title: Sequential photochemical-biological degradation of chlorophenols.
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.
authors.affiliation: Department of Biotechnology, Lund University, P.O. Box 124, S-22100 Lund, Sweden.
authors.forename: Tamer
authors.initials: T
authors.lastname: Essam
authors.forename: Magdy Aly
authors.initials: MA
authors.lastname: Amin
authors.forename: Ossama
authors.initials: O
authors.lastname: el-Tayeb
authors.forename: Bo
authors.initials: B
authors.lastname: Mattiasson
authors.forename: Benoit
authors.initials: B
authors.lastname: Guieysse
mesh_terms: D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D002733:Chlorophenols / Q000737:chemistry* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004785:Environmental Pollutants / Q000737:chemistry* / Q000378:metabolism; D004787:Environmental Pollution / Q000517:prevention & control*; D006207:Half-Life; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D010777:Photochemistry / Q000379:methods*; D012722:Sewage / Q000382:microbiology; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D002733:Chlorophenols; D004785:Environmental Pollutants; D012722:Sewage; C009495:titanium dioxide; D006861:Hydrogen Peroxide; D014025:Titanium