A Study On Trichloroethylene Degradation By Aerobic Cometabolism And Volatile Model

Chlorinated hydrocarbons have a widespread use in industry and agriculture,because of their accidental spills, leakages and improper use, which caused greatconcern by environmental staff. Trichloroethylene (TCE) is one of the most extensivecontaminants in groundwater. Because of convenient operation, lower expense andusing selected microbes to remove organic compounds, biological treatment forTCE-contaminated waters becomes a hot topic. TCE is efficiently biodegraded byaerobic cometabolismIn the Ph. D. dissertation, six aromatic compounds, including toluene, benzene,chlorobenzene, phenol, benzoic acid and aniline, were used TCE cometabolicsubstrates to acclimate the activated sludge. The biodegradability of the sixacclimated substrates and that of TCE through cometabolism are conducted bymeasuring oxygen consumption with Warburg respirometer.The biodegradation kinetics of the six cometabolic substrates and that of TCE bycometabolic degradation were studied. In order to compare with TCE cometabolicdegradation kinetic rates, the degradation kinetics of TCE using TCE as the solecarbon source was conducted. The results were shown that a first-order linear rate lawapplied to TCE biodegradation under the conditions mentioned aboved. The first orderrate constant relationship of TCE was as follows: Ksa phenol > Ksa toluene > Ksabenzoic acid > Ksa aniline > Ksa benzene > Ksa TCE > Ksa chlorobenzene,and therate constant was 0.3078, 0.1698, 0.1254, 0.0443, 0.0286, 0.0268, 0.0147 L/g?h,respectively. The biodegradation kinetics experiments of the metabolic substrateswithout TCE and under cometabolic conditions were conducted. The results wereshown that the six metabolic substrates confirmed to the first order equation underboth conditions. Compared to TCE cometabolic rate constant, conclusions weredrawn that phenol was the most suitable cometabolic substrate, toluene second, andbenzene third;chlorobenzene was not suitable substrate. Space descriptor ofcometabolic substrate was the effective factor in cometabolic biodegradation processby Quantitative structure biodegradability relationships(QSBR)study.The volatile model of TCE was discussed in autoclaved sludge and activatedsludge systems in the laboratory. Results suggested that the volatile rate constant ofTCE in activated sludge was apparently lower than that of TCE in autoclaved sludge,due to the biodegradation.The volatile rate constant of TCE in both systems at 25℃was within the range of the estimate value in aquatic phase, which expressed thevolatile model was also applied in sludge system.