Case Studies from Turkey: Xenobiotic-containing Industries, Wastewater Treatment and Modeling (original) (raw)
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In the removal of organic xenobiotics from waste-waters, biodegradation is an interesting alternative to conventional physical and chemical processes. Biodegradation in biological wastewater treatment plants has the potential advantages of removing the xenobiotics from the environment, transforming them into nontoxic products such as carbon dioxide and new biomass, and being relatively low in cost. Many xenobiotics have been found to be biodegradable as sole carbon and energy source under aerobic conditions, while under anaerobic conditions many chlorinated hydrocarbons can be biodegraded by re-ductive dechlorination processes. The main limits of biodegradation processes are the limited time for adaptation to the xenobiotics, the very low xenobio-tics concentration in the influent, the competition with abiotic removal mechanisms, the limited availability of external substrates for cometabolism, and the intrinsic nonbiodegradability. Existing biological wastewater treatment processes can be modified by using higher values of the solids retention time, bioaugmentation, addition of readily biodegradable substrates to support cometabolism, and the use of anaerobic-aerobic processes.
Biodegradation of Xenobiotics in Environment and Technosphere
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Microorganisms play an important role in the removal of synthetic organic compounds from the environment. This chapter gives an overview of the evolution of biodegradation pathways and describes the strategies that microorganisms have evolved to transform important molecular structures. The actual effectiveness of biodegradation in the environment is determined by the bioavailability of the compounds. As a general rule, one could state that the release rates of synthetic compounds should not exceed the environment's ability to degrade them.
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The compounds as 1, 2-dibromoethane, 1, 2-dichloroethane and phenol are ones of the most dangerous pollutants in the environment. 1, 2-Dibromoethane (DBE) is a synthetic organic chemical that is mainly used as a gasoline additive. It is also one of the widely used pesticide fumigants. 1,2Dichloroethane is one of the most commonly used chlorinated industrial products and falls into the environment by using it as a chemical intermediate in the synthesis of a number of chlorinated hydrocarbons. Phenol is a waste product from the plastics, petroleum and pharmaceutical industries. There are different methods for treating wastewater containing the listed xenobiotics. Applied physicochemical methods are often economically ineffective and may cause other toxic products to occur. For this reason, microbiological treatment methods are preferred. We tested three different bacterial strains: Pseudomonas putida, Bradyrhizobium japonicum and Xanthobacter autotrophicus GJ10. In our studies for a p...
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Organic chemical mixtures are prevalent in waste waters from industrial and municipal sources as well as in contaminated groundwater. Phenols are pollutants found in wastewaters from oil refineries, chemical plants, explosives, resins and coke manufacture, coal conversion, pesticide and textile industries. The main contaminants of refinery wastewater include phenols, polycyclic aromatic hydrocarbons (PAHs) as well as heavy metals. Among these toxic pollutants, phenols are considered to be the most hazardous ones, and they are certainly the most difficult to remove. Phenolic compounds are toxic at relatively low concentration. Because of these low concentrations the most suitable methods for their removal are the microbial ones. The present work is a review of biodegradation of phenol. Degradation of phenol occurs as a result of the activity of a large number of microorganisms including bacteria, fungi and actinomycetes. There are reports on ma33ny microorganisms capable of degrading...
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Although the technologies available today can produce high quality water even from wastewater, most wastewater treatment plants are not designed to remove emerging xenobiotic contaminants such as endocrine disrupting compounds (EDCs) and pharmaceutical and personal care products (PPCPs). The majority of EDCs and PPCPs are more polar than most regulated contaminants and several have acidic or basic functional groups. EDCs and PPCPs properties, together with their occurrence at trace levels, create unique challenges for the removal processes and the consequent upgrading of wastewater treatment plants. Therefore, in this study ten different wastewater treatment trains are proposed in order to upgrade the conventional wastewater treatment plants. These schemes are based on the multi-barrier concept and include different advanced treatment processes such as membrane processes (membrane bio-reactors, nanofiltration, and reverse osmosis), adsorption on activated carbon (GAC) or biological activated carbon (BAC), advanced oxidation processes (AOPs). Based on the existing data on the effectiveness of these treatment processes for the removal of EDCs and PPCPs, the proposed treatment schemes appear very effective in the removal of a wide range of compounds at trace levels in domestic wastewater. In order to evaluate and compare the feasibility of the proposed different treatment schemes the cost per cubic metre of treated water (Total Unit Cost, TUC) was calculated for several sizes of plant. Therefore, obtained cost functions may be used to estimate the treatment cost for the upgrade of the plant size of interest.
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Different methods for determining the toxicity and biodegradability of hazardous compounds evaluating their susceptibility to biological treatment were studied. Several compounds including chlorophenols and herbicides have been evaluated. Toxicity was analyzed in terms of EC 50 and by a simple respirometric procedure based on the OECD Method 209 and by the Microtox Ò bioassay. The values of EC 50 obtained from respirometry were in all the cases higher than those from the Microtox Ò test. The respirometric inhibition values of chlorophenols were related well with the number of chlorine atoms and their position in the aromatic ring. In general, herbicides showed lower inhibition, being alachlor the less toxic from this criterion. For determination of biodegradability an easier and faster alternative to the OECD Method 301, with a higher biomass to substrate ratio is proposed. When this test was negative, the Zahn-Wellens one was performed in order to evaluate the inherent biodegradability. In the fast test of biodegradability, 4-chlorocatechol and 4-chlorophenol showed a complete biodegradation by an unacclimated sludge upon 48 h. These results together with their low respirometric inhibition, allow concluding that these compounds could be conveniently removed in a WWTP. Alachlor, 2,4-dichlo-rophenol, 2,4,6-trichlorophenol and MCPA showed a partial biodegradation upon 28 days by the Zahn-Wellens inherent biodegradability test.
Science of The Total Environment, 2020
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Includes bibliographical references and index. Issued in print and electronic formats. ISBN 978-1-77188-362-7 (hardcover).--ISBN 978-1-77188-363-4 (pdf) 1. Bioremediation. 2. Biodegradation. 3. Xenobiotics. 4. Sustainable development. I. . He has published more than 120 articles in peer-reviewed journals and conference proceedings, and has published many book chapters and technical reports on cell culture engineering, secondary metabolites, natural products, biomaterials, bioenergy, environmental remediation, drug delivery, photocatalysts, and chemical sensors. Dr. Abdullah obtained an MEng degree in chemical engineering and biotechnology from the University of Manchester Institute of Science and Technology, United Kingdom, under a PETRONAS Scholarship, and a PhD in Bioprocess Engineering from Universiti Putra Malaysia under a UPM Scholarship.