Sequential photochemical-biological degradation of chlorophenols |
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Authors: | Essam Tamer Amin Magdy Aly el-Tayeb Ossama Mattiasson Bo Guieysse Benoit |
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Institution: | aDepartment of Biotechnology, Lund University, P.O. Box 124, S-22100 Lund, Sweden bMicrobiology Department and Microbial Biotechnology Center, Faculty of Pharmacy, Cairo University, 51 Kasr El-Aini Street, 11562 Cairo, Egypt |
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Abstract: | UV/TiO2/H2O2, UV/TiO2 and UV/H2O2 were compared as pre-treatment processes for the detoxification of mixtures of 4-chlorophenol (4CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) prior to their biological treatment. When each chlorophenol was initially supplied at 50 mg l?1, UV/TiO2/H2O2 treatment supported the highest pollutant removal, COD removal, and dechlorination efficiencies followed by UV/TiO2 and UV/H2O2. The remaining toxicity to Lipedium sativum was similar after all pre-treatments. Chlorophenol photodegradation was always well described by a first order model kinetic (r2 > 0.94) and the shortest 4CP, DCP, TCP and PCP half-lives of 8.7, 7.1, 4.5 and 3.3 h, respectively, were achieved during UV/TiO2/H2O2 treatment. No pollutant removal was observed in the controls conducted with H2O2 or TiO2 only. Inoculation of all the photochemically pre-treated mixtures with activated sludge microflora was followed by complete removal of the remaining pollutants. Combined UV/TiO2/H2O2-biological supported the highest detoxification, dechlorination (99%) and COD removal (88%) efficiencies. Similar results were achieved when each chlorophenol was supplied at 100 mg l?1. COD and Cl mass balances indicated UV, UV/H2O2, and UV/TiO2 treatments lead to the formation of recalcitrant photoproducts, some of which were chlorinated. |
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Keywords: | Advanced oxidation processes Biodegradation Hazardous pollutants Industrial wastewater Photodegradation |
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