plants around the world (Abma et al., 2007).

Project

Application

Design capacity

Load achieved

(kg N/d)

(kg N/d)

Start up time

Waterboard Hollandse Delta, The Netherlands

Municipal

(2 units)

(reject water)

490

750

3.5 years

Tannery

325

1501

1 year

Potato processing

1200

7001

6 months

Semiconductor

220

220

2 months

IWL, The Netherlands (2 units) Waterstromen, The Netherlands (1 unit) Mie prefecture, Japan (2 units) 1

No more nitrogen available.

170


Under the denomination of deammonification (DEMON), there are other two full scale plants in Austria (500 m3, 300 kg N/d) and Switzerland (400 m3, 250 kg N/d) treating the supernatant of sludge digesters (Wett, 2006; 2007). The start up length of the first plant was 2.5 years while the plant located in Switzerland, inoculated with sludge from the first one, got its design load in only 50 days. Economic estimations were calculated with data obtained from these full scale plants and compared to those obtained when the nitrification-denitrification process is used. The results showed important economic and environmental benefits (Table 6). Table 6. Comparison between traditional treatment and partial nitrification-anammox process. Nitrificationdenitrification

1

Energy (kWh/kg N) Methanol (kg/kg N) Sludge production (kg VSS/kg N) CO2 emissions (kg/kg N) Total costs1 (Euros/kg N)

Capital and operational costs included.

2.8 3 0.5-1.0 4.7 3-5

Partial nitrificationAnammox 1 0 0.1 0.7 1-2

The application of this process to reject water would suppose important saving costs (Siegrist et al., 2008). Most of the municipal WWTPs designed only for organic matter removal were equipped with primary settlers with a hydraulic retention time (HRT) of 2–3 h to reduce the organic matter applied to the biological reactor. Albeit the requirement of nitrogen removal caused that the HRT of primary settlers was reduced to less than 1 h in order to ensure the availability of organic matter during denitrification. This fact implied the decrease of biogas generated during sludge anaerobic digestion. If the partial nitrificationanammox process is applied to treat reject water, the denitrification capacity of the WWTP could be decreased without negative effects on the overall nitrogen removal efficiency. This would allow increasing again the HRT of the primary settler to enhance production of biogas and significantly decrease the requirement of oxygen in the aerobic tank to remove organic matter. On basis of a nitrogen removal efficiency of 75%, the treatment of reject water would allow decreasing a 25% the denitrifying capacity. Then, this process would need 25% less organic matter which can be separated in the primary settler by adding flocculant increasing the biogas production in 25% (Figure 12). Taking into account that oxygen requirements for organic matter removal and nitrification suppose 70-80% of the total energetic costs of the plant, this new configuration could achieve a reduction up to 50% of the energy consumed (Table 7).

Novel Biological Nitrogen-Removal Processes: Applications and Perspectives Nitrogen balance

171

Denitrification Primary effluent 6,0 g N/p·d 4,5 g N/p·d

10,5 g N/p·d 8,5 g N/p·d

Inlet

Biological treatment

Primary settler

Outlet

a 10 g N/p·d b 10 g N/p·d

2,5 g N/p·d 2,5 g N/p·d Primary sludge 1,0 g N/p·d 1,5 g N/p·d

1,5 g N/p·d 0 g N/p·d

Anammox

Supernatant Digester supernatant

2,0 g N/p·d 1,5 g N/p·d Digested sludge Sludge digester

1,5 g N/p·d 1,5 g N/p·d

1,5 g N/p·d 1,5 g N/p·d

1,5 g N/p·d

Degraded

COD balance

Primary effluent 85 g DQO/p·d 65 g DQO/p·d

Inlet

Secondary sludge

Primary settler

40 g DQO/p·d 30 g DQO/p·d Biological treatment

Outlet

a 110 g DQO/p·d b 110 g DQO/p·d

5 g DQO/p·d 5 g DQO/p·d Secondary sludge

Primary sludge 25 g DQO/p·d 45 g DQO/p·d

40 g DQO/p·d 30 g DQO/p·d

Digested sludge

Biogas 30 g DQO/p·d 40 g DQO/p·d

Sludge digester

35 g DQO/p·d 35 g DQO/p·d

Figure 12. N and COD balances of a municipal WWTP with two possible configurations of the primary settler: a) HRT: 0.5-1 h; b) HRT: 2 h, addition of flocculant and treatment of reject water with the partial nitrification-anammox process (Adapted from Siegrist et al., 2008).

Table 7. Estimation of the energy net consumption based on mass flows presented in Figure 12 (Siegrist et al., 2008). Mass flow (g/p·d) Case a Case b Electric energy consumption -COD removal -Nitrogen removal Electrical power for pumping and mixing Electrical power generated from biogas Net energy consumption

40 22

30 22

30

40

Energy (kW/p·d) Case a Case b 0.040 0.022 0.020 0.038 0.044

0.030 0.022 0.020 0.051 0.021

Comparison of the available technologies to treat rejected water The bioaugmentation, partial-denitrification and partial nitrification-anammox technologies are applied to optimize the nitrogen removal in WWTP (van Loosdrecht and Salem, 2006). The selection of one of the strategies will depend on the specific limitations in the nitrogen removal of each plant according to the decision tree represented in Figure 13. The first decision concerns whether the limiting step in the nitrogen removal in the main plant

172


is the nitrification or the denitrification process. In case nitrification or denitrification is limited by the volume of the aerobic or the anoxic tank, respectively, the bioaugmentation is the recommended technology. However, if the aeration or the organic matter is limiting the nitrogen removal, the ―nitrite route‖ processes are recommended. WWTP must reach full nitrification in order to apply these processes since the selective increase of ammonia-oxidizers could cause the presence of nitrite in the final effluent. The ammonium counter-ion plays an important role and will determine the most suitable technology to be applied. In most WWTP this counter ion will be the bicarbonate ion which works as pH buffer in the nitrification process and the recommended technology would be the partial nitrification-Anammox. Finally, if the sludge is dried the counter-ion will be the acetate ion; in this case, the partial nitrification-denitrification will be the most suitable technology. Besides these aspects, the start-up time, the risk of failure, the flexibility of the process, etc. will also determine the decision of what technology to implement.

3.4. ANANOX (Anaerobic-Anoxic-Oxic) The anaerobic treatment of effluents containing sulfate (canneries, petrochemical industries, tanneries, etc.) implies generation of sulfide. This compound presents some problems such as: a) odour problems and toxicity; b) decrease of organic matter removal efficiency and, therefore, less methane generated; c) corrosion problems; d) the need for biogas conditioning and postreatment of effluents. A simple method to remove sulfide is autotrophic denitrification. Nowadays, only one plant is applying this process at full scale which is called ANANOX (Figure 14). This plant is located in Italy and treats municipal wastewater (Garuti et al., 2001). Supernatant

Nitrification space

Nitrification Limiting factor

Limiting process

Denitrification

Limiting factor

BABE

Aeration capacity

Denitrification space

Organic matter

Counter-ion NH4+

Acetate

HCO3-

SHARON

SHARON ANAMMOX

Figure 13. Diagram of selection of the best technology to treat reject water.


173

NO3-

Influent

Activated sludge reactor

Sludge tramp

Anaerobic

Settler Effluent

Anoxic

Thickening tank

Water line Sludge line

Sludge purge

Figure 14. ANANOX process.

This technology is based on a two units configuration. The first unit is an anaerobic reactor with three compartments (2 anaerobic + 1 anoxic) containing flocculant sludge. The second unit is a conventional activated sludge system with a settler. In the first unit, anaerobic digestion of organic matter and sulfate reduction into sulfide are carried out. During autotrophic denitrification, sulfide is again oxidized into sulfate with the nitrate coming from the effluent recirculated. Activated sludge reactor Influent

Primary settler

Anaerobic

Anoxic

Aerobic

Effluent

Secondary settler

Thickening tank Secondary sludge

Thickening tank Primary sludge

Water line

Thermal hydrolysis reactor

Dehydration system

Sludge line

Biogas Dehydrated sludge Sludge digester Crystallization unit

CANON system

P recovery

Figure 15. Application of sludge reduction techniques in WWTPs.

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4. APPLICATION PERSPECTIVES 4.1. Municipal WWTPs Improvement Excess sludge treatment and disposal of conventional WWTPs supposes between 50 and 60% of operational costs. For this reason, recently, a great effort in the development of new technologies to reduce sludge production was done (Kroiss, 2004). When a sludge digester is already present in the WWTP, the implementation of a sludge disintegration unit (for example, thermal hydrolysis) previous to the anaerobic digester is the best option to maximize the recovery of energy from the sludge (Figure 15). This treatment would allow an increase in methane production and would decrease the HRT of the sludge digester. Ammonia concentration in the digester supernatant would increase, the application of a CANON system would be even more profitable from an economical point of view. This system could be operated to obtain an effluent with a stoichiometric NH4+/PO4-3 ratio to obtain struvite (Equation 11). The phosphorus recovered can be used as fertilizer. Mg+2 + NH4+ + HPO4-2 + OH- + 5H2O

MgNH4PO4· 6H2O

[11]

4.2. New Concept of WWTPs Anaerobic digestion could be an interesting alternative to the aerobic process to treat domestic wastewater since it is a net energy producing process with a lower sludge production (1/10 ratio compared to aerobic systems). Since the rate of the anaerobic processes strongly decreases at temperatures lower than 20 C, systems with a good biomass retention capacity, such as the upflow anaerobic sludge blanket (UASB) reactor or expanded granular sludge bed (EGSB) reactor are needed to make anaerobic treatment of municipal wastewater a feasible option. Nevertheless, the low hydraulic retention time applied to these systems causes that the HRT is not long enough to carry out the hydrolysis of retained particulates when temperature is lower than 20 C. Therefore, solids accumulate in the granular sludge bed which deteriorates the overall methanogenic activity and the reactor performance. Several strategies could be applied to avoid this deterioration of sludge quality: a) Wastewater may be pretreated to remove suspended solids (Aiyuk et al., 2006); b) the use of a two step system (hydrolytic reactor + UASB reactor) (Álvarez et al., 2008); c) The use of anaerobic membrane bioreactors (Liao et al., 2006). Since anaerobic digestion is only able to remove organic matter, the CANON process should be suitable to remove ammonia (Figure 16). This process was only applied to effluents with temperatures ranged between 30-40 ºC since it is the optimum range of temperature for Anammox bacteria. However, some works showed that the Anammox process could be successfully operated at temperatures around 20 ºC (Dosta et al., 2008) and nitrogen removal rates up to 1.1 kg NH4+-N /(m3·d) can be achieved at this temperature (Vázquez-Padín et al., 2009a; 2009b).


175

This proposed scheme would allow: a) Reducing the size of the WWTP; b) Obtaining a positive net balance of energy in the WWTP; c) Reducing both sludge generation and CO2 emissions.

4.3. Ground Water Bioremediation In the last years, nitrate levels in ground waters exceeding the European Regulation (11.3 mg NO3--N/L) were observed. The conventional method to remove nitrate is ionic exchange although the application at full scale of reverse osmosis also gave good results. Nevertheless, both processes generate a residual stream which needs a postreatment. An alternative to these technologies is the denitrification. In the case of heterotrophic denitrification, organic matter (ethanol or methanol) must be added as electron donor that leads to a secondary contamination. This can be avoided if nitrate removal is done by autotrophic bacteria using elemental sulfur since it is not a toxic compound and it is insoluble in water. This process will generate sulfate and is recommended to apply to ground water with low endogenous sulfate levels to avoid sulfate concentrations higher than 400 mg SO4-2/L. The application of autotrophic denitrification to ground water has been limited by the low biomass retention. Therefore, recent works are focused on combining this process with membrane (McAdam y Judd, 2006) or biofilm technologies (Soares, 2002) to achieve a complete retention of the biomass. The configurations proposed are the following (Figure 17): (a) Bioreactor with extractive membrane: In this configuration, nitrate is extracted from water by molecular diffusion through the membrane to a stream containing both denitrifying biomass and electron donor (Figure 17a). Biogas FeCl3 + Flocculant (SS and P removal)

Influent Effluent

Primary settler

Sludge

UASB reactor

CANON system

Figure 16. Municipal wastewater treatment using a CANON system to remove nitrogen.

(b) Bioreactor with filtration membrane: Denitrifying biomass is mixed with polluted ground water and electron donor. In this case, the membrane is used to separate biomass from treated water by application of pressure (Figure 17b). (c) Biofilm reactor: Elemental sulfur particles could be used as both electron donor and support of autotrophic denitrifying biomass. A column filled with elemental sulfur granules and operated in an upflow mode could be a system very simple, stable and easy to maintain (Figure 17c).

176

J.L. Campos, J.R. Vázquez-Padín, M. Figueroa et al. Recirculation

A

Treated water

Denitrifying bacteria Sulfur

Water with nitrate

Membrane Denitrifying biomass Residual water

B Water with nitrate

Denitrifying biomass

Water with nitrate

Treated water

Membrane

Denitrifying bacteria Sulfur Water with nitrate

Treated water

Membrane

Residual water

Membrane

C

Denitrifying bacteria

Water with sulfate

Water with nitrate

Sulfur

Water with nitrate

Figure 17. Systems to remove nitrate from ground water: a) bioreactor with extractive membrane, b) bioreactor with filtration membrane and c) biofilm reactor.

4.4. Nitrate Removal from Recirculating Aquaculture Systems Factors such as limitations of water quality, land costs, disposal requirements and environmental impact are driving the aquaculture sector to more intensive practices. The use of recirculating systems allows reducing water used and disposed during aquaculture activities. Besides, it has another advantages: a) Saving of pumping costs; b) Control of pH and temperature which optimize fish production; c) Presence of pathogens is minimized which reduces mortality during the broodstock stage. Since ammonia is toxic for fish at concentrations higher than 1.5 mg NH4+-N/L, this compound must be removed by a nitrifying biofilter to avoid its accumulation in the system. Ammonia is oxidized into nitrate which is less toxic for fishes, its recommended limit being around 50 mg NO3--N/L. However its effect depends on the specie and growth stage and, therefore, its removal is advisable. The use of denitrifying biofilter with elemental sulfur would be the most suitable option to maintain nitrate concentration as low as possible (Figure 18). The sulfate generated during the autotrophic denitrification would cause neither environmental nor toxicity problems when marine species are cultured (Vidal et al., 2002).


177

5. CONCLUSIONS Implantation of bioaugmentation, partial nitrification or anammox processes in the reject water stream of WWTPs supposes an economical and feasible alternative to improve effluent quality in terms of nitrogen content. The most suitable technology must be chosen depending on the WWTP operational conditions. Perspectives of advanced nitrogen removal processes application are very promising in fields such as wastewater, drinking water or aquaculture systems. Fresh water

Sedimentation zone

Fish culture tank

UV unit Effluent

Solid wastes

Recycling water

NH4+ Organic matter

Denitrifying biofilter SO4-2

NO3-

Nitrifying biofilter

Figure 18. Recirculating aquaculture system.

ACKNOWLEDGMENTS This work was funded by the Spanish Government (TOGRANSYS project CTQ200806792-C02-01/PPQ and NOVEDAR_Consolider project CSD2007-00055).

6. REFERENCES Abma, W., Schultz, C., Mulder, J. M., van Loosdrecht, M., van der Star, W., Strous, M. & Tokutomi, T. (2007). The advance of Anammox. Water 21, Feb. 2007, 36-37. Aiyuk, S., Forrez, I., Lieven, K., van Andel, A. & Verstraete, W. (2006). Anaerobic and complementary treatment of domestic sewage in regions with hot climates- A review. Bioresource Technology, 97, 2225-2241. Álvarez, J. A., Armstrong, E., Gómez, M. & Soto, M. (2008). Anaerobic treatment of lowstrength municipal wastewater by a two-stage pilot plant under psychrophilic conditions. Bioresource Technology, 99, 7051-7062.

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Berends, D. H. J. G., Salem, S., van der Roest, H. F. & van Loodsdrecht, M. C. M. (2005). Boosting nitrification with BABE technology return sludge. Water Science and Technology, 52(4), 63-70. Campos, J. L., Carvalho, S., Portela, R., Mosquera-Corral, A. & Méndez, R. (2008). Kinetics of denitrification using sulfur compounds: Effects of S/N ratio, endogenous and exogenous compounds. Bioresource Technology, 99, 1293-1299. Dapena-Mora, A., Campos, J. L., Mosquera-Corral, A., Jetten, M. S. M. & Méndez, R. (2004). Stability of the Anammox process in a gas-lift reactor and a SBR. Journal of Biotechnology, 110, 159-170. Dapena-Mora, A., Fernández, I., Campos, J. L., Mosquera-Corral, A., Méndez, R. & Jetten, M. S. M. (2007). Evaluation of activity and inhibition effects on Anammox process by batch tests based on the nitrogen gas production. Enzyme and Microbial Technology, 40, 859-865. Dosta, J., Fernández, I., Vázquez-Padín, J. R., Mosquera-Corral, A., Campos, J. L., Mata, J. & Méndez, R. (2008). Short- and long-term effects of temperature on the Anammox process. Journal of Hazardous Materials, 154, 688-693. Fajardo, C., Mosquera-Corral, A., Campos, J. L. & Méndez, R. (2008). Depuración conjunta de aguas ricas en nitratos y efluentes con compuestos reducidos del azufre. Retema, 127, 38-51. Fux, C. & Siegrist, H. (2004). Nitrogen removal from sludge digester liquids by nitrification/denitrification or partial nitritation/anammox: environmental and economical considerations. Water Science and Technology, 50(10), 19-26. Garuti, G., Giordano, A. & Pirozzoli, F. (2001). Full-scale ANANOX system performance. Water SA, 27, 189-197. Gijzen, H. J. (2001). Anaerobes, aerobes and phototrophs - A winning team for wastewater management. Water Science and Technology, 44, 123-132. Gong, Z., Yang, F. L., Liu, S. T., Bao, H., Hu, S. W. & Furukawa, K. J. (2007). Feasibility of a membrane aerated biofilm reactor to achieve single-stage autotrophic nitrogen removal based on Anammox. Chemosphere, 69, 776-784. Hellinga, C., Schellen, A. A. J. C., Mulder, J. W., Van Loosdrecht, M. C. M. & Heijnen, J. J. (1998). The Sharon process: An innovative method for nitrogen removal from ammonium-rich waste water. Water Science and Technology, 37(9), 135-142. Kampschreur, M. J., van der Star, W. R. L., Wielders, H. A., Mulder, J. W., Jetten, M. S. M. & van Loosdrecht, M. C. M. (2008). Dynamics of nitric oxide and nitrous oxide emission during full-scale reject water treatment. Water Research, 42, 812-826. Khin, T. & Annachhatre, P. (2004). Novel microbial nitrogen removal processes. Biotechnology Advances, 22, 519-532. Kroiss, H. (2004). What is the potential for utilizing the resources in sludge? Water Science and Technology, 49(10), 1-10. Liao, B. Q., Kraemer, J. T. & Badgley, D. M. (2006). Anaerobic Membrane Bioreactors: Applications and Research Directions. Critical Reviews in Environmental Science and Technology, 36, 489-530. Liu, S., Yang, F., Gong, Z. & Su, Z. (2008). Assessment of the positive effect of salinity on the nitrogen removal performance and microbial composition during the start-up of CANON process. Applied Microbiology and Biotechnology, 80, 339-348.


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McAdam, E. J. & Judd, S. J. (2006). A review of membrane biorreactor potencial for nitrate removal from drinking water. Desalination, 196, 135-148. Mosquera-Corral, A., González, F., Campos, J. L. & Méndez, R. (2005). Partial nitrification in a SHARON reactor in the presence of salts and organic carbon compounds. Process Biochemistry, 40, 3109-3118. Park, S. & Bae, W. (2009). Modeling kinetics of ammonium oxidation and nitrite oxidation under simultaneous inhibition by free ammonia and free nitrous acid. Process Biochemistry, 44, 631-640. Pynaert, K., Smets, B. F., Beheydt, D. & Verstraete, W. (2004). Start-up of autotrophic nitrogen removal reactors via sequential biocatalyst addition. Environmental Science and Technology, 38, 1228-1235. Salem, S., Berends, D. H. J. G., Heijnen, J. J. & Van Loodsdrecht, M. C. M. (2002a). Bioaugmentation by nitrification with return sludge. Water Research, 37, 1794-1804. Salem, S., Berends, D., Heijnen, J. J. & van Loosdrecht, M. C. M. (2002b). Model-based evaluation of a new upgrading concept for N-removal. Water Science and Technology, 45(6), 169-176. Salem, S., Berends, D. H. J. G., van der Roest, H. F., van der Kuij, R. J. & Van Loodsdrecht, M. C. M. (2004). Full scale application of the BABE technology. Water Science and Technology, 50(7), 87-96. Siegrist, H., Salzgeber, D., Eugster, J. & Joss, A. (2008). Anammox brings WWTP closer to energy autarky due to increased biogas production and reduced aeration energy for Nremoval. Water Science and Technology, 57(3), 383-388. Sliekers, A. O., Tirad, K. A., Abma, W., Kuenen, J. G. & Jetten, M. S. M. (2003). CANON and Anammox in a gas-lift reactor. FEMS Microbiology Letters, 218, 339-344. Sliekers, O., Derwort, N., Campos-Gomez, J. L., Strous, M., Kuenen, J. G. & Jetten, M. S. M. (2002). Completely autotrophic nitrogen removal over nitrite in a single reactor. Water Research, 36, 2475-2482. Soares, M. I. M. (2002). Denitrification of groundwater with elemental sulphur. Water Research, 36, 1392-1395. Tanaka, K., Sumino, T., Nakamura, H., Ogasawara, T. & Emori, H. (1996). Application of nitrification by cells immobilized in polyethylene glycol. In: R. H. Wijjfels, R. M. Buittelaar, C. Bucke, & J. Tramper (Eds.), Immobilized Cells: Basics and Applications. Amsterdam: Elsevier Science, 622-632. Van der Star, W. R. L., Abma, W. R., Blommers, D., Mulder, J. W., Tokutomi, T., Strous, M., Picioreanu, C. & van Loosdrecht, M. C. M. (2007). Startup of reactors for anoxic ammonium oxidation: Experiences from the first full-scale anammox reactor in Rotterdam. Water Research, 41, 4149-4163. Van Dongen, U., Jetten, M. S. M. & Loosdrecht, M. C. M. (2001). The SHARON®Anammox® process for treatment of ammonium rich wastewater. Water Science and Technology, 44(1), 153-160. Van Kempen, R., Mulder, J. W., Uijterlinde, C. A. & van Loosdrecht, M. C. M. (2001). Overview: full scale experience of the SHARON process for treatment of rejection water of digested sludge dewatering. Water Science and Technology, 44(1), 145-52. Van Loosdrecht, M. C. M. & Salem, S. (2006). Biological treatment of sludge digester liquids. Water Science and Technolology, 53(12), 11-20.

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Vázquez-Padín, J. R., Fernández, I., Figueroa, M., Mosquera-Corral, A., Campos, J. L. & Méndez, R. (2009a). Applications of Anammox based processes to treat anaerobic digester supernatant at room temperature. Bioresource Technology, 100, 2988-2994. Vázquez-Padín, J. R., Pozo, M. J., Jarpa, M., Figueroa, M., Franco, A., Mosquera-Corral, A., Campos, J. L. & Méndez, R. (2009b). Treatment of anaerobic sludge digester effluents by the CANON process in an air pulsing SBR. Journal of Hazardous Materials, 166, 336-341. Vidal, S., Rocha, C. & Galvao, H. (2002). A comparison of organic and inorganic carbon controls over biological denitrification in aquaria. Chemosphere, 48, 445-451. Wett, B. (2006). Solved upscaling problems for implementing deammoniﬁcation of rejection water. Water Science and Technology, 53(12), 121-128. Wett, B. (2007). Development and implementation of a robust deammonification process. Water Science and Technology, 56(7), 81-88. Wiesmann (1994). Biological Nitrogen Removal from Wastewater. In: Fletcher A. (ed.), Advances in Biochemical Engineering Biotechnology, vol. 51. Spinger-Verlag, Berlín. 113-154. Windey, K., de Bo, I. & Verstraete, W. (2005). Oxygen-limited autotrophic nitrificationdenitrification (OLAND) in a rotating biological contactor treating high-salinity wastewater. Water Research, 39, 4512-4520.



Chapter 7

APPLICATION OF MICROBIAL MELANOIDINDECOMPOSING ACTIVITY (MDA) FOR TREATMENT OF MOLASSES WASTEWATER Suntud Sirianuntapiboon* and Sadahiro Ohmomo Department of Environmental Technology, School of Energy, Environment and Materials, King Mongkut‘s University of Technology, Thonburi (KUMTT), Bangmod, Thung Khru, Bangkok 10140, Thailand.

ABSTRACT This review will discuss the melanoidin-decomposing activity (MDA) among microorganisms. The focus will be on the potential use of the microbial-MDA to treat the wastewater discharged from factories using molasses as the raw material (molasses wastewater: MWW) because molasses is one of the most useful raw materials in various types of industries, such as the fermentation and animal feed industries. However, the wastewater discharged from factories using molasses contains a large amount of dark brown pigment, melanoidin pigment: MP, which is poorly decomposed and/or decolorized by normal biological treatment processes, such as the activated sludge or anaerobic treatment systems (anaerobic pond or anaerobic contact digester), because, the microorganisms in those wastewater treatment systems showed very poor MDA. The distribution of MDA among microorganisms and the mechanism of decomposing activities, in particular, were reviewed. Also, the application of the isolated strains having the MDA to treat molasses wastewater in the wastewater treatment plant was tested.

Keywords: Melanoidin, Molasses, Molasses wastewater, Decolorization, Alcohol distillation, Microbial decolorization, Chemical decolorization.

*

Corresponding author: E-mail: [email protected]

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Suntud Sirianuntapiboon and Sadahiro Ohmomo

INTRODUCTION A large body of scientific research has been conducted on the conversion of renewable biomass to useful materials for political and practical concerns over the state of the environment (Underfolker and Hickely, 1954). In particular, bio-fuel from renewable biomass is expected to help alleviate the ongoing energy crisis. Molasses, a by-product from sugar cane or sugar beat in sugar industries, is one of the largest sources of biomass and a very important material worldwide. Molasses consists of about 50% sugar (reducing sugar) or related substrates, about 10% non-sugar organic substances, and about 10% minerals (Underfolker and Hickely, 1954). Due to these components, molasses was widely used in various fermentation industries, such as alcohol fermentation, amino acid fermentation, antibiotics fermentation, and baker‘s yeast fermentation, (Chang and Yang, 1973; Chaung and Lai, 1978), as a low-cost and readily available raw material when diluted with water. Molasses from sugar cane is mainly produced in tropical areas of the world, especially in south-east Asia (Philippines, Indonesia, Thailand, etc). Wastewater from the fermentation processes using molasses is densely colored by molasses pigment, called melanoidin pigment (MP), and contains a large amount of organic matters, which leads to high biological oxygen demand (BOD5) and chemical oxygen demand (COD) values (Sirianuntapiboon et al., 1988a; Antonia et al, 2000). Therefore, the wastewater can be treated by normal biological treatment processes, such as the activated sludge system, aerated lagoon, or anaerobic pond, to remove the organic matter. However, MP is poorly decomposed and still remains in the wastewater after treatment by above processes. No suitable method for the treatment of large amounts of this type of wastewater has been developed yet, so this is a problem that still needs to be solved. For example, this problem has led to an increase in the production cost of the ethyl alcohol fermentation process from molasses, because about 75% of potential energy in ethyl alcohol is wasted due to the popular treatment process as concentration and combustion of the wastewater (Chaung and Lai, 1978; Chang and Yang, 1973). Therefore, the development of a low-cost and simple wastewater treatment system that utilizes microbes to decompose and decolorize MP is urgently needed. In this paper, the MP-decomposing activities (MDA) in microorganisms are reviewed with a focus on the distribution of MDA in microorganisms, the mechanisms of their activities, and the application process for the treatment of wastewater from the factories using molasses.

1. MELANOIDIN PIGMENTS (MP) (Monica et al., 2004; Kwak et al, 2005; Kato and Hayase, 2002; Fogliano et al, 1999; Yaylayan et al, 1998): MP is synthesized from carbonyl compounds, such as sugar and amino compounds, amino acids, or proteins (Monica et al, 2004; Kato and Hayase, 2002), as shown in Figure 1. This is a non-enzymatic browning reaction and a type of amino-carbonyl reaction called Maillard reaction (Monica et al., 2004). This reaction is promoted under the alkaline condition and the coloration of MP changes from yellow to dark brown with increased MPcondensation (Fogliano et al, 1999). MP grows large molecular weight substances (more than

Biological Removal of Melanoidin Pigments

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100,000 Dalton) and the condensed-MP precipitates under acidic conditions of pH less than 3. The color-density of MP solution under acidic conditions (pH 5.0) is weakened by about 20% in comparison with the alkaline condition and shows a maximum absorption at a wavelength of 475 nm (Ohmomo et al, 1985a; Sirianuntapiboon et al, 1988a). The colored substances in some foods, such as Shoyu and Miso (Japanese seasoning), as well as molasses, are typical MPs (Ohmomo et al., 1985a).

2. SCREENING OF MICROORGANISMS HAVING MP-REMOVAL ACTIVITY (MPRA) (Ohmomo et al., 1988a; Watanabe et al., 1982; Sirianuntapiboon et al., 1988a): MP is known as a poorly biologically-decomposed substance because of its complicated-structure (Monica et al., 2004; Kato and Hayase, 2002 ). Several researchers tried to isolate the microorganisms which have MPRA as shown in Table 1. It was found that several types of microorganisms such as mushroom (Watanabe, et al., 1982; Ohmomo, et al., 1985a; Kumar, et al., 1998; Miyata, et al., 2000), mold (Miyata, et al., 2000; Ohmomo et al, 1987a; Sirianuntapiboon et al, 1988b; Fahy et al, 1997; Kim and Shoda, 1999; Dahiya et al, 2001a; Jimenez et al, 2003), yeast (Sirianuntapiboon et al, 2004b) and bacteria (Ohmomo et al, 1988b; Francisca et al, 2001; Sirianuntapiboon et al, 2004a; Kumar and Chamdra, 2006) showed the MPRA. Some of them showed very strong MP-adsorption ability (Ohmomo et al, 1988b; Watanabe et al, 1982) or MP-degradation ability (Fahy et al, 1997) while the other showed both MP-adsorption and MP-degradation abilities (Sirianuntapiboon et al, 1995). It was understood that microorganisms having MDA were not common habitants. At first, the microbial-MDA was screened among the white-rod fungi (mushroom) due to their lignindecomposing activity by a research group of Kyushu University, Japan (Watanabe et al., 1982). They succeeded in isolating a strain Coriolus sp. No. 20 and suggested that the MDA in this strain was led by a sorbose oxidizing enzyme: sorbose oxidase (Watanabe et al., 1982). This was the first report for microbial MDA in the world. After this, our research group also found the MDA in some white-rod fungi to be especially strong in Coriolus versicolor Ps4a (Ohmomo et al., 1985a; Ohmomo et al., 1985b; Ohmomo et al., 1985c; Aoshima et al., 1985), and succeeded in confirming that there was MDA among various groups of microorganisms, such as fungi, bacteria, and yeast (Ohmomo et al., 1987a; Ohmomo et al., 1987b; Ohmomo et al., 1987c; Sirianuntapiboon, et al., 1988a; Sirianuntapiboon, et al., 1988b; Sirianuntapiboon, et al., 2004a; Sirianuntapiboon, et al., 2004b).

2.1. MP and MP Solution Preparation Two kinds of MP solutions were used in screening the microorganisms for MDA and MDA determination as natural-MP (NMP) and synthetic-MP (SMP) solutions. The NMP solution was fundamentally prepared from the MWW (Ohmomo et al., 1987a; Sirianuntapiboon et al., 1988a). Two kinds of MWW as stillage from an alcohol factory (U-MWW) and treated-MWW especially from an anaerobic pond (An-MWW) could be used for preparation of the NMP solution. However, the molecular weight distribution of NMP solution was not always

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equalized, because of the conditions of the sugar making process, fermentation of molasses, and treatment process and condition of MWW (Sirianuntapiboon and Chairattanawan, 1998). Due to these uncertainties, synthetic-MP (SMP) was more widely used for the screening of microbial-MDA. SMP was synthesized by heating the solution containing 1 mol/L glucose, 1 mol/L glycine and 0.5 mol/L Na2CO3 at 1210C for 3 hr (Sirianuntapiboon, et al., 1988a; Ohmomo et al., 1985a). After heating, the solution was adjusted to a pH of 7.0 with 1.0 mol/L NaOH solution and ultra-filtrated using membrane filters of molecular weight cut-offs between 1,000 Dalton and 10,000 Dalton. The fractions having molecular weights from 1,000 to 10,000 Dalton was harvested and freeze-dried to make a SMP powder. The solution of SMP is prepared as giving an optical density of 3.5 (OD=3.5) at a wavelength 475 nm in 0.1 mol/L acetate buffer (pH 5.0) before being used in the experiments.

2.2. Screening Methods for Isolation of Microbial Strain Having MDA The medium containing SMP or NMP was used for screening the microorganisms having MDA. Fungal and bacterial strains were isolated by using media containing MP. The testedmicroorganisms were inoculated on the surface of an agar medium suitable for growth (the media contained MP) and were cultured to make a colony. If the tested-microorganism had MDA, a clear zone around the colony was formed (Sirianuntapiboon, et al., 1988a). Furthermore, the microorganisms forming the clear zone around the colony was cultured in a liquid medium suitable for the growth and the medium color intensities before and after cultivation were compared in order to calculate the decolorization yield (Sirianuntapiboon, et al., 1988a). If the tested-strain produced organic acids and reduced medium pH, the color density of the culture filtrate was reduced due to the acidic-pH. Therefore, the color intensity of culture filtrate should be measured after dilution with 0.1 mol/L acetate buffer (pH 5.0) to prevent the error of the color intensity reduction in acidic-pH condition (Sirianuntapiboon, et al., 1988a).

Figure 1. Outline for the formation of MP: Maillard‘s reaction (Monica et al., 2004)


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Table 1. MP removal mechanisms of various types of microorganisms. Type of Microorganisms Mushroom

Name of microorganism (Genus and species) Coriolus sp. No.20 Coriolus versicolor Ps4a

Coriolus versicolor

Coriolus hirsutus

Mold

Aspergillus fumigatus G-2-6

Rhizoctonia sp. D90

Aspergillus oryzae Phanerochaete chrysosporium

Geotrichum candidum Dec 1 Phanerochaete chrysosporium JAG-40 Penicillium decumbens Flavodon flavus

Yeast

Citeromyces sp. WR-43-6

Bacteria

Lactobacillus hirgardii

Oscillatoria boryana BDU 92181 Acetogenic bacteria BP103

MP removal mechanisms Decolorization by sorbose oxidase enzyme Decolorization by intracellular enzyme (inducible enzyme by MP) Decolorization by sorbose oxidase, sugar oxidase and manganese dependent peroxidase MP degradation by Intracellular enzyme (sugar oxidase) MP degradation by Intracellular enzyme (Inducible enzyme by MP) MP removal by adsorption, absorption and decomposition MP removal by adsorption MP decomposing enzyme (showed highest ability at the stationary phase of growth curve) MP degradation by peroxidase enzyme MP degradation by extracellular enzyme MP removal by degradation and/or adsorption MP degradation by glucose oxidase and hydrogen peroxide enzymes MP degradation by sugar oxidase enzyme. MP removal by assimilation and degradation peroxidase enzyme MP removal by assimilation and peroxidase enzyme MP degradation by sugar oxidase enzyme

References Watanabe et al., 1982 Ohmomo et al., 1985

Kumar et al., 1998

Miyata et al., 2000

Ohmomo et.al., 1987

Sirianuntapiboon et al., 1988 Fahy et al., 1997; Ohmomo et al, Kim and Shoda, 1999

Dahiya et al., 2001 Jimenez et al., 2003 Raghukumar et al., 2004 Raghumar and Mohandass, 2001 Sirianuntapiboon et al., 2004 Ohmomo et al., 1988

Francisca et al., 2001 Sirianuntapiboon et al.,2004

2.3. MDA in the Fungal Strain Several fungal strains belonging to the classes of Basidiomycetes, Ascomycetes and Dueteromycetes showed MPRA were isolated. The strain belonging to class Basidiomycetes was first isolated as the MDA strain. Most of the white-rod fungi strains that have the ability to decompose lignin, showed MDA, and especially strong MDA were detected in Coriolus versicolor Ps4a, Coriolus hirsutus, Fomitopsis cytisina, Irpex lactens, and Pleurotus ostreatus

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(Watanabe, et al., 1982; Ohmomo, et al., 1985a; Raghukumar and Rivonkar, 2001; Miyata, et al., 1998; Fitzgibbon, 1998). But, the strains of brown-rod fungi having the ability to decompose cellulose never showed the MDA (Aoshima et al., 1985). Most of the fungi having MDA grew well on shaking cultures using a medium containing glucose, sucrose, or maltose and showed very strong MDA (Watanabe, et al., 1982). However, the MDA was weak on the cultures using xylose or arabinose as the carbon source, while the growth rate was high. Additionally, nitrogen sources were also affected to growth and MDA. Organic nitrogen sources, such as peptone and casamino acid were the best nitrogen source in obtaining a high growth rate and strong MDA. Ammonium salt was also good for growth, but it gave only half level of MDA of that with peptone. Nitrate salts gave poor growth and weak MDA. The highest decolorization yield (75-80%) of Coriolus versicolor Ps4a was obtained in a shaking culture using a MP-medium containing 5% glucose and 0.5% peptone at 30oC for 4-6 days, and the MDA was the decomposition of MP by decreasing the molecular weight of the MP (Ohmomo et al., 1985b). A research group at Kobe University also screened for MDA among white-rod fungi and detected a strong MDA from Coriolus pubescens, Hirschioporus fuscoviolaceus, Polyporellus brumalis, etc., and at the same time, they found strong browning activity in some unidentified fungi (Tamaki et al., 1985). Moreover, Trametes versicolor (Benito et al., 1997), Phanerochaetes chrysosporium (Fahy et al., 1997; Kumer et al., 1998; Kumer et al, 1997; Fitgibbon et al., 1998; Dahiya, 2001a), Coriolus hirsutus (Miyata et al., 1998), Flavodon flavus (Raghkumar et al., 2004) and others have since been reported as having MDA. For the screening of thermophilic fungi, the stain of Ascomycetes, mainly belonging to the genus Aspergillus, strain G-2-6 was isolated as showing the strongest MDA and identified as Aspergillus fumigatus. The strain gave the maximum decolorization yield of 75% on a shaking culture using a medium containing glycerin and peptone as the carbon and nitrogen sources, respectively, at 45oC for 3 days, and the MP-removal mechanism was the decomposition of MP (Ohmomo et al., 1987a). At the same time, strain Y-2-32 was also isolated as showing the strongest MDA and identified as Aspergillus oryzae. However, the MDA of this strain was not the MP-decomposition mechanism, but MP was only adsorbed onto the surface of mycelia (Ohmomo et al., 1988). The ability to adsorb MP among living mycelia and dead mycelia was almost the same and was recovered after washing of mycelia with buffer solution. The reuse of mycelia after washing was possible (Ohmomo et al., 1988b). Aspergillus niger 180 was also selected (Miranda et al., 1996) and the MDA of Aspergillus niger when combined with Penicillium decumbens and Penicillium lignorum was also confirmed (Antonia et al., 2003). Additionally, Rhizoctonia sp. D90 (=Mycelia sterilia D90), which belongs to class Deuteromycetes, was screened as having strong MDA (Sirianuntapiboon et al., 1988a, Sirianuntapiboon et al., 1988b; Sirianuntapiboon et al., 1995). This strain gave the maximum decolorization and COD removal yields of more than 90% and 80%, respectively (Sirianuntapiboon et al., 1988a; Sirianuntapiboon et al., 1988b; Sirianuntapiboon, 1995). The MDA of Geotrichum candidum (Kim and shoda, 1999), Oscillatoria boryana (Kalavathi et al., 2001) and Paecilomyces canadensis (Terasawa et al., 2000) were also detected.


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2.4. MDA in the Bacterial Strain Both aerobic bacteria and anaerobic bacteria strains having MDA were isolated (Ohmomo et al, 1987b; Ohmomo et al, 1988a; Sirianuntapiboon et al, 2004b), and both strains were applied to the conventional wastewater treatment systems (in the laboratory scale), activated sludge system and anaerobic treatment system, respectively (Kumar et al, 1997; Mohana et al, 2007; Ghosh et al, 2002). Lactic acid bacteria strains were isolated in order to find a strain of anaerobic bacteria with MDA that could be applied in an anaerobic treatment system (Kumar et al., 1997; Kumar et al., 1998; Mohana et al, 2007; Ohmomo et al, 1987b). Among them, a hetero-fermentative strain W-NS identified as Lactobacillus hilgardii showed the strongest MDA and the maximum decolorization yield was about 30% for sugar cane molasses, about 40% for beat molasses, and about 65% for synthetic glycine-glucoseMP under the presence of 1% glucose at 35-40oC (Ohmomo et al., 1987b). Furthermore, acetogenic bacteria BP103, an aerobic bacteria, was isolated from Thailand showed a strong MDA. This strain decolorized 75-80% of molasses wastewater under the presence of 3% glucose and 0.5% peptone at 30oC (Sirianuntapiboon et al., 2004a). The MDA was also detected in Bacillus smithii, which decolorized about 36% of molasses wastewater at 55oC within 20 days (Nakajima-Kambe et al., 1999). The MDA were also detected in Pseudomonas fluorescens (Jagroop et al., 2001; Dahiya et al., 2001), Pseudomonas putida (Ghosh et al., 2002) and some strains belonging to the genus Methanothrix and Methanosarcina (Boopathy and Tilche, 1991; Boopathy, 1992). In addition, the mixed culture of Streptomyces warraensis and Basidiomycetes fungi was also tested for decolorization of MWW (Terasawa et al., 2000).

2.5. MDA in the Yeast Strain Our research group tried to isolate the yeast strain having MDA from several sources of fruit and soil in Thailand. Citeromyces sp. WR-43-6 was first isolated as the MDA strain in the yeast group. This strain gave a maximum decolorization yield of more than 70% and at the same time, BOD5 and COD were removed by more than 76% and 98%, respectively (Sirianuntapiboon et al., 2004b).

3. MECHANISM OF MICROBIAL MDA The microbial-MDA or removal mechanisms were investigated by several research groups. The fungal enzyme system related to the MDA was partially purified in Coriolus sp. No.20 (Watanabe et al., 1982) and Coriolus versicolor Ps4a (Ohmomo et al., 1988a). Some steps, such as adsorption of MP onto the cell surface and incorporation of MP in the cell were suggested in fungi (Sirianuntapiboon et al, 1998; Ohmomo et al, 1988b). However, the mechanism of microbial MDA was hardly elucidated. Because, some isolated-strains showed strongly on the MP-degradation mechanism, while the others showed strongly on the MPadsorption mechanism. For the observation of MDA mechanism of the Rhizoctonia sp. D-90 strain, MDA mechanism by Rhizoctonia sp. D-90 involved in absorption of the MP by the

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cells as a macromolecule and its intracellular accumulation in the cytoplasm and around the cell membrane as a MP complex, which was then gradually degraded by an intracellular enzyme. However, the main-MP decolorization or removal mechanisms of each MPdecolorization strain was different. The details of MDA and MP-removal mechanisms are described below:

3.1. Microbial-Decomposition of MP Few papers related to the mechanism of the enzyme system in MDA have been published, despite the numerous publications on the decolorization and decomposition of MP from molasses. As a first step in resolving the mechanisms in microbial MDA, sorbose oxidase was partially purified from the mycelia of white-rod-fungi, Coriolus sp. No. 20 (Watanabe et al., 1982). It was thought that the mechanism of MDA by this enzyme system would act by oxidizing sorbose and release activated-oxygen (oxygen radical) to decompose MP. However, no clear evidence for this system was found. Two enzymes, P-III and P-IV, related to the decolorization of MP were partially purified from the mycelia of Coriolus versicolor Ps4a (Ohmomo et al., 1985a; Ohmomo et al, 1985b). Enzyme P-III with a molecular weight of about 50,000 Dalton gave the decolorization yield of about 11% under aerobic conditions and in the presence of glucose. However, enzyme P-IV with a molecular weight of about 45,000 Dalton gave the decolorization yield of about 13% under anoxic conditions and without glucose. The maximum decolorization yield of each enzyme was low; however, the multiplicative effect (Figure 2) for decolorization with both enzymes was observed with the decolorization yield of about 40%, which was higher than that calculated sum of decolorization yields of both enzymes of 24%. Decolorization activity of enzyme PIII and PIV was 11% and 13%, respectively. Furthermore, lactic acid and various amino acids were detected as the reaction products of these enzymes (Ohmomo et al., 1985c). Conversely, the relation of manganese-dependent peroxidase to the decomposition of MP was suggested in Coriolus hirsutus (Miyata et al., 1998, 2000) and Flavodon flavus (Raghkumar and Rivonkar, 2001, Raghukumar et al, 2004). For the determination of molecular weight distribution of MP decomposed by microorganisms, it was found the molecular weight of MP of the treated SMP or NMP solutions were shifted to smaller molecular weight fractions than that of the initial solutions, as shown in Figure 3, and this shift was also detected in the case of fungi and bacteria (Ohmomo et al., 1988; Sirianuntapiboon et al., 1988b). In addition, the production of hydrogen peroxide and activated oxygen by photo-synthetic cyanobacteria closely participated in the decomposition of MP by Oscillatoria boryana BDU 92181 (Kalavathi et al., 2001). Further, the induction at low level MP (10 g/liter) and the inhibition at high level MP (20 g/liter) for the production of peroxidase was reported in Geotricum candidum (Lee et al., 2000).


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A: shows the decolorization by P-IV after complete decolorization by P-III. B: shows the decolorization by P-III after complete decolorization by P-IV. C: shows the decolorization by a mixture of P-III and P-IV. Symbols: , actual decolorization yield; , decolorization yield (calculated from the individual decolorization yields of P-III and P-IV); ↓, shows the addition of an enzyme. Figure 2. Multiplicative effect between enzyme P-III and P-IV for the MP Decolorization (Ohmomo et al., 1985a).

Chromatograms of MP solution were obtained by using gel filtration on a Sephadex G-50 column. Symbols: , initial MP solution; , solution treated by Citeromyces sp. WR-43-6. Figure 3. Molecular weight distribution in MP solution before and after decolorization by Citeromyces sp. WR-43-6 (Sirianuntapiboon et al., 2004b).

3.2. Microbial-Adsorption of MP The adsorption of MP onto the cell surface was suggested in Aspergillus oryzae Y-2-32, which strongly decolorized MWW. The decolorization of this strain was due to the adsorption of MP onto the cell surface, and its yield depended on the amounts of cell mass. However, the MP adsorption ability disappeared when washed with 0.1% Tween 80 solution or 0.1% SDS

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solution. This means that there is a relation between the cell surface components, such as muco-polysaccharides, and MP adsorption (Ohmomo et al.,a 1988b). The adsorption of MP onto the cell surface should be the first step of the MDA, and this strain has no next step, such as incorporation of MP into the cell and/or decomposition of MP. However, the electron microscopic observation for the adsorption and incorporation of MP onto the cell (cell membrane and cytoplasm) of Rhizoctonia sp. D90 (= Mycelia sterilia D90) was reported (Sirianuntapiboon et al., 1995). Tremetes versicolor gave a strong decolorization yield, maximum 80%, and about 10% of the yield was due to the adsorption onto the cell surface (Benito et al., 1997). These reports could suggest that the MDA displays a two-step reaction of adsorption of MP onto the cell surface and incorporation of MP into the cell as shown in Figure 4 and Figure 5.

a

b

a

a: Cross-section of 7-day-old mycelium, grown in synthetic melanoidin medium, showing electrondense materials distributed in the cytoplasm. b: Cross-section of 7-day-old mycelium, grown in potato dextrose medium, showing well-defined cell organelles such b as the cell wall (cw) and the cell membrane (cm). Figure 4. Electron Micrographs of Rhizoctonia Sp. D-90 in SMP medium and potato dextrose medium (Sirianuntapiboon et al., 1995).

a

b

a: Cross-section of mycelium that had been grown in potato dextrose medium for 7 days (100,000 x magnification), showing the clear cytoplasm and cell membrane (cm). b: Cross-section of mycelium that had been grown in potato dextrose medium for 7 days and then in SMP-medium for another 4 days (100,000 x magnification), showing electron-dense materials distributed in b the cytoplasm. Figure 5. Electron micrographs of Rhizoctonia sp. D-90 collected at various stages of cultivation (Sirianuntapiboon et al., 1995).


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Continuous decolorization was carried out in a bubbling column (diameter 26 mm x length 400 mm) at 30 0C with aeration. The column contained 100 ml of waste water and 25 g of immobilized mycelia (corresponding to 0.8 g dry mycelial weight). → shows the start of continuous decolorization at a dilution rate of 0.022 hr-1. Figure 6. Continuous decolorization by immobilized mycelia of Coriolus versicolor Ps4a (Ohmomo et al., 1985b).

4. APPLICATION OF MICROBIAL-MDA FOR TREATMENT OF MWW 4.1. Application of Fungal Strain Many studies have been conducted on the decolorization process of MWW using fungal mycelia. For example, the mycelia of Coriolus versicolor Ps4a maintained a decolorization yield of about 75% for the continuous process under a dissolved oxygen (DO) concentration of 1 mg/L, dilution rate of 0.03 hr-1, and with the addition of 0.5% glucose and 0.05% peptone. This mycelia, immobilized in Ca-alginate gel, maintained the decolorization yield of about 65% for the continuous decolorization process under the dilution rate of 0.022 hr-1 for 16 days operation and removed about 53% of the COD value and 46% of the total carbon concentration, as shown in Figure 6 (Ohmomo et al., 1985b). Furthermore, the continuous decolorization of molasses wastewater by mycelia of Coriolus sp. No. 20 (Sirianuntapiboon and chairattanawan, 1998), the decolorization of MWW by the mycelia of Phanerochaetes chrysosporium immobilized into Ca-alginate gel (Fahy et al., 1997), the continuous decolorization of MWW by a mixture of immobilized-Coriolus versicolor IFO 30340 and Paecilomyces canadensis NC-1 strains (Terasawa et al., 2000), the decolorization of MWW by the mycelia of Coriolus hirsutus IFO 4917l in conjunction with the activated sludge process (Miyata et al., 2000) and the decolorization of MP from MWW by the immobilized mycelia of Flavodon flavus (Raghkumar et al., 2001) were also reported. In addition, under batch-type conditions, Mycelia sterilia D90 gave a maximum decolorization yield of about 80% and COD removal yield of about 70% in a three time replacement reaction for a continuous 24 day operation (Sirianuntapiboon et al., 1988b). Aspergillus fumigatus G-2-6 immobilized into a Ca-alginate gel maintained a decolorization yield of about 60% in the continuous replacement reaction for 18 days of operation and more than 70% in the continuous decolorization process under the dilution rate of 0.014 hr-1 with removal yields of about 51% (BOD5) and 56% (COD) (Ohmomo et al., 1987a). Aspergillus niger 180 maintained a decolorization yield of about 40% and a simultaneous COD removal

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yield of about 70% in the continuously fed batch system with MWW (Miranda et al., 1996). The decolorization of wastewater from alcohol fermentation using beat molasses was tested by using a process that combined the mycelia of Penicillium decumbens with the mycelia of Penicillium lignorum and Aspergillus niger, which resulted in a maximum decolorization yield of about 70% and a simultaneous COD removal yield of about 50% (Antonia et al., 2003). Also, Fujila et al (2000) also reported that polyurethane foam-immobilized white root fungi could be applied into the bioreactor for treatment of the molasses wastewater

4.2. Application of Bacteria Lactobacillus hilgardii W-NS immobilized into Ca-alginate gel gave about a 35% decolorization yield on the 7 times replacement decolorization process (for 30 days cultivation) and about 30% decolorization yield for continuous process under the dilution rate of 0.02 hr-1 and no aeration for 16 days, as shown in Figure 7 (Ohmomo et al., 1987b). Acetogenic bacteria BP 103 gave the decolorization yield of about 70% on the 6 times continuous replacement reaction for 30 days operation; however, it maintained only a 30% decolorization yield on the continuously fed batch reaction for 30 days operation (Sirianuntapiboon et al., 2004). Pseudomonas fluorescens adsorbed onto cellulose and coated by collagen gave about a 94% decolorization yield for the continuous replacement decolorization process (for 4 days operation) (Jagroop et al., 2001). A two-step column bioreactor using two bacteria strains of Pseudomonas putida U and Acetomonas sp. Ema was applied for the decolorization of molasses wastewater (Ghosh et al., 2002). The results showed that the COD and color intensity of MWW were reduced by 44.4% and 60.0%, respectively, in the first step by Pseudomonas putida U. Then the COD of the effluent of the first reactor was reduced by 44.4% in the secondary step with Acetomonas sp. Ema.

4.3. Application of Yeast Strain The continuous feeding system for decolorization of MWW by Citeromyces sp. WR-43-6 was tested and obtained a stable MP, COD and BOD5 removal efficiencies of about 50 - 60%, 99% and 89%, respectively, as shown in Figure 8. (Sirianuntapiboon et al., 2004b).

5. DISCUSSION MP is recognized as a material difficult to decompose (MDD) because it is hardly removed (decolorized or adsorbed) by normal biological treatment processes, such as the activated sludge system, aerated lagoons, anaerobic ponds, etc (Boopathy, 1992; Boopathy and Tilche, 1991; Sirianuntapiboon et al, 1988b). This review has outlined the potential application for microbiological removal of MP from MWW. Actually, the MDA has been detected among various groups of microorganisms, in spite of the classification of MP as an MDD. Although the removal or decolorization of MP by microbial processes is still only done on a laboratory-scale level, it is evident from this review that the microbial-MDA can be a useful process to treat, at least to decolorize, MWW. Among the microbial-MDA, the


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potential ability of lactic acid bacteria (LAB) should be useful for the development of the treatment process because LAB is a facultative bacteria and the treatment process requires noaeration. Immobilized LAB cells should be particularly advantageous because the treatment process is very simple and it is expected to be a low cost operation. And organic acids were generated was the raw material for the metanogenic bacteria group in the methane fermentation step of anaerobic treatment process. However, the MDA of LAB has only been detected on Lactobacillus hilgardii WN-S (Ohmomo et al., 1987c) and the decolorization yield was not very high when compared to some fugal strains, such as Coriolus versicolor Ps4a (Ohmomo et al., 1985b) and Aspergillus fumigatus G-2-6 (Ohmomo et al., 1987a). The screening of LAB having higher decolorization yields is expected. The fungal-MDA mentioned above and the yeast cells have a significantly higher decolorization yield. However, these abilities are unsuitable for treating MWW because these microorganisms are aerobic microorganisms and require oxygen for growth and MDA. Nevertheless, microbial-MDA has great potential for decolorizing MP. It is hoped that the MDA, such as those discussed in this review, will be exploited to their maximum potential in the near future. Also, the review article was consisted mostly our research group activity, we believed that the use of microbiological process to treat MWW was more suitable according to low cost, reusable of the end product and intermediate. It is therefore, recommended that further research regarding the MDA mechanism (both biological adsorption and degradation mechanisms) be conducted to further advance the understanding of biological MP removal. Also, the observation of some operation parameters of activated sludge systems (both aerobic and anaerobic process) such as dilution rate, organic loading, MP loading, sludge age and so on was necessary for the application of the potential-isolated strain in the conventional wastewater treatment processes.

Continuous decolorization was carried out in a bubbling column (diameter 26 mm x length 400 mm) at 37 °C. The column contained 100 ml of waste water and 60 g of immobilized cells mycelia (corresponding to 13.2 mg dry mycelial weight). Continuous decolorization was started by the feeding of wastewater after decolorization for 4 days (showed ↑and↓). The feeding rate was adjusted to 2.0 ml/hr (dilution rate of 0.02 hr-1). Symbols: , wastewater adjusted to pH 5.0 by NaOH; , wastewater adjusted to pH 7.3 by Ca(OH)2. Figure 7. Continuous decolorization of molasses waste water by immobilized cells of Lactobacillus hirgardii W-NS (Ohmomo et al., 1987c).

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Decolorization was carried out in an μ-carrier magnetic stirrer containing 10 ml of cells (4 x 109 cells/ml) and 1 liter of waste water added 2.0% of glucose, 0.1% of NaNO3 and 0.1% of KH2PO4 (pH 6.0) at 30℃ at an impeller speed of 150 rpm. From after 8 days culture, 100 ml of fresh medium was added into the system everyday. ↓ shows the time for feeding 10% of fresh medium. Symbols: , decolorization yield; , reducing sugar; , medium pH; ▲, dry cell weight. Figure 8. Decolorization in continuous feed system of molasses wastewater by Citeromyces sp.WR-436 (Sirianuntapiboon et al., 2004b).

6. CONCLUSION The microbial-MP removal process is the most suitable way to treat wastewater from factories that use molasses as a raw material. However, it is still only carried out on a laboratory scale. Many types of microorganisms, such as fungi (class Basidiomycetes and Ascomycetes and Dueteromycetes) and bacteria (Lactic acid bacteria and Acetogenic bacteria) were found to have MDA. The mechanisms of microbial-MDA might be the adsorption of MP on to the cell (cell membrane and cytoplasm) and/or the adsorbed or adsorbed MP was degraded by both intracellular and extracellular enzymes. Some of the microbes showed MP adsorption ability as the main activity, but others showed both MPadsorption and MP-adsorption activities. MDA was both induced and inhibited by the level of MP. Also, the aerobic, facultative, and anaerobic conditions of the microbial-MP removal processes were investigated. Rhizoctonia sp D-90 and Coriolus sp. No.20 were applied to the conventional wastewater treatment processes to treat MWW under aerobic conditions. Lactic acid bacteria was also introduced the anaerobic wastewater treatment process to decolorize MWW. Both Acetogenic bacteria BP 103 and Cyteromyces sp. WR-43-6 showed MDA with MWW under both aerobic and facultative conditions. Suspended growth (batch type and continuous type) and attached growth (Bio-film reactor) systems were tested for the microbial-MDA process for the treatment of molasses wastewater. However, all the experiments were still in the laboratory scale.


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REFERENCES Antonia, M., Rafael, J. B. & Antonio, M. (2000). Aerobic–anaerobic biodegradation of beet molasses alcoholic fermentation wastewater, Process Biochemistry, Vol.38(9), 12751284. Aoshima, I., Tozawa, Y., Ohmomo, S. & Ueda, K. (1985). Production of decolorizing activity for molasses pigment by Coriolus versicolor Ps4a. Agric. Biol. Chem., 49, 2041-2045. Benito, G. G., Miranda, M. P. & De Los Santos, D. R. (1997). Decolorization of wastewater from an alcohol fermentation process with Trametes versicolor. Biores. Technol., 61, 33-37. Boopathy, R. (1992). Pelletization of biomass in a hybrid anaerobic baffled reactor (HABR) treating acidified wastewater. Biores. Technol., 40, 101-107. Boopathy, R. & Tilche, A. (1991). Anaerobic digestion of high strength molasses waste water using hybrid anaerobic baffled reactor. Water Resource, 25, 785-790. Chang, T. C. & Yang, W. L. (1973). Study on feed yeast production from molasses distillery stillage, Taiwan Sugar, 20(5), 422-427. Chaung, T. C. & Lai, C. L. (1978). Study on treatment and utilization of molasses alcohol slop, In: Proceeding of the International Conference on Water Pollution Control in Developing Countries, Thailand: Asia Institute of Technology, 475-480. Dahiya, J., Singh, D. & Nigam, P. (2001a). Decolourisation of synthetic and spentwash melanoidins using the white-rot fungus Phanerochaete chrysosporium JAG-40, Bioresource Technology, 78(1), 95-98. Dahiya, J., Singh, D. & Nigam, P. (2001b) Decolorization of molasses wastewater by cells of Pseudomonas fluorescens immobilized on porus cellulose carrier. Biores. Technol., 78, 111-114. Fahy, V., Fitzgibbon, F. J, McMullan, G., Singh, D. & Marchant, R. (1997). Decolorization of molasses spent wash by Phanerochaete chrysosporium. Biotech. Lett., 19, 97-99. Fitzgibbon, F., Fahy, V., McMullan, G.., Singh, D. & Marchant, R. (1998). The effect of phenolic acid and molasses spent wash concentration on distillery wastewater remediation by fungi. Process Biochem., 33, 799-803. Fogliano, V., Monti, S. M., Musella, T., Randazzo, G. & Ritieni, A. (1999). Formation of coloured Maillard reaction products in a gluten-glucose model system, Food Chemistry, 66(3), 293-299. Francisca Kalavathi, D., Uma, L. & Subramanian, G. (2001). Degradation and metabolization of the pigment-melanoidin in distillery effluent by the marine Cyanobacterium Oscillatoria boryana BDU 92181, Enzyme and Microbial Technology, 29(4-5), 246-251. Fujita, M., Era, A., Ike, M., Soda, S., Miyata, N. & Hirao, T. (2000). Decolorization of heattreatment liquor of waste sludge by a bioreactor using polyurethane foam-immobilized white rot fungus equipped with an ultramembrane filtration unit, Journal of Bioscience and Bioengineering, 90(4), 387-394. Ghosh, M., Ganguli, A. & Tripathi, A. K. (2002). Treatment of anaerobically digested distillery spentwash in a two-stage bioreactor using Pseudomonas putida and Aeromonas sp. , Process Biochemistry, 37(8), 857-862.

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Jagroop, D., Dalel, S. & Poonam, N. (2001). Decolourisation of molasses wastewater by cells of Pseudomonas fluorescens immobilised on porous cellulose carrier, Bioresource Technology, Vol. 78(1), 111-114 Jimenez, A. M, Borja, R. & Martin, A. (2003). Aerobic-anaerobic biodegradation of beet molasses alcoholic fermentation wastewater, Process Biochemistry, 38, 1275-1284. Kalavathin, D. F., Uma, L. & Subramanian, G.. (2001). Degradation and metabolization of the pigment–melanoidin in distillery effluent by the marine cyanobacterium Oscillatoria boryana BDU 92181. Enzyme and Microbial Technol., 29, 246-251. Kato, H. & Hayase, F. (2002). An approach to estimate the chemical structure of melanoidins, International Congress Series, 1245, 3-7(38). Kim, J. S. & Shoda, M. (1999). Decolorization of molasses and a dye by a newly isolated strain of the fungus Geotrichum candidum Dec 1, Biotechnology and Bioengineering, 62(1), 114-119. Kumar, P. & Chandra, R. (2006). Decolourisation and detoxification of synthetic molasses melanoidins by individual and mixed cultures of Bacillus spp. Bioresource Technology, 97(16), 2096-2102. Kumar, V., Wati, L., Banat, I.M., Yadav B.S., Singh D. & Marchant R. (1998). Decolorization and biodegradation of anaerobically digested sugarcane molasses spent wash effluent from biomethanation plants by white-rot fungi, Process Biochemistry, 33(1), 83-88. Kumar, V., Wati, L., Nigam, P., Banat, I. M., McMullan, G., Singh D. & Marchant, R. (1997). Microbial decolorization and bioremediation of anaerobically digested molasses spent wash effluent by anaerobic bacteria cultures. Microbios, 89, 81-90. Kwak, E. J., Lee, Y. S., Murata, M., Homma, S. (2005). Effect of pH control on the intermediates and melanoidins of nonenzymatic browning reaction LebensmittelWissenschaft und-Technologie, 38(1), 1-6. Lee, T. H., Aoki, H., Sugano, Y. & Shoda M. (2000). Effect of molasses on the production and activity of dye-decolorizing peroxidase from Geotricum candidum, J. Biosci. Bioeng., 89, 545-549. Miranda, M. P., Benito, G. G.., Cristobal, N. S. & Nieto C. H. (1996). Color elimination from molasses wastewater by Aspergillus niger, Biores. Technol., 57, 229-235. Miyata, N., Iwahori, K. & Fujita M. (1998). Manganese-independent and–dependent decolorization of melanoidin by extracellular hydrogen peroxide and peroxidase from Coriolus hirstus pellets. J. Ferment. Bioeng., 85, 550-553. Miyata, N., Mori, T. Iwahori, K. & Fujita, M. (2000). Microbial decolorization of melanoidin-containing wastewaters: Combined use of activated sludge and the fungus Coriolus hirsutus, Journal of Bioscience and Bioengineering, 89(2), 145-150. Mohana, S ; Desai, C. & Madamwar, D. (2007). Biodegradation and decolourization of anaerobically treated distillery spent wash by a novel bacterial consortium, Bioresource Technology, 98(2), 333-33. Monica, C., Garcia, M. T., Gonzalez, G., Pena, G. & Garcia, J. A. (2004). Study of colored components formed in sugar beet processing, Food Chemistry, 86(3), 421-433. Nakajima-Kambe, T., Shimomura, M., Nomura, N., Chanpornpong, T. & Takahara, T. (1999). Decolorization of molasses wastewater by Bacillus sp. under thermophilic and anaerobic conditions. J. Biosci. Bioeng., 87, 119-121.


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Ohmomo, S. Aoshima, I. Tozawa Y. & Ueda K. (1985b). Detection of lactic acid and amino acids from melanoidin decolorized by enzymes of Coriolus versicolor Ps4a. Agric. Biol. Chem., 49, 2767-2768. Ohmomo, S., Aoshima, I., Tozawa, Y., Sakurada, N. & Ueda, K. (1985a). Purification and some properties of melanoidin decolorizing enzymes, P-III and P-IV, from mycelia of Coriolus versicolor Ps4a. Agric. Biol. Chem., 49, 2047-2053. Ohmomo, S., Daengsubha, W., Yoshikawa, H., Yui, M., Kozaki, K., Nakajima, T. & Nakamura, I. (1988a). Screening of anaerobic bacteria with the ability to decolorize molasses melanoidin, Agric. Biol. Chem., 52, 2429-2435. Ohmomo, S., Itoh, N., Watanabe, Y., Aoshima, I., Tozawa Y. & Ueda K. (1985c). Continuous decolorization of molasses wastewater with mycelia of Coriolus versicolor Ps4a, Agric. Biol. Chem., 49, 2551-2555. Ohmomo, S., Kainuma, M., Kmimura, K., Sirianuntapiboon, S., Aoshima, I. & Atthasampunna, P. (1988b). Adsorption of melanoidin to the mycelia of Aspergillus oryzae Y-2-32, Agric. Biol. Chem., 52, 381-386. Ohmomo, S., Kaneko, Y., Sirianuntapiboon, S., Somchai, P., Atthasampunna P. & Nakamura, I. (1987a). Decolorization of molasses wastewater by a thermophilic strain, Aspergillus fumigatus G-2-6, Agric. Biol. Chem., 51, 3339-3346. Ohmomo, S., Yoshikawa, H., Nozaki, K., Nakajima, T., Daengsubha, W. & Nakamura, I. (1987b). Continuous decolorization of molasses wastewater using immobilized Lactobacillus hilgardii Cells, Agric. Biol. Chem., 52, 2437-2441. Raghukumar, C., Mohandass, C., Kamat, S. & Shailaja, M. S. (2004). Simultaneous detoxification and decolorization of molasses spent wash by the immobilized white-rot fungus Flavodon flavus isolated from a marine habitat, Enzyme and Microbial Technology, 35, 197-202. Raghukumar, C. & Rivonkar, G. (2001). Decolorization of molasses spent wash by the whiterod fungus Flavodon flavus, isolated from a marine habitat, Appl. Microbial Biotechnol., 55, 510-514. Sirianuntapiboon, S., Phothilangka, P. & Ohmomo, S. (2004a). Decolorization of molasses wastewater by a strain No. BP103 of acetogenic bacteria, Journal of Bioresource Technology, 92, 31-39. Sirianuntapiboon, S., Sihanonth, P., Somchai, P., Atthasampunna P. & Hayashida S. (1995). An absorption mechanism for the decolorization of melanoidin by Rhizoctonia sp. D-90. Biosci. Biotech. Biolchem., 59, 1185-1189. Sirianuntapiboon, S., Somchai, P., Ohmomo S. & Atthasampunna P. (1988a). Screening of filamentous fungi having the ability to decolorize molasses pigments. Agric. Biol.Chem., 51, 387-392. Sirianuntapiboon, S., Somchai, P., Sihanonth, P., Atthasampunna, P. & Ohmomo, S. (1988b). Microbial decolorization of molasses waste water by Mycelia sterilia D90. Agric. Biol. Chem., 52, 393-398. Sirianuntapiboon, S., Zohhsalam, P. & Ohmomo, S. (2004b). Decolorization of molasses wastewater by Citeromyces sp. WR-43-6, Process Biochem., 39, 917-924. Sirianuntapiboon, S. & Chairattanawan, K. (1998). Some properties of Coriolus sp. No. 20 for removal of color substances from molasses wastewater, Thammasart Int. J. Sc. Tech., 3, 74-78.

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Tamaki, H., Umetani, I., Tsuchida, H., Komoto, M., Arita I. & Hiratsuka, N. (1985). Decolorization of cane sugar molasses by action of Basidiomycetes (Part 1) - Screening of Basidiomycetes having high decolorization activity, Mem. Grad. School Sci. and Technol., Kobe Univ., A-3, 63-70. Terasawa, N., Murata, M. & Homm S. (2000). Decolorization of brown pigment in foods by immobilized mycelia of Coriolus versicolor IFO 30340 and Paecilomyces canadensis NC-1, J. Food Sci., 65, 870-875. Underkofler, L. A. & Hickely, J. (1954). Alcohol Fermentation of Molasses Industrial Fermentation, industrial Fermentation; Chemical Publishing Company, New York, 1-20. Watanabe, Y., Sugi, R., Tanaka, Y. & Hayashida, H. (1982). Enzymatic decolorization of melanoidin by Coriolus sp. No. 20, Agric. Biol. Chem., 46, 4623-1630. Yaylayan, V. A. & Kaminsky, E. (1998). Isolation and structural analysis of maillard polymers: caramel and melanoidin formation in glycine/glucose model system, Food Chemistry, 63(1), 25-31.



Chapter 8

WASTEWATERS FROM OLIVE OIL INDUSTRY: CHARACTERIZATION AND TREATMENT

1

L. Nieto Martínez1, Gassan Hodaifa*2, Mª Eugenia Martínez1 and Sebastián Sánchez3

University of Granada, Department of Chemical Engineering, 18071 Granada, Spain. 2 Complutense University of Madrid, Department of Chemical Engineering, 28040 Madrid, Spain. 3 University of Jaén, Department of Chemical, Environmental and Materials Engineering, 23071 Jaén, Spain.

ABSTRACT Countries in the Mediterranean basin are among the main producers of olive oil. The elaboration of olive-oil is typically carried out by small companies in small facilities. The olive-oil plants produce high and variable amounts of residual waters of olives and oliveoil washing (OMW) that has a great impact in the environment. According to the procedure used different types of OMW with different chemical oxygen demand can be generated, the OMW from the three phase process (COD = 150 g O2 L-1) and the OMW from olives washing (COD = 0.8-4.5 g O2 L-1) and olive oil washing (COD = 1.1- 6 g O2 L-1) in the two-phase process. The uncontrolled disposal of OMW is a serious environmental problem, due to its high organic load, and because of its high content of microbial growth-inhibiting compounds, such as phenolic compounds. The improper disposal of OMW to the environment or to domestic wastewater treatment plants is prohibited due to its toxicity to microorganisms, and also because of its potential threat to surface and groundwater. These waters normally are stored in great rafts of accumulation for their evaporation during the summer. This solution among others until the moment dose not represent a definitive solution for this problem, especially as the administrations more and more demanding the preparation of this spill and the constructive quality of the rafts. Today, effective technologies have been proposed such as the chemical oxidation process using ferric chloride catalyst for the activation of H2O2 as a treatment of OMW produced from two-phase process. In the previous works the authors have described the *

Corresponding author. E-mail: [email protected] (G. Hodaifa), Tel.: +34 913 944 115; Fax: +34 913 944 114.

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L. Nieto Martínez, Gassan Hodaifa, Mª Eugenia Martínez et al. experimental results on laboratory-scale. These results have been taken to pilot-industrial scale, making the chemical oxidation in the optimum conditions of operations: [H2O2] = 5% (w/v), using a ferric chloride catalyst with a relation of [FeCl3]/[H2O2] = 0.25 (w/w), at OMW pH and environmental temperature. The final average value of COD obtained next to 370 mg L-1 (%CODremoval = 86.2%), and the water obtained can be destined to irrigation or disposed directly to the municipal wastewater system for their tertiary treatment. OMW from three-phase process does not allow direct chemical and biological purification for its content in phenolic compounds and generally used natural and forced evaporation process. Another way of using is the application of OMW nutrients to the growth of microorganisms such as microalgae.

1. INTRODUCTION Olive oil extraction produces vast amounts of liquid and solid wastes. The elimination of olive mill wastewater (OMW) is one of the main environmental problems related to the olive oil industry in Mediterranean countries, where Spain and Italy are the greatest producers. The OMW was genrated during a few months of the year (November-February). This liquid waste comes from the vegetable water of the fruit and the water used in the different steps of oil production and contains olive pulp, mucilage, pectin, oil, etc. suspended in a relatively stable emulsion. Olive oil is obtained by the traditional method of discontinuous pressing or by the continuous centrifugation of a mixture of milled olives and hot water. In both systems three phases are produced: (i) olive oil; (ii) solid by-product (olive pomace); and (iii) aqueous liquor, which represent 20, 30 and 50%, respectively, of the total weight of processed olives. The disposal of highly pollutant olive by products, especially the aqueous liquor, is an important environmental problem which needs to be solved. The aqueous liquor comes from the vegetation water and the soft tissues of the fruits. The mixture of this by-product with the water used in the different stages of oil elaboration constitutes olive mill wastewater (alpechin in Spanish). The quantity of OMW produced in the process ranges from 0.5 to 2 L kg-1 of olive, depending on the oil extraction system. In the main olive-oil-producing countries the implementation of systems based on the olive-pomace centrifugation has become more widespread. These include three- and twophase centrifugation systems. Effluents from two-phase systems are composed essentially by olive oil and olive-mill wastewater. The olive-oil and the wastewater must be separated. Continuous three phase extraction systems are still widely used in olive oil mills, especially in Italy, where in most cases they have not yet been replaced by more recent twophases systems, which involve a reduction of OMW volumes but an increased concentration in organic matter [1]. Three phases extraction systems involve the addition of large amounts of water (up to 50 L/100 kg olive paste), resulting in the worldwide production of more than 30 millions m3 per year of OMW [2]. This represents a great environmental problem, since this by-product is characterized by a high organic load; among the different organic substances found in OMW, including sugars, tannins, phenolic compounds, polyalcohols, pectins and lipids [3]. The toxicity, the antimicrobial activity and the consequent difficult biological degradation of OMW are mainly due to the phenolic fraction [4]. The partition coefficients (oil/water) of most olive phenols, ranging from 6 10-4 to 1.5 are in fact in favour of the water phase: the olive fruit is very rich in phenolic compounds, but only 2% of

Wastewaters from Olive Oil Industry: Characterization and Treatment

201

the total phenolic content of the olive fruit passes in the oil phase, while the remaining amount is lost in the OMW (approximately 53%) and in the pomace (approximately 45%) [5]. On the other hand, the phenolic compounds, which are very abundant in the OMW and are the major responsible of their polluting load, are characterized by a strong antioxidant activity [6]. The production of olive oil generates large volumes of wastes that vary in composition depending on which of the three production systems is used. The traditional method, which is based on the combined use of a crusher and hydraulic press, does not require the addition of water and yields a very high-quality olive oil. However, the system presents significant disadvantages to bulk production such as elevated labour requirements and a discontinuous process. This system has almost disappeared in many production areas. The three phase ‗continuous system‘, on the other hand, has many advantages, such as low labour costs and continuous production. However, it has disadvantages in the amount of wastewater produced. In some countries this system has almost disappeared due to the introduction of the two-phase decanter system. The two-phase decanter system is the newest system and is able to operate without water and thus dramatically reduces processing costs and the amount of wastewater produced. However, the semi-solid cake produced by this method has a high moisture content (55– 60%). One of the main disadvantages of the waste from 2- and 3-phase decanter systems is the presence of polyphenolic compounds in both the cake and the vegetation water. The presence of polyphenols limits the use of cake in animal food, since it can cause digestion problems in cattle [7]. Polyphenols also have been identified as being responsible for damage to soil when used for irrigation since they inhibit the growth of soil microflora [8]. The semi-solid waste from the two-phase decanter system cannot be purified by traditional methods so alternative solutions such as incineration and composting have been adopted for its treatment [9]. To solve the problems associated with OMW, different elimination methods have been proposed based on evaporation ponds, thermal concentration and physical-chemical and biological treatments, as well as its direct application to agricultural soils as an organic fertilizer. However, the most frequently used methods nowadays are the direct application to agricultural soils and storage in evaporation ponds, which produces a sludge. The disposal of OMW is becoming a critical problem in the Mediterranean countries. Traditionally the olive oil production sector was made up of a large number of small mills widespread throughout the production area. The volume of OMW produced in each mill was very small and its disposal was very widespread. These effluents rarely reached the water courses and their negative effects were only noticed in those places close to the mills. During the 1950s the industrialization of the olive oil production sector started, with the concentration of small producers in co-operatives and the creation of big factories with high milling capacities. Larger mills meant a greater local concentration and volume of OMW, which was discharged into the rivers without treatment. For this reason in 1981 the Spanish Government prohibited the discharge of OMW into the rivers and subsidized the construction of ponds for its storage during the milling period and the evaporation of its water during the warm Andalusian summer. Chemical oxidation based on Fenton‘s reagent (hydrogen peroxide in the presence of ferric salts) has been used to decompose organic and inorganic compounds in the laboratory, and also real effluents from several sources such as the textile and chemical industry, or

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L. Nieto Martínez, Gassan Hodaifa, Mª Eugenia Martínez et al.

refineries [10]. The process is based on the formation of various oxidizing agents which degrade pollution in wastewaters, but the nature of these species is under discussion [11,12]. Assays by Fenton at the end of the 19th century demonstrated that hydrogen peroxide and ferrous-salt solutions could oxidize tartaric and malic acids as well as other organic compounds. Later, Haber and Weiss [13] suggested that reaction (1). These radicals could react via the oxidation reaction) or via the attack on organic matter:

Fe2

Fe3

H2O2

Fe2

HO HO ; k 76Lmol-1 s-1

Fe3

HO

RH HO H2O

OH was formed through the of Fe2 to Fe3 (unproductive

(2)

HO

ROH H3O

(1)

oxidizedproducts

(3)

At pH < 3.0, the reaction is autocatalytic, since the Fe3+ decomposes H2O2 to O2 and H2O through a chain reaction:

Fe3

Fe OOH2

H2O2

Fe OOH2 Fe2

H2O2

H

HO2 Fe2

HO2 Fe3 HO H2O2

(5)

HO HO

(6)

HO2

(7)

O2 H

(8)

H2O HO2

(9)

Fe3

HO2 Fe2

(4)

Fe3

Fe2

The process is potentially useful to remove pollutants, as it is very effective in generating

HO . However, an excessive amount of Fe2 ions could trap or consume them (reaction 2), as happens with halogens, H2O2, or the radical perhydroxyl:

HO HO2

O2 H2O

(10)

Today, it is thought that other species of Fe(IV) or Fe(V) (such as FeO2 and ferrule complexes), are the actual active agents of the process. In the presence of peroxide, the Fe2+ concentration is low compared to the Fe3+concentration, since the reaction (4) is slower than reaction (6). Both radicals, HO and HO2 , react with organic matter, but HO2 is less reactive. The speed constant for the reaction of ferrous ion with H2O2 is high, and Fe(II) is oxidized to Fe(III) after a few seconds or minutes in excess H2O2. Therefore waste destruction through Fenton‘s reagent is thought to be a process catalysed only by Fe(III)– H2O2 and Fenton‘s reaction with an excess of H2O2 is essentially a process of Fe3+/H2O2. For


203

this reason these kinds of reactions also occur with transition metal ions such as Fe(III) or Cu(II), and they are known as Fenton-type reactions:

Men

H2O2

Me(n 1)

HO HO (Me = Fe3+, Cu2+)

(11)

As a general rule, the degree and total mineralization speed are independent of the initial oxidation state of the Fe. However, the initial efficiency and speed of demineralization are higher when starting from Fe(II). On the contrary, Fe(III) salts produce an stationary Fe(II) concentration. In this case a pH lower than 2.8 must be used. Fenton‘s process has been effective for the degradation of aliphatic compounds and aromatic chlorates, PCBs, nitro aromatics, azoic colorants, chlorobenzene, phenols, chlorate phenols, chlorates, octachloro-p-dioxin, and formaldehyde. Only a few compounds cannot be attacked by this reagent, such as acetone, acetic acid, oxalic acid, paraffins, and organochlorinated compounds. This reagent is a good oxidizer for herbicides and other soil pollutants such as hexadecane or Dieldrin. It is used to decompose dry-cleaning solvents and to decolour wastewater containing different kinds of colorants and other industrial wastes, reducing its COD. Fenton‘s reaction has been successfully applied to reduce the COD of municipal and underground water and also for the treatment of lixiviates. It is highly useful for the pre-treatment of non-biodegradable compounds. The advantages of this method are the following: Fe2+ is an abundant non-toxic substance, and hydrogen peroxide is easy to handle and environmentally friendly. Unlike other oxidative techniques, chlorinated compounds do not result and there are no masstransfer limitations because the system is homogeneous. The reactor design for the technological application is very simple. However, it requires continuous and stoichiometric addition of Fe2+ and H2O2 as well as a high Fe concentration. It is important to take into account that excessive Fe2+ amounts may cause the proper conditions for HO to be trapped, according to the above-mentioned equations. At pH > 5.0 particulate Fe3+ is generated, although this produces sludges demanding later management, and, at the end of the process, water is usually alkalinized by means of simultaneous addition of flocculants to remove waste iron. The molar stoichiometric H2O2/substrate reaction should theoretically oscillate between 2 and 10 if a reagent is used for the destruction of soluble compounds. In practice, however, this relation may reach values of up to 1000, since the destructible compound of many environmental samples is usually accompanied by other compounds that can be attacked by HO . The peroxide/Fe/compound relation may be maintained by intermittently adding oxidizer or be fixed at the beginning of the reaction. In the laboratory, the metal aggregate is traditionally made in the form of pure ferrous salts, but high prices of these salts hamper their use at the industrial level. Instead of salts, Fe2(NH4)2SO4 containing 20% active iron is used. Other iron compounds have been used, including some solids such as goethite to remove trichloroethylene [14]. In such cases total mineralization is not reached, but some intermediaries resistant to the treatment are created (carboxylic acids), that react slowly with HO , and there is a predomination of the unproductive reaction where ferrous ion is converted to ferric ion. More toxic products than the initial ones, such as quinones, can sometimes form, and these must be thoroughly controlled.

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Rivas et al., [15] have recently studied the oxidation of p-hydroxybenzoic acid (PHB) with Fenton‘s reagent, a pollutant usually found in effluents generated by the food industry. An optimal molar relation Fe/H2O2/pHB of around 5.10-3/2.65/1.10-2 was established. The addition of tert-butyl alcohol, an HO trap, had very little influence on the process, and therefore it is interpreted that other radicals were present, as mentioned above. The formation of phenol, catechol, hydroquinone and trihydroxybenzene indicates that a degradation mechanism acted via decarboxylation. They also studied the action on atrazine, its derivatives, and other pesticides. Microalgae contribute to sustainability in environmental conservation by the photosynthetic fixation of CO2 from atmosphere and gaseous industrial effluents, as well as through the consumption of different C, N, and P compounds in urban and industrial wastewaters. These actions of microalgae, either naturally or induced by humans, are possible due to the different nutritional modes presented by most microalgae. The opposite situations are autotrophic and heterotrophic nutrition. Diluted OMW from the three-phase system can be used as nutrient medium for the growth of Scenedesmus obliquus. This study report the characterization of different wastewaters from modern olive oil industry. Concretely, the use of Fenton‘s reaction and microalgae to treatment the wastewater from the two and three phase process, respectively.

2. EXPERIMENTAL 2.1. Wastewater In the Andalusian provinces of Jaén and Córdoba (Spain) wastewater samples were collected from several oil mills operating with olive-cleaning and vertical-centrifugation equipment of different trademarks.

2.2. OMW Treatment by Fenton’s Reaction After the analysis and characterization of the samples, one with high chemical-oxygen demand was collected, and a mixture of olives and olive-oil wastewaters in a proportion of 1:1 (v/v) was prepared in the laboratory. The pH, electric conductivity, and COD were determined. Chemical oxidation based on the Fenton‘s reagent was used for the treatment of the effluents generated by olive-oil mills operating with a continuous two-phase system. Optimal operating conditions at room temperature included the hydrogen peroxide concentration, as well as the catalyzer concentration and type, and the coagulant concentration was identified previously [16,17]. The best catalyst ferric chloride (efficiency and low cost) from among different compounds was chosen. The COD value of water at the end of the chemical oxidation at different concentrations (5, 7.5, 10, and 30% w/v) was determined for each catalyst, maintaining a relationship [catalyst]/[H2O2] = 0.05 (w/v).


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The [catalyst]/[H2O2] (w/w) was varied between 0.1 and 1.5 with the aim of determining the optimum value for the maximum degradation of organic matter and phenol compounds. The oxidation process was completed with pH-neutralization and separation phases (solidliquid) to produce the irrigation water. The experiments were made in a stirred tank reactor. During the experiments, the pH, temperature, and electric conductivity values were determined in relation to time. 500 mL of wastewater with a COD = 7.2 g O2/L, electric conductivity = 1.52 mS/cm and a pH = 4.6 was mixed with the appropriate amount of ferric catalyst and H2O2. The catalyst and H2O2 dissolution were added gradually during the course of oxidation. The mixture was stirred for 2.5 h, which is enough time to complete the oxidation. The reaction is exothermic only when a catalyst is used. The solid phase and the liquid phase were separated by decanting. The final COD in the liquid phase was determined and from this value the reduction percentage in this parameter was calculated.

2.3. OMW Treatment by Microalgae The freshwater microalga used was Scenedesmus obliquus CCAP 276/3A, supplied by Culture Centre for Algae and Protozoa, Oban (United Kingdom). The experiments were performed in stirred batch tank reactors on a laboratory scale. The photobioreactors, 5 total, were situated in a culturing facility described elsewhere [18,19]. Each reactor had 0.75 L capacity (70 mm in diameter and 200 mm in height) with thermostatically controlled water circulation, magnetic stirring, and aeration. The culture medium wastewater was prepared with ultrapure water (Millipore, mod. Milli-Qplus) for concentrations of 2.5%, 5%, 10% and 20% OMW (v/v). The pH was adjusted to an initial value of 7.0 and maintained over the course of the culture. The working temperature was 25ºC. All the cultures were mechanically stirred at 350 rpm and supplied air sterilized by filtration (0.2 m pore size), at a specific rate of 1 v/v/min. The illumination was continuous, at an intensity of 298 E m-2 s-1 (QSL 2100, Biospherical Instruments, Inc.). The mean value of the initial biomass concentration was 0.0124 g L-1 and the standard deviation SD = 0.0080 and the initial cells number was 0.315 109 cell mL-1 and SD = 0.197 109.

3. RESULTS 3.1. Characterization of OMW 3.1.1. OMW from two phase process The physical-chemical composition of wastewater from the olive-oil industry changed during the collecting campaign for several reasons, especially for the type of olive variety, geographic location, form of collection and if olive soil or not. In the Table 1 are reflected the values for the parameters analyzed in some of the wastewaters of examined washer machines of olives. It is observed that almost all the waters

206


practically fulfil the values demanded in the normative one (The waters should not overcome the values for the following parameters: pH = 6-9, suspended solids = 600 mg L-1, BOD5 = 1.000 mg O2 L-1, COD = 1.000 mg O2 L-1, Spain legislation). Only one of them has an inferior pH to 6 units. The suspended solids are always inferior to 600 mg L-1. Only three samples overcome allowed COD and BOD5. It is deduced that, in general, most of the present total solids is from mineral character to the being the superior percentage of ashes to the percentage of organic matter. Only in a case flotation is detected, that is to say a layer floating whose composition denotes that it is probably and reasonable oil of the sweat of broken or damaged olives. A treatment of chemical oxidation, with energetic oxidizers, with a later alkaline correction of pH followed by a sedimentation or filtration would be enough, to adapt the water to the demanded requirements. After a short period of natural sedimentation, it would lose a part of the small fraction of suspended solids and it could be clever for its use in watering. In the Table 2 are reflected the values of the parameters analyzed for wastewater of vertical centrifuges of olive oil of the same almazaras for those that we are took waters of olive laundry. Contrary to that exposed previously for the waters of olive washers, in this case all the samples overcome the reference values, to exception of the suspended solids since is not detected sedimentation neither separation of phases. The muddiness of the samples should be caused by the fine emulsion of oil in water. In all the cases the COD is bigger than the allowed values. As expected, in many cases the quantity of total solids is smaller than in the wastewater of olive washers and in this case the percentage of the organic matter is bigger than the percentage of the mineral matter. As it was already exposed in the introduction the biggest quantity in organic matter of these waters it is due to the own composition of the oil and they should be rich in phenolic compounds, natural and recalcitrant antioxidants to their microbial degradation and therefore their concentration will be reflected difficultly in the figures of BOD5 and if on the contrary in those of COD. It seems therefore that this water is the main wastewater to try. A priori it has been thought of subjecting it in the first place and for their sour character to processes treatment of chemical oxidation, with energetic oxidizers, H2O2 with iron salts (Fenton treatment). The first experiments carried out lead to an important decrease of the colour and the COD, as well as to an increase of the pH whose value is inside the allowed limits (pH < 6). Table 1. Parameters of wastewater of olive washers. Sample 1 (Co) 2 (Co) 3 (Co) 4 (Co) 5 (J) 6 (Co)

pH 6.34 5.65 6.22 6.66 6.02 6.03

Total solids (%) 0.27 0.49 0.23 0.18 0.28 0.87

Ashes (%) 0.17 0.27 0.07 0.08 0.21 0.53

Organic matter (%) 0.10 0.22 0.15 0.10 0.07 0.34

Suspended solids (%) n.s.f n.s.f 0.005 0.006 0.006 n.s.f

Sediment Solids (%) n.d. n.d. 0.225 0.174 0.274 n.d.(Flot.)

BOD5 mg L-

COD mg L-

500 1820 348 148 121 1145

810 4858 1640 223 810 4494

1

1

n.s.f = Separation of phases is not observed after one hour; n.d = Sedimentation is not detected; Flot. = Flotation is observed with a superficial layer. CO = Cordoba (Spain); J = Jaén (Spain).


207

Table 2. Parameters of wastewater of vertical centrifuges. Sample 1 (Co) 2 (Co) 3 (Co) 4 (Co) 5 (J) 6 (Co)

pH 5.69 5.40 5.67 5.73 5.11 5.16

Total solids (%) 0.18 0.15 0.24 0.33 1.47 0.59

Ashes (%) 0.04 0.05 0.04 0.07 0.05 0.10

Organic matter (%) 0.14 0.10 0.20 0.26 1.42 0.49

Suspended solids (%) n.s.f. n.s.f n.s.f n.s.f n.s.f n.s.f

Sediment Solids (%) n.d n.d n.d n.d n.d n.d

BOD5 mg L-

COD mg L-

790 520 465 690 915 790

2875 5935 3806 4231 12078 10931

1

1

n.s.f = Separation of phases is not observed after one hour; n.d = Sedimentation is not detected; Flot. = Flotation is observed with a superficial layer CO = Cordoba (Spain); J = Jaén (Spain).

Table 3. Parameters of wastewater from three phase process. Parameters pH Moisture (%) Total solids (%) Organic substances (%) Fats (%) Ash (%) BOD5 (g O2 L-1) COD (g O2 L-1) Conductivity (mS cm-1) % C (% dry matter) % N (% dry matter) % H (% dry matter) % O (% dry matter) % S (% dry matter) % P*** % K*** Polyphenols (% dry matter)*** Carbohydrates (% dry matter)***

Raw OMW* 5.4 93.4 6.6 5.8 1.54 0.9 42.0 151.4 7.9 50.9 1.4 7.1 40.5 0.1 0.19 5.24 2.21 12.2

Filtered OMW* 5.6 95.4 4.6 3.9 0.8 n.a** n.a** 7.1 42.0 1.1 5.3 51.5 -

*OMW, Wastewater from the three phase process of olive oil extraction (3 phases: Solid + Liquid + Liquid) **n.a., not available ***Reported by Paredes et al. (1999)

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3.1.2. OMW from three phase process The three-phase process, still used in many olive-oil extraction mills, generates a residual effluent (OMW) that has a high organic load. OMW, a dark brown wastewater, contains vegetable water from the olive fruit itself, from the washing of the fruit, from the washing of the olive oil, and from other activities in the mill. This wastewater is markedly acidic. Although the BOD5 and COD values are 21 and 13 fold greater than those found in the residual waters produced by the two-phase process, respectively. The filtration of the raw wastewater decreased the C and N content by 17.5 and 21.4%, respectively. OMW has a high content in total solids, reaching 66 g L-1 compared to 5 g L-1 for OMW from two phase (Table 3) and 1.2 g L-1 for untreated, highly loaded urban sewage. Its fatty content accounts for 1.54%. Table 3 also lists the contents P, K, polyphenols, and carbohydrates provided by Paredes et al. [20]. The ratios H:C, N:C, O:C, and P:C of the OMW were 0.13, 0.026, 1.22 and 0.005, respectively, while the ratios of microorganism biomass according to the elemental formula of Harrison [21] C H1.64 N0.16 O0.52 S0.0046 P0.0054 were 0.14, 0.19, 0.69, and 0.014, indicating a certain deficiency in N and P in the wastewater. The ratio N:P of the OMW and biomass 5.8:1, 13.6:1 reflected a larger N deficit.

3.2. OMW Treatment by Chemical Oxidation (Fenton’s Reaction) In all the experiments the values of pH, electrical conductivity and temperature was determined with the course of the chemical oxidation reaction (Figure 1). A temperature increase was detected in all the experiments, due to the strong exothermal reaction. This increase over the ambient temperature was determined for the different peroxide concentrations used. Electrical conductivity also increased with the course of the oxidation reaction, this increase is logical considering that the amount of catalyst added (Fe source) increased during the experiment. Moreover, it is important to point out the decrease in the pH to values around 3.0, which is an optimal value for Fenton‘s reaction (Figure 1).

0

pH, Conductivity (mS/cm) and T ( C)

45 40 35 30 8 6 4 2 0 0

20

40

60

Time (min)

Figure 1 The values of pH, electric conductivity, and temperature variation with the course of chemical oxidation reaction (□ pH, ● electric conductivity and ∆ temperature) maintaining a rate [catalyst]/[H2O2] = 0.05 w/v, catalyst used Fe(NH4)2(SO4)6H2O, temperature 25 ºC, [H2O2]initial = 5% w/v.


209

Table 4. Final values of COD, purification efficiency and sediment solids determined for the water treated by chemical oxidation reaction (initial conditions: COD = 7.2 g O2/L, electric conductivity = 1.5 mS/cm, T = 25 ºC). CODFinal (g O2/L)

Ferric chloride

5.0 7.5 10.0 30.0

1.27 1.46 1.44 2.38

Purification Efficiency (% COD) 82.3 79.7 80.0 76.0

4000

12

3500 COD (mg O2/L)

Sediment solids v/v 0.80 -

10

3000 8

2500 2000

6

1500

4

1000 2

500 0 0.0

0.2

0.4

0.6

0.8

1.0

total phenols (mg/L)

[H2O2] % (w/v)

[Fe] or

Catalyst applied

0 1.2

FeCl3/H2O2 (w/w)

Figure 2. Relationship between the values for COD (■), [Fe] (▲) and total phenols (○) of treated water and the [FeCl3]/[H2O2] relationship. Operating conditions: initial values of COD = 4104 mg O2/L, total phenols = 290 mg/L, and [Fe] = 5 mg/L.

Table 4 shows the degradation results expressed as the final values of COD and the depuration efficiency (reduction percentage in the final COD) for ferric chloride salt. Also, Table 4 shows the sediments solid determined after the neutralization of water treated and separation test in Imhoff cone during 1 h. The best concentrations of hydrogen peroxide to work was varied in the range from 5 to 10% w/v, where the depuration efficiency has varied between 76 and 82%. The highest value of sediment solids (0.8 v/v) has been obtained. For the determination of the best catalyst/H2O2 relation, a series of experiments was performed using ferric chloride. The relation was varied between 0.1 and 1.5. Figure 2 shows a downward trend of all the parameters for the values of the Fe/H2O2 relation between 0.25 and 0.5 (w/w). For this reason, the following experiments were performed with Fe/H2O2 values of 0.25, in order to reduce catalyst consumption. From Figure 1, it can be deduced that the pH fell from 4.0-5.0 of the treated water to values of around 3.0, at which the reaction occurs optimally. For this reason, a neutralization process of the oxidized water was performed in order to adjust the pH to neutrality, as the use regulations demand. At the same time, the iron ion found was removed as hydroxide, which is difficult to precipitate. For the precipitation, several flocculants were tested and an oil-based

210


anionic one from the Nalco Company was chosen. For the determination of the concentration needed, several experiments were performed to determine the influence of the flocculant concentration with relation to the time necessary for settlement in an Imhoff cone, the COD, and the remaining amount of Fe in the treated water. The resulting values were indicated no significant influence on the COD, while the Fe concentration decreased to a concentration of 1 mg/L and, from this value, the concentration remained stable. As mentioned above, the experiment was conducted at a pilot-plant scale (3-5 m3 h-1) in S.A.T. Olea-Andaluza olive-oil mill factory in Baeza, Jaén (Spain). In this olive-oil mill factory, function and verification tests of the results found at the laboratory scale were performed. Only the environmental conditions changed, because, although the plant was roofed in, it was exposed to the elements (environmental temperature between 1-7ºC during the mornings). The plant worked intermittently during the 2004/05 harvest and subsequently was automated in order to work continuously for the 2005/06 season. The process in the plant consisted of: 1. Natural sedimentation in independent holding pools for water from olives and olive-oil washing; 2. Chemical oxidation tank, 3. Neutralization tank and coagulant addition; 4. Separation of solid and liquid unite by decanting; 5. Filtering unite. As explained above, the plant worked with mixtures of approximately 1:1 (v/v) of wastewater from olives and olive-oil washing. Table 5 shows the values of the parameters analysed in all the streams. The working conditions except the temperature (which was the ambient temperature) were deduced in the laboratory: a relation of [FeCl3]/[H2O2] of 0.25 (w/w), neutralizing agent NaOH, and coagulant concentration 1 mg/L. Some 4-5 m3 per charge were used intermittently, the oxidation time being 2.5 h. The final filtration was performed first with sand and afterwards with a biomass filter (olives stone). Also, Table 5 shows the same parameters for oxide water at the outlet of the reactor. A COD value decrease of about 61% and the total phenolic compound content of about 68% can be deduced. At the same time, there was an expected increase in electrical conductivity caused by the addition of a catalyst; part of that increase was eliminated in the stage of decantation and filtration. At the exist of pilot plant practically all the phenolic compounds were removed, and the Fe decreased by about 78% and COD value by about 76%. Independently of what happened in the neutralization (Fe(OH)3 precipitation), which in principle should not carry organic matter, these decreases were due to the filtration process used, in which the biomass fill of one of the filters (olives stone) acted as an adsorbent of heavy metals. The water obtained was taken to a waterproof storage pool for use in irrigation. Today, the plant is computerized for continuous functioning and its treatment capacity is about 3 m3 h-1 that is, enough to treat the wastewater produced by an olive-oil mill factory with a capacity of approximately 600.000 kg olives day-1, which corresponds to a medium/large olive-oil mill factory.

3.3. OMW from Three Phase Process Treatment by Microalgae For all the experiments, growth curves showed no lag phases, the first phase being exponential growth followed by a phase of linear increase in biomass with time. In some experiments, the stationary phase was observed, and even the onset of cell death.


211

Table 5. Characterization of industrial wastewaters from olives and olive-oil washing, wastewater in the oxidation reactor, waters at the exit of oxidation reactor and at the outlet of pilot plant. Wastewater in the oxidation reactor* 6.10 2.25 2763 282.6 7.74 555 7.2

pH Conductivity, mS/cm COD, mg O2/L Total phenols, mg/L [Fe], mg/L [Cl], mg/L [H2O2]residual, mg/L Total pesticides, µg L1

Water at the exit of oxidation reactor 7.0 4.02 1077 90.1 5.87 716 615 n.d.**

Water treated at the exit of pilot plant 7.4 3.91 661 0.005 1.67 834 n.d.**

*This wastewater formed mixing the wastewaters from olives and olive-oil washing with the ratio of 1 v/v.

The specific growth rates, μ = d(lnx)/dt, during the exponential-growth phases, μm, was calculated according to Eq. (12)

ln

x x0

(12)

a μm t

were plotted against the initial OMW concentration So, expressed in % (v/v), Figure 3. 0.06

%OMW (v/v) WC RL WF UW

0.05

0.03

m

h

0.04

0.02 0.01 0.00 0

5

10

15

20

25

% [S0], v/v

Figure 3. Variation of the maximum specific growth rates with the initial concentration of OMW (WC: OMW without color, RL: Rodríguez-López medium, WF: OMW without fatty matter, UW: urban wastewater from secondary treatment as the medium culture). Common conditions: aeration 1 v/v/min, agitation speed 0 350 rpm and illumination intensity = 298 E m-2 s-1.

The variation of μm with So, appears to indicate an inhibitory effect in the wastewater. This was to be expected, as the OMW may contain fats, organic acids, phenolic compounds, and the remains of pesticides, which are known to harm microalgal growth [22].

212


From the different inhibition models by substrate and toxicity assayed, the one that best reproduced the experimental variation observed was the Teissier [23] one of inhibition by substrate, Eq. (13), solid line in Figure 3. Table 6. Reduction in the contaminant load of the OMW. [S0] (%OMW v/v) 2.5 5 10 20 WF WC

x-x0 (g L-1) 0.0156 0.0419 0.0876 0.0577 0.0506 0.113

BOD5, initial (mg O2 L-1) 1100 2200 4400 8800 2100 2100

BOD5, end (mg O2 L-1) 190 1650 1900 3100 849 950

BOD5,removal (mg O2 L-1) 83 550 2500 5700 1251 1150

Initial concentration of the biomass at t = 0 h was 0.0124 g L-1.

μm μm, max e

S0 Ki

-

e

S0 Ks

%BOD5,removal 82.7 25.0 56.8 64.8 59.6 54.8

BOD5, removal/x-x0 (g g-1) 5.3 13.1 28.5 98.8 24.7 10.2

(13)

Though the values μm, max = 0.032 h-1 ([S0] = 10 v/v), Ki = 87%, and Ks = 2.83% are consistent with what observed. At low initial OMW concentration the S. obliquus has a high affinity for the limiting quantity of the substrate, resulting in a low Ks value. Roughly speaking it is the division between the lower concentration range where μm is strongly (linearly) dependent on S0, and the higher range, where μm becomes independent of S0. The high value of Ki (87% v/v) indicated that the inhibition effect can be observed only in a high concentration range (cultures with OMW > 10%). All the cultures received the same aeration level (1 v/v/min), agitation velocity and the illumination intensity kept the same, 298 E m-2 s-1, but the attenuation of the light, by the coloration of the medium, was greater the higher the %OMW, and thus the variation expected, in μm , being light the limiting factor. This fact was confirmed in the control

experiment WC (OMW without color) where the μm value was increased to 0.04 h-1 for the same culture concentration (5% v/v). But the main factor limiting growth was the fat matter, where the value of μm registering for WF experiment (OMW without fatty matter) was 0.05 h1

similar to that determined for the mineral medium RL. This can be explained may be determine the greater distortion in the composition of the biomass, increasing the fatty matter percentage with the augment of %OMW in the culture, of an oily nature, can be adsorbed onto the cell surface, hampering the access of nutrients. However, in the culture formed with urban wastewater (UW) it has been determined 0.052 h-1 for μm slightly major than for mineral medium (RL). On the other hand, at the end of the cultures, it was determined the contaminant load for the wastewater after separation from the biomass (Table 6). A greater net reduction of BOD5 was achieved in cultures with 20% OMW (5.7 g O2 L-1). But the higher %BOD5, removed was determined in the culture with 2.5% OMW. The decline in BOD5 shows the use of organic compounds by the microalga. The maximum biomass generated values and BOD5, removed are


213

detected in the culture with 10 and 20% OMW, respectively. This circumstance at 20% OMW may determine the greater distortion in the composition of the biomass, as components of the undiluted wastewater, of an oily nature, can be adsorbed onto the cell surface, hampering the access of nutrients (especially O2). The control experiments WF and WC are registering an increments in the net biomass generation and in the %BOD5, removed (Table 6). This confirms the effect of an oily nature medium in access nutrients to the cells and the importance of light in the net biomass generation.

4. CONCLUSIONS OMW from Two Phase Process Treatment by Fenton Reaction’s The chemical oxidation (Fenton reaction) studied in this work are able to treat olive mill wastewater precedent from two phases continuous system. The best removal efficient was achieved for COD (76%). The phenolic compounds were destroyed. Treated water resulting from this process is used to irrigate. This process offers a solution for reducing the environmental effect of wastewaters generated by two-phase centrifugation system of oliveoil industry. The catalyst used (FeCl3) containing ferric iron ions which lead to savings in the consumption of oxidizer (to avoid rust ions Fe II to III). The sediments obtained in the decanter are dredging mud creamy rich in iron. Water obtained are a fully transparent without odors, phenolic compounds or pesticides.

OMW from Three Phase Process Treatment by Microalgae Obviously, this wastewater without pre-treatment is not an appropriate medium for the cultivation of the microalga S. obliquus. The strong inhibition of growth during the exponential phase and nitrogen deficiency necessitate a pre-treatment prior.

REFERENCES [1] [2] [3] [4]

Roig, A., Cayuela, M. L. & Sánchez-Monedero, M. A. (2006). An overview on olive mill wastes and their valorisation methods. Waste Management, 26, 960-969. Borja, R., Alba, J. & Banks, C. J. (1997). Impact of the main phenolic compounds of olive mill wastewaters (OMW) on the kinetics of acetoclastic methanogenesis. Process Biochem., 32, 121-133. D‘Annibale, A., Crestini, C., Vinciguerra, V. & Giovannozzi Sermanni, G. (1998). The biodegradation of recalcitrant effluents from an olive mill by a whit-rot fungus. J. Biotechnol., 61, 209-218. Bisignano, G., Tomaino, A., Lo Cascio, R., Crisafi, G., Uccella, N. & Saija, A. (1999). On the in-vitro antimicrobial activity of oleuropein and hydroxytyrosol. J. Pharm. Pharmacol., 51, 971-974.

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[12] [13] [14] [15] [16]

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[18] [19] [20]

L. Nieto Martínez, Gassan Hodaifa, Mª Eugenia Martínez et al. Rodis, P. S., Karathanos, V. T. & Mantzavinos, A. (2002). Partitioning of olive oil antioxidants between oil and water phases. J. Agr. Food Chem., 50, 596-601. Obied, H. K., Allen, M. S., Bedgood, D. R., Prenzler, P. D. & Robards, K. (2005). Investigation of Australian olive mill waste for recovery of biophenols. J. Agr. Food Chem., 53, 9911-9920. Molina, E. & Nefzaoui, A. (1996). Recycling of olive oil by-products: possibilities of utilization on animal nutrition. Int. Biodeterior. Biodegrad., 38, 227-235. Cappasso, R., Evidente, A. & Schivo, L. (1995). Antibacterial polyphenols from olive mill wastewaters. J. Appl. Bacteriol., 79, 393-398. Tomati, U., Galli, E., Fiorelli, F. & Pasetti, L. (1996). Fertilisers from composting of olive mill wastewaters. Int. Biodeterior. Biodegrad., 38, 155-162. Bigda, R. J. (1996). Fenton‘s chemistry: an effective advanced oxidation process. J. Adv. Sci. Eng., 6(3), 34-37. Bossmann, S. H., Oliveros, E., Göb, S., Siegwart, S., Dahlen, E. P., Payawan, L., Straub, M. Jr., Wörner, M. & Braun A. M. (1998). New evidence against hydroxyl radicals as reactive intermediates in the thermal and photochemically enhanced Fenton reactions. J. Phys. Chem. A., 102, 5542-5546. Pignatello, J. J., Liu, D. & Huston, P. (1999). Evidence for additional oxidant in the photoassisted Fenton reaction. Environ. Sci. Technol., 33, 1832-1836. Haber, F. & Weiss, J. (1934). The catalytic decomposition of hydrogen peroxide by iron salts. Proc. Roy. Soc., 147, 332-351. Teel, A. L., Warberg, C. R., Atkinson, D. A. & Watts, R. J. (2001). Comparison of mineral and soluble iron Fenton's catalysts for the treatment of trichloroethylene. Wat. Res., 35(4), 977-984. Rivas, F. R., Beltrán, F. J., Frades, J. & Buxeda, P. (2001). Oxidation of phydroxybenzoic acid by Fenton's reagent. Wat. Res., 35(2), 387-396. Martínez-Nieto, L., Rodríguez, S., Giménez, J. A., Lozano, J. L., Cobo, A., Ortega, J. & Hodaifa, G. (2003). Efluentes de la industria del aceite de oliva: contribución al estudio de la composición y tratamiento de las aguas de lavado de aceituna y de lavado de aceite. In: Estudio de la composición y tratamiento como subproducto de las aguas de lavado de aceituna y aceite, 13-44, Ed. Infaoliva, Granada, Spain. Martínez-Nieto, L., Rodríguez, S., Giménez, J. A., Lozano, J. L., Cobo, A. & Hodaifa, G. (2004). Procesos oxidativos en el tratamiento de las aguas de lavado de aceituna y de lavado de aceite. In: Aguas de lavado de aceituna y aceite: procesos de tratamiento, 73-102, Ed. Infaoliva, Córdoba, Spain. Hodaifa, G. (2004). Aprovechamiento de las aguas residuales de la industria oleícola en la producción de biomasa de microalgas. PhD Thesis, University of Jaén, Faculty of Experimental Science, Jaén, Spain. Sánchez, S., Martínez, M. E. & Espínola, F. (2000). Biomass production and variability of the microalga Isochrysis galbana in relation to culture medium. Biochem Eng J, 6, 13-18 . Paredes, C., Cegarra, J., Roig, A., Sánchez-Monedero, M. A. & Bernal, M. P. (1999). Characterisation of olive mill wastewater (alpechin) and its sludge for agricultural purposes. Bioresource Technol., 67, 111-115.


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[21] Harrison, J. S. (1967). Aspects of commercial yeast production. Process Biochem., 2, 41-45. [22] Kobayashi, H. & Rittmann, B. E. (1982). Microbail removal of hazardous organic compounds. Environ. Sci. Technol., 16, 170-181. [23] Teissier, G. (1936). Les lois quantitatives de la croissance. Ann. Physiol-Chim. Biol., 12, 527-573.



Chapter 9

USABILITY OF BORON DOPED DIAMOND ELECTRODES IN THE FIELD OF WASTE WATER TREATMENT AND TAP WATER DISINFECTION

(a)

Hannes Menapace(a*), Stefan Weiß(b), Markus Fellerer(a), Martin Treschnitzer(a) and Josef Adam(a) Institute for Sustainable Waste Management and Technology - University of Leoben, Franz-Josef-Strasse 18, 8700 Leoben, Austria. (b) Umweltbundesamt GmbH, Spittelauer Laende 5, 1090 Vienna, Austria.

ABSTRACT Over the past few years one main focus on the research efforts at the Institute for Sustainable Waste Management and Technology (IAE) has been on possible applications for reactors with boron doped diamond electrodes (BDD) in the field of (waste) water treatment. This article deals with the technical construction of the electrodes used (continuous reactor with a different number of plate electrodes), which were produced by a spin-off of the institute. The electrodes consist of conductible industrial diamond particles (< 250 µm), which are mechanically implanted on a fluoride plastic substrate. These electrodes showed a high mechanical and chemical stability in different test runs. At the institute, treatment methods for micro pollutants (e.g. pharmaceuticals and complexing agents) were developed with electrochemical oxidation by BDD. In this case test runs were made on laboratory scale and technical scale treatment units and elimination rates up to 99 % were achieved. In this project the analytic is partly provided by the ―Umweltbundesamt GmbH‖ (UBA), one of the project partners. This agency has been a project partner in different studies about pharmaceuticals in the ecosystem. These techniques could also be used for the waste water treatment of alpine cabins. Pilot projects have been set up. On the basis of these results a follow-up project was launched last October, in which an alternative treatment process for oil-in-water emulsions and mixtures was developed by the usage of electrochemical oxidation with BDD. A third possible application is the disinfection of drinking water from contaminated ground and *

Corresponding author: E-mail: [email protected], Phone: +43 3842 402 5105, Fax: +43 3842 402 5102.

218

Hannes Menapace, Stefan Weiß, Markus Fellerer et al. spring water. In this process oxidation agents like ozone or OH radicals produced in situ by the BDD reactor from the treated water are used to eliminate bacterial contaminants (for example e. coli) in the water.

1. DIAMOND ELECTRODES Due to their mechanical and chemical stability boron doped diamond electrodes are well suited for the treatment of fluid waste and media. During the so called electrochemical advanced oxidation process oxidizing agents are directly produced out of the organic matrix of the treated fluid. The chemical structure of the organic matrix and pollutants are degraded by these agents and the chemical oxygen demand (COD) will be decreased. For instance the double bonds in the chemical structure of the pollutant are split up and functional groups are cracked. Thus biodegradability is increased. Based on experimental research at various universities, several spin-offs have been established since the year 2000. These companies conduct research, distribute diamond electrodes, diamond coatings for applications in the field of water and waste water treatment. In Europe the distribution of such electrodes and reactors is dominated by three companies.

1.1. Producers and Different Electrode Types The following chapter gives an overview on three main producers of boron doped diamond electrodes (BDD-electrodes) regarding treatment of fluid waste.

1.1.1. Adamant Adamant Technologies SA was founded 2005 in Switzerland. It is a spin-off company of CSEM, Centre Suisse d‘Electronique et de Microtechnique S.A.. The production facility is located in the Science and Technology Park Neode, in La Chaux-de-Fonds (NE). The fields of activities lay mainly in Diamond Coating Technology. Regarding water treatment applications the so-called Adamant®-Electrodes and complete systems (DiaCell®Technology) are available. Additionally, the company is active in water process monitoring. The diamond coatings are produced by chemical vapor deposition technique (CVD). [1] 1.1.2. Condias The CONDIAS GmbH is a spin-off of the Fraunhofer Institute for Thin Films and Surface Technology. The company was founded in 2001 and has its headquarters in Itzehoe, near Hamburg, Germany. The main products are diamond electrodes with the trade name DIACHEM®. These electrodes, also produced by the chemical vapor deposition technique (CVD) on different base materials like Nb, Ta, Ti, Graphite, Si or conductive ceramics, are primarily used for waste water treatment and electrochemical synthesis. CONDIAS produces diamond coated areas up to 100 x 50 cm² with diamond layer thickness up to 15 µm. [2] 1.1.3. Pro aqua The pro aqua GmbH is a spin-off company of the University of Leoben. It was founded 2002 and has its headquarter in Niklasdorf, Austria. Primarily the company produces and sells

Usability of Boron Doped Diamond Electrodes…

219

boron doped diamond electrodes with a layer of titanium oxide. In contrast to the other two producers of BDD electrodes mentioned, diamond particles up to a size of 250 µm are mechanically implanted on the metal substrate. In 2006 a new electrode type was developed and patented. The old model of the titanium substrate was replaced by a film of fluorinated plastic. The company distributes smaller flow rate reactors for waste water treatment and disinfection of supply and tap water, but also standard BDD electrodes with a maximum area of 16 cm x 16 cm. Greater electrode areas are supplied by a special welding methode [3]

1.2. Construction and Design of BDD Electrodes In the following chapter the construction of BDD electrodes is explained on the basis of the pro aqua patent concerning the bipolar diamond electrodes with a substrate of fluorinated plastic. This type of electrodes was used for the different degradation tests which were conducted on the Institute for Sustainable Waste Management and Technology (IAE) at the University of Leoben, Austria. Furthermore, the advantages and disadvantages of characteristic settings are discussed.

1.2.1. Comparison of Different Electrode Types During the first few years of the electrode development titanium was used as the coating material. Several techniques for application of the doped diamond particles on a titanium layer were investigated. Technical problems occurred in all investigations. For example the so called passivation effect, the formation of an oxide layer between the boundary layer of the diamond particle and the titanium, could not be prevented. This effect leads to a continuous decrease of the active surface of the electrode. As a result, the production rate of the oxidizing agents and the treatment efficiency decreases. A second problem is caused by different material expansion coefficients of diamond and titanium. Cracking fissures on the electrode surface result in the chipping of the diamond particles. Due to these technical problems, the concept for the pro aqua electrode was completely reviewed in 2006 and fluorinated plastic was chosen as coating material in 2007 [4]. Neither a passivation effect nor the described cracking fissures arose. This electrode type shows a wide range of application due to its mechanical and chemical stability. Therefore it has been successfully used in several research projects, carried out by the Institute. The invention of the pro aqua GmbH [4] relates to a method of producing a diamond electrode comprising synthetically produced and electrically conductive (doped) diamond particles (2) which are embedded in a support layer (1) made of electrically nonconductive material. The doped diamond particles (2) are introduced as a single layer between two films that form the support layer (1). The films are then permanently connected to each other, and the diamond particles are exposed on both sides of the support layer (1). A scheme of the objective electrode is shown in Figure 1.

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Hannes Menapace, Stefan Weiß, Markus Fellerer et al.

Figure 1. Diamond electrode comprising a support layer of electrically non-conductive material [4]

Table 1. Currently available electrode types [1,2,3,4]. Property Types Dopant Available current density Coating methods Layer materials Feeding electrodes Interelectrode distance Active Area Pretreatment Polarity reversal frequency

Available Settings Monopolar and bipolar Boron In the research on the IAE densities up to 100 mA/cm² were applied. The value varies depending on application Chemical vapor deposition (CVD), mechanical implementation Si, Nb, TI, Graphite, conductive ceramics Cu, Al, Pt, mixing oxides 2 – 10 mm up to 5.000 cm² Filtration recommended 1 min to 90 min


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1.2.2. Comparison of Different Electrode Types A short overview of the currently available electrode types is shown in the following Table 1. Furthermore, some characteristic settings are explained. Interelectrode distance vs. conductivity Depending on the particular application different gaps between the electrode plates in the treatment reactor are needed. Especially fluids with a high content of suspended solids require interelectrode distances. Otherwise fouling would be the result. The greater the gap between the electrodes the higher is the potential drop per electrode plate. Hence, for the treatment of fluids with a low conductivity (< 500 mS/cm) a smaller gap is recommended. Polarity change Through an automatic polarity changer lime precipitation on the electrodes will be avoided. Hereby it‘s guaranteed that the active electrode area is constant during the treatment process.

1.3. Advanced Oxidation Process with Diamond Electrodes In the field of waste water treatment and fluid waste disposal, the anodic oxidation process is a rather new technology, which is not widely used. This treatment method falls into the category of electrochemical oxidation processes and is an ideal additional treatment step for conventional disposal systems, especially if no biodegradable substances should be treated or in presence of toxic chemicals which would inhibit biodegradation processes. [5] The chemicals commonly used for this purpose are oxygen, hydrogen peroxide, ozone, permanganate or persulfate. The higher the oxidation potential of the reagent used, the more efficient the chemical oxidation process is. The most powerful oxidant in water is the hydroxyl radical with a redox potential of 2.8 V relating to normal hydrogen electrode (VNHE) [6]. Organic contaminants are degraded into inorganic substances such as H2O, CO2, and the waste water is additionally disinfected by the agents produced. In general the higher the oxidation potential, the higher the efficiency of the treatment process. Table 2 shows the oxidation potential of some chemical substances. Table 2. Oxidation potential of some oxidation agents [6]. el.-chem. Potential (V)

Potential rel. Chlorine (%)

Oxidation agent

Symbol

Fluorine

F2

3.06

2.25

Hydroxyl radical

*OH

2.80

2.05

Oxygen atom

*O

2.42

1.78

Ozone

O3

2.08

1.52

Hydrogen peroxide

H2O2

1.78

1.30

Hypochlorous acid

HClO

1.49

1.10

Chlorine

Cl2

1.36

1.00

Chlorine dioxide

ClO2

1.27

0.93

Oxygen

O2

1.23

0.90

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Figure 2. Working range of different electrode materials relating to the potential of the standard hydrogen electrode [6].

The anodic oxidation can be ascribed to the Advanced Oxidation Process (AOP). This term comprises all oxidative methods, which have hydroxyl radicals as the main oxidation agent. Hydroxyl radicals act as the main oxidation agent. As can be seen in the table, the OH.radical with an oxidation potential of 2.8 V is a fairly strong oxidation agent in water. During the anodic oxidation process the boron doped diamond electrodes form the basis of the process. These synthetic diamond electrodes differ from other electrodes due to their high mechanical and chemical stability and the manner in which water electrolysis is carried out. Whereas during the electrolysis of water with conventional electrodes the water molecule is split into oxygen and hydrogen, during treatment with a diamond electrode, highly reactive hydroxyl radicals are formed. This is due to the high potential of a diamond electrode. Previous tests conducted with graphite or carbon bearing electrodes have shown that the use of these materials is not advantageous as they do not exhibit the necessary potential to produce hydroxyl radicals [5]. Moreover, signs of wear appear all too readily due to the fact that, in addition to the formation of oxygen, CO2 formation also occurs leading to the breakdown of the electrode material. Even electrodes comprised of PbO2, SnO2 or Pt do not show enough efficiency in the production of OH radicals and are not suiTable due to their low mechanical and chemical stability [5]. Figure 2 shows the range of activity of the different electrode materials vs. the hydrogen potential (left side), oxygen (right side). The potential required to create hydroxyl radicals lies at 2.8. In contrast, boron doped diamond electrodes work with an energy efficiency of more than 90%. This means that in the anodic oxidation process the OH radicals are formed in an electro-chemical manner directly from the waste water treated and the impurities are mineralized or at least transformed into biologically degradable materials, without producing any further residues or waste. The hydroxyl radicals formed react with the impurities in the waste water by splitting hydrogen. [6] H2O  OH + e- + H+

(1)


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Figure 3. Combined chlorine content depending on active electrode area and applied current density, UB untreated water sample, R3K 9 plates, R2K 6 plates and R1K 3 plates.

The most suitable alternative method is chemical oxidation, aiming for the total mineralization or the production of harmless or biodegradable compounds by use of oxidants. By using the electrochemical production of hydroxyl radicals, no additional chemical substances are necessary. The process can be performed at affordable costs, determined by the power required for driving the electrochemical process and without the common AOP drawbacks. Electrochemical water disinfection by producing disinfecting agents (mainly active chlorine produced from the naturally dissolved chloride ions) during electrolysis of water is another common water treatment process. The amount of electrochemical produced oxidizing agents (for example chlorine content shown in Figure 3) manly depends on the two parameters active area and current density. Figure 3 shows the content on combined chlorine for different reactor sizes. Therefore a different number of BDD electrode plates (active area per plate) were installed in each reactor. To achive a better efficiency of the process, a static mixer was implemented in downstream of the reactor R1K in the test run R1K SM.

2. FIELDS OF APPLICATION 2.1. Treatment of Pharmaceuticals and Complexing Agents in Waste Water 2.1.1. Introduction Pharmaceuticals are discharged into the sewer system with human or animal excrements and finally end up in the municipal sewage plant. Because of their complex chemical structure some drugs (e.g. Carbamazepine) or chelating agents (for example

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EDTA and NTA) cannot be eliminated using conventional waste water treatment procedures, so they pass into the aquatic system [7, 8]. As an example the release of pharmaceuticals into surface waters may lead to increased dissemination of antibiotic resistance [9], endocrine substances like hormones are suspected to promote feminizing effects on organisms in ecosystems [10]. Complexing agents like EDTA may cause a remobilization of sedimented heavy metals in surface waters. While there are already statutory thresholds for EDTA and NTA implemented in Austria (QZV Chemie OG 2006) [11] according to the EU directive 2000/60/EC [12], a regulation for pharmaceuticals is expected in the near future. To be able to meet these requirements two innovative treatment procedures have been designed. One is the anodic oxidation with boron doped diamond electrodes and the other one the ozonation. For the second method a new sort of ozone generator is used and the ozone is injected into the water flow in a venturi injector. The development of both procedures is in a testing phase. During research at the Institute for Sustainable Waste Management and Technology at the University of Leoben a new process design was developed in two steps. First a small lab unit was constructed (flow rates ranged from 380 L/h). Treatment sources included synthetic waste water, cleaned waste water from the local municipal waste water treatment plant and a wide range of sectoral waste water. The technical results from this first phase were used for the design and construction of the technical scale unit.

2.1.2. Theoretical process background The basic idea for the treatment of pharmaceuticals and industrial chemicals was to combine the anodic oxidation and the ozonation, as both process steps are able to provide the needed oxidants (O3 and Hydroxyl radicals). These two processes are quite different, so both are described briefly. When using boron doped diamonds electrodes, oxidants (O3 and hydroxyl radicals) are extracted directly from the waste water's organic matrix, which is done by applying direct current to the electrodes. These oxidants are able to eliminate the organic compounds thus no additional chemicals are needed. For ozonation, the oxidant (O3) was generated by electrical production at the beginning and subsequently is being produced by a sort of dielectric barrier discharge. 2.1.3. Description of equipment During the research project two technical plants were constructed and are being operated: a small plant in laboratory scale located at the institutes laboratory and a medium sized technical scale unit located at the local municipal waste water treatment plant. 2.1.3.1. Bench-scale unit During the first phase of the project, the lab-scale unit (Figure 4) was used to determine the process parameters relevant for further process design and to gain insight on the essential parts and sizes for constructing the technical scale unit. In the second step, the small plant was utilized for several test series treating different sources of sectoral waste water.


225

Figure 4. Sketch of the of the laboratory scale unit - a combination of anodic oxidation and ozonisation.

The first laboratory scale unit (Figure 4) was used in the first project step to determine the process parameters relevant for further process design and to gain insight on essential parts and sizes for constructing the tech scale unit. In the second step, the small plant is utilized for several test series treating different sources of sectoral waste water from hospital and industry. The plant follows a modular design concept and consists of two independent segments, one represents a flow reactor for the anodic oxidation, the other a reaction well with the attached ozone generator. The parts operate either separately or in combination. Hydraulic conveyance of the waste water to a particular reaction circuit is provided by diaphragm pumps (Sera R203-2,4E 3 L/h) and flexible-tube pumps (Gardener, Watson-Marlow 323e max. 86 L/h).

2.1.3.1.1. Anodic Oxidation The treatment unit for the anodic oxidation in the laboratory scale consists of a flow reactor, which is equipped with eight parallel plate electrodes (total area 352 cm²). The treated medium seeps through this reactor, process parameters are determined by downstream sensors. As experiences gained in the preliminary tests pointed out, treatment improved when using a downstream catalyst based on metal oxide, so this type of catalyst was used for an after-reaction for the follow up test series. Voltage supply for the electrodes is provided by an EA-HV 9000-600-2000 power supply (I = 0 ~ 3 A), while the current density is kept at a constant level.

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2.1.3.1.2. Ozonisation The ozonisation process consists of two steps: the production of O3 and the treatment reactor for contacting the oxidant with the waste water. This has the advantage of there being two ways to optimize the treatment plant. In laboratory scale different sorts of production and insertion were investigated. At the beginning diamond electrodes located on titanium oxide plates were used, but as these caused technical problems (electrode lifetime, operating stability) the process was finally substituted by an advanced corona-discharge generator for the ozone. Reduction tests were carried out in counter current flow at the beginning, in subsequent project steps a venturi injector was used to mix waste water and ozone. Similar to the anodic oxidation, interconnection of sensors is possible. 2.1.4. Tech scale unit The technical scale unit (TSU) consists of four parallel waste water flows, three are equipped with electrochemical reactors, manufactured by "pro aqua Diamantelektroden GmbH", of different electrode areas (3, 6 and 9 electrodes per reactor). This plant design (Figure 5) permits a reference value on the fourth water flow and the possibility to take three samples at the same time for comparison. Furthermore, the unit is equipped with an automatic polarity changer to avoid lime precipitation on the electrodes. During the next stage of research, an automatic sample collector and a fluid level indicator for the waste water source were connected to the plant further increase automation. 2.1.5. Test series From January to September 2007 miscellaneous test series were carried out using the laboratory scale unit (LSU) on the Institute for Sustainable Waste Management and Technology (IAE) to examine the single procedure steps and combinations of the reactors used in waste water treatment process. To gain knowledge about the interaction of the different chemicals in the matrix and to optimize the treatment the fluid flow rate and the current density were varied. Based on these experiments, test series on the technical scale unit and series with sectoral waste water were started in the second project phase (Table. 2)

Figure 5. Tech scale unit; left side: controlling station, right side: reactor unit.


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Table 2. Overview of the test series. Projec t phase

I

II

Experiment parameter

Synthetic waste water with EDTA

Aggregate Laboratory scale Technica unit l scale unit Anodic Ozoni Oxidatio n sation x x

Degradability experiments with pharmaceutics endowment Real waste water without additional endowment Variation of current densities and flow rates Different contact methods Treatment combinations

x

x

x

x

x

x

x

x x

Experiments with industrial waste water Variation of current densities and flow rates Serial connections of the reactors

x x

x x

Venturi injector for the ozone contact Ozonization as reference method

x x

x x

2.1.6. Sample preparation For determination of so called principal parameters fixing agents have to be added immediately after sampling. Thus further degradation of ingredients is prevented. To prevent breakdown of pharmaceuticals 100 mg NaN3/L sample is added, to fixate chelating agents. Formaldehyde (w = 37 %, 10 mL/L) provided the capabilities needed. The samples then were sent to the UBA in cooling boxes. 2.1.7. Analytics The process parameters temperature, pH-value and redox potential were directly monitored by sensors and the anodic oxidation current and voltage were recorded. The analysis of pharmaceuticals and chelating agents (Table 3) was carried out by the 'Umweltbundesamt' (UBA), where similar projects had been carried out before [10, 13]. During the first preliminary tests of the two technologies applied on the LSU an analysis of the EDTA elimination was made. A complexometric titration according to DIN method DIN 38406-3 [14] for determination of calcium and magnesium ions in water by EDTA was used. Titrating with a calcium solution of defined concentration gives the possibility to calculate the amount of EDTA in the treated solution. For this EDTA was added to the untreated water sample. After treatment 50 mL samples were taken and sodium hydroxide (NaOH, 2 mol/L) and an indicator salt were added. The sample was then titrated with a calcium chloride solution (CaCl 2, 50 mg/L) until a colour

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change from blue to purple occurred. The concentration of EDTA in the titrated sample was then calculated according to the DIN standard DIN 38406-3.

Table 3. Analysis program. Substance groups Sum parameter

Pharmaceutical

Complexing agent

Experiment parameter

IA E

DOC

x

Redox potential, pHvalue, conductivity COD, mg/L Carbamazepine Caffeine Roxithromycine Erythromycine-H2O Josamycine Diazepame Trimethoprime Sulfamethoxazole EDTA, µg/L NTA, µg/L DTPA, µg/L 1,3-PDTA, µg/L

x

LOQ: Limits of Quantification, LOD Limits of Detection.

UB A

LOQ ng/L 10 mg/L ---

x x x x x x x x x x x x x

15 2.0 20 20 20 20 2.0 20 20 1 1 2.5 1

LO D ng/L ------1,0 10 10 10 10 1.0 10 10 1 1 5 1

2.1.7.1. Pharmaceuticals For analysis of pharmaceutical compounds 500 mL of the samples were acidified, spiked with an isotopically marked surrogate standard mixture and subsequently enriched by means of solid phase extraction. Analytes were eluted using dichlormethane, ethylacetate and methanol. The resulting extract was concentrated under a gentle stream of nitrogen and solvents were changed to acetonitrile and water. The final extract was spiked with an internal standard to follow instrument stability and compensate for matrix effects. Samples were analyzed by means of liquid chromatography-electrospray ionization-tandem mass spectrometry. Quantification was performed by external standard method. 2.1.7.2. Complexing agents For analysis of complexing agents isotopically marked surrogates and an internal standard were added to the samples. Samples were concentrated to dryness on a sand bath at 120 °C, and the residue was resolved in 1M hydrochloric acid. After evaporation of the acid the residues were esterified with a mixture of n-butanol and acetylchloride. After the reaction was stopped by addition of sodium hydroxide solution, the resulting esters were extracted with n-hexane and dried over sodium sulphate and finally analyzed with gas chromatography-


229

mass spectrometry in Single Ion Recording (SIR) mode. Quantification was performed with internal standard method by means of isotope dilution.

2.1.8. Analysis During the experiments (Figure 6) we observed a strong dependency of the treatment success on the applied current density, the reactor surface and the time of contact could be observed. The results also showed a different degradability of the individual substances as Carbamazepine showed a better degradability than Diazepam. The degradability of Complexing agents showed a deterioration of the degrading performance at a low concentration range (µg/L-Area). 2.1.9. Summary With the experiments completed thus far, the applicability of the treatments used for a continuing waste water treatment was proven [15]. Furthermore, the experiments on the TSU were performed under the most realistic conditions possible to collect data material for the optimization (e.g. reactor dimension to increase the contact time). Based on a comparison of the success of a particular treatment of the municipal and industrial waste water, a statement concerning the applicability for central and decentral waste water treatment was made. In addition to the treatment success the costs of investment and the costs of treatment should be considered. Based on 0.07 €/kWh and after a first estimation for the flow rate with 200 L/h the costs for the treated waste water depending on current densities from 30.2 to 42.3 mA/cm² will range between 0.16 and 0.60 €/m³.

Figure 6. Actual rates of elimination for the Anti-epileptic drug Carbamazepine, TSU – different current densities and flow rates.

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2.2. Treatment of Oil-Water-Emulsions and Mixtures In all companies where waste is disposed of with state-of-the-art technology, a fat separator will be built in. The discharge of waste water into the sewer system should meet the legal parameters such as COD, temperature, pH value and the rate of lipophilic substances. However, the high content of lipophilic materials in waste water that has not be precleaned leads to fat depositions in the pipe system of the sewer system. Reduced pipe cross section, blockage and smell nuisances are the results. So an alternative secondary treatment step of the waste water from fat separators is of utmost priority. By means of an anodic oxidation process by BDD electrodes, oil water mixtures from a chemically - physical (CP) treatment system have been treated at the IAE in a research study since October 2008. the COD will be analyzed in the experiments. Furthermore, the parameters of conductivity, pH value and temperature will be continuously logged. Flow reactors which are equipped with bipolar pro aqua diamond electrodes are used as a main item for this electrochemical oxidation process. Feeding electrodes made of mixing oxide are used for the power supply of the reactor. To gain knowledge about the energy input degradation tests with different current density are carried out. The following degradation test carried out with an oil water mixture sample from a chemical physical treatment system. The sample was taken before the ultrafiltration step of the facility. In Table 4 the technical data for the used reactor is shown. Table 4. Technical data of the used flow reactor. proaqua-reactor-1: Diamond electrodes Active area per electrode Total area Gap between electrodes max. current density Feeding electrodes Housing material Seals Flow rate

4 plates 32,5 cm2 130 cm2 3 mm 50 mA/cm2 Ru/Ir coated titanium sheet Polypropylene Viton max. 50 L/h

Table 5. Technical data – power supply. Power supply EA-HV 9000-600-2000: Main AC voltage

230 V/AC

Max. output DC voltage

0 - 600 V/DC

Max. output DC current

0 – 3,3 A

Type

linear and adjustable

Reversion of polarity

0,05 Sec. - 24 h.. (adjustable)

In this case 2.000 mL of emulsion were treated in a batch-system with a flow reactor, applied with BDD diamond electrodes under a flow rate of 21.8 L/h. A current density of 83.3 mA/cm² was reached by an active electrode surface per plate of 4 x 30 cm² and a constant


231

current of 2.5 A. The duration of the process was limited to 5 h 30 min. Figure 7 shows the resulting degredation effect by a current density of 83.3 mA/cm².

Figure 7. Degradation of COD for oil-water emulsion after ultra-filtration – 83.3 mA/cm², 21.8 L/h.

2.3. Treatment of Pesticides in Drinking Water Exemplified by Atrazine Contamination Atrazine, a prioric substance according to the European Water Framework Directive [12], is a herbicide which was used mainly for the weed control on sweet corn cultivation, vini- and pomicultire and along stretches of rail road. Along with the main metabolites desethylatrazine, desisopropylatrazine and hydroxyatrazine, atrazine is in the triazine group . Due to its effectiveness and in lieu of alternatives the inexpensive chemical agent was applied in great quantities and on a large scale. In 1994 the usage of atrazine was banned in Germany, one year later the herbicide was also banned in Austria according to the Plant Protection Act. On the European level the ban was adopted about ten years later in 2004. In 1991 an active agent amount of approximately 400,000 kg were placed into circulation, in the following years the consumption decreased rapidly down to 5,000 kg in 1995 [16]. These data were obtained by reason of notification requirement according the Austrian Plant Protection Act. The main areas of atrazine and desethylatrazine contamination are found in the agriculture regions of Southeastern and Eastern Austria.

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Figure 8. Concentration of atrazine and its metabolites in spring water treated with BDD electrodes.

Although atrazine displays only a marginal acute toxizity, studies showed critical effects in the field of body weight gain, inhibition of ovulation and effects on the heart function. Furthermore, the substance is suspected to have carcinogenic effects. Hence, for consumers an ADI value (Acceptable Daily Intake) of 0.005 mg/kg bw (body weight)/d (day) was defined. Moreover, endocrine effects were detected for atrazine. [17, 18, 19] Depending on the local factors such as rainfall, soil moisture and the adsorptive properties of the soil, atrazine finds its way into the groundwater. Due to its higher mobilization rate the risk of desethylatrazine getting into groundwater is higher in comparison to atrazine. [20] Within the scope of a smaller project, degradation tests of atrazine and disethylatrazine contaminated spring water were conducted at the Institute. In this case the unpurified water samples were taken from a spring in an area with intensive agricultural usage. For the treatment a flow reactor according the specifications of Table 4 was used. Figure 8 shows the degredation effect for atrazine and its metabolites at an applied current density of 45.5 mA/cm². After treatment (batch as well as continuous operation mode) of the herbicide contaminated spring water, the concentration of desethylatrazin was below the threshold according to the Austrian Drinking water directive.

2.4. Disinfection of Tap and Drinking Water In the alpine region of middle Europe thousands of alpine lodges and mountain inns were built in exposed positions. In view of the sensible ecosystem and in fact that many lodges were built above the catchment area of drinking water abstraction, untreated waste water


233

disposal is forbidden. A biological step alone, such as a decrease of degradation performance at sinking temperature, is frequently not sufficient. In a project supported by the local Styrian government, the biological treatment step at a lodge (1,524 m above sea level) was upgraded with an additional disinfection system based on BDD electrodes. The scientific support of the optimization of these added treatment steps was supported by the IAE. In a second work in this sector, the bacteriological pollution of spring water was treated by anodic oxidation with BDD electrodes. A reactor cell from the pro aqua GmbH was used to support drinking water quality according to the specifications of the Drinking Water Ordinance. For both problems samples were taken and treated by anodic oxidation. The disinfection effect for waste water effluents with the objective reactor was verified by an expert opinion. In different studies successfully tests were made with BDD electrodes to inactivate legionella in water samples. [22, 23] Using BDD electrodes with direct current supply under galvanostatic conditions lead to an electrolytic generation of oxygen based disinfectants like peroxodisulfate, peroxodicarbonates, hydrogen peroxide and OH radicals on the active electrode area. These agents could be used to eliminate bacteria and other organic components. For the test runs two different arrangements were used. In addition to treatments in a batch operation, investigations with a continuously treatment were also tested. The used reactor is composed of bipolar four plate electrodes with an active area of 32.5 cm² per electrode and two feeding electrodes made of mixing oxide. During the tests a 2 mm gap between the BDD electrodes was used. A batch operation mode mainly is reasonable for the treatment of highly contaminated waste water when the contact time of the media in one stroke through the reactor is insufficient. For the validation of the treatment effect under laboratory scale conditions the following parameters were tested Escherichia coli Enterococci Coliformic germs Colony forming units (CFU) at 22 °C and 37 °C The treatment of the waste water from the alpine lodge shows the dependence between disinfection efficiency on the one hand and the parameters flow rate and current density on the other hand (Table 6). Sample 1: Untreated influent (8 °C water temperature; 2.5 mS/cm conductivity) Sample 2: effluent after the disinfection step at a pumping capacity of approx. 30%. Sample 3: effluent after the disinfection step at a pumping capacity of approx. 22%. Sample 4: effluent after the disinfection step at a pumping capacity of approx. 36%. In the test runs with the contaminated spring water, values for the treated water below the quantification limits could be achieved. According to the results a continuous operation mode of the reactor (current density of 36.92 mA/cm² and a flow rate of 43.5 L/h) seems sufficient for the treatment.

234

Hannes Menapace, Stefan Weiß, Markus Fellerer et al. Table 6. Treatment results alpine lodge. Parameters

unit

CFU at 22 °C CFU at 37 °C Enterococci

CFU/mL CFU/mL CFU/100 mL

Sample 1 93

Sample 2 30

Sample 3 1.7 x 104

Sample 4 1.9 x 104

4.8 x 104 0

675

9.8 x 103

9.9 x 103

0

0

509

Table 7. Microbiotic Parameters – DVGW-Analysis (unfiltrated waste water treatment plant effluent, temperature: 20 °C, sample volume: 2500 mL, flow rate: 50 L/h, Applied Voltage: 60 V; current: 0.5 A, treatment time: 100 min [24]. Parameter

Unit

Escherichia coli

CFU/100 mL CFU/100 mL CFU/100 mL CFU/100 mL

California germs Enterococci CFU (36°C)

Waste water effluent before treatment 2.807

Waste water effluent after treatment 0.05). This confirmed findings by Etiégni and Campbell (1991) that generally during wood ash leaching experiments, more than 90% of materials is expected to leach out after 30 minutes. ELCHAS reduced BOD by between 47 and 88%, ELCAS between 28 and 78%, while ELPHOS removed BOD between 51 and 90% and the differences were statistically significant (P< 0.05), although the wide variation in the recorded BOD removal values could not be easily explained. Wood ash was the primary source of hydroxide ions that enhanced the process for colour and BOD removals and probably led to reduced power consumption. Low power consumption could also be attributed to the catalytic properties of metal oxides such as MgO Mn2O3, Cr2O3, PbO2 found in wood ash and phosphate rock. The catalytic properties of these metal oxides on the surface, or in the space between the anode and cathode during electrocoagulation has been recognised in previous studies and might have assisted the reduction of the time for current flow as reported by Ahonen (2001). Reduction of BOD by ELPHOS in this experiment was in some instances higher than the values reported by both Springer et al. (1995) of 70% and Ahonen (2001), and yielded a final BOD value of between 20 and 40 mg/l, the higher end of which is not acceptable by local discharge standards.

Power Reduction Electrolysis combined with phosphate rock (ELPHOS) proved to be the best in terms of power consumption (68% reduction) compared to ELCAS (57% reduction) and ELCHAS (58% reduction), and the differences were statistically significant (P< 0.05) although it also depended on the quantity of supporting electrolyte (SE) added to the effluent. The effect of various SE concentrations on the treatment efficiency and power reduction of coffee factory

Batch Treatment for Colour Removal from a Coffee Factory Effluent…

287

effluent is shown in Figure 6. Wood ash, coffee husks ash and phosphate rock used as supporting electrolytes helped reduce power consumption (Figure 6). Soaking seemed to avail more supporting electrolyte to the colour removal process, although this may not be true with phosphate rock. Of the three supporting electrolytes, coffee husks ash had the least impact on colour removal when not soaked, followed by wood ash and phosphate rock. The latter showed no significant difference between soaked and not soaked supporting electrolyte. This stems from its low solubility which has been observed in studies where phosphate rock was used in agriculture for pH control. When the concentration of the supporting electrolyte (SE) in solution increased, power consumption reduced probably as a result of increased conductivity (Figure 7). If the required voltage of the electrocoagulation reaction is expressed as follows: where EC EA δA δC IRcell IRcircuit

V = EC - EA- δA- δC - IRcell - IRcircuit

(2)

= Electrical Potential at the cathode = Electrical potential at the anode = Zeta potential at the anode = Zeta potential at the cathode = voltage of the electrocoagulation cell = voltage of the electrical circuit

The removal of colour may have resulted from the combined effect of Fe2+ and Fe3+ generated in the solution during electrolysis of iron electrodes (Othman et al., 2006). It took on average between 33 to 54 minutes, depending on the SE concentration, for the effluent colour to be completely removed. These results could help determine the reactor‘s volume needed based on the detention time for complete decolourization of the coffee factory‘s effluent, if there is need for a continuous flow reactor:

Volume Detention time = Effluent flow rate 0

165

330

500

665

830

1000

Power (kW/Yr)

4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

ELCAS BH6 ELCAS SH3 ELPHOS BH6 ELPHOS DH3

ELCAL

Figure 7. Power consumption for different treatment system and SE concentrations.

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L. Etiégni, D. O. Oricho, K. Senelwa et al.

It shows that the necessary voltage v to access a certain current density had reduced because of the introduction of the SE, so that the consumed electrical energy had also decreased (Kashefialasl et al., 2006). SE is said to compress the double layer which in turn reduces the Zeta potential of the substrate ions and helps their agglomeration or coagulation. The reduction of power consumption in this experiment was slightly lower than the 80% reduction reported by Etiegni et al. (2005) or Orori et al. (2005), probably because of the higher electrode surface coverage of 80 m2/m3 used in these experiments. Higher surface coverage normally lead to high efficient color removal. The presence of metal ions such as Ca, Fe, Al may have also helped the coagulation process. Chemical analysis of wood ash in previous studies has showed a significant presence of several chemical elements such as Ca and Fe in the form of their corresponding oxides which can act as coagulant when dissolved in water (Etiégni and Campbell, 1991).

Color Removal Colour was effectively removed from the coffee factory‘s effluent through electrocoagulation method. There appeared to be a positive effect of supporting electrolyte as ELCHAS, ELCAS and ELPHOS removed 100% colour confirming the effectiveness of this SE in electrocoagulation (Prasad and Joyce, 1991; Koparal and Gütveren, 2002). ELCHAS, ELCAS and ELPHOS had a negative effect on the treated effluent pH as it increased by between 27 and 75% for ELCHAS, 19 and 47% for ELCAS and between 9 and 22% for the ELPHOS as shown Table 1. The pH from ELPHOS was lower than ELCAS probably because of the slow reactivity of phosphate rock compared to wood ash. ELCHAS had a much higher impact on the coffee effluent final pH. Aeration had the effect of reducing the factory treated effluent COD (Figure 8). Using ELCAS followed by over-night aeration, COD was reduced to almost 5 mg/l after an initial spike to 68 mg/l, while with ELPHOS, COD of the treated effluent remained almost constant at 45 mg/l. This shows that after treatment with ELCAS, normal aeration often carried out in most wastewater treatment processes could further reduce the coffee factory wastewater parameters.

ELPHOS ELCAS

COD (mg/l)

80 60 40 20 0 1

2

3

4

5

Time (hr) Figure 8. COD reduction as a function aeration time.

6


289

Total Solids There was a considerable reduction in solids in the treated effluent from the coffee factory. The reason for such behaviour could be due to the fact that the EC treatment may have induced the settling velocity of the suspended particles in which more suspended particle agglomerates cloaked together. The exposure of wastewater to EC treatment would contribute to a greater ionic charge so that more particles would collide and this would eventually help in enhancing particles‘ attraction and agglomeration (Othman et al., 2006). Table 1. Wastewater parameter for raw and treated effluent followed by aeration (with ash socked for six hours). Parameter Temperature (oC) pH TS (mg/l) TDS (mg/l) TSS (mg/l) TVS (mg/l) COD (mg/l) BOD5 (mg/l) EC (μΩ/cm) Colour (0H) Alkalinity (mg/l)

Effluent discharge Standards Kenya < 30 6.5-8.5 1200 30 50 30 15 -

Raw effluent 19 5.2 1920 400 1520 1070 1845 851 556 2500 129

ELCHAS

ELCAS

ELPHOS

20

20

20

6.6-9.1 220-300 40-160 120-220 160-300 164-624 102-456 705-773 0 149-202

5.3-7.9 220-340 40-180 140-180 160-320 320-899 186-616 508-677 0 114-156

5.9-6.8 220-300 40-160 120-180 80-180 114-594 86-420 197-270 0 55-76

Table 2. Chemical Analysis of raw and treated coffee factory’s effluent. Chemical element Cd Co Cr Cu Fe K Mg Mn Na P Pb Zn

Raw effluent 0.058 0 0.506 0.016 1.014 0.089 8.132 0.150 4.40 3.56 0.08 0.0273

Concentration (mg/l) ELCAS ELPHOS effluent effluent 0.005 0.002 0 0 0.100 0.506 0 0.026 0.203 0.006 9.0 0.017 0.265 2.094 0.4518 0 440.0 0.59 0 2.72 0 0.07 0.2352 0.0708

Effluent Standards 0.01 2.0 1.0 0.01 0.5

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L. Etiégni, D. O. Oricho, K. Senelwa et al. Table 3: Amount of power and chemical required for effluent treatment. Treatment ELPHOS ELCAS ELCHAS

Best concentration (mg/L) 4000 4000 3000

Amount to be used per year (tonnes) 24 24 18

R/water

OSA

Power consumption per m3 (WH) 42 48 42

NSA

OSC

Power consumption per year (KWH) 252 288 252

NSC

OSR

Total cost for treatment $/ year 6816 2504 2216

NSR

1400 1200 1000 EC

800 600 400 200 0 0

1000

2000

Concentration

3000

4000

(g/m 3)

Figure 9. Effect of SE on electrical conductivity of coffee factory effluent.

Effluent electrical conductivity (EC) and alkalinity results are also described in Table 1. The results show that ELCHAS increased EC by between 27 and 39%, ELCAS process increased slightly the effluent EC by between 8.7 and 21%, while ELPHOS reduced EC by as much as 51% and their net effect were statistically significant. An analysis of treated effluent in Table 2 shows that ELPHOS did not substantially increase minerals, even P for which it is used in agriculture. However ELCAS increased Na and Mn concentrations in the treated effluent making it unfit for certain uses such as agricultural irrigation.

R/water

OSA

NSA

OSC

NSC

OSR

NSR

Alkalinity (eq/m 3)

600 500

400 300 200

100 0 0

1000

2000

3000

Concentration (g/m 3)

Figure 10. Effect of SE on the effluent alkalinity.

4000


291

Electrical Conductivity As mentioned earlier, the electrical conductivity of the treated effluent increased with the volume of supporting electrolyte. There seemed however to be a maximum in this increase which shows that maximum EC was achieved at 2000 mg/l or g/m3 except for never-soaked ash which exhibited a maximum EC at 4000 mg/l (Figure 9). The effect of phosphate rock on EC was negative. The difference between 2000 and 4000 mg/l was statistically significant (P< 0.05). Because of the negative impact of phosphate rock on EC, its overall positive effect on the removal of colour and other coffee effluent parameters cannot be explained through its impact on EC. Other factors such as the presence of CaO and MgO in phosphate rock may have played a role in helping treat the factory‘s effluent (van Kauwenbergh, 1991).

Alkalinity Alkalinity from ELCHAS increased from 15.0 to 56.0%, while ELPHOS first reduced alkalinity by as much as 59% (Table 1, Figure 10). The difference in the effect of these two processes was statistically significant (P< 0.05). The effect of ELCAS on coffee factory‘s effluent alkalinity was almost insignificant. The alkalinity value of the treated coffee factory effluent indicates that on average, the treated waste water could be more amenable to biological treatment if there was further need to improve the effluent characteristics prior to its discharge.

COST OF TREATMENT Assuming a discharge of effluent per year of 6000 m3, the average power consumption for selected best concentrations of SE are shown in Table 3. ELCAS and ELPHOS performed best at a concentration of 4000 mg/L while ELCHAS at 3000 mg/l. ELPHOS cost was twice that of ELCAS. The successful treatment of coffee factory‘s effluent using a 100 litre tank shows that this surface to volume ratio of 75 m2/m3 could be used as a scale-up ratio to fullscale treatment unit.

SCALE-UP OF A PROTOTYPE FOR COLOR REMOVAL In order to scale-up the laboratory reactor, instead of color, we can choose a compound present in the factory‘s effluent which will be called component (A), and the batch reactor below:

Feed Initial mole of Component (A) = NAO

Outlet Final mole of component (A) = NA

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Initial conversion of Component (A) = XAO=0 Initial molar Flow rate of Component (A) = FAO

Final Conversion=XA Final molar flow rate=FA

Reaction rate (-rA)

Figure 11: Batch reactor If a material balance is written around Figure 11, the equation around the reactor is: Feed in = Feed out + rate of reaction + rate of accumulation ………. …………………. 3 Feed in = Feed out = 0; since no feed is going in and no feed is coming out (batch treatment). So equation 3 becomes: (rate of accumulation: dNA/dt) = rate of reaction * volume of the reactor: (-rA)V ……….4 dNA/dt = (-rA)V ………………………………………………………...…………………5 NA = NAO(1-XA) Putting the value of NA into equation 5 We obtain: d[NAO(1-XA)]dt = (-rA)V …………………………………………………………………6 Since NAO is constant, its differentiation is equal to zero; so equation 6 yields: -[NAO dXA/dt] = rAV

………………………………………………………………….7

The following equation can be used to calculate for volume V Vt= [NAO]*[ dXA/rA] To do that, what one needs is to plot 1/rA versus XA; the area under the curve will be = V*t/NAO. Since in our experiment we did not study the reaction kinetic, we cannot get the plot 1/rA versus XA, which will be the ideal way to estimate the volume V. All things being equal we could use the volume Ratio. But since a direct ratio of Vp/Vlab = 150 is deemed too large, to get around the problem, we can use flow system of two to three reactors (Constant Stirrer Tank Reactors) in series. In the absence of the flow system, we will scale-up the reactor using the surface to volume ratio mentioned earlier.

i)

OPTION ONE Dimensions of tank before scaling-up Length 1 width 1 (cm) (cm) 65.0

45.0

height 1 (cm) 47.0

Volume 1 (cm3) 137475

Batch Treatment for Colour Removal from a Coffee Factory Effluent… ii)

293

Scaling-up factor to construct a 15 m3 tank (0.65) x (0.47) x (0.45) X3 = 15 m3 X = (15/0.137)-1/3 = 4.78

iii)

Dimensions of new tank with 15 cubic meter capacity Length 2 width 2 height 2 (m) (m) (m) 3.11 2.15 2.25

iv)

Dimensions of each electrode 7/8 height width (cm) (cm) 42.0 30.0

Volume 2 (m3) 15.0

thickness (cm) 0.20

In the laboratory tank reactor, there were 6 cells each with three electrodes occupying a total surface area of 4.54 m2. To maintain a surface to volume ratio of 75 m2/m3 for a total volume of 15 m3, we need a total electrode surface area of 1125 m2. We calculate the total length of a cell in the laboratory reactor as 6.6 cm. Number of cells to fit in the length of the scaled-up reactor, after removing approximately 5 cm from either ends: (311.0 -10)/6.6 = 45.6 cells For this option, we will use 45 cells or 45 x 3 = 135 electrodes. CALCULATION OF CURRENT DENSITY Number of positive electrodes 45. Area of an electrode in the scaled-up tank is: 1125 m2/135/2 = 4.17 m2 At a required current density equals 1.20 Amps/m2, Current per electrode (one positive cell) is equal = 1.2 x 4.17 = 5.0 Amps Total reaction current in Amperes equals = 5.0 x 45 = 225 Amps CALCULATION OF POWER REQUIRED If the voltage per cell is equal to 40 volts, the minimum power required to run the color removal reaction is equal to: 40 x 225 = 9,000 W or 9.0 kW Assuming a Transformer and Rectifier with combined efficiency of 85% at 0.95 power factor (pf), the power rating is: 9.0 kW = 11.15 kW or 11.15 x (54/60) = 10.0 0.85 x 0.95 At US$0.25 the cost of a kWh in Kenya, the factory will be spending 10.0 x 0.25 = US$ 2.50 per day to treat its wastewater. Initial capital is may be high due cost of 15 m3 tank, hoists for the electrodes and their insulators. In addition there will be the need to adapt a welding transformer and a rectifier to provide a DC reactor current for only 54 minutes per day. OPTION TWO No scale-up of the laboratory tank, but setting 12 equal tanks side by side with a total volume of 1.2 m3

294

L. Etiégni, D. O. Oricho, K. Senelwa et al. The reactors are operated in batch processes simultaneously:

Process:

1234-

Filling of tanks Color removal reaction Discharge to the stream

Preparation for the next batch Total time required for 1 single batch process

2 minutes 54 minutes 2 minutes

2 minutes 60 minutes

Volume per tank 0.10 m3 Number of tanks 12.0 Total volume 1.2 m3 3 Time required to treat 15 m wastewater from the factory per day: 15 (m3) 1.2 (m3/batch)

x

60 (minutes) batch

x

(1) (hr) (60 minutes)

= 12.5 hours

Active surface area of an electrode = 0.126 m2. Since there are twelve (12) positives electrodes in a tank, the total surface is 0.126 x 12 = 1.51 m2. For a current density of 1.2 Amps/m2, the total current going into a tank is 1.2 x 1.51 = 1.81 Amps. There are twelve tanks in this option. The amount of current required is 1.81 x12 = 21.74 Amps per batch. Assuming we maintain the same voltage of 40 volts, the power rating here will be: 40 x 21.74 = 869.6 W or 0.869 kW per batch. Assuming a Transformer and Rectifier with combined efficiency of 85% at 0.95% power factor (pf), the power rating will be: 0.869/(0.85 x 0.95) = 1.08 kW Knowing that there will be 12.5 batches per day of 60 minutes each, the total power consumed will be: 1.08 x 12.5 = 13.5 kW or 13.5 x (60/60) = 13.5 kWh Total cost of power consumed = 13.5 x 0.25 = US$ 3.36 per day to run the color removal reactors. In each of the two options presented above, the costs of control equipment (pumping, draining, logic control) as well as the cost of labor has not been included. It appears that the 1st option is the less expensive of the two.

CONCLUSION AND RECOMMENDATION This project has shown that rock phosphate can be a good substitute for wood ash during electrochemical colour removal. ELPHOS can also yield an effluent whose quality can be considered for re-use in the factory for cleaning purposes. However, the high cost of this process of $6,816/year may be a deterrent for an otherwise effective method that can completely remove colour and substancially reduce COD and BOD. Using these results, we have showed that it is possible to determine the reaction time and volume of an industrialscale reactor required to treat effluent from a coffee factory effluent. However additional studies are necessary to verify these results and further refine parameters for industrial application. It is therefore suggested that more studies be carried out to make this method more economical by, for instance, increasing the electrode surface area or by recycling the treated water.


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ACKNOWLEDGMENT The authors wish to acknowledge the assistance of Moi University, Kenya for funding this project and Ms Abigael Nekessa and Mr. Thuita Moses, graduate students at Moi University, Department of Soil Science, School of Agriculture and Biotechnology for providing the necessary information on phosphate rock used in this experiment.

REFERENCES Ahonen, H. (2001). A Review of General Information on Electrochemical Process Wastewater Treatment. Finland Laboratories 7p. Arudel, J. (2000). Sewage and Effluent Treatment. Wiley and Sons, Great Britain, 45-90. ASTM. (1983). Standard Practice for Coagulation-Flocculation Jar Test of Water. Annual Book of ASTM Standards. 1101. Coste, R. (1992). Coffee - The plant and the product. MacMillan Press, London. Etiégni, L. & Campbell, A. G. (1991). Physical and Chemical Characteristics of Wood Ash Bioresource Technology, Vol. 37, 173-178. Etiégni, L., Orori, B. O. & Rajab, M. S. (2004). An Electro-coagulation Method of Color Removal in Wastewater or Water with Low Power Consumption. International Patent (PCT/ KE2005/000012). Ikeheta, Z. P. & Buchanan Q. S. (2000). Decolorization of pulp mill effluents with immobilized lignin and manganese peroxidase from Phanerochaete chrysosporium. Environ. Technol., 19, 521-528. Kashefialasl, M., Khosravi, M., Marandi, R. & Seyyedi, K. (2006). Treatment of dye solution containing colored index acid yellow 36 by electrocoagulation using iron electrodes. Int. J. Environ. Sci. Tech., Vol. 2(4), 365-371. Koparal, A. S. & Gütveren, Ö. B. Ü. (2002). Removal of nitrate fromwater by electroreduction and electrocoagulation, J. Hazard. Mater, B 89, 83-94. Muleta, D. (2007). Microbial inputs in coffee (Coffea arabica L.) production systems, South Western Ethiopia. Implications for promotion of Biofertilizers and Biocontrol agents. Doctoral thesis, Swedish university of Agricultural Sciences. Orori, O. B., Etiégni, L., Rajab, M. S., Situma, L. M. & Ofosu-Asiedu, K. (2005). Decolorization of a pulp and paper mill effluent in Webuye Kenya by a combination of electrochemical and coagulation methods. Pulp and Paper, Canada, Vol. 106, No. 3, T50T55, 21-26. Orori, O. B. (2003). Colour removal from wastewater of a Pulp and Paper Mill in Kenya, by a combination of electrochemical and coagulation method. Mphil. Thesis, Department of Wood Science & Technology, Moi University, Eldoret, Kenya, 146. Othman, F., Sohaili, J., Ni‘am, F. M. & Fauzia, Z. (2006). Enhancing suspended solids removal from wastewater using Fe electrodes. Malaysian Journal of Civil Engineering, 18(2), 139-148. Prasad, D. Y. & Joyce, T. W. (1991). Colour removal from Kraft bleach plant effluents by Trichoderma sp. TAPPI J., Vol. 65, No. 1, 165-169.

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Springer, A. M., Vincent, C. H. & Timothy, S. J. (1995). Electrochemical Removal of Colour and Toxicity from Bleached Kraft Effluents. TAPPI J., Vol. 78, No. 12, 85-91. UNEP. (1981). Environmental Management in the Pulp and Paper Industry, Vol. 1, 234. UNESCO/WHO. (1978). Water Quality Surveys - A guide for Collection and Interpretation of Water Quality Data. United Kingdom, 350. Van Kauwenbergh, S. J. ( 1991). Overview of phosphate deposits in Eastern and Southern Africa. Fert. Res., 30, 127-150. Wei-Lung, C., Chih-Ta, W. & Kai-Yu, H. (2009). Effect of operating parameters on indium (III) ion removal by iron electrocoagulation and evaluation of specific energy consumption. Journal of Hazardous Materials, In press doi:10.1016.



Chapter 14

WATER AS A SCARCE RESOURCE: POTENTIAL FOR FUTURE CONFLICTS M. A. Babu* Department of Environment, Islamic University in Uganda; P.O .Box 2555, Mbale- Uganda.

ABSTRACT The major aim of this paper is to review the major problems of water resources in the developing countries. It is based on problems related to population growth and pollution and how these are more likely to lead to future conflicts. We know that fresh water is only 3 % of the total global water and 78% of this is in glaciers. This makes it a scarce and precious resource which must be sustainably managed. The paper also analyses some of the already existing and potential conflicts based on water resources. It reviews the potential threats to Ugandan water resources and problems which are most likely to occur as a result of these threats. Factors hindering treatment of wastewater as a remedy to pollution in developing countries have also been discussed. The methodology used in this paper is based on literature review of the most current issues that affect water resources world-wide. The review is limited to scientific facts and no political factors affecting water resources have been included. It has been found that although Uganda is endowed with 66km2/year of renewable water resources, population increase, deforestation, degradation of wetlands and pollution are major threats to its water resources. Problems associated with water quality and quantities are more likely to result into internal conflicts which are bound to spread beyond Ugandan borders.

Keywords: Water scarcity, deforestation, population, wetlands, pollution, conflicts.

*

Corresponding author: Phone: +256 45 33502, Fax: +256 45 34452, Email: [email protected]

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INTRODUCTION Oil is an invaluable resource to mankind; it makes us fly, drive, generate power, till the land and even drive military hardware. It is a potential threat to the western world and source of conflict in the world politics. It is believed to be the major destabilizing factor in the Middle East (Darwish, 1994). It is a luxury that mankind cannot afford to live without. On the other hand, water is part of us - the human body is composed of 70- 95% water, the food we eat is water in a different form. It is an essential component that drives the ecosystem and the food chain. It is a resource with inherent values that cannot be comparable and measurable. Imagine if water were to be mined like oil, would we live and survive? Imagine New York City without water for 24 hours! Water is a basic need; it is not a luxury that mankind can live without. Water is becoming an increasingly vital resource and is thought to over take oil as the potential cause of conflict in the Middle East. President Anwar Sadat once said Egypt will never go to war except when its water resources are threatened. According to UN- reports, the population in the Middle East is increasing rapidly (Table 1.0) and it is predicted that this will exert more pressure on the already existing problems associated with water resources. In the UN report, 18 countries will be on the list of water scarce countries by 2025. These include: Algeria, Israel/Palestine, Qatar, Saudi Arabia, Somalia, Tunisia, United Arab Emirates, Yemen, Egypt, Ethiopia, Iran, Morocco, Oman and Syria. Water scarcity can be described as when country has less than 1,700 m3 per capita, it is said to be experiencing water stress, while less than 1000 m3 is regarded as water shortage. This list includes most countries that are already in the volatile Middle East region hence the possibility of conflict cannot be ruled out. Past experience of the 1960s is testimony to the conflicts. Cross border raids on water schemes' between Israel, Syria and Jordan culminated into the six day war in 1967 (Darnish, 1994). Although natural water resources can be replenished through the hydrological cycle, then one might urge that the natural cycle will take care of the situation. The average renewal rate for rivers are about 18 days while large lakes and deep aquifer can take up to thousand of years. The Nubian aquifer in North Africa- known as the world's oldest aquifer were thought to be filled in past geological years. When depleted, it is not known how long it would take to recharge (Darnish, 1994). Climate change, pollution and the demand to feed large populations makes the problem more complex. It is predicted that the main conflicts in Africa in the next 25 years could be over water. It is thought that countries will fight each other to have access to this precious and scarce resource (Russel, 2007). According to the UNDP report as cited by Russel, (2007), 12 African countries will join the list of water scarce countries. This means that a person will have less than 1000 m3 of water per year. Water requirement for domestic use depends on lifestyle and availability. For instance, about 400, 200 and 10 - 20 litres per person per day are consumed in North America, Europe and Sub-Saharan Africa respectively (World Water Council, 2000). As can seen, the current consumption in Sub-Saharan Africa is the lowest and it is thought to worsen in the next 50 years. The Nile, Niger, Volta and Zambezi basins are believed to be major areas of conflicts. Other potential water war areas in Southern Africa will involve Botswana, Namibia and Angola. There are already tensions in these regions.

Water as a Scarce Resource: Potential for Future Conflicts

299

Table 1.0. Prediction of population (in Millions) of some selected Middle East countries. Country Israel Palestine Libya Egypt

1990 4.7 4.5 58

2025 8 7 12.9 101

(Source: Darnish, 1994)

Figure 1. Possible regions of water wars in Africa (UNDP, 2007).

According to Lester Brown (as cited by Russel, 2007), the head of environmental research institute Worldwatch, the combined population of Ethiopia, Sudan and Egypt – will rise from the current 150 million to 340 million in 2050. This will result intense competition for increasingly limited water resources. "There is already little water left when the Nile reaches the sea," he says. Egypt is ready to use force to protect its vital water resources. It is much more concerned with dams that might be constructed in the Ethiopian highlands which are thought to affect the flow of the Nile. Egypt is not in compromising position as regards this. In 1989, the Ethiopian ambassador in Egypt was summoned to explain the presence of Israel hydrologists around the areas of the Blue Nile. During the same period, the Egyptian parliamentarians declared their willingness to back their government in taking military action against Ethiopia if it becomes necessary (Darwish, 1994). In the Niger basin, Senegal and Mauritania have already fought two short wars in 1987 & 1989 over the Senegal River. The cause of this was that Mauritanian tribesmen searching for vegetation crossed to the other bank, violating Senegalese sovereignty (Darwish, 1994).

UGANDAN SCENARIO Uganda is naturally endowed with water resources; renewable water resources are estimated to be 66km2/year which corresponds to 2800m3/person/year. Open water surface covers 15% of the total land cover (Figure 2). Uganda also receives annual average rainfall of 900-2000mm of which 7-20% of this recharges the underground water.

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M. A. Babu

Figure 2. Major Lakes and Rivers of Uganda (WWAP, 2006).

The recharge to ground water is high as compared to the current abstraction volumes hence there is no over exploitation at current situation. However, it should be noted that Uganda has 106 towns of which 56 towns have piped water supply. Of the 56 towns, 15 large towns are mainly supplied with lake or river water. The remaining 41 small towns depend on high yield boreholes (WWAP, 2006). It should be borne in mind that these towns are rapidly expanding and the demand for water may result into tapping more of underground water sources. At same time, there are also 69 other small towns that do not have piped water supply. If we are to meet the target for the Millennium development goals by supplying water to the towns, the underground sources may be strained.

Major Threats to Water Sources Uganda has not yet fitted into the larger picture of water wars. Whether it will feature or not can be established through, analysing major factors that may drag it into action. In this context, these are limited to only scientific and not political factors. In our own opinion, threats to water sources may become future points of conflict as time goes by. The following anthropogenic activities may be considered as threats to Ugandan water resources:

(a) Deforestation It is well documented that areas of high altitude with dense rain forest covers receive high precipitation (WWAP, 2006).The forests provide moisture in the hydrological cycle required for rainfall formation. At the same time, vegetation cover traps and holds rain water; realising it slowly hence recharging rivers, streams and underground wells throughout the year.


301

2000000 1800000

Forest cover ( ha)

1600000 1400000 1200000 1000000 800000 600000 400000 200000 0 2005

2010

2015

2020

2025

2030

2035

Time (years)

Figure 3. Forest cover predicted to be lost in the next 30 years.

Of recent, there has been enormous pressure on forest systems. According to Environmental profile of Uganda (2005), Uganda had total forest cover of 3,627,000 ha (prior to 1970) but this has been reduced by 50% from 1971-1987. Again from 1990-2005, 26.3% of the remaining forest covers has been lost through deforestation. The country profile also reports annual deforestation rates of 2.2% per year for a period from 2000-2005. Taking a conservative approach and assuming that by 2007 the forest cover is 50% of 3,627,000 ha and the annual deforestation rates of 2.2% per year is maintained, the total forest cover will be less than 200,000 ha in the next 100 years (Figure 3). Forests have been cleared for settlement, agriculture as well as development. Notable cases include the recent proposal of give away of Mabira forest. Already, some of the forests on the Islands of L.Victoria have been given away for palm tree growing. The forests around Mt. Elgon region are already generating conflicts between the local community and Uganda Wild Life Authority. The net result of forest loss is reduction in precipitation thus many river systems running dry. The water holding capacity of vegetation will be eliminated hence water will be flushed through rivers at faster rate; leaving them dry especially in the dry seasons. The highlands of Uganda are big producers of fruits and vegetables like cabbages, tomatoes and onions, as well as non vegetable crops like Irish potatoes bananas, maize and coffee. Loss of soil fertility due to soil erosion coupled with increased flushing of rivers will affect the livelihoods of many people. Water availability, proximity, quality and quantity have been strongly linked to poverty (UN, 2007). Siltation of rivers and poor water quality will be come common, diseases and poverty will be alleviated and this may be a flash point of conflict within the communities. The export of virtual water and nutrients in crops from areas already constrained by water shortage and loss of nutrients (due to erosion) will further make producing areas poorer. Unfortunately, the water and nutrients in crops are exported to urban areas where they are flushed down the drain without a possibility of recycling. It also known that the highland forests act as catchments for the wetlands down stream, a case in point being the Manafa – Doho drainage system. The extent of flooding in the plains

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down stream will be limited to smaller areas that can be sustained by the little water from the mountains. Competition for the limited wet areas available will cause tension in the rice growing communities. Of recent, violence linked to possession of wetlands has been reported in this area. It is also thought that rifts may develop between the communities up and down streams as they scramble for little water available. Worthy noting, there be will silent conflicts between man and biodiversity for the limited resources.

(b) Wetlands Uganda has a total wetland area of 30,000km2. Like forests, wetland degradation is on the increase. For instance, it is estimated that 45 % of the Nakivubo wetland has been modified or reclaimed (Emerton et al, 1999). The Nakivubo wetlands as well as those in Eastern and other parts of Uganda are under pressure. Key activities that degrade wetlands include agriculture, development, settlement and solid waste disposal. It has also been found that most of the wetlands of the valley bottoms have been converted to agricultural use. This has led to change in micro climate and even lowering of water table as seen in Kabale and Bushenyi (WWAP, 2006). There are 3 hydrological functions of wetlands which are important in maintaining the hydrological balance. First, wetlands act as holding water basins slowly releasing water into rivers and streams thus ensuring continuous flow throughout the year. Secondly, the holding basins also provide more time for seepage and recharge of underground water and thirdly, wetlands play a vital role in providing water directly to its beneficiaries. It is estimated that wetlands directly provide water to 5 million people in Uganda (WSSP, 2001).Hence, off setting the hydrological balance will lead to drying up of most rivers, streams and wells. The quantity of underground water sources is expected to decline. Loss of wetlands may mean loss of many livelihoods. Many wetlands are used for fishing, grazing, agriculture and for materials used in shelter. Effects of wetland loss are likely to be felt by the poor rural communities who largely depend on them. Loss of livelihood may become source to conflicts.

(c) Pollution This is a major problem mainly facing urban areas. L.Victoria is of major interest since it is a vital component in the Nile basin, being a resource shared by many riparian countries. It is the second largest fresh water lake in the world with an area of 69,000km2. The lake is increasingly receiving pollution from un-treated sewage as well as industrial effluent. Odada et al., (2004) report that the number of people without sewers in urban areas of L. Victoria region is high and yet the population growth is over 5- 10%. This raises concern in regard to the lake quality. According to UNEP-SEO report (2004-2005), the lake is experiencing severe impact on microbial contamination, eutrophication and suspended solids. It is also seen that the Congo basin which is within the catchments areas of L.Victoria is under severe eutrophication (Table 2.0).In fact, it is anticipated that the cost of water treatment for Kampala city is bound to rise due to increased levels of phytoplankton in the lake. The city draws its raw water from the lake yet the demand for water supply is fast tracking the rise in population.


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Table 2.0. Water pollution in selected water bodies (UNEP, SEO Report, 2004/2005).

Most industries located in Kampala and probably elsewhere in Uganda do not have effluent treatment systems but drain their wastes into the lakes, rivers and environment. It has been found that industries release 1,045kg/d BOD5, 96kg/d of nitrogen and 105kg/d of phosphorous into the lake (WWAP, 2006). The BOD exerts oxygen demand on the water affecting fish and other aquatic organisms. Nitrogen and phosphorous cause algal blooms, which may cause skin irritation, production of toxins as well as increasing oxygen depletion in the lake. Cholera cases have become common in Kampala and cases of dysentery have increased from 2300 in 1999 to 8300 in 2002 (WWAP, 2006). Apart from the industrial effluent into L.Victoria, there are a number of flower farms being established on the shore line of the lake. Flower farms are known to extensively use fertilizers and pesticides. If this is left unchecked, water from the lake may become unfit for consumption or else we pay the heavy price of treating pesticides. As for the rural areas, small towns are rapidly cropping up and more pit latrines are being sunk. Underground water will be contaminated and incidences of water borne diseases will be high. Much as Uganda is endowed with water resources, lack of mitigation to pollution will result in loss of this precious resource.

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(d) Population growth Uganda like many developing countries is experiencing rapid population growth. With the invention and perfection of the Haber process in the 1960‘s, population and food production has increased synonymously. The Haber process has greatly improved the manufacture of nitrogen based fertilizers. Nitrogen in the fertilizers is transformed to proteins in the food chain and upon consumption followed by excretion, large amounts of nitrogenous products are released into the environment (Mulder, 2003). This is known to pollute the receiving water bodies. Nitrogenous wastes, organic matter and pathogens found in wastewater have affects on public health and harmful ecological impacts on the environment (Gijzen and Mulder, 2001). The growing concern of nitrogen, organic and pathogen pollution therefore calls for the need of wastewater treatment before discharge into natural watercourses. At present, there is hardly any infrastructure for effective treatment of sewage in developing countries. Municipal sewerage system coverage and the extent of domestic and industrial wastewater treatment are inadequate. Treatment level is insufficient in most urban situations (Gijzen et al., 2004). For example in Latin America, only 14% of collected sewage receives treatment (WHO/UNICEF, 2000). Even when the facilities exist, poor maintenance and operation results in failure of treatment processes causing pollution of the receiving surface waters (Gijzen et al., 2004). In Sub-Saharan Africa, 42% of the population (as per 2002) lacked water supply and 64% lacked basic sanitation (WHO-UNICEF, 2006). Reduction of these proportions will definitely have environmental effects. Even if these percentages are spread to both urban and rural communities, the ultimate end of the waste is the environment. This poses a challenge to most governments. The major hindrance to sewerage coverage and treatment systems in most developing countries is the weak economies. Priority in these states is given to security, health and education. For instance in Uganda, the 1998/1999 budget for sanitation dropped from 46%18% while that of education increased from 14-47% (WSP, 2004). Also the cost of conventional wastewater treatment infrastructure is prohibitive for the majority of these developing countries, Uganda being inclusive (Gijzen et al., 2004). The implementation of conventional wastewater collection and treatment in developing countries to attain EU standards is therefore unrealistic, except maybe in densely populated urban centres where the average income is much higher. However, this should not be generalised as most urban areas are facing problems of their own. Population growth in these areas is seen to out grow the existing wastewater treatment infrastructure (Gijzen and Khonker, 1997; Yu et al, 1997). Weak economies, corruption, increased demand for urban land and unplanned development seems to make the expansion of the existing infrastructure nearly impossible (WWAP, 2006). Although the millennium development goals emphasize strong water and sanitation component- which is good, there is a possibility that this will compound the problem of water pollution further if not well handled. Goal seven for instance proposes reduction of half of the proportion of people without access to safe drinking water and basic sanitation by 2015 (UN, 2007). It is estimated that 2.6 billion people lack access to sanitation (WHO-UNICEF, 2006). If this goal is to be achieved; there will be increased generation of wastewater. Mara et al., (1992) estimate that 80-90% of water consumed is converted to wastewater. Increased production of wastewater will put more burdens on the already strained waste management.


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From this point of view, it is realistic that governments should think of strategies of solving problems of water pollution if they are to achieve the millennium development goals and avoid future conflicts. They should make use of low cost treatment technologies through best approach to improve effluent quality. Much as there is evidence of success of conventional approach, the concept still needs to be reconsidered from sustainability point of view (Gijzen et al., 2004). As such, efforts on improving nutrient removal using natural wastewater treatment technologies like wastewater stabilization ponds and wetlands that are widely applied in developing countries become paramount. This will entail protection of the environment from pollution resulting from wastewater discharge. Governments should reduce the pressure on the already existing treatment infrastructure by avoiding the centralized approach of sewerage collection. It is recommended that they delocalize collection systems to many smaller but effective treatment systems. It is expected that with the growing population coupled with destruction of forests, wetlands and increased pollution, the quality and quantity of available water will reduce. This is most likely to spark conflicts in regions which are already facing water scarcity.

What Do We Learn? If issues of deforestation, wetland degradation, and pollution and population growth are not addressed; Uganda is bound to face problems of water quality and quantity. There will be more internal conflicts based on water resources. Seasonal rivers will dry up, tribal conflicts will be elevated and pastoralists will be forced to move to other areas in search of water and pasture. Already the Balalo and Basongora pastoralists in Uganda have generated a lot of ethnic sentiments. Internal conflicts in Uganda may spread beyond its borders. Sudan and Egypt will be definitely affected and Egypt may be forced to extend its long arm to Uganda. Cost of water treatment in Uganda will increase and the less privileged who cannot afford will be vulnerable to water borne diseases and exposure to pollution. Poverty eradication may be a dream. Water is a scarce and precious resource which must be managed and used sustainable. If not well, managed water is likely to cause conflicts world wide.

ACKNOWLEDGMENTS Am grateful to Dr. N. Sarah for sparing her time to read and review this work. Her contributions have added invaluable knowledge to this paper.

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REFERENCES Darwish, A. (2004). A Lecture on Environment and Quality of Life, June 1994. Geneva conference. Emerton, L., Iyango, L., Luwum, P. & Malinga, A. (1999). The Present Value of Nakivubo Urban Wetland, Uganda. National Wetlands Conservation & Management Program/ IUCN. Environmental profile (2005). Forest cover of Uganda. www.rainforests.mongabay.com Gijzen, H. J, Bos, J. J., Hilderink, H. B. M., Moussa, M., Niessen, L. W. & de Ruyter van Steveninck, E. D. (2004). Quick scan health benefits and costs of water supply and sanitation. Netherlands Environmental Assessment Agency. National Institute for Public Health and the Environment – (MNP-RIVM), The Netherlands Gijzen, H. J & Mulder, A. (2001). The global nitrogen cycle out of balance. Water, 21, Aug 2001, 38-40. Gijzen, H. J. & Khondker, M. (1997). An overview of ecology, physiology, cultivation and application of duckweed, Literature review. Report of Duckweed Research project. Dhaka, Bangladesh. Mara, D. D., Alabster, G. P., Pearson, H. W & Mills, S. W. (1992). Waste stabilization ponds, a design manual for Eastern Africa, Lagoon Technology International Leeds, England. Mulder, A. (2003). The quest for sustainable nitrogen removal technologies. Wat Sci. Tech., 48(1), 67-75. Odada, E. O., Olago, D. O., Kulindwa, K., Ntiba, M. & Wandiga, S. (2004). Mitigation of environmental problems in L. Victoria, East Africa: Casual chain and policy option analyses. Ambio, Vol. 33(1-2), Feb. 2004. Russell, S. (2007). Africa’s Potential Wars, BBC online. www.bbc.com UN (2007). The Millennium Developments Goals Report 2007, New York. WHO-UNICEF (2006). Meeting the MDG drinking water and sanitation target: the urban and rural challenge of the decade, WHO press, Geneva. World Health Organisation / UNICEF. (2000): Global Water Supply and Sanitation. Assessment 2000 Report. Geneva, World Health Organisation. World Water Council (2000). World Water Vision, Making water everybody’s business. The Use of Water Today, The Hague, Netherlands WSP, (2004). Strengthening Budget Mechanisms for Sanitation in Uganda. WSSCC (2004). Resource packs on the water and sanitation Millennium development Goals. Water supply and sanitation collaborative council, Geneva. WSSP, (2001). Wetland Sector Strategic Plan 2001-2010. Wetlands Inspection Division, Ministry of Water, Lands & Environment – Uganda. WWAP (2006). Uganda National Water Development Report, UN report. Yu, H., Tay, J. & Wilson, F. (1997). A sustainable municipal wastewater treatment process for tropical and subtropical regions in developing countries. Wat. Sci. Tech., 35(9), 191-198.



Chapter 15

RECYCLING WASTEWATER AFTER HEMODIALYSIS: AN ENVIRONMENTAL AND COST BENEFITS ANALYSIS FOR ALTERNATIVE WATER SOURCES IN ARID REGIONS Faissal Tarrass*1, Meryem Benjelloun 1, and Omar Benjelloun 2 1

2

Hassani Hospital Center, Nador, Morocco Hospital Universitario Central de Asturias, Oviedo, Spain

ABSTRACT Water is a vital aspect of hemodialysis. During the procedure, large volumes of water are used to prepare dialysate and to clean and reprocess machines. This paper evaluates the technical and economical feasibility of recycling hemodialysis wastewater for irrigation uses, such as watering gardens and landscape plantings. Water characteristics, possible recycling methods, and the production costs of treated water are discussed in terms of the quality of the generated wastewater. A cost-benefit analysis is also performed through comparison of intended cost with that of seawater desalination, which is widely used in irrigation.

Key words: Hemodialysis, Environment, Wastewater, Water quality, Recycling, Membrane technology

INTRODUCTION Water is essential to all known forms of life, but this resource is under threat [1]. Growing national, regional, and seasonal water scarcities in much of the world pose severe challenges for national governments, international development, and environmental policies [2-5]. In this context, alternative water sources such as wastewater recycling offer a partial solution by creating fresh water for industry and agriculture [6].

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Faissal Tarrass, Meryem Benjelloun, and Omar Benjelloun

Hemodialysis, a method for replacing renal function in patients suffering from renal failure by the removal of excess water and wastes, requires a large volume of water. Water is used in long-term dialysis facilities to prepare dialysate and to rinse and reprocess dialysis membranes and machines [7,8]. Assessing the recycling potential of hemodialysis wastewater must give consideration to both the environmental and economic aspects. This study was undertaken to analyze hemodialysis wastewater at a Moroccan dialysis facility in order to examine the feasibility of advanced wastewater treatment for agricultural uses such as watering gardens and landscape plantings.

WASTEWATER GENERATION IN HEMODIALYSIS Water is a vital aspect of hemodialysis. During hemodialysis, assuming a dialysate flow rate of 500 mL/min, a patient is exposed to 120 liters of purified water during a typical 4-hour dialysis session. The yearly consumption of water for a single-pass dialysis system operating 12 hours per day and 6 days a week is estimated to be 112 m3 [8], without considering water that is rejected during treatment by the carbon filters and reverse osmosis membranes prior to dialysis use [8]. In Morocco, there are 135 dialysis centers, offering 1589 hemodialysis stations. The number of patients under treatment is estimated to be 5737 patients on September 2007, with a number of treatments of 8 x 104 per year approximately [9]. A simple calculation shows that the total consumption of water by hemodialysis facilities exceeds 50 million US gallons per year (1 m3 = 264 US gallons). This figure is excessive for a country experiencing drought [10]. Minimizing this water expenditure is of importance to Morocco and other water-poor countries in which scarcity of water sources represents a serious impediment for long-term development [2-6].

IMPACTS OF RECYCLING Hemodialysis wastewater can enter municipal and natural water systems via residential or commercial discharges, including hospital effluent. There is a lack of data about the possible direct and indirect impact of hemodialysis wastewater discharges on the environment. However, benefits of recycling may result in reduced discharge of wastewater into natural water bodies and the potential water savings for hospitals. In terms of economic impacts, it is known that integrating wastewater treatment in agriculture can bring benefits such as partial cost recovery [1,2]. For hospitals, recycling wastewater may provide a purchase price reduction [11]. In this study, we analyze the potential economic benefit of using recycled hemodialysis wastewater for irrigating the hospital grounds.

Recycling Wastewater After Hemodialysis: …

309

METHODOLOGY Wastewater Sampling Water samples were obtained from a single dialysis facility. Using sterile 500-mL bottles, wastewater was collected from the outflow pipe that drains all hemodialysis sewage (including waste dialysate and water rejected during treatment by the carbon filters and reverse osmosis membranes) directly into the municipal sewage line. All samples were placed in a closed cooler during transit to the laboratory.

Wastewater Chemical Analyses and Physical Characteristics Wastewater samples were analyzed in an accredited laboratory for biochemical oxygen demand, total Kjeldahl nitrogen, phosphorus, chloride, and sulfate using spectrophotometry (Hache Lange Company, Noisy le Grand, France) [12]. Biochemical oxygen demand is a measure of the amount of oxygen utilized in the biochemical oxidation of organic matter present in water. Temperature, pH, and conductivity analyses were also performed.

Wastewater Microbiological Analyses Samples for bacteriological testing were processed within 1 to 2 hours. Samples were cultured using the membrane filtration technique. In brief, membrane filters were placed aseptically on trypticase soy agar and incubated at 36ºC for 48 hours [12,13]. Total viable colony counts were documented and isolates identified using standard microbial techniques.

Wastewater Quality Criteria The suitibility of hemodialysis wastewater use in agriculture was evaluated through the comparison of its characteristics with the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) standards for wastewater use for agricultural applications [14,15]. The optimum procedure for treatment to reach standards is discussed according to the quality of the generated wastewater.

Cost Estimation Analyses CapdetWorks, a preliminary design and costing program available from (Hydromantis, Inc, Ontario, Canada) was used for the design and cost estimation of wastewater treatment plants. The design and cost estimation of reverse osmosis plants was modeled with WTCost, which is a preliminary design and costing program for processing plants developed with the support of the US Bureau of Reclamation [16]. Both tools incorporate water quantity (average daily, maximum, and minimum flow), water quality (influent wastewater characteristics and

310


desired effluent quality), and land requirements. The cost report produced by the two programs includes equipment, operation and maintenance cost (materials and supplies, energy, and labor). A cost benefits analysis was also performed in which the cost of water treatment was compared with that of seawater desalination to produce water of equivalent quality. Data for cost estimates of water desalination for agricultural applications were based on the proceedings of the FAO expert consultation on water desalination for agriculture [17].

RESULTS Hemodialysis Wastewater Composition and Pollution Risk Chemical characteristics of the wastewater are displayed in Table 1, as well as information on other residual wastewater that is commonly recycled, and the FAO/WHO standards for wastewater use in agriculture [14,15,18-21].

Table 1. Comparison of hemodialysis wastewater composition with other commonly recycled waters, wastewaters and quality standards for agriculture Parameter

Hemodialysis wastewater (this study)

Temperature (°C) 30 PH 7.84 Conductivity (µs/cm) 13200 Biochemical oxygen 24.2 demand (mg/l) Ammonia nitrogen (mg/l) Kjeldahl nitrogen (mg/l) 29 Chloride (mg/l) 289 Sulfate (mg/l) 80.4 Phosphorus (mg/l) 54 Bacterial count 450 (CFU/ml) TDS (mg/l)

Seawater Municipal [20,21] Morocco United (LYDEC) States [19] [18]

Industry

22 – 30 7.6 – 7.9 50000 3.5 – 9.6

30 5.5 – 8.5 7.3 – 7.7 2520 500 110 – 400

30 6.5 – 8.5 2700 2190 50 – 600 204

0.2 – 1.1

12 – 50

18900 2649

34483

12 – 50

150 – 200 20 – 85 120 4 – 15 22 x 108 500

Morocco United [19] States [18]

FAO/WHO standards for irrigation water [14,15] 6 – 8.5 300 – 700 5 – 45

39.5

0–5

397 270 11.2

0 – 30 0 – 20 0–2 2x104– 10x104

250 – 850 50 – 600 1406

< 450

Abbreviations: LYDEC, Lyonnaise des eaux de Casablanca; FAO, Food and Agriculture Organization of the United Nations; WHO, World Health Organisation; CFU, Colony-forming unit; BOD, Biochemical oxygen demand = quantity of oxygen utilized in the biochemical oxidation of organic matter present in water; TDS, Total Dissolved Solids = solids that either float on the surface or are suspended in water


311

These results show that apart from an increased but expected conductivity value, biochemical oxygen demand, Kjedahl nitrogen, chloride sulfate, and phosphorus concentrations did not exceed the FAO standards, with the exception of the conductivity value. Bacterial count of the wastewater showed 450 colony-forming units/mL, but coliform organisms (specifically Escherichia coli species) were undetectable. The primary challenge for use of hemodialysis wastewater can be its high conductivity. By contrast, concentrations of dissolved organic substances were under applicable emission standards for discharges [18,19], and the bacterial count was under WHO standards for wastewater use in agriculture [14].

Treatment Options for Recycling Wastewater Due to the high conductivity of hemodialysis wastewater, the use of membrane technology could be suitable for the treatment of such wastewater [22,23]. This technology has proven to be efficient and cost saving in comparison with other processes [24,25]. Computed simulations for cost estimation were performed for two possible membrane filtration processes, nanofiltration and reverse osmosis. Technical parameters of both processes are shown in Table 2.

Table 2. Technical characteristics of the nanofiltration and reverse osmosis systems for wastewater recycling Parameter Pressure (psi) (bar) Flow (m3/h) (US Gallon /day) Recovery (%) Power (System + Pumps) (kWh) Membrane life (year) Price (US$)

Nanofiltration

Reverse osmosis

100 – 150 7 – 10.5

100 – 150 7 – 10.5

1 – 1.2 6500 – 7500 30 2.2 3 3500

0.9 – 1.0 5500 – 6500 30 3 4 4500

Note: Values shown are for a thin film composite (TFC) membrane type. Abbreviations: psi, per square inch; kWh, Kilowatt hour

Cost Benefits Total costs for the two treatment techniques, including capital equipment, operating, and maintenance costs, are presented in Table 3. Costs were calculated based on current membrane and equipment prices. Energy, labor, and maintenance were calculated based on the average Moroccan prices for energy and labor. Membrane life was set at 3 and 4 years for nanofiltration and reverse osmosis respectively.

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The cost for treating hemodialysis wastewater to achieve a quality that is suitable for irrigation using nanofiltration and reverse osmosis is 0.70 US$/m3 and 0.74 US$/m3, respectively.

Table 3. Estimation of costs for wastewater recycling calculated on 288 working days per year, and 20 working hours per day Item Equipment (US$) Operating (O&M) Energy/working hour (US$) Labor/year (US$) Membrane replacement (US$) Cleaning chemicals/week (US$) Repair and maintenance/year (US$) Total costs/year (US$) Cost of production (US$/m3)

Nanofiltration 16500

Reverse osmosis 18000

0.0946* 14400 1050 0.90 175 3253 0.70

0.129* 15600 900 – 220 3423 0.74

Note: The plant capital was calculated on current membrane and equipment prices. The energy costs were based on Moroccan prices 26 (*0.043US$/kWh), labor costs on average Moroccan costs and the membrane replacement on an average 3 and 4 years replacement respectively.

For comparaison, the costs associated with various techniques for desalination of seawater for agricultural use are listed in table 4. With the exception of the latest reserve osmosis technologies, costs are in excess of 1.15 US$/m3 Given the average cost of 1 US$/m3 for seawater desalination [17], this could result in cost savings (or benefit) of 20 to 30% in comparison to desalination of seawater (Table 4).

Table 4. Comparison of costs of hemodialysis wastewater treatment versus desalination Parameter

Sea water desalination for agriculture use [17] Multistage flash (US$ /m3)

HD wastewater treatment for agriculture use

Capital cost Energy Fuel Electricity

0.301

Multipleeffect distillation (US$/m3) 0.520

Vapour compression (US$/m3)

Reverse osmosis (US$ /m3)

Nanofiltration Reverse (US$/m3) osmosis (US$ /m3)

0.548

0. 301

0.358

0.39

0.62 0.18 – 0.19

0.55 0.08 – 0.09

0 0.60 – 0.66

0 0.26 – 0.32

0.118

0.161

Labor Chemicals Membrane replacement Maintenance Payback costs Total costs

0.038 – 0.043 0.036 – 0.048 0.064 – 0.096 0.021 – 0.097 0.312 0.033 – 0.047 0.028 – 0.038 0.022 – 0.038 0.019 – 0.056 0.009 0 0 0 0.001 – 0.043 0.227

0.338

0.021 – 0.038 0.021 – 0.038 0.019 – 0.032 0.021 – 0.038 0.037 0.40 – 0.42 0.40 – 0.42 0.43 – 0.45 0.18 – 0.26 1.32 – 1.38 1.15 – 1.21 1.15 – 1.29 0.54 – 0.85 0.70

0.047

Note: Values were converted from Euro to US$ (1 Euro = 1.20 US$ as of 27 April 2007)

0.195

0.74


313

COMMENTS Arid and semi-arid regions are facing increasingly more serious water shortage problems. As the population grows in these areas, water is an increasingly valuable and limited resource. Every effort must be made to use water more efficiently, and new practices are being developed and implemented in the field of water use and water conservation [27,28]. Hemodialysis represents an environmental challenge, in part due to high water consumption [8]. In regions with water scarcity, high consumption of water during by hemodialysis units is a compelling argument supporting wastewater recycling. This paper discusses the technical and economic feasibility of recycling this type of wastewater for potential use in irrigation. Observed values show that organic matters and bacterial biomass were under the acceptable limits; however, conductivity values exceeded FAO standards [15]. Due to this high conductivity, wastewater must be treated to accepted standards prior to use for irrigation [22,23]. Membrane separation has proven to be the preferred treatment process for such high conductivity wastewaters [22,23,29]. Moreover, this technology has previously been shown to be efficient and economical in comparison with other approaches [24,25,30,31]. In this study, computer simulations were executed with two models of membrane treatment (nanofiltration and reverse osmosis) based on the characteristics of the influent and the desired effluent wastewater quality and assumptions obtained from prior literature [30,32]. The simulations suggested that both methods showed greater benefit compared to desalination of seawater, resulting in a cost savings (or benefit) of 20 - 30%. Membrane separation is a widely used process for the treatment of various types of wastewater. However, to our knowledge, application of this technology to hemodialysis wastewater has not been performed. Also, in reviewing the literature, we were unable to document any engineering application system related to hemodialysis wastewater treatment. Consequently the result of our analysis calls for further investigations in this area. In conclusion, due to the high water consumption in hemodialysis, it is essential to study its potential for recycling. Through analysis and evaluation of the technical and economic feasibility of hemodialysis wastewater treatment, this study draws attention to this important but neglected aspect of hemodialysis therapy.

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Rosegrant MW, Cai X, Cline SA. World Water and Food to 2025: Dealing With Scarcity. Washington DC, International Food Policy Research Institute, 2002 Berrittella M, Hoekstra AY, Rehdanz K, Roson R, Tol RS. The economic impact of restricted water supply: a computable general equilibrium analysis. Water Res. 2007; 41: 1799-813. Moe CL, Rheingans RD. Global challenges in water, sanitation and health. J Water Health. 2006; 4 Suppl 1: S41-S57. Tal A. Seeking sustainability: Israel's evolving water management strategy. Science. 2006; 313: 1081-4.

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Faissal Tarrass, Meryem Benjelloun, and Omar Benjelloun Gaan N. Environmental scarcity of water and Indo-Nepal conflict: towards environmental integration and cooperation. Asian Profile 2001; 29: 417-28. Wang XC, Jin PK. Water shortage and needs for wastewater re-use in the north China. Water Sci Technol 2006; 53: 35-44. Lusamvuku A, Hermelin-Jobet I, Boudard B, Bracquemont MC, Lebas J. Hemodialysis water production: evaluation and assurance quality management. J Pharm Clin 1999; 18: 300-5. Cousin P. Traitement d'eau en hémodialyse. Stage de Perfectionnement à l'Ingénierie Hospitalière, Université de Technologie de Compiègne 1998-99, pp 59. http://www.utc.fr/~farges/spibh/98-99/Stages/Cousin/Cousin.htm, Assessed : 28th February 2008. Moroccan Ministry of Health. Strategy of care from 2008 to 2012. Available at: http://www.sante.gov.ma/Leministre/Communique/communique2008/corruption.htm, Accessed: 5th March 2008. Kingdom of Morocco Water Sector Review. Report No 14750-MOR. Washington DC, World Bank, 1995. Pauwels B, Verstraete W. The treatment of hospital wastewater: an appraisal. J Water Health. 2006; 4: 405-16. American Public Health Association. Standard methods for the examination of water and wastewater. 20th ed. Washington: Washington DC, American Water Works Association, Water Environment Federation, 1998. Association for the Advancement of Medical Instrumentation. American National Standard Hemodialysis Systems. ANSI/AAMI RD5-1993. Arlington, VA: AAMI; 1993. Carr RM, Blumenthal UJ, Mara DD. Guidelines for the safe use of wastewater in agriculture: revisiting WHO guidelines. Water Sci Technol 2004; 50: 31-8. Food and Agriculture Organization of the United Nations. Wastewater treatment and use in agriculture, Rome, FAO, 1992. Moch I. Development of a CD-ROM cost program for water treatment projects, Memb Technol 2003; 6: 5-8. Food and Agriculture Organization of the United Nations. Water desalination for agricultural applications, Rome, FAO, 2006. Asano T, Smith RG, Tchobanoglous G: Municipal wastewater: Treatment and reclaimed water characteristics. in Pettygrove GS, Asano T (eds): Irrigation With Reclaimed Municipal Wastewater—A Guidance Manual. Chelsea, MS, Lewis, 1985, pp 1-26. Soudi B, Xanthoulis D. Projet de gestion des ressources en eau: Élaboration des dossiers techniques relatifs aux valeurs limites des rejets industriels dans le domaine public hydraulique. Rome, FAO, 2006. Cotruvo JA. Water Desalination Processes and Associated Health and Environmental Issues. Water Cond Purif 2005; 47: 13-7. Gupta AK, Gupta SK, Patil RS. Statistical analyses of coastal water quality for a port and harbour region in India. Environ Monit Assess 2005; 102: 179-200. Magesana GN, Williamsona JC, Yeatesb GW, Lloyd-Jones AR. Wastewater C:N ratio effects on soil hydraulic conductivity and potential mechanisms for recovery. Bioresource Technol 2000; 71: 21-27.


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[23] Gerhart VJ, Kane R, Glenn EP. Recycling industrial saline wastewater for landscape irrigation in a desert urban area. J Arid Environ 2006; 67: 473-86. [24] Moch I, Chapman M, Steward D. Estimating membrane water treatment costs Membr Technol 2003; 8: 5-7. [25] Cote P, Masini M, Mourato D. Comparison of membrane options for water reuse and reclamation. Desalination 2004; 167: 1-11. [26] Office National de l‘Electricité: Customer space. Available at: www.one.org.ma. Accessed 28th February 2008. [27] Bakir HA. Sustainable wastewater management for small communities in the Middle East and North Africa. J Envir Manag 2001; 61: 319-28. [28] Abu-Zeid KM. Recent trends and developments: reuse of wastewater in agriculture. Envir Manag Health 1998; 2: 79-89. [29] Marcucci M, Ciabatti I, Matteucci A, Vernaglione G. Membrane technologies applied to textile wastewater treatment. Ann NY Acad Sci 2003; 984: 53-64. [30] Noronha M, Mavrov V, Chmiel H. Simulation model for optimisation of two-stage membrane filtration plants; minimising the specific costs of power consumption. J Membr Sci 2002; 202: 217-32. [31] Hafez A, Khedr M, Gadallah H. Wastewater treatment and water reuse of food processing industries. Part II: Techno-economic study of a membrane separation technique. Desalination 2007; 214: 261-72. [32] Moch I, Chapman M, Steward D. Development of a CD-ROM cost program for water treatment projects. Membr Technol 2003; 6: 5-8.



Chapter 16

PB (II) IONS REMOVAL BY DRIED RHIZOPUS OLIGOSPORUS BIOMASS PRODUCED FROM FOOD PROCESSING WASTEWATER 1

H. Duygu Ozsoy1* and J. Hans van Leeuwen2,3,4 Dept. of Environmental Engineering, Engineering Faculty, Mersin University,

33340, Mersin, Turkey. Dept. of Civil, Construction and Environmental Engineering. 3 Dept. of Agricultural and Biosystems Engineering. 4 Dept. of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA. 2

ABSTRACT Heavy metal pollution is a serious problem in many developed and developing countries. Lead had been recognized as a particularly toxic metal and comes into water bodies mainly from metallurgical, battery, metal plating, mining and alloy industries. In order to minimize the impacts of this metal on human health, animals and the environment, lead-contaminated water and wastewater need to be treated before discharge to water bodies. This chapter concerns an investigation of potential usage of corn-processing wastewater as a new alternative low-cost substrate to produce biosorbent and evaluate this biosorbent to remove Pb(II) ions from aqueous solutions. For this aim, Rhizopus oligosporus cultivated on corn-processing wastewater and dried biomass of these fungi was used as an adsorbent. The adsorption experiments were conducted in a batch process and the effects of contact time (1-48 hours), initial pH (2-7), initial metal ion concentration (20-100 mg L-1) and adsorbent dosage (0.5-5 g L-1) on the adsorption were investigated. Pb (II) ion concentrations before and after adsorption were measured using Inductively Coupled Plasma-Mass Spectrometry. Maximum adsorption capacity was achieved at pH 5.0. The isothermal data of dried fungal biomass could be described well by the Langmuir equation and monolayer capacity had a mean value of 59.88 mg g-1. The *

Corresponding author: Phone: +90 324 361 00 01/7102, Fax: +90 324 361 00 99, E-mail: [email protected] (H.D. Ozsoy)

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H. Duygu Ozsoy and J. Hans van Leeuwen pseudo-second order reaction model provided the best description of the data with a correlation coefficient 0.99 for different initial metal concentrations. This result indicates that chemical sorption might be the basic mechanism for this adsorption process and Fourier Transform Infrared Spectroscopy analyses showed that amide I and hydroxyl groups play an important role in binding Pb (II). Because of the high activation capacity of adsorbent and low cost of process dried R. oligosporus biomass presents a good potential as an alternative material for removal of Pb (II) ions from the aqueous solutions.

Keywords: Biosorption, Food processing wastewater, Heavy metals, Pb (II), Rhizopus oligosporus.

1. INTRODUCTION Removal of heavy metals from aqueous solutions is one of the major problems in industrial wastewater treatment because most of them are toxic even at very low concentrations. The amount of these pollutants in water has been increased with industrial applications including mining, refining, electroplating and production of textiles, paints and dyes [1]. Lead had been recognized as a particularly toxic hazardous environmental pollutant and comes into water bodies mainly from metallurgical, battery, metal plating, lead smelting, mining and alloy industries. In order to minimize the impacts of this metal on human health, animals and the environment, lead-contaminated water and wastewater need to be treated before discharge to water bodies [2]. The conventional methods for removing metals from aqueous solutions include chemical precipitation, chemical oxidation or reduction, electrochemical treatment, reverse osmosis, solvent extraction, ion exchange and evaporation. However, these techniques have several disadvantages such as high chemical cost, low removal efficiency, low selectivity, high energy requirements, and generation of secondary toxic slurries [3-5]. Therefore removal of toxic heavy metals in a cost-effective and environment-friendly manner assumes great importance. Adsorption is a highly effective and economical technique for removal of heavy metals from aqueous solutions. Commercial activated carbon is a well-known and highly effective adsorbent, but the high cost of activated carbon limits its use as an adsorbent especially in developing countries [6]. From this standpoint, numerous investigations were conducted by scientists in this growing and important field of research for the exploration of alternative methods using less expensive natural materials [7]. Metal-sorption by various types of biomaterials like metabolically inactive dried biomass of algae, bacteria and fungi can find useful application for removing metals from solution because of their unique chemical composition [8-11]. Research indicated that biosorption is a very effective method to remove metals from the water and wastewater. Cultivation of microorganisms requires a bioreactor and nutrients such as carbon, nitrogen and trace elements [12,13]. Therefore, cultivation cost is the most important factor to produce these biosorbents. This chapter presents experimental results on removal of Pb (II) ions from aqueous solution by dried fungal biomass produced from corn-processing wastewater. These results

Pb (II) Ions Removal by Dried Rhizopus Oligosporus…

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show that it is possible to use food-processing wastewater as a substrate for cultivating the fungal biomass to reduce operational costs of adsorption processes. Using the wastewaters would be particularly attractive and cost effective because there are many food-processing plants in USA and many other countries that could provide suitable industrial wastewater for cultivating the microbial biomass, such as fungi. The wastewater needs to be treated to address discharge objectives and therefore, the biomass is produces at minimal cost. The goal of the method was to investigate the efficacy of dried fungal biomass as adsorbent for removal of Pb (II) ions from aqueous solution and reduce the treatment costs using another wastewater as a substrate for fungi.

2. EXPERIMENTAL The experimental program comprised two phases. (a) Rhizopus oligosporus were grown on food-processing wastewater. (b) The harvested and dried fungi used for adsorption of Pb (II) ions.

2.1. Cultivation of Rhizopus Oligosporus Rhizopus oligosporus was obtained from American Type Culture Collection (Rockville, MD). The culture was rehydrated and revived in yeast-malt (YM) nutrient broth at 24 ºC. The revived culture was transferred on to numerous potato dextrose agar (PDA) plates and incubated at room temperature (24 ºC) for 7 days. Then fungal sporangiospores were harvested from the surface of PDA plates into sterile distilled water containing 0.85 % (w/v) saline solution (NaCl) and 0.5 % (v/v) of Tween 80. The harvested cultures were diluted further to achieve a spore count of 106 to 107 spores/mL, determined by haemocytometer counts. Glycerin (20 %; v/v) was added to the spore suspension as a cryoprotectant for ultralow frozen storage at –75 oC in 2 mL cryo-vials for future use as a bioreactor inoculum. The inocula were used as a seed in laboratory-scale continuous attached growth tank reactors using corn-processing wastewater as organic substrate. The wastewater was supplied from the ADM wet corn milling facility in Cedar Rapids, IA, US. The reactors were operated at a hydraulic retention time (HRT) of 8 h and solids retention time (SRT) of 2 days. These HRT and SRT values were found to be optimal for the maximum growth of the Rhizopus oligosporus [14]. The micro-fungi were growing in the form of attached mycelia and harvested daily from the bioreactor by natural sloughing off the attachment surface and subsequent gravity settling. The mycelia were washed with deionised water and dried at 65 ºC for 24 h. The dried fungal pellets were ground and sieved (0.5 mm< diameter).

2.2. Adsorption of Heavy Metals The effects of contact time, initial pH, initial metal ion concentration and temperature on adsorption efficiency were examined through a series of shaker flask tests. After determining

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the optimum conditions, a series of adsorption tests were conducted to determine the isotherm for Pb (II) ions.

2.3. Chemicals A 1 g L-1 stock solution of lead was prepared with single reagent grade metal solution (Claritas, Fisher Chemicals) in deionized water. The metal solution was diluted to appropriate concentrations as needed and stored at 4 oC until further use. HNO3 and NaOH were obtained from Fisher Chemicals and used for pH value adjustment.

2.4. Adsorption Experiments All sorption tests were conducted using single reagent grade metal to minimize the variability of metal concentrations and to avoid competitive adsorption of mixed metals on adsorbent. 100 mL of metal solution was added to each of flask containing 0.1 g (dry weight) of R. oligosporus. The flasks were placed on an orbital shaker table running at 150 rpm at 30±1 C (except the temperature experiments) until equilibrium was reached. The residual concentration of Pb (II) ions in the aqueous phase (obtained by centrifugation, 1000 g-10 min) was determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). All tests were conducted in triplicate. The concentrations of the Pb (II) ions the in aqueous phase were used to determine the adsorption capacity of R. oligosporus. Equilibrium sorption isotherms were determined by mass balance. The amount of adsorbed Pb (II) ions at equilibrium, qeq (mg g-1) was calculated as follows: qeq =

[(Co Ceq )V ] x

(1)

where Co and Ceq are the initial and equilibrium concentrations of Pb (II) ions (mg L-1), V volume of solution and x the weight of sorbent (g).

2.5. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) Analysis Measurements were performed with a Hewlett Packard 4500 Series ICP-MS using external calibration. The instrument was calibrated before each measurement. Operating parameters are summarized in Table 1.

2.6. Equilibrium Isotherms and Kinetics of Adsorption The Langmuir isotherm was used first to describe observed sorption phenomena. The Langmuir isotherm applies to adsorption on a completely homogenous surface with negligible interaction between adsorbed molecules [15,16]. The linear form of the equation can be written as;


321

Table 1. ICP-MS operating conditions. Rf power Rf matching Sample depth Plasma gas flow Auxiliary gas flow

1200 W 2V 7.8 mm 16 L min-1 1.4 L min-

Carrier gas flow

1.0 L min-

Acquisition time Resolution

22.83 sec 300

Ceq qeq

=

1 1

Ceq 1 + bqmax qmax

(2)

where Ceq is the equilibrium concentration of Pb (II) ions, qeq is the amount of adsorption at equilibrium, qmax is the mono-layer capacity, and b is an equilibrium constant of Langmuir. The Freundlich isotherm (empirical model adsorption in aqueous systems) was also tested with our experimental data. The linear form of the equation can be written as: lnqeq= lnKf +

1 n

lnCeq

(3)

where Kf is the measure of sorption capacity, 1/n is the sorption intensity. Pseudo-first order and pseudo-second order kinetic models were applied to data to analyse the sorption kinetics of Pb (II) ions. A simple pseudo first-order equation due to Lagergren was used by different researchers [17,18]: log (qeq-qt) = log qeq-

kad 2.303t

(4)

where qe and qt are the amount of adsorption at equilibrium and at time t respectively, and kad is the rate constant of the pseudo first-order adsorption process. A plot of log (qeq-qt) vs. t would provide a straight line for first-order adsorption kinetics, allowing computation of the adsorption rate constant, kad. Ho‘s second-order rate equation, which has been called a pseudo-second order kinetic expression, has also been applied widely [19,20]. The linear form of the kinetic rate equations can be written as follows:

t qt

1 kqeq2

1 t qe q

(5)

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where k is the rate constant of sorption (dm3 mg-1 min-1), qe is the amount of metal ion sorbed at equilibrium (mg g-1), and qt is the amount of metal ion sorbed at time t (mgg-1). The constants can be determined experimentally by plotting t/qt against t.

2.7. FT-IR Analyses Fourier Transform Infrared Spectroscopy (FT-IR) analysis in the solid phase was performed using a Fourier Transform Infrared Spectrometer (Varian 2000 FT-IR). Pure biosorbent powders were used and spectra of the fungal biomass before and after Pb(II) sorption were recorded.

3. RESULTS 3.1. The Effect of the Contact Time The major fraction of Pb (II) ions, adsorbed within the first 6h and dissolve Pb remained nearly constant afterwards. This suggested that the biosorption process reached saturation within 6h. For this reason a 6h contact time was used for the further experiments. Figure 1 shows the effect of contact time on adsorption of Pb(II) ions onto the dried R. oligosporus biomass.

3.2. The Effect of the Initial pH Results of the experiments using 100 mg L-1 Pb (II) solutions and 1 g L-1 adsorbent showed that efficiencies of adsorption were increased with increasing pH from 2.0 to 6.0 (Figure 2). At the low pH ranges, a high concentration of protons in the solution may have competed with metal ions in forming a bond with the active sites on the surface of the fungi. These bonded active sites thereafter became saturated and were unavailable to other cations. 60.00

q (mg/g)

50.00 40.00 30.00 20.00 10.00 0.00 0

5

10

15

20

25

30

35

40

45

50

55

t (hour)

Figure 1. The effects of contact time on adsorption of Pb(II) ions (100 mg l-1) to the dried R.oligosporus biomass (adsorbent dosage: 1g l-1; pH:5.0; temperature: 30 C).


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60.00

q (mg/g)

50.00 pH2 pH3 pH4 pH5 pH6

40.00 30.00 20.00 10.00 0.00 0

1

2

3

4

5

6

7

t (hour)

Figure 2. The effects of the initial pH on adsorption of Pb(II) ions (100 mg l-1) to the dried R.oligosporus biomass (adsorbent dosage:1g l-1; contact time: 6h; temperature: 30 C) 60

q(mg/g)

50 40 30 20 10 0 0

20

40

60

80

100

120

140

160

Co(mg/L)

Figure 3. The effects of initial metal concentration on adsorption of Pb(II) ions to the dead R.oligosporus biomass (adsorbent dosage:1g l-1; contact time: 6h; pH:5.0).

3.3. The Effect of the Initial Metal Concentrations The adsorption of Pb (II) by the dried R. oligosporus biomass was studied at different Pb (II) ion concentrations in the range from 20 to 150 mg L-1. Equilibrium sorption capacity of the dried R. oligosporus biomass increased with increasing initial Pb (II) ion concentrations (Figure 3). The initial concentration provides an important driving force to overcome all mass transfer resistance of Pb (II) ions between the aqueous and solid phases. Hence a higher initial concentration of Pb (II) ions may increase the adsorption capacity.

3.4. The Effect of Adsorbent Dosage Experimental results indicated that the efficiency of biosorption was decreased with increasing adsorbent dosage ranging from 0.5-5 g L-1 (Figure 4). This However the percentage of the Pb(II) ions biosorption was increased with increasing biomass because of higher surface area. This can be explained by concentration gradient between the solute

324


concentration in the solution and the one in the surface of the adsorbent. When the adsorbent dosage is higher, there is a very fast adsorption onto the adsorbent surface, which results in a lower Pb(II) ion concentration in the solution. However, the adsorption sites on the adsorbent surface remain unsaturated when the Pb(II) ion concentration in the solution drops to a lower value. Thus, the amount of Pb(II) ions adsorbed onto per unit weight of adsorbent gets reduced with the adsorbent dosage increasing [25].

3.5. Adsorption Isotherms and Kinetics of Adsorption

q (mg/g)

Two equilibrium models were employed: The Langmuir and Freundlich isotherm equations. The correlation coefficient of Freundlich isotherm (R2) was 0.8824 (Figure 5). The Langmuir model was the best-fit isotherm for adsorption of Pb (II) to the dried R. oligosporus biomass. Langmuir isotherm model parameters, qmax and b, were estimated from the intercept and slope of Ceq/qeq vs. Ceq , according to Eq. (2) and obtained as 59.88 (mg g-1) and 0.042 (L g-1), respectively. The correlation coefficient of the Langmuir isotherm (R2) was 0.9820 (Figure 6). 90 80 70 60 50 40 30 20 10 0

0.5 1 3 5

0

1

2

3 4 t (hour)

5

6

7

lnqe

Figure 4. The effects of adsorbent dosage on adsorption of Pb (II) ions to dried R. oligosporus biomass (contact time: 6h; pH:5.0; temperature: 30 C) 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

y = 0.4115x + 2.0629 R2 = 0.8824

2

2.5

3

3.5

4

4.5

5

lnCe

Figure 5. The Freundlich adsorption isotherm for Pb(II) adsorption on to dried R. oligosporus biomass (adsorbent dosage:1g l-1; pH: 5.0; initial metal concentration of 20-100 mg l-1; temperature: 30 C).


325

2.500 y = 0.0167x + 0.398 R2 = 0.982

Ce/qe

2.000 1.500 1.000 0.500 0.000 0

20

40

60

80

100

120

Ce (mg/L)

Figure 6. The Langmuir adsorption isotherm for Pb(II) adsorption on to dried R. oligosporus biomass (adsorbent dosage:1g l-1; pH 5.0; initial metal concentration of 20-100 mg l-1; temperature: 30 C). 20 mg/L 40 mg/L 60 mg/L 80 mg/L 100 mg/L

25.00

t/qt

20.00 15.00

R2 = 0.995 R2 = 0.9982 R2 = 0.9929

10.00

R2 = 0.9924 R2 = 0.9981

5.00 0.00 0

100

200 t (min)

300

400

Figure 7. The plots of pseudo-second order kinetics with respect to different initial Pb(II) ion concentrations (adsorbent dosage:1g l-1; pH 5.0; temperature:30 C).

Kinetic studies were carried out for biosorption of Pb (II) as a function of contact time at various initial Pb (II) concentrations ranging from 20-100 mg L-1. Experimental results indicated that the pseudo-second order reaction model provided the best description of the data with a correlation coefficient 0.99 for different initial metal concentrations (Figure 7). Table 2. Pseudo-second order reaction rate regression results. Initial metal concentration (mg L-1) 20 40 60 80 100

Rate constant (L mg-1 min1 ) 8.9 x10-4 5.0 x10-4 3.9 x10-4 3.8 x10-4 3.7 x10-4

Correlation coefficient (R2) 0.9950 0.9982 0.9929 0.9924 0.9981

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Figure 8. FTIR spectra of the dried R. oligosporus biomass.

Figure 9. FTIR spectra of the dried R. oligosporus biomass after Pb(II) ions adsorption.

Reaction rate constants for pseudo-second order equations are shown at Table 2. The results indicated that the adsorption system studied follows a pseudo-second order kinetic model at all time intervals and pseudo-second order rate constants were affected by initial Pb (II) ions concentration.


327

3.6. FT-IR Analysis Fungal biomass is a complex material containing protein, lipid and polysaccharides (cellulose, chitin) as major constituents. Therefore biosorption may occur at the polar functional groups of cellulose and chitin, which include amino, hydroxyl and carboxyl groups as chemical bonding agents. The FTIR analyses of dried R. oligosporus biomass before and after Pb(II) adsorption is shown in Figure 8-9. Spectra analyses of FTIR spectrum showed that there was a decrease in the adsorption intensity of amide I and –OH groups at 1644 cm-1, 1402cm-1 respectively and this indicates that amide I and hydroxyl groups played an important role in binding Pb(II).

4. CONCLUSION To development of an efficient and cost-effective removal process, fungal biomass produced from food industry wastewater is a good alternative biosorbent. Experimental results showed that based on the Langmuir coefficients, the total capacity (monolayer saturation at equilibrium) of the dried R. oligosporus biomass for Pb (II) ions was about 60 mg g-1 (biosorbent dose of 1g/L, 6h contact time, initial Pb (II) concentration of 100 mg/L and optimum pH of 5.0). Experimental results also indicated that the pseudo-second order reaction model provided the best description of the data with a correlation coefficient 0.99 for different initial metal concentrations. The fit of the experimental data to this model suggest that the process controlling the rate may be chemical sorption. The FTIR analyses showed that amide I and hydroxyl groups plays an important role in binding of Pb(II). With the advantage of high metal biosorption capacity, R.oligosporus biomass, produced from corn-processing wastewater, has the potential to be used as an effective and economic biosorbent material for the removal of Pb (II) ions from wastewater streams.

ACKNOWLEDGMENTS Authors are thankful to Dr. Basudeb Saha for technical assistance (ICP-MS measurements) and Iowa State University for their financial support.

REFERENCES [1] [2] [3]

Aguado, J., Arsuaga, J. M., Arencibia, A., Lindo, M. & Gascon, V. (2009). Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica. Journal of Hazardous Materials, 163, 213-221. Yurtsever, M. & Sengil, I. A. (2009). Biosorption of Pb(II) ions by modified quebracho tannin resin, Journal of Hazardous Materials, 163, 58-64. Ozsoy, H. D. & Kumbur, H. (2006). Adsorption of Cu(II) ions on cotton boll. Journal of Hazardous Materials, B136, 911-916.

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H. Duygu Ozsoy and J. Hans van Leeuwen Rakhshaee, R, Giahi, M. & Pourahmad, A. (2009). Studying effect of cell wall‘s carboxyl-carboxylate ratio change of Lemna minor to remove heavy metals from aqueous solution. Journal of Hazardous Materials, 163, 165-173. Gupta, V. K. & Rastogi, A. (2009). Biosorption of hexavalent chromium by raw and acid-treated green alga Oedogonium hatei from aqueous solution. Journal of Hazardous Materials, 163, 396-402. Boujelben, N., Bouzid, J. & Elouear, Z. (2009). Adsorption of nickel and copper onto natural iron oxide-coated sand from aqueous solutions: Study in single and binary systems, Journal of Hazardous Materials, 163, 376-382. Aziz, A., Ouali, M. S., Elandaloussi, El. H., De Menorval, L. C. & Lindheimer, M. (2009). Chemically modified olive stone: a low-cost sorbent for heavy metals and basic dyes removal from aqueous solutions. Journal of Hazardous Materials, 163, 441-447. Ahluwalia, S. S. & Goyal, D. (2007). Microbial and plant derived biomass for removal of heavy metals from wastewater. Bioresource Technology, 98(12), 2243-2257. Ozsoy, H. D, Kumbur, H & Ozer, Z. (2007). Adsorption of copper (II) ions to peanut hulls and Pinus brutia sawdust. International Journal of Environmental Pollution, 31, 125-134. Chen, C. & Wang, J. (2008). Removal of Pb2+, Ag+, Cs+ and Sr2+ from aqueous solution by brewery‘s waste biomass. Journal of Hazardous Materials, 151, 65-70. Ozsoy, H. D, Kumbur, H., Saha, B. & van Leeuwen, J. H. (2008). Use of Rhizopus oligosporus produced from food processing wastewater as a biosorbent for Cu(II) ions removal from the aqueous solutions. Bioresource Technology, 99, 4943-4948. Yurekli, F., Unyayar, A., Porgali, Z. B. & Mazmanci, M. A. (2004). Effects of cadmium exposure on phytochelatin and the synthesis of abscisic acid in Funalia trogii. Engineering in Life Sciences, 4, 378-380. Mazmanci, M. A. & Unyayar, A. (2005) Decolorisation of Reactive Black 5 by Funalia trogii immobilized on Luffa cylindirica sponge. Process Biochemistry, 40, 337-342. Jasti, N., Khanal, S. K., Pometto III, A. L. & van Leeuwen, J. H. (2008). Converting corn wet milling effluent into high-value fungal biomass in an attached growth bioreactor. Biotechnology & Bioengineering, 101(6), 1223-1233. Yu, B., Zhang, Y., Shukla, A., Shukla, S. S. & Dorris, K. L. (2001). The removal of heavy metals from aqueous solutions by sawdust adsorption-removal of lead and comparison of its adsorption with copper. Journal of Hazardous Materials, B84, 83-94. Ho, Y. S. (2004). Pseudo-isotherms using a second order kinetic expression constant. Adsorption, 10, 151-158. Ho, Y. S. & McKay, G. (1998). Sorption of dye from aqueous solution by peat. Chemical Engineering Journal, 70, 115-124. Bhattacharyya, K. G. & Sharma, A. (2005). Kinetics and thermodynamics of methylene blue adsorption on neem (Azadirachta Indica) leaf powder. Dyes and Pigments, 65, 51-59. Ho Y. S. & McKay, G. (2000). The kinetics of sorption of divalent metal ions onto sphagnum moss peat. Water Resource, 34(3), 735-742. Ho, Y. S. (2005). Effect of pH on lead removal from water using tree fern as the sorbent. Bioresource Technology, 96, 1292-1296.


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[21] Fiol, N., Villaescusa, I., Martinez, M., Miralles, N., Poch, J. & Serarols, J. (2006). Sorption of Pb(II), Ni(II), Cu(II) and Cd(II) from aqueous solutions by olive stone waste. Separation and Purification Technology, 50, 132-140. [22] Pavasant, P., Apiratikul, R., Sungkhum, V., Suthiparinyanont, P., Wattanachira, S. & Marhaba, T. F. (2006). Biosorpion of Cu2+, Cd2+, Pb2+ and Zn2+ usind dried marine green macroalga Caulerpa lentillifera. Bioresource Technology, 97, 2321-2329. [23] Liu, Y., Chang, X., Guo, Y. & Meng, S. (2006). Biosorption and preconcentration of lead and cadmium on waste Chinese herb Pang Da Hai. Journal of Hazardous Materials, B135, 389-394. [24] Martinez, M., Miralles, N., Hidalgo, S., Fiol, N., Villaescusa, I. & Poch, N. (2006). Removal of lead(II) and cadmium(II) from aqueous solutions using grape stalk waste. Journal of Hazardous Materials, B133, 203-211. [25] Jiang, Y., Pang, H. & Liao B. (2009) Removal of copper(II) ions from aqueous solution by modified bagasse. Journal of Hazardous Materials, 164, 1-9.



Chapter 17

CONTROL OF PLASTICIZERS IN DRINKING WATER, EFFLUENTS AND SURFACE WATERS Rosa Mosteo, Judith Sarasa, Mª Peña Ormad and Jose Luis Ovelleiro Department of Chemical Engineering and Environmental Technologies, University of Zaragoza-Spain.

ABSTRACT The main objective of this research work is to determine the presence of di(2ethylhexyl) phthalate, di(2-ethylhexyl) adipate and diisodecyl phthalate, in different water samples (drinking waters, effluents and surface waters). Different analytical methods were studied in order to know the best methodology for the quantification of these compounds. Solid-liquid and liquid-liquid extraction were investigated and finally the liquid-liquid extraction and analysis by gas chromatography followed by mass spectroscopy was chosen because of offering the highest recovery rate. In the whole of this research study, the control of background pollution by reagents and material was extremely important. The problem of background pollution is more serious in the trace analysis of phthalates and adipates as a consequence of their presence in almost all equipment and reagents used in the laboratory. Respect to the control of the selected plasticizers in the different water samples, bis (2-ethylhexyl) phthalate and bis (2-ethylhexyl) adipate were detected in drinking water, effluents and surface waters. On the other hand, diisodecyl phthalate was not detected in any sample.

INTRODUCTION Phthalates have been in use for almost 40 years and are used in the manufacture of PVC and other resins, as well as plasticizers and insect repellents [1]. Plasticizers are used in building materials, home furnishing, transportation, clothing, and, to a limited extent, in food packaging and medicinal products [2]. There is also concern regarding the potential health

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Rosa Mosteo, Judith Sarasa, Mª Peña Ormad et al.

effects of several phthalates because these compounds are used to impart softness and flexibility to normally rigid PVC products in children‘s toys. Phthalates can enter the environment through losses during manufacture and by leaching from the final product. This is because they are not chemically bonded to the polymeric matrix [1]. These compounds have low water solubilities and tend to adsorb to sediments and suspended solids. Therefore, they have the potential to leach into their surrounding environment. Certain phthalates have also shown estrogenic behaviour [3, 4] so they can be classified as potential endocrine disruptors. Many endocrine disrupting substances, or potential endocrine disrupters (EDCs), were previously classified as organic micropollutants. Therefore, many substances, such as foodstuffs, flavonoids, lignans, sterols, fungal metabolites and synthetic chemicals of widely varying structural classes (e.g. phthalates, PCBs), can interact with hormone receptors and modulate the endocrine system [5]. Phthalates are classified as EDCs in several lists of compounds by various organizations [6], for example: -

UKEA: United Kingdom Economics Account [7]. USEPA: U.S. Environmental Protection Agency [8]. OSPAR: Oslo and Paris Commissions [9].

The most of Phthalates and adipates used as plasticizers are being included in list of priority contaminants of different countries. In the United Stated, the Environmental Protection Agency established concentration limits in drinking waters for both di(2ethylkhexyl)phthalate (6 µg/l) and di(2-ethylhexyl)adipate (0.4 mg/l) [10]. In the European Union there are not contamination limits for phthalates and adipates, although it is known that these limits will be established in the near future. The di(2-ethylkhexyl)phthalate is included in the priority list [11] and identified as priority hazardous substance in the field of water policy. The guideline value in drinking water proposed by the World Health Organization in the 1993 Guidelines [12, 14] for the Di(2-ethylhexyl)adipate is 80 µg/l and in the case of Di(2-ethylhexyl)phthalate the guideline value is 8 µg/l. Di(2-ethylhexyl)adipate is also known as DEHA. This compound is mainly used as a plasticizer for synthetic resins such as PVC, but significant amounts are also used as lubricants and for hydraulic fluids [13]. Reports of the presence of DEHA in surface water and drinking water are scarce, but DEHA has occasionally been identified in drinking-water at levels of a few micrograms per litre. As a consequence of its use in PVC films, food is the most important source of human exposure (up to 20 mg/day). Di(2-ethylhexyl)phthalate is also known as DEHP. This compound is primarily used as a plasticizer in many flexible polyvinyl chloride products and in vinyl chloride co-polymer resins. It has also application as replacement for polychlorinated biphenyls in dielectric fluids for small (low-voltage) electrical capacitors [13]. This compound has been found in surface water, groundwater and drinking-water in concentrations of a few micrograms per litre. In polluted surface water and groundwater, concentrations of hundreds of micrograms per litre have been reported. Numerous manufactures are trying to substitute the DEHP for the diisodecyl phthalate, which is a plasticizer less toxic than di(2-ethylhexyl) phthalate (DIDP). As a consequence of the necessary control of these pollutants in different waters, analytical methodologies should be established in order to improve the quantification of these compounds. Methodologies commonly used to analyze organic compounds in trace levels are based on liquid-liquid or solid-liquid extraction following chromatographic analysis. In this

Control of Plasticizers in Drinking Water, Effluents and Surface Waters

333

study, two methodologies have been developed in order to find the best one for the analysis of the interest compounds. Both of them are modifications of the 506 and 606 EPA methods [15, 16]. In this research work the presence of bis (2-ethylhexyl) phthalate, bis (2-ethylhexyl) adipate and diisodecyl phthalate, plasticizers frequently used by manufacturers, has been evaluated in different water samples (drinking waters, effluents and surface waters). Different analytical methodologies, using solid-liquid extraction or liquid-liquid extraction prior to analysis by GC/MS, were studied in order to know the best methodology for the quantification of these compounds. A study about the background pollution is carried out since they are present in the majority of equipment and reagents used in the laboratory.

EXPERIMENTAL PROCEDURE Analytical Methodology for the Control of DEHP, DIDP and DEHA Standard of DEHP, DIDP and DEHA purchased from Dr. Ehrenstorfer were used. A stock solution for each compound is prepared in methanol. In the case of the DEHP, the stock solution presented concentration of 1000 mg/l, the DIDP 1520 mg/l and the DEHA 1000 mg/l. The chemical structure of DEHP, DIDP and DEHA are shown in Figure 1. The chromatographic conditions are shown in Table 1. DEH P

DEH A

DIDP

Figure 1.Chemical structure of DEHP, DEHA and DIDP.

Table 1. Chromatographic conditions. Gas Chromatographer TRACE GC 2000 (TermoFinnigan) Column DB5 (J&W, 30 m, 0,25 mm, 0,25 μm) Program of temperature 60 ºC (1.5 min)-10 ºC min-1-240 ºC (30 min)-10 ºC min-1-260 ºC (5 min) Temperature of injector 300 ºC Volume of injection 2 μL, splitless 0.8 min Carrier gas He, 1 mL min-1 Mass Espectrometer POLARIS (ThermoFinnigan) Energy of ionization 70 eV Mode of acquisition SIM Range of masses 50-450 amu Velocity of screened 1 scan s-1

334

Rosa Mosteo, Judith Sarasa, Mª Peña Ormad et al. 506 and 606 U.S EPA methods

506 U.S EPA method Sample (4ºC)

Sample (4ºC)

Sample dilution with MIlliQ water (if necessary) 506 Method + Na Cl

Liquid-liquid extraction 3 extactions with CH2Cl2 506 method:+1extaction C6H6

Concentration with N2 in TurboVap

Sample dilution with MIlliQ water (if necessary)

Solid-liquid extraction C18 cartridge

- Cartridge preparation (CH2Cl2/MeOH/H2O) - Compound adsorption - Cartridge dried with air

Elution of compounds with CH2Cl2 (5 ml, pressure)

Extract dried with Na2SO4 anhidrous


Concentration with N2 (volume 1 ml)


GC/MS analysis

GC/MS analysis

Figure 2. Diagrams of liquid-liquid extraction (506 and 606 EPA methods) and solid-liquid extraction (506 EPA method).

The extraction methods used in this study are schematized in the Figure 2. The liquidliquid extraction has been carried out taking into account both methods 506 EPA method (use of NaCl during the process) and 606 EPA method (without NaCl). The solid-liquid extraction is related to 506 EPA method.

RESULTS Analysis by GC/MS of Standards In Figures 3, 4 and 5 are reflected the chromatograms and spectrums for DEHP, DEHA and DIDP standards, respectively.


335

26.07

Figure 3. Chromatogram and MS spectrum of DEHP

23.01

Figure 4. Chromatogram and MS spectrum of DEHA.

Table 2. Identification by GC/MS for each compound. Compound DEHA DEHP DIDP

Retention time (min) 26.06 23.01 36-48

Characteristic mass (m/z) 149 129 149

A summary of the retention time and the characteristic mass used for the identification of DEHP, DEHA and DIDP is shown in Table 2.

336


149

RT: 29.92 - 56.14 NL: 6.68E5

41.45

100

TIC MS 25ppm

95 90 85 80

39.64

42.33 40.73

75

43.43

70

Relative Abundance

65

43.74 44.09

60

45.19 38.94

55 37.88

50

46.17

45 36.92

40 31.18

35

33.94 35.06

37.25

47.45 47.95 48.62 49.81

35.65

55.63 50.62 51.47 52.81 54.50

30 25 20 15 10 5 0 30

32

34

36 36

38

40

42 44 Time (min)

46

48 48

50

52

54

56

Figure 5. Chromatogram and MS spectrum of DIDP

As it can be observed in Figure 5, the diisodecyl phthalate (DIDP) is not identified by only one peak in the chromatogram since it is a mixture of isomers. Therefore, for its identification it is necessary to consider the time range 36-48 min. The quantification of di(2-ethylhexyl)phthalate (DEHP) and di(2-ethylhexyl)adipate (DEHA) was based on the retention time and their characteristic mass (m/z=149 and m/z=129 for DEHP and DEHA, respectively). In the case of the DIDP the quantification was made taking into account two options: (a) Considering the most representative isomers. The quantification is based on the retention times of these isomers (39.60 min and 41.45 min) and their characteristic masses (m/z=149). (b) Considering the area of all the isomers peaks as a whole. The quantification is based on the manual integration of the total area and the characteristic mass (m/z=149). For this reason, three calibration curves were established for the DIDP: 1. Calibration DIDP t=39 : The peak at 39 min is considered as representative of this compound. 2. Calibration DIDP t=41 : The peak at 41 min is considered as representative of this compound. 3. Calibration DIDP total : The total area of all isomers is considered as representative.


337

Table 3. Details of the calibration curves obtained in this study. R2 0.9983

Linear range 5-250 µg l-1

QL* 5µg l-1

0.9981

5-250 µg l-1

5 µg l-1

DIDPt=39

Calibration curve FR=6.8655*10-5+0.0004348*C (µg l-1) FR=-0.001073+0.00024809*C (µg l1 ) FR=-0.0368+0.0215*C (mg l-1)

0.9977

3.12-75 mg l-

3.1 mg l-1

DIDPt=41 DIDPtotal

FR=-0.1469+0.0446*C (mg l-1) FR=-3.4716+0.8841*C (mg l-1)

0.9994 0.9981

6.5-75 mg l-1 6.5-75 mg l-1

6.5 mg l-1 6.5 mg l-1

DEHP DEHA

1

*QL = quantification limit / FR= factor response

Deuterated Anthracene (AD10) (retention time= 16.53 min, m/z= 188) was used as an internal standard for the quantification of target compounds by GC/MS analysis. The calibration curves, the linear ranges and the quantification limits obtained for DEHP, DEHA and DIDP are shown in Table 3.

Study of the Background Pollution The background pollution was evaluated in the different stpes involved in the analytical method used to quantify the compounds of interest (DEHA, DEHP and DIDP). This problem of background contamination has been more serious in the trace analysis of plasticizers than in the studies of many other pollutants because these compounds are present in almost all equipments and reagents used in the laboratory. Different commercial reagents were evaluated (Carlo Erba, Merck…) with the aim of selecting the commercial brand most appropriate for carrying out these analyses. The obtained results are shown in Table 4. Table 4. Study of Background pollution.

1

Materials and reagents Dichloromethan e Hexane NaCl Methanol Water

Brands analysed

Brand selected

Carlo Erba1, Merck2 Carlo Erba1, Merck2, SDS3 Carlo Erba1, Merck2 SDS4 MilliQ5,Mineral water A6, Mineral water B7, mineral water C8

Merck Merck Merck SDS Mineral water A

Glass wool Teflon tube (Nitrogen)

Panreac, Carlo Erba1, Merck2 N95: Carburos metalicos (air products)

Merck ----

99% purity, analysis quality quality for organic traces 3 quality for pesticides analysis 2

338


4

HPLC quality5 Ultrapure Milli Q water Mineral Water A (bottled in glass) 7 Mineral Water B (bottled in glass) 8 Mineral Water C (bottled in carton) 6

Modified liquid-liquid method

Modified solid-liquid method Sample (4ºC)

Sample (4ºC)

If it‘s necessary: Dilution with mineral water A+ NaCl

Liquid-liquid extraction 3 extractions with CH2Cl2 +1 extraction C6H6

Concentration in rotatory evaporator (2-4ml)

C6H6 addition until volume=10 ml

Drying of the extract with Na2SO4 anhidrous


GC/MS analysis

If necessary: Dilution with mineral water A Sample dilution with MIlliQ water (if it‘s necessary)

Solid-liquid extraction C18 cartridge

- Cartridge preparation CH2Cl2/MeOH/H2O df fffffff(Mineral water A) - Compound adsorption -Drying cartridge with N2

Elution of compounds with CH2Cl2 (3-4 ml, gravity)

C6H6 addition until volume=10 ml



GC/MS analysis

Figure 6. Modified methods in accordance with the background pollution study.

As a consequence of this study, the analytical methodologies previously described in the experimental procedure section have been modified to avoid as much as possible the background pollution. The main modifications are related to avoid DEHA and DEHP pollution since DIDP contamination was not detected (Table 4). For this reason, mineral water A bottled in glass was used instead of MilliQ water. Furthermore, the extract concentration has been modified and the reagents most adequate have been chosen (Table 4).The modified methodologies are described in Figure 6.


339

Study of the Recovery of Each Method The following analytical methodologies have been compared in order to know which one is the most appropriate for the analysis of DEHP, DEHA and DIDP:   

Modified solid-liquid extraction + GC/MS analysis Modified liquid-liquid extraction + GC/MS analysis Modified liquid-liquid extraction with addition of NaCl+ GC/MS analysis

The synthetic samples were prepared by diluting stock solution in mineral water A, obtaining concentrations of 30 µg l-1 for DEHA, 60 µg l-1 for DEHP and 1.2 mg l-1 for DIDP. The recovery results obtained for each analytical method are shown in Figure 7. As it can be observed in Figure 7, the recoveries obtained with the solid-liquid extraction were very low, probably due to polarity of the adsorbent. As a consequence, this method was rejected. In the case of liquid-liquid methodologies the recoveries were higher. It is also noticed that the NaCl addition, used to saturate water and to help the movement of the compounds to organic phase, improved the liquid-liquid method. The DEHA and DEHP recoveries were twice and four times higher respectively whereas DIDP recovery increased slightly. Therefore the liquid-liquid extraction with NaCl addition was selected for the analysis of the target pollutants.

Control of DEHA, DEHP and DIPD in Real Waters Control in different mineral waters and tap water This study was carried out with different brands of mineral waters and tap water (water B) from the city of Zaragoza (Spain).

Figure 7. % Recoveries obtained for DEHP, DEHA and DIDP using different methods of extraction.

340


The main features of the studied mineral waters, taking into account that A, C, D,…are the brands, are the following:       

- Mineral water A bottled in PET. - Mineral water A bottled in glass. - Mineral water C bottled in PET. - Mineral water C bottled in Carton. - Mineral water D bottled in PET - Mineral water E bottled in PET. - Mineral water F bottled in HPDE.

The obtained results are reflected in Figure 8. It is observed that the tap water was the most polluted (11.8 µg l-1 DEHA and 29.2 µg l-1 DEHP). The mineral water C bottled in carton and the mineral water A bottled in glass presented the less concentration of DEHA (1.1 µg l-1) and DEHP (6.9 µg l-1). Considering all the studied samples, the range of DEHA concentration was 1.1-3.5 µg l-1 and with respect to DEHP the range was 6.9-23.3 µg l-1. The DIDP compound was not detected in the analyzed waters.

Figure 8. Control of DEHP, DEHA and DIDP in tap and mineral waters.

Furthermore, from Figure 8 it can be concluded that the concentration of the target pollutants depends on the material of which the bottle is made of. In order to compare in a better way the concentrations of the target compounds, in Figure 9 are shown the results for mineral water A and C, bottled in glass, PET and carton. The main difference between mineral waters was due to the DEHP concentration, which was lower in glass bottle.


341

Figure 9. Concentration of DEHP and DEHA in mineral water A and C.

Figure 10. Concentration of DEHP and DEHA in mineral waters bottled in PET.

In Figure 10, the mineral waters bottled in PET are compared. As it can be observed, the DEHA concentration was very similar for all the analyzed mineral waters. However, the DEHP concentration showed a great variation. In fact, the DEHP concentration in mineral waters A and D was twice the concentration in mineral water C and E.

Control in wastewaters generated in PVC manufacturing and surrounding groundwater In this section, it is shown the control of the target compounds in both real wastewaters produced during the PVC manufacturing and in the groundwater used by the manufacturing plant for their own supply. The different analyzed wastewaters were the following:

342

Rosa Mosteo, Judith Sarasa, Mª Peña Ormad et al.  

Wastewater I: Generated during the process of polymer synthesis. Wastewater II: Produced during the process of polymer transformation by the additives addition (plasticizers). This transformation takes place at high temperature and the analyzed wastewater was the refrigeration water used in this installation.

Figure 11. Presence of DEHP and DEHA in wastewaters and groundwater

Figure 12. Chromatogram of groundwater.

Two different samples of these wastewaters were analyzed and the results obtained are shown in Figure 11 and it is observed that the DEHP concentration was always higher than DEHA concentration. DIDP compound was not detected in any sample. The chromatograms obtained for analyses of groundwater and wastewater II (sampling b) are reflected in Figure 12 and 13, respectively.


343

The chromatogram of wastewater II (sample b) (Figure 13), shows previous peaks to DEHP peak (m/z=149) which are probably related to some plasticizers containing a lower number of carbon atoms. These substances appear in significant concentrations.

Figure 13. Chromatogram of wastewater II (sample b).

CONCLUSION -

-

-

-

The study of background pollution during the determination of di(2-ethylhexyl) phthalate, di(2-ethylhexyl) adipate and diisodecyl phthalate in aqueous samples is essential and the use of solvent of adequate quality is important as well. Due to the presence of these plasticizers in almost all equipments and reagents used in the laboratory, their control in each stage of the analytical methodology is necessary. The liquid-liquid extraction with NaCl addition followed by GC/MS was selected for the analysis of the target pollutants since the highest recoveries were obtained (80.5% for DEHA, 119% for DEHP and 139.9 % for DIPD). The control of the target pollutants in groundwater, wastewaters and mineral waters indicate that the presence of DEHP was important in all the samples and its concentration was higher that the DEHA concentration. DIDP compound was not detected in any sample. The detected concentration of DEHP and DEHA is significantly higher in the case of tap water than in the case of the analyzed mineral waters. In all the samples, the DEHA concentration always presented a concentration lower than the limit established by the EPA (0.4 mg/l) for drinking waters [17]. Respect to the control of these compounds in groundwater and wastewaters, it was observed that the DEHP concentration is always higher than the DEHA concentration. The wastewater generated during the process of polymer transformation by the additives addition is the most polluted by these plasticizers.

344


REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

Fromme, H., Kuchler, T., Otto, T., Pilz, ,K. Muller, J. & Wenzel, A. (2002). Occurrence of phthalates and bisphenol A and F in the environment. Water Research, 36, 14291438. Staples, C. A., Peterson, D. R., Parketon, T. F. & Adams, W. J. (1997). The environmental fate of phthalate esters: a literature review. Chemosphere, 35, 667-749. Harris, C. A., Henttu, P., Parker, M. G. & Sumpter, J. P. (1997). The estrogenic activity of phthalate esters in vitro. Environmental Health Perspectives, 105, 802-811. Jobling, S., Reynolds, T., White, R., Parker, M. G. & Sumpter, J. P. (1995). A variety of environmentally persistent chemical, including some phthalate plasticizers, are weakly estrogenic. Environmental Health Perspectives, 103, 582-587. Combes, R. D. (2000). Endocrine disruptors: a critical review of in vitro and in vivo testing strategies for assessing their toxic hazard to humans. ATLA, 28, 81-118. Birkett, J. W. & Lester, J. N. (2003). Endocrine disrupters in wastewater and sludge treatment processes. London, Lewis Publisher. United Kingdom Economics Account (2000). Endocrine disrupting substances in the environment: The environment Agency‘s strategy. Environment Agency. U.S. Environmental Protection Agency. (1997). Special Report on Environmental Endocrine Disruption: An effects Assessment and Analysis, Report Nº EPA/630/R96/012, Washington D.C. Oslo and Paris Commisions. (1998). OSPAR strategy with regard to hazardous substances. OSPAR convention for the protection of the marine environment of the North-East Atlantic. OSPAR 98/14/1, Annex 34. U.S Environmental Protection Agency. (1991). National Primary Drinking Water Regulations; Fed. Reg., Part 12, 40 CFR Part 141, p.395, U.S. Environmental protection agency, Washington, DC. Decision nº 2455/2001/EC of the European Parliament and of the council of 20 November 2001 establishing the list of priority substances in the field of water policy and amending Directive 2000/60/EC. World Health Organization Guidelines for Drinking Water quality (1993), set up in Geneve. International Agency for Research on Cancer. (1982). Some industrial chemicals and dyestuffs. International agency for Research on Cancer, IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, 29, 257-267. Guidelines for drinking water quality (1996). 2nd ed. Vol. .2. Health criteria and other supporting information. World Health Organization, Geneva. U.S. EPA. (1995). 600/R-95-131. Method 506. Determination of Phtalate and adipate esters in dringing water by liquid-liquid extraction or liquid-solid extraction and chromatography with photoionization detection. CD-1DWSU. U.S. EPA. (1996). 821/B-96-005, Method 606., Determination of phtalates in municipal and industrial wastewater, 40 CFR, part 136 Appendix A, CD 40_136. U.S. EPA (1997). Public Health Goal for Di(2-Ethyl-hexyl)Phthalate (DEHP) in drinking water, pesticide and environmental Toxicology section, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency.

INDEX A abatement, 42, 108 absorption, 9, 87, 88, 93, 95, 98, 122, 136, 137, 181, 183, 185, 195 acceleration, 119, 252 accelerator, 95 acceptor, 53, 56, 57, 59, 137, 140, 162 accounting, 280 accuracy, 112, 123 acetate, 54, 55, 56, 57, 63, 68, 69, 70, 140, 141, 149, 152, 170, 182, 237 acetic acid, 53, 68, 69, 140, 157, 201, 262 acetone, 61, 69, 201 acetonitrile, 226 acid, 10, 13, 17, 20, 45, 53, 55, 57, 62, 63, 68, 69, 75, 76, 78, 79, 84, 87, 136, 140, 147, 149, 150, 151, 157, 177, 180, 184, 185, 186, 191, 192, 193, 195, 201, 202, 212, 219, 226, 237, 262, 277, 297, 330, 331 acidic, x, 6, 9, 17, 30, 36, 50, 56, 60, 62, 80, 81, 83, 85, 88, 106, 136, 141, 181, 182, 206, 236 acidification, 67 acidity, 281 ACM, 139 activated carbon, 82, 108, 320 activation, xii, xvi, 113, 158, 197, 320 activation energy, 158 active site, 324 acute, 114, 121, 130, 154, 230, 276 adaptation, 64, 75, 158, 233, 246 additives, 2, 22, 108, 114, 344, 346 adhesion, 7 adipate, xvi, 333, 334, 335, 338, 346, 347 adjustment, 17, 84, 236, 322 administration, 126 adsorption, xiv, xvi, 2, 5, 7, 31, 50, 62, 83, 88, 89, 95, 96, 108, 113, 114, 115, 181, 183, 185, 187,

188, 191, 192, 249, 250, 254, 255, 259, 260, 261, 262, 281, 319, 321, 322, 323, 324, 325, 326, 327, 329, 330, 331 aerobic, xi, 51, 52, 58, 65, 73, 115, 135, 143, 144, 147, 149, 152, 156, 160, 162, 163, 168, 170, 172, 185, 186, 191, 192, 238, 240, 267, 268, 271, 272, 273, 276 aerobic bacteria, 58, 185 aerosols, 136 Africa, 46, 47, 280, 282, 297, 300, 306, 308, 317 Ag, 330 agar, 57, 59, 182, 311, 321 age, 12, 191 agents, xiii, 10, 46, 60, 61, 82, 83, 114, 200, 215, 216, 217, 219, 221, 222, 225, 226, 227, 231, 238, 240, 297, 329 aggregates, 7, 83, 87, 239 aggregation, 5, 7, 240, 243 aging, 5 agricultural, xiii, xiv, xv, 30, 49, 199, 213, 230, 235, 236, 237, 238, 240, 242, 244, 245, 246, 279, 291, 304, 310, 311, 312, 314, 316 agricultural crop, xiv, 236, 244 agriculture, ix, xiii, 51, 52, 65, 230, 235, 246, 288, 291, 303, 304, 309, 311, 312, 313, 314, 316, 317 air, xiii, 14, 31, 84, 86, 87, 89, 107, 114, 127, 136, 143, 147, 160, 178, 203, 235, 245, 255, 262, 339 air quality, 136 alcohol, 62, 68, 69, 180, 181, 190, 193, 202, 273 alcohols, 53, 54, 59, 61, 62, 141, 237 aldehydes, 61, 62 algae, 122, 144, 154, 320 Algeria, 300 aliphatic compounds, 54, 201 ALK, 54 alkali, 61, 62, 85, 92, 95, 108, 109, 139 alkaline, 6, 17, 30, 50, 62, 98, 106, 109, 137, 139, 146, 148, 180, 204, 245 alkalinity, 16, 156, 161, 162, 283, 291, 292

346

Index

alkane, 79 alkanes, 54, 75, 76 alternative, ix, xi, xii, xiii, xvi, 1, 42, 82, 122, 136, 143, 147, 149, 153, 172, 173, 175, 199, 215, 221, 228, 235, 237, 244, 271, 309, 319, 320, 329 alternatives, xi, 30, 82, 135, 148, 163, 230, 243, 282 aluminosilicates, 92, 102, 103, 104 aluminum, ix, 1, 5, 7, 9, 10, 13, 15, 17, 18, 19, 23, 25, 27, 28, 41, 43, 45, 46, 84, 108, 109 Aluminum, 6, 32, 43, 45, 46 aluminum surface, 10 ambient air, 136 amendments, 77 AMF, 241 amide, xvi, 320, 329, 330 amine, 330 amino, 53, 54, 75, 180, 186, 195, 236, 329 ammonia, 154, 155, 156, 157, 158, 159, 160, 162, 163, 164, 166, 170, 173, 175, 177, 239 ammonium, 23, 39, 44, 50, 114, 154, 170, 177, 178 amorphous, x, 7, 81, 83, 90, 92, 98, 106, 108 amorphous phases, x, 81, 92, 98, 106 Amsterdam, 132, 178, 234 anaerobe, 139 anaerobes, 52, 53, 58 anaerobic bacteria, 58, 74, 76, 138, 139, 140, 141, 185, 194, 195, 237, 240 anaerobic digesters, 156, 158, 236, 245 anaerobic granular sludge, 78 anaerobic sludge, 77, 173, 178 Angola, 300 animal health, xiii, 235 animals, xvi, 60, 238, 319, 320 anode, ix, 1, 5, 8, 9, 10, 11, 16, 17, 19, 20, 23, 47, 287, 288 anodes, 6, 7, 10, 11, 17, 22, 44 anoxic, 75, 79, 141, 155, 156, 160, 163, 170, 171, 178, 186 antagonists, 56 antenna, 75 anthropogenic, ix, 49, 50, 51, 52, 53, 63, 66, 74, 122, 136, 154, 302 antibiotic, 222, 242, 244, 246, 277 antibiotic resistance, 222, 242, 246 antibiotics, 180, 233, 242, 246 antimony, 65 antioxidant, 199 aquaculture, xii, 153, 175 aqueous solution, xvi, 11, 23, 107, 148, 319, 320, 330, 331 aqueous solutions, xvi, 11, 23, 148, 320, 330, 331 aqueous suspension, 46 aquifers, 77, 78

Arabia, 1, 279, 300 arbuscular mycorrhizal fungi, 241 archaea, 56, 59 argument, 315 arid, 244, 245, 246, 315 Arizona, 241, 247 aromatic compounds, 54, 113, 268 aromatic hydrocarbons, 53, 59, 62, 77, 78, 113, 114, 115, 124 aromatics, 201 arsenic, 12, 65, 108, 114, 122, 237, 262 arsenobetaine, 122 ash, x, xv, 2, 12, 17, 22, 23, 24, 25, 28, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 82, 108, 109, 110, 237, 251, 279, 281, 282, 284, 285, 286, 287, 288, 289, 290, 292, 296 Asia, 180, 193 Asian, 316 Aspergillus niger, 184, 189, 194 assessment, 108, 109, 112, 124, 126, 130, 244, 275, 276, 278, 283 assessment techniques, 112 assimilation, 155, 183 assumptions, 315 ASTM, 282, 296 asymptotically, 118 Athens, 131 Atlantic, 77, 347 atmosphere, 66, 89, 112, 136, 154, 202, 237 atmospheric pressure, 61, 136 atoms, 345 ATP, 55, 56 attachment, 321 AU, 22 Australia, 113, 120, 121, 125 Austria, 167, 215, 216, 217, 222, 230, 233, 280 autarky, 177 automation, 224 autotrophic, xii, 72, 76, 137, 145, 146, 153, 155, 158, 160, 161, 170, 171, 173, 174, 175, 176, 177, 178, 202 availability, 2, 104, 115, 123, 142, 167, 168, 284, 300, 303

B Bacillus, 185, 194, 238 back, xv, 13, 36, 237, 244, 253, 280, 301 bacterial, xiii, 76, 77, 121, 152, 182, 194, 216, 236, 238, 241, 242, 313, 315 bacterial strains, 182, 242 bacterium, 75, 76, 77, 79, 143, 145, 148, 151, 242 ballast, 60

Index bananas, 303 band gap, 11 Bangladesh, 308 barium, 114 barrier, 31, 76, 222 batteries, 66 battery, xvi, 319, 320 beet molasses, 48, 193, 194 behavior, 20, 83, 107 Beijing, 86 Belgium, 48 benefits, x, xiv, 2, 167, 236, 237, 244, 246, 278, 308, 310, 312 benign, xi, 135 benzene, 54, 58, 76, 80, 121, 126 beverages, 60 bicarbonate, 170 binding, x, xvi, 82, 84, 88, 101, 106, 320, 329, 330 bioaccumulation, 113, 121 bioaerosols, 238 bioassays, 122 bioavailability, 114, 126 biocatalyst, 151, 177 bioconversion, 143, 149 biodegradability, 114, 216, 266, 269, 273, 276, 277 biodegradable, 50, 59, 201, 219, 221, 266, 267, 268, 269, 270, 271, 276, 278 biodegradation, xiv, 51, 52, 54, 59, 60, 63, 67, 68, 69, 70, 71, 74, 76, 80, 112, 113, 114, 115, 193, 194, 212, 219, 237, 265, 269, 273, 275, 276, 278 biodiversity, 304 biofilms, 63, 140, 152 biogas, 69, 168, 169, 170, 177, 237, 240, 244, 246 biological activity, 146 biological processes, 2, 114, 137, 152, 154, 243, 271 biological systems, 137 biomarker, 122, 241 biomass, xvi, 51, 64, 139, 143, 144, 146, 154, 158, 160, 162, 164, 166, 173, 174, 180, 193, 203, 206, 208, 209, 210, 211, 239, 241, 244, 266, 268, 269, 315, 319, 320, 324, 325, 326, 328, 329, 330, 331 biomaterials, 320 bioreactor, 52, 64, 73, 74, 78, 137, 141, 143, 145, 146, 150, 151, 174, 190, 193, 320, 321, 331 Bioreactor, 150, 173, 174 bioreactors, 53, 63, 64, 69, 137, 139, 140, 142, 145, 146, 173 bioremediation, 54, 67, 72, 76, 78, 79, 194 biosorption, 320, 324, 326, 328, 329, 330 biosphere, 49, 154 biota, 122, 125, 126, 247 biotechnological, xi, 135, 136, 142, 147, 148 biotechnology, xi, 51, 52, 71, 72, 135

347

biotic, 146 biotransformation, 51, 52, 63, 65, 78, 80 bipolar, 26, 46, 47, 217, 218, 228, 231 bisphenol, 347 bleaching, 8, 12 blends, 107, 278 blocks, 142 blood, 154, 276 blue baby, 154 body weight, 230 boilers, 30 boiling, 61 bonding, 7, 92, 95, 329 bonds, x, 12, 82, 102, 104, 216, 236 boreholes, 302 Boron, viii, 10, 215, 218 Boston, 149 Botswana, 300 Brazil, 131, 280 breakdown, 220, 225 breeding, 60 Britain, 8, 296 British Columbia, 151 broad spectrum, ix broodstock, 175 Brussels, 245 bubble, 15, 16, 17, 18, 20, 139, 148 bubbles, 7, 8, 11, 13 Bubbles, 45 buffer, 17, 170, 182, 184 Bureau of Reclamation, 311 burning, 89, 91 butadiene, 61 butyric, 69 by-products, 12, 50, 68, 212, 269

C Ca2+, x, 31, 81, 100, 106, 285 cadmium, x, 22, 44, 65, 82, 102, 114, 237, 244, 331 calcium, 10, 11, 30, 43, 52, 63, 77, 92, 114, 225, 234 calcium carbonate, 10, 30, 77 calibration, 123, 322, 338, 339 Canada, 43, 47, 77, 124, 297, 311 cane sugar, 196 capillary, 88 capital cost, 13, 261 carbohydrates, 53, 54, 68, 144, 206, 236 Carbon, 45, 149 carbon atoms, 345 carbon dioxide, 55, 68, 69, 72, 74, 137, 144, 152, 237, 267 carbon monoxide, 150

348

Index

carbonates, 30, 52, 63, 114 carboxyl, 329, 330 carboxylates, 53 carboxylic acids, 201 carcinogenic, 154, 230 carrier, 64, 156, 192, 193, 194 case study, xi, 46, 111, 113, 124, 127, 130, 276, 278 casein, 58, 60 cash crops, 280 catalysis, 67 catalyst, xii, 109, 136, 197, 202, 203, 206, 207, 208, 211, 223 catalytic properties, 287 catchments, 303, 304 catechol, 54, 79, 202 cathode, 5, 8, 10, 11, 16, 17, 23, 287, 288 cation, 7, 9, 15, 106, 107 cattle, 199 cell, 13, 15, 23, 57, 67, 69, 72, 113, 137, 142, 147, 154, 185, 187, 188, 192, 203, 209, 211, 231, 240, 242, 284, 288, 294, 295, 330 cell death, 209 cell membranes, 113 cell metabolism, 240 cell organelles, 188 cell surface, 185, 187, 188, 211 cellulose, 184, 190, 193, 194, 281, 329 cement, 82 ceramics, 64, 82, 108, 109, 110, 216, 218 CH3COOH, 56, 68 CH4, xi, 70, 111, 113 channels, 250, 281 charged particle, 2 cheese, 60, 77 chelating agents, 221, 225 chemical approach, 130 chemical bonds, x, 82, 104, 236 chemical engineering, 15 chemical industry, 199 chemical oxidation, xii, 197, 202, 204, 206, 207, 211, 219, 221, 269, 320 chemical properties, 241, 242, 243, 246, 247 chemical reactions, 106, 114 chemical reactivity, 100 chemical stability, xiii, 95, 215, 216, 217, 220 chemical vapor deposition, 216 chemicals, 11, 13, 121, 124, 156, 219, 222, 224, 233, 239, 266, 268, 271, 272, 273, 314, 334, 347 chicken, 272, 273 chickens, 277 China, 46, 81, 84, 86, 87, 316 chitin, 329

chloride, xii, 23, 28, 107, 197, 202, 207, 221, 225, 311, 313, 334 chlorination, 154 chlorine, 12, 18, 19, 221 chlorobenzene, 201 chlorophyll, 144 Cholera, 305 chromatograms, 337, 345 chromatography, xvi, 226, 333, 347 chromium, 9, 16, 17, 18, 19, 20, 21, 67, 109, 114, 262, 330 Chromium, 16, 19, 21, 32, 43, 44, 45, 47 circulation, 63, 115, 127, 203, 230 civil engineering, 94 clams, 144 classes, 183, 242, 334 classical, 51 classification, 119, 120, 123, 190 clay, 64, 82, 85, 106, 109, 244 cleaning, xv, 10, 60, 61, 148, 201, 202, 237, 280, 296 cloning, 241 CO2, xii, 17, 39, 49, 53, 55, 56, 69, 70, 85, 96, 137, 140, 144, 149, 153, 168, 173, 202, 219, 220 coagulation, ix, 1, 2, 5, 7, 12, 13, 23, 46, 47, 48, 50, 83, 84, 281, 284, 289, 296, 297 coagulation process, 289 coal, 18, 107, 136, 280 coastal areas, x, 111, 112, 120, 124 coatings, 216 cobalt, 65 coconut, 251, 262 co-existence, 70 coffee, ix, xv, 2, 11, 25, 36, 37, 41, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 296, 297, 303 coke, 136 collagen, 190 colloidal particles, 2, 4, 5, 7, 13, 142 colloids, 2, 3, 31 Columbia, 151 combined effect, 288 combustion, 30, 32, 107, 108, 110, 136, 180 combustion processes, 136 commodity, 250, 280 communities, xiii, 57, 58, 74, 79, 121, 235, 241, 242, 243, 245, 246, 250, 261, 303, 304, 306, 317 community, xiv, 43, 59, 80, 115, 122, 126, 236, 239, 241, 242, 243, 245, 246, 255, 303 competition, 70, 140, 141, 301 competitive advantage, 145 complement, 122, 124, 126 complexity, ix, 1, 14, 16, 122, 123 compliance, 266

Index components, x, 50, 59, 70, 81, 83, 85, 87, 88, 95, 104, 106, 122, 180, 188, 194, 231, 238, 269, 271 composites, 108 composition, xiv, 16, 30, 31, 32, 36, 46, 50, 51, 60, 61, 64, 67, 91, 94, 106, 112, 113, 120, 122, 177, 199, 203, 204, 211, 234, 236, 245, 246, 312, 320 compost, 146, 244 composting, 199, 212, 238 compressive strength, 83, 84, 88, 94, 95, 96, 98, 100, 106 computation, 323 computer simulations, 315 concrete, 109, 233, 281 condensation, 23, 180 conditioning, 12, 170, 237 conductive, 11, 14, 216, 217, 218 conductivity, ix, 1, 12, 14, 22, 23, 27, 29, 31, 32, 43, 127, 202, 203, 206, 207, 208, 219, 226, 228, 232, 233, 239, 282, 283, 286, 288, 291, 292, 311, 313, 315, 316 configuration, 11, 36, 38, 156, 157, 163, 166, 169, 171, 173, 284 conflict, 300, 302, 303, 316 Congress, 194 conservation, 83, 128, 202, 315 construction, x, xiii, 82, 83, 199, 215, 217, 222, 255, 257, 259, 261 construction materials, 83 consultants, 130 consumers, xiv, 230, 236 consumption, x, xii, xv, 2, 9, 12, 13, 17, 20, 23, 24, 25, 26, 27, 28, 36, 41, 43, 44, 59, 83, 102, 144, 153, 169, 202, 207, 211, 230, 279, 282, 284, 287, 288, 289, 291, 293, 297, 300, 306, 310, 315, 317 contact time, xvi, 139, 227, 231, 319, 321, 324, 325, 327, 328, 329 contaminant, 121, 126, 210, 211 contaminants, ix, xi, xiii, 1, 5, 21, 109, 111, 114, 120, 122, 126, 216, 219, 243, 250, 334 contaminated soils, 109 contamination, 82, 173, 230, 244, 304, 334, 339, 341 control, xvi, 10, 14, 79, 108, 136, 141, 145, 148, 149, 150, 151, 152, 156, 158, 163, 164, 194, 210, 211, 229, 239, 241, 242, 271, 276, 288, 296, 333, 334, 344, 346 conversion, 73, 77, 83, 137, 138, 140, 142, 143, 144, 147, 149, 154, 180, 236, 293 conversion rate, 140 cooling, 11, 60, 93, 225 cooling process, 93 Copenhagen, 142, 144, 152 copper, x, 22, 44, 65, 79, 82, 102, 114, 237, 330, 331 copper oxide, x, 82, 102

349

corn, xvi, 229, 276, 319, 320, 321, 330, 331 corona, 224 correlation, xvi, 242, 320, 326, 328, 330 correlation coefficient, xvi, 320, 326, 328, 330 correlations, 269 corrosion, 10, 11, 23, 45, 114, 122, 140, 170 corrosive, 142, 237 corruption, 306, 316 cost benefits, 312 cost of power, 296 cost saving, 164, 313, 314, 315 cost-benefit analysis, xv, 309 cost-effective, ix, 2, 130, 320, 329 costs, xii, xiii, xv, 25, 30, 50, 51, 136, 153, 156, 158, 163, 164, 165, 168, 169, 172, 175, 199, 221, 227, 233, 235, 250, 296, 308, 309, 313, 314, 317, 321 cotton, 269, 273, 330 coupling, 137, 143 crack, 92 cracking, 61, 62, 88, 217 crops, 238, 239, 280, 303 crude oil, 53, 54, 61, 62, 73, 79, 80, 151 crustaceans, 122 crystalline, x, 81, 90, 91, 92, 93, 96, 97, 98, 100, 102, 103, 104, 106 crystalline solids, 103 crystallinity, 91, 92 crystallization, x, 81, 84, 90, 98, 102, 103 crystals, 91, 92, 98, 101, 102, 106 cultivation, 149, 154, 182, 188, 190, 211, 229, 242, 280, 308, 320 culture, 51, 52, 58, 59, 63, 65, 70, 137, 148, 160, 182, 184, 185, 192, 203, 210, 211, 213, 267, 321 CVD, 216, 218 cyanobacteria, 144, 186 cyanobacterium, 194 cycles, 161, 163 cycling, xiii, 235 Cyprus, 277, 278 cysteine, 57, 58 cysts, 9 cytochrome, 56 cytometry, 147, 246 cytoplasm, 185, 188, 192

D dairy, 50, 53, 58, 60, 63, 75, 80, 143, 151, 277 dairy industry, 50, 60, 80 data set, 128 database, 87, 92, 102 death, 154, 209 decane, 54

350

Index

decay, 116 decision makers, 126, 130 decisions, 125, 130, 275 decomposition, xiii, 54, 55, 59, 68, 69, 70, 74, 85, 98, 109, 154, 183, 184, 186, 188, 212, 235, 241 decomposition reactions, 98 defects, 113 deficiency, 13, 206, 211, 267 deficit, 206 definition, 59 deforestation, xv, 299, 303, 307 degradation, xiii, xv, 12, 50, 75, 76, 78, 79, 80, 114, 115, 121, 124, 145, 146, 181, 183, 185, 191, 198, 201, 202, 203, 204, 207, 217, 225, 228, 230, 231, 235, 236, 237, 240, 241, 242, 283, 299, 304, 307 degradation mechanism, 185, 191, 202 degradation process, 114, 121, 236 degrading, 75, 141, 227 degree of crystallinity, 92 dehydrogenase, 243 demobilization, 67 denitrification, xi, xii, 153, 154, 155, 156, 157, 159, 160, 161, 163, 164, 165, 167, 168, 170, 171, 173, 175, 176, 178 denitrifying, 67, 143, 151, 155, 156, 158, 161, 168, 173, 174, 175 density, ix, xv, 1, 14, 15, 18, 19, 20, 21, 23, 24, 26, 27, 36, 42, 65, 83, 87, 88, 89, 94, 95, 96, 115, 117, 118, 119, 126, 128, 129, 181, 182, 218, 221, 223, 224, 227, 228, 229, 231, 232, 240, 279, 284, 289, 294, 295 Department of Energy, 249 Department of Interior, 132 deposition, 216, 218 deposits, x, 10, 47, 50, 52, 53, 63, 64, 65, 66, 67, 111, 112, 297 depreciation, 25 derivatives, 12, 75, 202 desalination, xvi, 309, 312, 314, 315, 316 desert, 317 destruction, 83, 107, 154, 200, 201, 307 detection, 140, 242, 244, 347 detention, 27, 33, 35, 288 detergents, 46 detoxification, 194, 195, 277 developed countries, 82 developing countries, xv, xvi, 82, 299, 306, 307, 308, 319, 320 deviation, 203 dextrose, 188, 321 dialysis, 310, 311 diamond, ix, xiii, 10, 11, 42, 215, 216, 217, 220, 222, 224, 228, 229, 232, 233

Diamond, viii, 11, 45, 46, 215, 216, 218, 219, 228, 233, 234 diamonds, 10, 222 diaphragm, 223 dielectric constant, 3 diesel, 61 differentiation, 293 diffraction, 30, 83, 88, 92 diffusion, 21, 58, 106, 173 digestion, 78, 87, 122, 141, 168, 171, 172, 173, 193, 199, 236, 238, 239, 240, 244, 253 dioxin, 201 direct costs, 25 discharges, 112, 118, 121, 124, 125, 126, 127, 130, 131, 132, 266, 271, 272, 273, 310, 313 diseases, 243, 303, 305, 307 disinfection, xiii, 215, 217, 221, 231, 232, 233 disorder, 154 dispersion, xi, 4, 5, 85, 111, 112, 114, 122, 123, 124, 125, 126, 127, 128, 130 dissociation, 30 dissolved oxygen, xi, 55, 135, 144, 145, 147, 150, 157, 158, 159, 162, 166, 189, 267, 269 distillation, 61, 62, 179, 314 distilled water, 32, 321 distribution, xii, 4, 53, 112, 113, 114, 121, 143, 151, 164, 179, 180, 181, 186, 187, 216, 240 diversity, xiv, 236, 241, 243 division, 210 DNA, 57, 245, 246 donor, 56, 57, 69, 139, 140, 142, 155, 158, 173, 174 donors, 53, 55, 57, 60, 144, 149, 152, 161 doped, ix, xiii, 10, 42, 215, 216, 217, 220, 222, 233 doping, 11 dosage, xvi, 20, 30, 319, 325, 326, 327 dosing, 15, 18 double bonds, 12, 216 drainage, 76, 140, 151, 303 dream, 307 drinking, x, xiii, xvi, 12, 81, 84, 107, 108, 148, 154, 175, 177, 215, 231, 233, 306, 308, 333, 334, 335, 346, 347 drinking water, xiii, xvi, 12, 107, 108, 148, 154, 175, 177, 215, 231, 233, 306, 308, 333, 334, 335, 346, 347 drought, 310 drugs, 221, 233 dry matter, 205, 239 drying, 108, 251, 254, 259, 261, 304 durability, 84, 98, 102 duration, 52, 71, 87, 229 dust, 251 dyes, 8, 320, 330

Index

E E. coli, 240 earth, xiii, 61, 65, 98, 109, 235, 250 ecological, 51, 112, 120, 121, 124, 126, 306 ecology, 77, 308 economic disadvantage, 143 economics, 142 ecosystem, xiii, xiv, 120, 126, 215, 231, 236, 242, 243, 244, 246, 300 ecosystems, 112, 114, 125, 130, 222, 241 ECSC, 245 effluents, xiv, xvi, 12, 43, 46, 49, 50, 66, 67, 122, 156, 157, 158, 162, 170, 173, 178, 199, 202, 212, 231, 265, 266, 267, 268, 269, 273, 277, 278, 282, 296, 297, 333, 335 Egypt, 300, 301, 307 elaboration, xii, 197, 198 electric charge, 2 electric conductivity, 202, 203, 207 electric field, 13 electric power, 22, 41, 42 electrical conductivity, 12, 27, 31, 32, 43, 206, 208, 282, 283, 286, 291, 292 electrical power, 17, 136 electrical properties, 2, 11 electricity, 250, 255, 261 electrochemical measurements, 45 electrochemical reaction, 8, 154 electrochemistry, 47 electrodeposition, 45 electrodes, ix, xiii, xv, 1, 5, 8, 9, 10, 11, 13, 15, 16, 17, 18, 20, 21, 22, 23, 25, 26, 27, 40, 41, 42, 43, 45, 46, 215, 216, 217, 218, 219, 220, 222, 223, 224, 228, 229, 230, 231, 232, 233, 279, 282, 284, 288, 294, 295, 297 electroflotation, 7, 11, 14, 16 electrolysis, xv, 7, 11, 13, 17, 18, 19, 24, 33, 220, 221, 279, 284, 288 electrolyte, x, 2, 9, 16, 22, 23, 24, 25, 31, 36, 41, 42, 43, 48, 286, 287, 288, 289, 292 electrolytes, x, 2, 11, 12, 22, 25, 37, 42, 45, 284, 288 electromagnetic, 61 electron, 11, 13, 53, 54, 55, 56, 57, 59, 60, 69, 72, 77, 87, 92, 137, 139, 140, 142, 144, 149, 155, 158, 161, 162, 173, 174, 188, 266, 267, 268, 269 electrons, 9, 22, 41, 53, 55, 72, 92, 106, 163, 267 electrophoresis, 7 electroplating, 11, 66, 109, 320 electroreduction, 297 electrostatic force, 3, 4 e-mail, 49, 265 emission, 49, 66, 108, 136, 177, 313

351

employment, 280 emulsification, 61 emulsions, xiii, 61, 62, 215 endocrine, 222, 230, 233, 334 endocrine system, 334 endothermic, 89, 90, 91, 96, 97, 98 energy consumption, x, xii, 2, 13, 17, 25, 27, 28, 44, 153, 169, 297 energy efficiency, 11, 220 energy supply, 136 England, 308 environmental conditions, 114, 125, 126, 147, 208 environmental effects, 124, 136, 306 environmental factors, 112 environmental impact, 125, 130, 175 environmental protection, 136 Environmental Protection Agency, 130, 133, 147, 334, 347 environmental regulations, 8, 82, 281 environmental resources, xi, 111 enzymatic, 67, 180, 242, 243 enzymes, 54, 60, 63, 68, 141, 183, 186, 192, 244 EPA, 130, 131, 133, 147, 336, 346, 347 epithelia, 122 epoxy, 61 epoxy resins, 61 equilibrium, 50, 104, 116, 315, 323, 324, 326, 329 equilibrium state, 104 erosion, 65, 303 Escherichia coli, 231, 232, 240, 245, 313 esters, 61, 226, 347 estuarine, 151 ethanol, 54, 55, 56, 57, 69, 70, 173 Ethanol, 68 Ethiopia, 280, 297, 300, 301 ethyl alcohol, 180 ethylbenzene, 54, 78 ethylene, 61 Eulerian, 123 Euro, 165, 314 Europe, 216, 231, 245, 280, 300 European Parliament, 233, 347 European Union, 334 eutrophication, 304 evaporation, xii, 112, 114, 197, 199, 226, 320 evolution, 9, 17, 125 examinations, 232 excess supply, 239 excrements, 221 excretion, 306 exothermic peaks, 91, 96 Expert System, 123 expertise, xiv, 236

352

Index

exploitation, xiii, 56, 66, 112, 122, 147, 244, 302 exports, 280 exposure, 124, 290, 307, 331, 334 Exposure, 113 extraction, x, xi, xvi, 50, 66, 87, 109, 111, 112, 113, 124, 125, 127, 130, 198, 205, 206, 226, 320, 333, 334, 335, 336, 341, 342, 346, 347

F fabric, 269, 273 failure, 156, 170, 306, 310 family, 72, 280 FAO, 293, 311, 312, 313, 315, 316 farmers, 240 farming, 63, 240 farmland, 240 farms, 49, 305 fat, 12, 60, 210, 228 fats, 60, 209, 236, 280 fatty acids, 55, 60, 62, 75, 76, 141, 236 February, 198, 277, 278, 316, 317 feces, 236, 240 Federal Register, 133 feeding, 146, 190, 191, 192, 231 feedstock, 142 feldspars, x, 81, 92, 97, 98, 102, 106 Fenton‘s reagent, 199, 200, 202 fermentation, xii, 54, 67, 68, 69, 70, 179, 180, 182, 190, 191, 193, 194, 237, 281 fern, 331 ferrous ion, 200, 201 fertility, 238, 243, 244, 303 fertilization, 239, 243 fertilizer, xiii, 66, 107, 142, 154, 172, 199, 235, 237, 238, 239, 240, 241, 242, 243, 245, 284 fertilizers, xiii, 50, 62, 63, 66, 235, 238, 239, 241, 244, 246, 305, 306 fiber, 12, 78, 278 field trials, 240 fillers, 64 film, 77, 192, 217, 313 filter feeders, 115 filters, 18, 84, 139, 182, 208, 310, 311 filtration, ix, 2, 5, 13, 14, 46, 74, 148, 174, 187, 193, 203, 204, 206, 208, 229, 311, 313, 317 financial support, 330 Finland, 80, 296 fish, 121, 122, 154, 156, 175, 305 fish production, 175 fishing, 304 fixation, 75, 102, 154, 202 flame, 283

flavonoids, 334 flexibility, 122, 170, 334 float, 312 flocculation, ix, 1, 2, 5, 7, 22, 31, 84, 115 flooding, 9, 303 flotation, 7, 11, 14, 15, 18, 20, 78, 107, 204 flow, xiv, 11, 15, 16, 22, 33, 35, 41, 51, 59, 64, 82, 120, 128, 137, 140, 147, 162, 169, 217, 222, 223, 224, 225, 227, 228, 229, 230, 232, 246, 249, 251, 252, 253, 255, 256, 257, 258, 259, 287, 288, 293, 294, 301, 304, 310, 311, 323 fluctuations, 166, 280 flue gas, xi, 135, 136, 137, 138, 139, 142, 147, 149, 237 fluid, ix, 11, 15, 112, 115, 116, 117, 118, 123, 125, 129, 216, 219, 224, 233 fluidized bed, 5, 143, 148, 151 fluorescence, 87 fluoride, xiii, 23, 45, 215 fluorinated, 217 flushing, 60, 61, 62, 303 focusing, 243 FOG, 12 food, 12, 49, 60, 67, 199, 202, 238, 239, 240, 242, 252, 280, 300, 306, 317, 321, 329, 331, 333, 334 food industry, 60, 202, 240, 329 food production, 306 foodstuffs, 334 Forestry, 1, 279 forests, 302, 303, 304, 307 formaldehyde, 201 fossil fuels, 136, 154 fouling, 10, 219, 284 Fourier, xvi, 320, 324 fractionation, xiv, 80, 265, 273, 275, 278 France, 280, 311 freeze-dried, 182 freight, 12 fresh water, xv, 53, 280, 299, 304, 309 freshwater, 203 Freundlich isotherm, 323, 326 fructose, 281 fruits, 198, 303 FTIR, 328, 329, 330 FT-IR, 324 FT-IR, 329 fuel, 61, 69, 82, 136, 180 fumaric, 55, 57 funding, 296 fungal, xvi, 183, 185, 189, 191, 319, 320, 321, 324, 329, 331, 334 fungal metabolite, 334

Index fungi, xvi, 64, 181, 183, 184, 185, 186, 190, 192, 193, 194, 195, 241, 319, 320, 321, 324 fungicide, 142 fungus, 193, 194, 195, 212

G gas, x, xi, xvi, 7, 8, 13, 53, 61, 73, 93, 96, 98, 108, 111, 112, 113, 114, 122, 124, 125, 127, 128, 130, 132, 135, 136, 137, 138, 139, 142, 143, 147, 148, 149, 150, 152, 155, 158, 160, 161, 176, 177, 226, 236, 237, 285, 323, 333, 335 gas chromatograph, xvi, 226, 333 gaseous waste, 66 gases, xi, xiii, 7, 16, 49, 58, 59, 84, 92, 93, 95, 96, 135, 136, 137, 139, 147, 148, 149, 235, 237 gasification, 82, 108, 136 Gaussian, 117 gel, 187, 189, 190 gene, 245, 246 gene transfer, 245, 246 generation, 7, 19, 22, 108, 158, 170, 173, 211, 231, 237, 250, 252, 273, 275, 306, 320 genes, 79, 241, 242, 246 Geneva, 307, 308, 347 geochemical, 152 geothermal, 53 Germany, 45, 148, 216, 230, 232 GFP, 246 glaciers, xv, 299 glass, 64, 82, 83, 85, 106, 108, 110, 340, 341, 342 glasses, 109 global warming, 237 glucose, 54, 182, 183, 184, 185, 186, 189, 192, 193, 196, 281 glucose oxidase, 183 glycerin, 184 glycine, 182, 185, 196 glycol, 61, 114, 126, 127, 178 goals, 122, 302, 306, 307 gold, 65, 150, 280 Gore, 133 government, 231, 301, 306, 307, 309 graduate students, 296 grain, 126 grains, 63, 64 Gram-negative, 80, 241 Gram-positive, 241 granules, 64, 174 graphite, 43, 220 grasses, 154 grassland, 245, 246 gravity, 42, 87, 119, 252, 253, 275, 321

353

grazing, 238, 304 Great Britain, 296 Greece, 277 green beans, 281 greenhouse, 82 ground water, xii, 153, 173, 174, 233, 241, 302 groundwater, xii, 12, 53, 177, 197, 230, 244, 334, 344, 345, 346 groups, xvi, 2, 12, 55, 57, 59, 65, 67, 69, 70, 71, 74, 88, 91, 92, 106, 123, 127, 142, 144, 181, 185, 190, 216, 226, 236, 244, 320, 329, 330 growth, ix, xii, xv, 2, 20, 50, 51, 55, 56, 57, 59, 64, 68, 69, 73, 76, 77, 93, 101, 121, 137, 141, 143, 146, 148, 149, 151, 156, 157, 164, 175, 182, 183, 184, 191, 192, 197, 199, 202, 209, 210, 211, 239, 244, 267, 276, 299, 304, 306, 307, 321, 331 growth rate, 121, 156, 157, 164, 184, 209, 210, 276 growth temperature, 56, 57, 141 guidelines, 125, 126, 316 Gulf of Mexico, 120, 121, 125 gut, 240

H H1, 206 H2, 6, 17, 57, 137, 139, 140 habitat, 195 haloalkaliphilic, 151 halogens, 200 handling, 82, 83, 107, 237, 250, 251, 266, 273 harbour, 316 hardness, 12, 100 harm, 209 harvest, 208, 280 harvesting, 12, 240 Hawaii, 245 hazardous substance, 334, 347 hazardous substances, 347 hazardous wastes, 109 hazards, 50, 250 health, xiii, xvi, 121, 235, 240, 245, 250, 306, 308, 315, 319, 320, 333 health effects, 334 heart, 9, 230 heat, 62, 83, 101, 103, 106, 136, 193, 237, 238, 240 heating, 61, 85, 87, 89, 97, 182, 238, 240 heavy metal, x, 12, 14, 52, 62, 65, 66, 67, 71, 72, 74, 76, 77, 78, 82, 83, 84, 86, 87, 101, 102, 103, 104, 105, 106, 107, 108, 109, 112, 140, 141, 148, 151, 152, 208, 222, 239, 240, 243, 320, 330, 331 heavy metals, x, 12, 52, 62, 65, 66, 67, 71, 74, 76, 77, 78, 82, 83, 84, 86, 87, 101, 102, 103, 104,

354

Index

105, 106, 108, 109, 112, 140, 141, 148, 151, 152, 208, 222, 239, 240, 243, 320, 330, 331 height, 203, 294 hemodialysis, xv, 309, 310, 311, 312, 313, 314, 315 hemoglobin, 154 herbicide, 229, 230, 231 herbicides, 59, 201 heterotrophic, 143, 146, 155, 156, 161, 173, 202, 267 heuristic, 14 hexane, 54, 226 high temperature, 31, 65, 102, 164, 344 highlands, 280, 301, 303 hips, 27, 45 holistic approach, ix, 1, 14 homogenized, 255 homogenous, 322 horizontal gene transfer, 246 hormone, 334 hormones, 222, 233 horse, 253 hospital, 223, 245, 310, 316 hospitals, 310 host, 242 hot water, 198 hotels, xiv, 265 household, 239, 240 household waste, 239, 240 households, 59 HPLC, 340 human, xiii, xvi, 49, 121, 221, 235, 237, 240, 242, 243, 300, 319, 320, 334 human exposure, 334 humans, 202, 238, 347 humic acid, 78, 245 humic substances, 48 hybrid, 193 hybridization, 140, 147, 149 hydrate, 97, 114 hydration, 2 hydraulic fluids, 334 hydro, xi, 2, 53, 59, 61, 62, 65, 77, 78, 79, 111, 112, 113, 114, 115, 121, 124, 237 hydrocarbon, xi, 75, 111, 121 hydrocarbons, xi, 53, 59, 61, 62, 77, 79, 111, 112, 113, 114, 115, 121, 237 hydrochloric acid, 226 hydrogen, 7, 8, 17, 52, 53, 55, 57, 60, 62, 69, 70, 71, 72, 73, 74, 78, 107, 114, 137, 140, 144, 149, 150, 151, 152, 183, 186, 194, 199, 200, 201, 202, 207, 212, 219, 220, 231, 237, 285 hydrogen gas, 7, 237, 285 hydrogen peroxide, 183, 186, 194, 199, 200, 201, 202, 207, 212, 219, 231

hydrogen sulfide, 78, 107, 137, 150, 151, 152 hydrological, 300, 302, 304 hydrolysis, 5, 10, 60, 67, 69, 114, 172, 173, 236 Hydrometallurgy, 79, 150, 152 hydrophobic, 2, 3 hydroquinone, 202 hydrothermal, 56, 144 hydroxide, 7, 8, 10, 18, 31, 43, 62, 208, 226, 287 hydroxides, ix, 1, 5, 7, 13, 114 hydroxyl, xvi, 7, 8, 11, 212, 219, 220, 221, 222, 320, 329, 330 hydroxyl groups, xvi, 320, 329, 330 hypothesis, 83

I IARC, 347 identification, 59, 102, 140, 147, 242, 268, 271, 338 IEA, 237, 244 illumination, 203, 210 images, 98 immobilization, 102, 108 impact assessment, 124 implementation, 123, 163, 164, 172, 178, 198, 218, 244, 306 impurities, 11, 220, 250 in situ, xi, xiii, 7, 10, 13, 26, 111, 121, 124, 126, 216 in vitro, 347 in vivo, 347 inactivation, 233 inactive, 154, 320 incidence, 243 incineration, x, 81, 82, 107, 108, 199, 237 inclusion, x, 2 income, 306 incubation, 51, 58, 238, 239 incubation period, 238 independence, 242 India, xiv, 44, 249, 251, 259, 316 Indian, xiv, 135, 249, 250, 262 indication, 4, 15, 126, 146, 285 indicators, 57, 276 Indigenous, 280 indium, 25, 44, 297 indole, 54 Indonesia, 180 inducible enzyme, 183 induction, 186 industrial application, xi, 135, 142, 296, 320 industrial chemicals, 222, 233, 266, 347 industrial combustion, 136 industrial sectors, xiv, 265 industrial wastes, 51, 52, 65, 74, 109, 136, 201, 277

Index industrialization, xi, 135, 199 industry, ix, 2, 50, 59, 60, 61, 63, 66, 80, 112, 130, 132, 137, 147, 198, 199, 202, 203, 211, 223, 240, 272, 273, 277, 278, 309, 329 inert, xiv, 265, 269, 270, 271, 273, 276, 277, 278 infants, 154 infertile, 241 infrared, 73, 108 infrared light, 73 infrastructure, 306, 307 ingestion, 122 inhibition, 23, 76, 79, 144, 147, 157, 158, 176, 177, 186, 209, 210, 211, 230, 236, 281 inhibitors, 56, 114, 267 inhibitory, 79, 137, 138, 209, 269 inhibitory effect, 209 initiation, 104 injection, 238, 335 innovation, 11 inoculum, 167, 321 inorganic, x, 50, 51, 59, 62, 64, 65, 72, 74, 81, 82, 85, 91, 97, 98, 107, 112, 114, 144, 154, 178, 199, 219, 240 inorganic salts, 62 insect repellents, 333 insertion, 224 insight, 107, 222, 223 Inspection, 308 instability, 4, 240 instruments, 87 insulators, 295 integrated unit, 14 integration, 316, 338 interaction, 88, 115, 154, 161, 224, 322 interactions, 8, 16, 102, interface, 5 intermediaries, 201 International Agency for Research on Cancer, 347 intrinsic, 91 invertebrates, 121, 144 investment, 25, 227 ion adsorption, 4 ionic, 2, 4, 31, 173, 290 ionization, 226, 335 ions, ix, x, xvi, 1, 4, 5, 7, 8, 10, 15, 16, 17, 18, 21, 23, 25, 31, 37, 55, 56, 63, 67, 81, 95, 100, 103, 106, 126, 147, 200, 201, 211, 221, 225, 287, 289, 319, 320, 321, 322, 323, 324, 325, 326, 327, 329, 330, 331 IR, 324, 329 Iran, 300

355

iron, ix, 1, 5, 7, 9, 10, 15, 17, 20, 25, 27, 41, 43, 44, 45, 47, 55, 56, 59, 65, 67, 72, 76, 79, 92, 114, 139, 154, 201, 204, 208, 211, 284, 288, 297, 330 irradiation, 238, 281 irrigation, xiii, xiv, xv, 198, 199, 203, 208, 249, 262, 291, 309, 312, 314, 315, 317 irritation, 305 Islamic, 299 isoelectric point, 4, 5 isolation, 58, 137 isomers, 338, 339 isothermal, xvi, 319 isotherms, 322, 331 isotope, 126, 227 Israel, 300, 301 Italy, 111, 132, 170, 198, 280 IUCN, 308

J JAG, 183, 193 Japan, 87, 167, 168, 181 Japanese, 181 Jordan, 300 judge, 102

K Kenya, x, xv, 1, 2, 43, 44, 46, 47, 279, 280, 281, 282, 285, 290, 295, 296, 297 ketones, 76 killing, 56 kinetic energy, 115, 119 kinetic model, 323, 329 kinetic parameters, 158 kinetics, 37, 108, 152, 177, 212, 278, 323, 327, 331 King, 131, 179 Kobe, 184, 196 Korean, 45

L LAB, 191 labeling, 91, 99, 103 labor, 25, 42, 296, 312, 313, 314 labour, xiv, 13, 199, 249, 261 lactic acid, 68, 186, 191, 195 lactic acid bacteria, 191 Lactobacillus, 183, 185, 190, 191, 195 lactose, 60 lagoon, 75, 180 Lagrangian, 123, 127, 128

356

Index

Lagrangian approach, 123 lakes, 72, 300, 305 lamina, 33 laminar, 33 land, xiv, 12, 36, 112, 175, 236, 237, 238, 240, 241, 242, 243, 244, 245, 247, 253, 300, 301, 306, 312 landfill, 11, 44, 46, 48, 82, 109, 156, 237, 240 landfills, 30, 47, 82 Langmuir, xvi, 319, 322, 323, 326, 327, 329 lanthanoids, 65 lanthanum, 65 larvae, 121 Latin America, 306 lattice, 7, 84, 90 laundry, 11, 204 law, 41 leach, 33, 104, 287, 334 leachate, x, xv, 2, 10, 11, 17, 18, 19, 20, 22, 23, 24, 25, 28, 31, 33, 36, 40, 41, 42, 43, 44, 46, 47, 48, 237, 279, 282, 285, 286 leachates, 25, 32, 42, 48, 156, 284 leaching, x, 31, 32, 36, 37, 50, 79, 82, 83, 84, 86, 87, 101, 102, 103, 104, 106, 109, 284, 286, 287, 334 leakage, 244 leather, 61 legionella, 231 Legionella, 234 legislation, 154, 204 Libya, 301 lifestyle, 300 lifetime, 224 lift, 139, 150, 152, 176, 177 ligand, 7 lignans, 334 lignin, 12, 181, 183, 296 likelihood, 242 limitation, 14, 76 limitations, 137, 140, 170, 175, 201, 243 limiting oxygen, 160 lindane, 237 linear, 145, 209, 229, 322, 323, 339 lipid, 329 lipids, 54, 198, 236 lipophilic, 228 liquid chromatography, 226 liquid fuels, 136 liquid phase, 50, 84, 88, 93, 95, 102, 203 liquidation, 80 liquids, 176, 178 liquor, 164, 166, 193, 198, 253 Lithium, 32 loading, 19, 20, 52, 138, 140, 143, 144, 145, 146, 147, 166, 191, 251

local community, 303 localised, 45 location, 106, 110, 118, 119, 203 LOD, 226 London, 7, 44, 150, 296, 347 long period, 104, 106, 241 longevity, 10 losses, 334 Low cost, 262 low molecular weight, 113, 115 low temperatures, 22, 283 LSU, 224, 225 lubricants, 334 Luxembourg, 245 lying, 250

M machinery, xiv, 249 machines, xv, 203, 309, 310 macronutrients, 237 magmatic, 65 magnesium, 10, 30, 32, 92, 225, 234 magnetic, 192, 203 Maillard reaction, 180, 193 maintenance, xiii, 10, 11, 13, 14, 25, 152, 164, 235, 306, 312, 313, 314 Maintenance, 314 maize, 303 Malaysia, 46 malic, 53, 200 maltose, 184 management, x, xi, xiv, 2, 66, 81, 82, 111, 130, 136, 158, 164, 176, 201, 237, 245, 262, 265, 266, 271, 306, 315, 316, 317 management technology, 82 manganese, 30, 65, 67, 114, 183, 186, 296 manufacturing, 27, 45, 142, 266, 269, 271, 273, 344 manure, 239, 246, 253 marine environment, xi, 111, 112, 113, 114, 120, 121, 122, 124, 125, 126, 127, 130, 132, 161, 347 market, 8, 25, 42, 284 marketing, 280 markets, 244 Martinique, 280 mass loss, 40, 41 mass spectrometry, 226, 227 mass transfer, 140, 326 matrix, 98, 103, 104, 125, 126, 216, 222, 224, 226, 242, 334 Mauritania, 301 maximum specific growth rate, 210, 276

Index MDA, vii, xii, 179, 180, 181, 182, 183, 184, 185, 186, 188, 189, 190, 191, 192 measurement, 112, 322 measures, 117, 119, 125, 126, 136 meat, 60, 277, 280 media, xi, 4, 54, 57, 59, 83, 135, 182, 216, 231, 281 Mediterranean, xi, xii, 111, 113, 120, 121, 124, 127, 197, 198, 199, 245 Mediterranean countries, 198, 199 melting, 93, 94, 95, 98 membranes, 113, 310, 311 Merck, 339 mercury, 65, 76, 114, 237 metabolic, 52, 75, 140, 145, 242, 273 metabolism, 51, 55, 67, 71, 75, 147, 152, 240, 241 metabolites, 77, 229, 230, 231, 334 metal content, 72, 239 metal hydroxides, 5 metal ions, 5, 8, 15, 16, 21, 95, 106, 147, 201, 289, 324, 331 metal oxide, 82, 85, 223, 287 metal oxides, 82, 287 metallurgy, 66, 67 metals, x, 12, 52, 62, 65, 66, 67, 71, 72, 74, 76, 77, 78, 79, 82, 83, 84, 86, 87, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 112, 114, 121, 140, 141, 148, 151, 152, 208, 222, 237, 239, 240, 243, 244, 320, 322, 330, 331 methane, xiii, 69, 82, 141, 170, 172, 191, 235, 236, 237, 240 methanogenesis, 63, 70, 71, 79, 147, 212 methanol, 54, 157, 164, 173, 226, 335 methemoglobinemia, 154 methylation, 76 methylene, 331 Mexico, 120, 121, 125 microaerophilic, 138, 139 microalgae, xiii, 198, 202 microbes, 180, 192 microbial, xi, xii, xiii, xiv, 75, 78, 79, 115, 135, 137, 143, 147, 148, 149, 150, 154, 177, 179, 181, 182, 185, 186, 190, 191, 192, 197, 204, 235, 236, 238, 239, 241, 242, 243, 244, 245, 246, 247, 266, 270, 271, 275, 278, 304, 311, 321 microbial agents, 238 microbial communities, xiii, 79, 235, 241, 242, 243, 245, 246 microbial community, xiv, 115, 236, 239, 241, 245, microbiota, 239 microcosms, 57, 58, 77, 80 microflora, 55, 199 micrograms, 334 micronutrients, 237

357

microorganism, 51, 52, 53, 57, 59, 64, 67, 69, 70, 182, 183, 206, 267 micro-organisms, 115, 245, 246 microscope, 87, 92 microstructures, 92,93, 98 Middle East, 300, 301, 317 migration, 21, 23 military, 300, 301 milk, 50, 60, 61, 62 Millennium, 302, 308 milligrams, 37 mineral oils, 62 mineral water, 339, 341, 342, 343, 344, 346 mineralization, 52, 74, 76, 141, 201, 221, 239, 242 mineralized, 220 minerals, 30, 79, 90, 98, 102, 137, 180, 291 Minerals Management Service, 132 mines, 62 mining, xvi, 49, 82, 319, 320 Minnesota, 79 misleading, 267, 269 missions, 136, 168, 173 mixing, ix, xi, 7, 15, 33, 86, 111, 112, 113, 115, 116, 118, 119, 121, 124, 127, 129, 130, 131, 169, 209, 218, 228, 231, 236, 251 MMS, 132 mobility, 3, 57, 65, 79, 104, 106 MOD, 133 model system, 193, 196 modeling, 278 models, 120, 122, 123, 124, 126, 131, 209, 266, 275, 315, 323, 326 modulus, 85 moisture, 199, 230, 237, 245, 302 moisture content, 199, 245 molar ratio, 160 molasses, xii, 48, 63, 179, 180, 181, 182, 185, 186, 189, 190, 191, 192, 193, 194, 195, 196 mold, 181 mole, 293 molecular weight, 113, 114, 115, 180, 181, 184, 186 molecular weight distribution, 181, 186 molecules, 10, 140, 322 molybdenum, 65 momentum, 15, 115, 118, 119, 120, 128 money, 250 monolayer, xvi, 319, 329 monomeric, 70 Moon, 108 Morocco, 300, 309, 310, 312, 316 morphological, 83, 84, 88, 96, 99 morphology, 92, 98, 126, 145 mortality, 154, 175

358

Index

motion, 2, 4, 13, 119 motors, 261 mountains, 304 movement, 22, 341 multidisciplinary, xi, 111, 113, 126, 127, 130 multidrug resistance, 245 multiplication, 57, 58 municipal sewage, xiii, 82, 221, 235, 244, 311 municipal solid waste, 82, 109 mycelium, 188

N Na+, 4, 31 Na2SO4, 23, 24, 63 NaCl, x, 2, 23, 24, 25, 62, 321, 336, 339, 341, 346 Namibia, 300 naphthalene, 58, 121, 277 National Bureau of Standards, 94 native plant, 245 natural, x, xi, xiii, 5, 9, 12, 22, 44, 46, 47, 49, 50, 51, 53, 57, 58, 59, 65, 66, 71, 72, 73, 74, 75, 83, 93, 111, 113, 121, 122, 123, 141, 152, 154, 181, 198, 204, 241, 250, 251, 273, 277, 300, 306, 307, 310, 320, 321, 330 natural environment, 49, 50, 51, 53, 57, 58, 65, 66, 71, 72, 73, 74 natural gas, xi, 53, 111, 113, 152 natural resources, 83 Nb, 216, 218 NCA, 46 Near East, 277, 278 neck, 93 neem, 331 Nepal, 316 Netherlands, 87, 121, 147, 149, 158, 163, 164, 167, 168, 308 network, 88, 92, 95, 100, 106 neutralization, 7, 47, 50, 66, 203, 207, 208 New Frontier, 77 New Jersey, 245 New York, 45, 46, 75, 80, 131, 132, 133, 151, 152, 165, 196, 234, 262, 276, 300, 308 Ni, 52, 85, 331 nickel, 65, 66, 67, 109, 114, 330 Nielsen, 53, 78 Niger, 300, 301 Nile, 300, 301, 304 niobium, 65 nitrate, 11, 23, 78, 143, 149, 154, 155, 156, 157, 161, 162, 163, 171, 173, 174, 175, 177, 241, 297 nitrates, 57 nitric oxide, 150, 177

nitrification, xi, 50, 153, 155, 156, 157, 158, 159, 160, 162, 164, 166, 167, 168, 169, 170, 175, 176, 177, 178, 241, 243 nitrifying bacteria, 156, 162 Nitrite, 154, 158, 160, 164 nitrogen, xi, xii, 49, 50, 61, 75, 153, 154, 155, 156, 158, 159, 160, 161, 162, 165, 168, 170, 173, 174, 175, 176, 177, 184, 211, 226, 237, 239, 243, 250, 305, 306, 308, 311, 312, 313, 320 nitrogen compounds, xii, 49, 153, 154, 161, 237 nitrogen fixation, 75, 154 nitrogen gas, 155, 158, 160, 161, 176 nitrogen oxides, 161 nitrosamines, 154 nitrous oxide, 177 non toxic, 130 non-enzymatic, 180 normal, xii, 12, 61, 157, 179, 180, 190, 219, 238, 285, 289 norms, 51 North Africa, 46, 300, 317 North America, 300 Norway, 121 NTU, 22 nucleic acid, 147 numerical tool, 123 nutrient, xi, xiii, 115, 144, 146, 153, 202, 235, 236, 246, 307, 321 nutrient cycling, xiii, 235 nutrients, xiii, 126, 142, 198, 211, 237, 238, 239, 242, 243, 250, 303, 320 nutrition, 202, 212

O observations, xi, 92, 98, 111, 112, 113, 122, 125, 126, 130 octane, 54 odors, 140, 211, 238 offshore, x, xi, 111, 112, 113, 114, 115, 120, 121, 122, 124, 126, 127, 130, 132 offshore oil, x, 111, 112, 127, 130, 132 oil, xi, xii, xiii, 11, 44, 50, 53, 54, 57, 61, 62, 73, 77, 78, 79, 80, 107, 108, 111, 112, 113, 114, 122, 124, 125, 127, 130, 132, 136, 151, 197, 198, 199, 202, 203, 204, 205, 206, 208, 209, 211, 212, 215, 228, 229, 239, 244, 245, 300 oil production, 198, 199 oil refineries, 50, 62 oil refining, 136 oil shale, 11 oils, 62

Index olive, ix, xii, 197, 198, 199, 202, 203, 204, 205, 206, 208, 209, 211, 212, 213, 330, 331 olive oil, xii, 197, 198, 199, 202, 204, 205, 206, 212 olives, xii, 197, 198, 202, 203, 204, 208, 209 Oman, 300 online, 151, 308 Operators, 125 optical, 73, 78, 182 optical density, 182 optimization, 14, 22, 147, 227, 231 oral, 122 ores, 66, 72, 150 organelles, 188 organic C, 241 organic compounds, 10, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 63, 67, 68, 69, 70, 72, 73, 74, 113, 140, 142, 144, 200, 211, 213, 237, 262, 267, 334 organism, 139, 145 organochlorinated, 201 orientation, 120 oscillation, 52 osmosis, 12, 173, 310, 311, 313, 314, 315, 320 osmotic, 9 osmotic pressure, 9 ovulation, 230 oxalic, 201 oxalic acid, 201 oxidants, 221, 222 oxidation rate, 145, 158 oxidative, x, 19, 82, 84, 104, 106, 201, 220 oxide, x, 10, 13, 30, 43, 53, 82, 83, 85, 95, 97, 98, 99, 102, 150, 177, 208, 217, 223, 228, 231, 330 oxide electrodes, 10 oxides, x, 13, 30, 81, 82, 83, 84, 85, 88, 95, 96, 100, 102, 161, 218, 287, 289 Oxygen, 47, 145, 151, 160, 178, 219, 262 oxygenation, 59, 67, 150 ozonation, 222, 234, 277 ozone, xiii, 49, 109, 154, 216, 219, 222, 224, 225 Ozone, 219

P Pacific, 131, 132 packaging, 333 PAHs, 113 paints, 66, 320 Palestine, 300, 301 palletized, 109 paraffins, 201 parameter, 15, 17, 18, 33, 116, 119, 120, 141, 203, 225, 226, 266, 267, 268, 269, 290 parasites, 246

359

Paris, 334, 347 Parliament, 233, 347 particle density, 83, 87, 88, 89, 95, 96 particles, xiii, 2, 4, 5, 7, 11, 13, 31, 33, 46, 64, 66, 88, 93, 100, 103, 113, 123, 142, 144, 174, 215, 217, 252, 290 particulate matter, 108, 121 partition, 114, 198, 255 passivation, 10, 13, 217 passive, 10, 49, 112 pasteurization, 240 pasture, 307 pathogenic, xiii, 52, 71, 83, 235, 236, 237, 240, 242, 243, 245, 246 pathogenic agents, 83 pathogens, 82, 175, 238, 240, 241, 244, 250, 306 patients, 310 Pb, viii, x, xvi, 21, 82, 84, 86, 101, 102, 103, 104, 106, 290, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331 PCBs, 201, 334 PCT, 36, 46, 233, 296 peat, 262, 331 pectin, 198, 281 per capita, 300 percolation, 253, 262 periodic, 14 permeability, 113 permeable membrane, 121 permit, 33 permittivity, 3 peroxide, 183, 186, 194, 199, 200, 201, 202, 206, 207, 212, 219, 231 pesticide, 66, 234, 347 pesticides, 59, 66, 202, 209, 211, 305, 340 PET, 342, 344 petrochemical, 43, 50, 53, 54, 57, 58, 61, 74, 170 petroleum, 77, 78, 80, 280 Petroleum, 61 petroleum products, 80 Petrology, 49 pH values, 9, 17, 141, 324 pharmaceutical, 69, 226, 233, 234 pharmaceuticals, xiii, 215, 222, 225 PHB, 202 phenol, 54, 58, 61, 62, 75, 78, 202, 203 phenolic, xii, 193, 197, 198, 204, 208, 209, 211, 212 phenolic acid, 193 phenolic compounds, xii, 197, 198, 204, 208, 209, 211, 212 Philippines, 180 philosophy, xiv, 265, 266, 271

360

Index

phosphate, x, xv, 2, 12, 36, 39, 43, 44, 47, 241, 279, 280, 282, 284, 285, 286, 287, 289, 292, 296, 297 Phosphate, xv, 24, 279, 284 Phosphogypsum, 80 phosphorous, 305 phosphorus, 50, 107, 108, 172, 250, 311, 313 phosphorylation, 55 photobioreactors, 203 photoionization, 347 photolysis, 113 photomicrographs, 93 photosynthetic, 12, 78, 137, 143, 150, 202 phototrophic, 77, 142, 144 phylum, 158 physical factors, 14 physical properties, 238, 244, 246 physicochemical, 114, 136, 164, 251, 255 physiological, 59, 246 physiology, 53, 145, 308 phytoplankton, 121, 304 pig, 239 pigments, 195 pipelines, 61 planar, 88 planning, xi, 111 plants, xi, xii, xiii, 30, 49, 51, 59, 60, 61, 62, 66, 73, 74, 75, 86, 136, 144, 153, 154, 157, 167, 194, 197, 222, 233, 235, 236, 239, 240, 244, 245, 246, 266, 267, 271, 311, 317, 321 plastic, xiii, 64, 66, 215, 217, 284 plasticizer, 334 plastics, 61, 69, 73 platforms, xi, 111, 113, 114, 115, 120, 121, 122, 124, 125, 126, 127, 128, 130 play, xvi, 63, 67, 95, 120, 125, 141, 147, 304, 320 Pleurotus ostreatus, 183 ploughing, 240 Poland, 49 polarity, 10, 11, 14, 115, 219, 224, 229, 341 politics, 300 pollutants, ix, xi, xiii, 1, 2, 7, 8, 12, 19, 20, 22, 49, 50, 51, 57, 58, 59, 61, 62, 63, 67, 69, 74, 83, 107, 108, 116, 117, 123, 130, 135, 200, 201, 215, 216, 237, 239, 243, 250, 320, 334, 339, 341, 342, 346 pollution, x, xi, xv, xvi, 2, 12, 13, 42, 49, 50, 51, 64, 73, 82, 83, 107, 111, 117, 136, 149, 154, 200, 231, 237, 241, 262, 267, 282, 299, 300, 304, 305, 306, 307, 319, 333, 335, 339, 340, 346 polyamide, 278 polycyclic aromatic hydrocarbon, 78, 124 Polyelectrolyte, 28, 30 polyethylene, 178 polymer, 66, 145, 334, 344, 346

polymer synthesis, 344 polymerization, 12 polymers, 196 polyphenolic compounds, 199 polyphenols, 199, 206, 212 polysaccharides, 188, 329 polyurethane, 190, 193 polyurethane foam, 190, 193 polyvinyl chloride, 334 pomace, 198, 199 pond, xii, 179, 180, 181 pools, 208 poor, xii, 146, 179, 184, 239, 303, 304, 306, 310 population, ix, xv, 2, 67, 146, 280, 299, 300, 301, 304, 306, 307, 315 population growth, ix, xv, 2, 299, 304, 306, 307 pore, 93, 95, 203, 240 pores, x, 81, 84, 88, 92, 93, 95, 98, 100, 104, 106 porosity, 83, 87, 88, 89, 95, 96, 98, 240, 243 porous, 92, 93, 100, 102, 106, 194 ports, 119, 120 potassium, 30, 37, 114 potato, 27, 45, 188, 321 potatoes, 303 poultry, 276 poverty, 303 powder, 30, 87, 92, 102, 182, 331 powders, 324 power, xi, xv, 9, 12, 17, 20, 22, 23, 24, 26, 28, 30, 36, 41, 42, 62, 136, 169, 221, 223, 228, 233, 237, 253, 258, 279, 282, 284, 287, 288, 289, 291, 293, 295, 296, 300, 317, 323 power plants, xi, 30, 62, 136 precipitation, 5, 53, 59, 66, 67, 71, 114, 208, 219, 224, 302, 303, 320, 324 preconditioning, 12 prediction, ix, 1, 14 preference, 9, 115 press, 44, 84, 87, 94, 151, 199, 246, 297, 308 pressure, ix, 2, 9, 61, 65, 136, 174, 246, 300, 303, 304, 307 prevention, 125 prices, 25, 201, 313, 314 printing, 66 probability, 92, 98 process control, 330 producers, xii, xiv, 30, 197, 199, 216, 217, 236, 303 production costs, xv, 309 productivity, 137 profit, 55 program, 226, 311, 316, 317, 321 prokaryotes, 80 prokaryotic, 140

Index proliferation, 156, 242 propylene, 61 protection, 50, 74, 136, 307, 347 protein, 12, 56, 60, 154, 329 proteinase, 241 proteins, 54, 55, 60, 142, 180, 236, 242, 306 Proteins, 61 protocol, 114, 130, 266 protocols, 268, 271 protons, 161, 324 protozoa, 237 pseudo, xvi, 14, 18, 320, 323, 327, 328, 329 Pseudomonas, 145, 185, 190, 193, 194, 246 public, 82, 123, 126, 306, 316 public administration, 126 public health, 306 pulp, ix, 2, 8, 12, 17, 20, 23, 40, 41, 43, 44, 47, 61, 69, 136, 198, 276, 277, 281, 282, 296, 297 pulp mill, 296 pumping, 169, 175, 232, 252, 257, 296 pumps, 223, 261 purification, xiii, 44, 109, 198, 207, 233 PVC, 333, 334, 344 pyrolysis, 82, 107, 108 pyruvic, 53, 55, 57

Q Qatar, 300 quality of life, 250 quartz, 91, 92, 98, 99, 102, 103 quinones, 201

R race, 237 radiation, 73, 87 rail, 229 rain, 59, 136, 302 rain forest, 302 rainfall, 230, 301, 302 rainwater, 79 random, xv, 4, 279 range, ix, x, 2, 8, 10, 12, 14, 17, 18, 25, 49, 50, 51, 56, 70, 74, 81, 88, 90, 95, 96, 122, 123, 125, 136, 138, 139, 140, 141, 144, 146, 173, 207, 210, 217, 220, 222, 227, 236, 245, 252, 273, 285, 326, 338, 339, 342 rangeland, 246 rare earth, 50, 65 rare earth elements, 65

361

raw material, xi, xii, 61, 83, 84, 85, 87, 88, 89, 91, 92, 93, 95, 102, 135, 179, 180, 191, 192 raw materials, xii, 83, 84, 85, 87, 88, 89, 91, 92, 93, 95, 102, 179 reaction order, 33 reaction rate, 13, 19, 21, 22, 37, 40, 328 reaction time, 21, 296 reactivity, 100, 109, 284, 289 reagent, 199, 200, 201, 202, 212, 219, 276, 322 reagents, xvi, 25, 333, 335, 339, 341, 346 receptor sites, 8 receptors, 334 reclamation, 142, 148, 240, 317 Reclamation, 311 reconditioning, 12 recovery, xvi, 13, 65, 66, 72, 77, 83, 137, 146, 150, 151, 172, 212, 244, 262, 278, 310, 316, 333, 341 rectification, 61 recycling, xiv, xv, 12, 82, 83, 156, 236, 237, 238, 244, 280, 296, 303, 309, 310, 313, 314, 315 redox, 17, 55, 57, 58, 59, 145, 150, 219, 225, 239 Redox, 226 reducing sugars, 281 REE, 65 refineries, xi, 50, 62, 66, 136, 200 refining, 53, 61, 62, 78, 80, 109, 136, 320 refractory, 150 refrigeration, 344 regeneration, 82, 137 regional, 122, 124, 309 regression, 328 regulation, 67, 130, 222 regulations, 8, 82, 125, 208, 244, 281 rejection, 114, 178 relationship, 3, 9, 18, 31, 41, 69, 70, 75, 104, 107, 119, 202, 207, 241 relationships, 15, 52, 59, 69 reliability, 123 remediation, 43, 193 renal, 310 renal failure, 310 renal function, 310 renewable energy, 136, 237, 244 reproduction, 154 reserves, 112 reservoirs, x, 53, 59, 78, 111, 113, 114, 246 residential, 136, 310 residuals, 107, 108 residues, 82, 107, 220, 226, 239, 240, 246 resins, 61, 62, 333, 334 resistance, 10, 25, 27, 77, 101, 140, 222, 240, 242, 245, 246, 326 resolution, 130

362

Index

resources, ix, x, xi, xv, 2, 81, 82, 111, 123, 177, 299, 300, 301, 302, 304, 305, 307 respiration, 52, 53, 56, 76, 163, 239 respiratory, 140, 239 restaurant, 11 restaurants, 239 retention, 27, 139, 150, 158, 164, 168, 173, 239, 251, 252, 254, 257, 259, 321, 338, 339 Reynolds, 15, 347 Reynolds number, 15 rice, 304 rings, 142 risk, 130, 170, 230, 233, 236, 237, 238, 240, 241, 242, 243 risks, xiv, 83, 112, 124, 125, 236, 240, 243, 244, 246 river systems, 303 rivers, 199, 233, 300, 302, 303, 304, 305, 307 rods, 5, 151 Rome, 111, 316 room temperature, 87, 108, 146, 178, 202, 321 room-temperature, 87 Royal Society, 47 rubber, 58, 61 runoff, 64, 127, 236, 238 rural, 250, 262, 304, 305, 306, 308 rural areas, 305 rural communities, 304, 306 rust, 211

S safe drinking water, 306 safety, 84 saline, 11, 18, 72, 317, 321 salinity, ix, 1, 126, 128, 177, 178 salt, 23, 148, 184, 200, 207, 225 salts, 23, 61, 62, 83, 126, 177, 184, 201, 204, 212 saltwater, 120 sample, xvi, 4, 5, 87, 221, 224, 225, 228, 232, 256, 267, 284, 333, 345, 346 sampling, xv, 20, 40, 41, 112, 121, 125, 126, 130, 225, 255, 279, 345 sand, 11, 14, 18, 64, 82, 109, 208, 226, 330 sanitation, 59, 250, 306, 308, 315 saturation, 15, 160, 324, 329 Saudi Arabia, 1, 279, 300 savings, 164, 211, 310, 314, 315 sawdust, 262, 330, 331 SBR, 176, 178 scaling, 294 Scanning electron, 87 scarcity, 299, 300, 307, 310, 315, 316 sea level, 231

sea urchin, 121, 122 search, 51, 59, 82, 307 searching, 83, 301 seawater, xvi, 7, 113, 114, 115, 120, 121, 126, 127, 309, 312, 314, 315 security, 306 sediment, 115, 122, 125, 126, 207 sedimentation, 5, 15, 61, 65, 83, 107, 113, 114, 204, 208, 252, 253 sediments, 53, 115, 122, 127, 151, 207, 211, 334 seed, 46, 253, 267, 321 seeds, 44, 45 seeps, 223 selecting, 88, 123, 339 selectivity, 320 SEM, 87, 92, 98 semiarid, 245, 246 semi-arid, 245 semi-arid, 246 semi-arid, 246 semi-arid, 315 semiconductor, ix, 2, 11 Senegal, 301 sensitivity, 67, 139 sensors, 223, 224, 225 separation, 16, 18, 25, 46, 61, 64, 114, 115, 203, 204, 207, 211, 253, 315, 317 sequencing, 241 series, 7, 26, 47, 50, 121, 154, 207, 222, 223, 224, 225, 236, 294, 321 settlers, 168 sewage, xiii, xv, 7, 12, 49, 50, 51, 53, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 69, 70, 71, 72, 73, 74, 75, 77, 82, 107, 108, 109, 149, 176, 206, 221, 232, 233, 235, 236, 237, 239, 240, 241, 242, 243, 244, 245, 246, 265, 266, 268, 273, 278, 304, 306, 311 Shanghai, 86 shape, 11, 57, 88, 91 shaping, 265 sharing, 251, 252, 254, 256, 257 shear, 2, 3, 120, 128, 129 shelter, 304 shock, 252 short period, 204 shortage, 300, 303, 315, 316 short-term, 67, 77, 84 sign, 2, 119, 220 silica, x, 12, 81, 92, 106, 109, 330 silicate, x, 31, 81, 85, 87, 88, 90, 91, 97, 100, 102, 106, 109 silicates, 30, 98, 100, 102, 103, 104 silver, 65 similarity, 15

Index simulations, 123, 130, 313, 315 sintering, x, 82, 83, 84, 85, 88, 89, 91, 92, 95, 98, 100, 101, 102, 103, 104, 106, 109, 136 SiO2, x, 39, 81, 83, 85, 86, 88, 89, 90, 91, 92, 93, 94, 97, 102, 106, 109, 110 SIR, 227 sites, 8, 50, 79, 237, 240, 255, 324, 326 skeleton, 88 skills, 123 skin, 93, 154, 305 slag, 64, 82 smelters, 62, 66 smelting, 320 SO2, xi, 96, 135, 136, 137, 138, 139, 147, 148, 151 sodium, 31, 57, 62, 85, 87, 92, 114, 139, 225, 226 sodium hydroxide, 62, 225, 226 software, 87, 123 soil, xi, xiii, xiv, 36, 50, 54, 66, 80, 82, 109, 135, 142, 154, 185, 199, 201, 203, 230, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 281, 303, 316 soil erosion, 303 soils, 53, 54, 57, 80, 109, 199, 241, 242, 245, 246 solar, 141 solid phase, 64, 203, 226, 324, 326 solid waste, 50, 51, 52, 63, 66, 71, 74, 82, 109, 198, 199, 277, 304 solidification, 101, 102, 104, 106, 107 sols, 2 solubility, 16, 39, 65, 104, 106, 110, 115, 288 solvent, 50, 137, 320, 346 solvents, 50, 201, 226 Somalia, 300 sorption, xvi, 66, 108, 234, 320, 322, 323, 324, 326, 330, 331 sorption isotherms, 322 sorption kinetics, 323 South Africa, 282 sovereignty, 301 soy, 311 Spain, 153, 197, 198, 202, 204, 205, 208, 212, 213, 309, 333, 341 spatial, 59, 113, 125, 126 speciation, 16, 83, 122 species, xiii, 5, 7, 16, 33, 54, 56, 57, 68, 69, 72, 107, 121, 122, 126, 145, 146, 152, 175, 183, 200, 235, 238, 241, 245, 250, 280, 313 specific adsorption, 5 specific gravity, 87 specific surface, 7 spectrophotometry, 311 spectroscopy, xvi, 333 spectrum, ix, xiv, 57, 87, 265, 267, 329, 337, 338

363

speed, 51, 64, 83, 87, 94, 126, 128, 192, 200, 201, 210, 251, 259 sperm, 121 spheres, 5 spills, 251 spin, xiii, 215, 216 spindle, 140 spore, 321 springs, 53 SPSS, xv, 279, 283 Sri Lanka, 47 SRT, 321 stability, xiii, 2, 4, 5, 10, 11, 16, 91, 92, 95, 101, 103, 106, 108, 128, 129, 216, 217, 220, 224, 226, 239 stabilization, x, 67, 82, 84, 86, 101, 104, 107, 109, 238, 307, 308 stages, 61, 63, 64, 65, 68, 69, 71, 74, 90, 147, 188, 198, 281 standard deviation, 203 standards, xiv, xv, 136, 249, 265, 266, 271, 280, 281, 287, 306, 311, 312, 313, 315, 337 Standards, 94, 290, 296, 336 statutory, 222 steady state, 14 steel, 10, 53 sterile, 311, 321 sterols, 334 stock, 49, 322, 335, 341 stoichiometry, 69 storage, 49, 199, 208, 240, 321 storms, 154 strain, 54, 75, 77, 79, 145, 151, 181, 182, 183, 184, 185, 187, 191, 194, 195 strains, xii, 54, 58, 76, 141, 179, 182, 183, 185, 189, 190, 191, 242 strategies, 14, 159, 160, 170, 173, 243, 307, 347 stratification, 112, 119, 120, 127, 128, 130 streams, xiv, 12, 66, 76, 142, 147, 149, 152, 208, 253, 265, 266, 268, 269, 271, 302, 304, 330 strength, x, 2, 4, 31, 81, 83, 84, 87, 88, 91, 94, 95, 96, 98, 100, 102, 106, 176, 193 Streptomyces, 185 stress, 148, 150, 300 stroke, 231 students, 296 subgroups, 269 Sub-Saharan Africa, 300, 306 substances, x, 13, 48, 49, 51, 57, 81, 82, 91, 96, 97, 115, 116, 117, 126, 127, 132, 144, 180, 195, 198, 205, 219, 221, 222, 227, 228, 234, 269, 313, 334, 345, 347 substitutes, 83 substitution, 100, 106, 271

364

Index

substrates, 23, 55, 69, 140, 144, 180, 236 sucrose, 184, 281 Sudan, 301, 307 suffering, 310 sugar, 60, 63, 180, 182, 183, 185, 192, 194, 196, 280 sugar beet, 194 sugar cane, 63, 180, 185 sugarcane, 194, 251 sugars, 198, 236, 281 sulfate, xi, 23, 75, 76, 77, 78, 79, 80, 84, 135, 136, 137, 138, 139, 140, 141, 142, 143, 145, 146, 147, 148, 149, 150, 151, 152, 161, 162, 170, 171, 173, 175, 311, 313 sulfites, 147 sulfur, xi, 75, 76, 77, 135, 136, 137, 138, 139, 142, 143, 144, 145, 146, 147, 149, 150, 151, 152, 161, 162, 173, 174, 175, 176, 237, 241 sulfur dioxide, 147, 149, 150 sulfuric acid, 10, 136 sulphate, ix, 52, 53, 55, 56, 57, 58, 59, 63, 67, 68, 69, 72, 76, 77, 78, 79, 80, 138, 139, 140, 141, 145, 146, 148, 149, 150, 151, 226 sulphur, 51, 52, 53, 55, 56, 57, 59, 62, 63, 65, 69, 70, 71, 72, 73, 74, 75, 77, 79, 114, 139, 144, 145, 146, 147, 148, 149, 150, 151, 177, 243 summer, xii, 120, 127, 128, 129, 130, 197, 199 sunlight, 154 supercritical, 110 supernatant, 87, 163, 167, 172, 178 supervision, 244 supply, 50, 51, 66, 72, 92, 106, 136, 137, 160, 163, 217, 223, 228, 231, 233, 237, 239, 250, 284, 302, 304, 306, 308, 315, 344 supply chain, 237 surface area, xv, 7, 15, 108, 251, 252, 279, 284, 294, 295, 296, 326 surface component, 188 surface properties, 142 surface tension, 15 surface water, xvi, 12, 46, 51, 82, 127, 222, 233, 238, 306, 333, 334, 335 surrogates, 226 survival, 240, 245, 246, 250 suspensions, 46, 50, 62, 112 sustainability, xiii, 202, 235, 307, 315 sustainable development, x, 82, 83 sweat, 204 Sweden, 235, 240 switching, 136 Switzerland, 46, 167, 216 syndrome, 154 synthesis, 216, 331, 344 Syria, 300

T Taiwan, 193 tandem mass spectrometry, 226 tanks, 18, 50, 61, 64, 156, 163, 251, 281, 295 tannin, 14, 273, 277, 330 tannins, 198, 277 tantalum, 65 Tanzania, 284 tar, 11 taste, 83 taxonomic, 71 tea, ix, 2, 11, 12, 46 technical assistance, 330 Teflon, 339 temporal, 113, 115, 125, 126 tension, 15, 114, 304 testimony, 300 textile, ix, 2, 25, 43, 45, 61, 66, 69, 199, 269, 276, 277, 278, 317 textile industry, 61, 278 textiles, 320 TGA, 84 Thailand, 179, 180, 185, 193, 246 thallium, 65 therapy, 315 thermal analysis, 83, 84, 88, 96 thermal properties, 96, 97 thermal resistance, 11 thermal treatment, 82, 101, 102, 104, 136 thermodynamic stability, 101 thermodynamics, 331 thermogravimetric, 87 thermogravimetry, 108 thermophiles, 141 thin film, 313 Third World, 30 threat, xii, 197, 300, 309 threatened, 300 threats, xv, 299, 302 three-dimensional, 124, 128 three-dimensional model, 124 threshold, 231 thresholds, 222 timing, 240 tin, 10, 65 tissue, 121 titanium, 11, 136, 217, 224, 228 Titanium, 32 titanium dioxide, 136 titration, 225 TOC, 70, 267, 268 Tokyo, 234

Index toluene, 54, 58, 75, 76, 80, 121, 126, 146, 149, 268 tomato, 303 total energy, 136 total organic carbon, 107, 243, 267 total organic carbon (TOC), 267 toxic, xi, xvi, 7, 11, 51, 52, 56, 60, 66, 67, 69, 71, 74, 79, 104, 111, 112, 113, 120, 122, 126, 130, 141, 142, 147, 154, 173, 175, 201, 219, 239, 240, 243, 244, 269, 319, 320, 334, 347 toxic effect, xi, 111, 112, 120, 122, 126, 130, 154 toxic metals, 67, 104 toxic products, 201 toxicity, xii, 12, 67, 84, 87, 114, 120, 121, 126, 146, 152, 170, 175, 197, 209, 271, 276, 277, 278, 281 toxins, 305 toys, 334 trace elements, 114, 320 tracers, 121, 126, 127 tracking, 304 trade, 42, 216 trademarks, 202 trade-off, 42 trading, 280 trajectory, 120, 125, 128 transfer, 11, 13, 103, 140, 154, 201, 242, 243, 245, 246, 251, 252, 253, 267, 326 transformation, 50, 65, 66, 71, 75, 91, 92, 96, 97, 102, 103, 114, 344, 346 transformations, 68, 119, 154, 241 transition, 90, 201 transmission, 238 transparent, 211 transport, 5, 55, 56, 61, 66, 112, 114, 116, 117, 122, 123, 124, 126, 272, 277 transport processes, 123 transportation, xiv, 42, 65, 249, 261, 280, 333 traps, 302 travel time, 12 treatment methods, xiii, 12, 50, 59, 215 trial, 239 tribal, 307 tribes, 54, 55, 71 trichloroethylene, 201, 212 tropical areas, 180 tumours, 154 Tunisia, 300 turbulence, 16, 114, 115, 116, 120, 124 turbulent, 115, 118 Turbulent, 131 turbulent mixing, 118 Turkey, 265, 280, 319 Turku, 80

365

U Uganda, xv, 299, 301, 303, 304, 305, 306, 307, 308 ultraviolet, 281 ultraviolet irradiation, 281 UNDP, 300, 301 UNEP, 281, 297, 304, 305 UNESCO, 283, 297 UNICEF, 306, 308 uniform, 252 United Arab Emirates, 300 United Kingdom, 203, 297, 334, 347 United Nations, 311, 312, 316 United States, 7, 312 universities, 216 uranium, 79 urban areas, 303, 304, 306 urban centres, 306 urbanized, 250 urine, 236, 240 USEPA, 87, 121, 133, 237, 334

V valence, 4, 92, 106 validation, 231 values, 4, 9, 15, 17, 60, 89, 94, 104, 119, 128, 129, 141, 158, 180, 201, 203, 204, 206, 207, 208, 210, 211, 232, 240, 243, 266, 267, 286, 287, 300, 315, 321, 324 van der Waals, 5, 31 van der Waals forces, 31 vanadium, 65 vapor, 31, 216, 218 variability, 16, 127, 213, 322 variables, 25, 33, 41 variance, 283 variation, 18, 88, 92, 106, 147, 207, 210, 287, 344 vegetables, 303 vegetation, 198, 199, 301, 302, 303 velocity, 114, 115, 118, 119, 120, 144, 210, 252, 290 versatility, 136 vessels, 58, 60 Victoria, 303, 304, 305, 308 village, 250 vinasse, 48 vinyl chloride, 334 violence, 304 virulence, 240 viruses, 9, 237 viscosity, 3, 93, 95, 98 vitamins, 60

366

Index

vitrification, 108, 110 voids, 87, 88, 93, 95 volatilization, x, 81, 97, 112

W war, 300 Warsaw, 49 waste disposal, ix, 219, 304 waste incinerator, 109 waste management, 66, 82, 237, 306 waste products, 239 waste treatment, 78, 139, 150 wastes, ix, 2, 44, 51, 63, 65, 66, 74, 82, 109, 110, 140, 199, 212, 233, 236, 244, 246, 305 wastewater treatment, ix, x, xii, xiv, 2, 7, 11, 12, 27, 37, 44, 81, 86, 145, 149, 151, 153, 157, 174, 179, 180, 185, 191, 192, 197, 236, 244, 249, 250, 251, 254, 255, 256, 258, 259, 260, 261, 262, 276, 289, 306, 307, 308, 310, 311, 314, 315, 317, 320 water absorption, 87, 88, 93, 95, 98 water policy, 233, 334, 347 water quality, xv, 74, 175, 231, 299, 303, 307, 311, 316, 347 water resources, ix, xv, 2, 299, 301, 302, 305, 307 water supplies, 43 water table, 304 water vapor, 31 water-soluble, 114, 122 wealth, 42 wear, 220 weathering, 65, 114 web, 245 weight gain, 230 weight loss, 89, 91, 96, 97 weight ratio, 95 welding, 217, 295 wells, 12, 282, 302, 304 West Indies, 280 wetlands, xv, 299, 303, 304, 307 wheat, 242, 280 whey, 53, 60, 80 WHO, 48, 283, 297, 306, 308, 311, 312, 313, 316 wide band gap, 11

wind, 114 winning, 69, 176 winter, 120, 127, 128, 129, 130, 242 wood, x, xv, 2, 12, 17, 22, 23, 25, 28, 30, 31, 32, 33, 36, 37, 41, 42, 43, 44, 63, 279, 282, 284, 285, 286, 287, 288, 289, 296 wood waste, 31 wool, 278, 339 workers, 239, 241 working conditions, 208 working hours, 314 workstation, 123 World Bank, 316 World Health Organization (WHO), 311, 334, 347 worms, 144

X xenobiotic, 59, 241, 271, 277 X-ray diffraction, 30, 83, 88, 92 X-ray diffraction (XRD), 30, 88 XRD, 30, 33, 83, 84, 87, 88, 91, 92, 96, 97, 98, 99, 102, 103 xylene, 54, 76, 77

Y yeast, 73, 158, 180, 181, 185, 191, 193, 213, 321 Yemen, 280, 300 yield, x, xiii, 2, 36, 123, 142, 158, 182, 184, 185, 186, 187, 188, 189, 190, 191, 192, 235, 238, 269, 284, 296, 302

Z Zambezi, 300 zeta potential, 2, 3, 4, 5, 22, 31 zinc, 32, 65, 66, 67, 79, 114, 122, 237 zirconium, 65 Zn, 52, 85, 86, 127, 239, 290

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