TRANSFORMATION OF 1,1,1-TRICHLOROETHANE IN AN ANAEROBIC PACKED-BED REACTOR AT VARIOUS CONCENTRATIONS OF 1,1,1-TRICHLOROETHANE, ACETATE AND SULFATE

Biotransformation of 1,1,1-trichloroethane (CH3CCl3) was observed in a n anaerobic packed-bed reactor under conditions of both sulfate reduct ion and methanogenesis. Acetate (1 mM) served as an electron donor. CH 3CCl3 was completely converted up to the highest investigated concentr ation of 10 mu M. 1,1-dichloroethane and chloroethane were found to be the main transformation products. A fraction of the CH3CCl3 was compl etely dechlorinated via an unknown pathway. The rate of transformation and the transformation products formed depended on the concentrations of CH3CCl3, acetate and sulfate. With an increase in sulfate and CH3C Cl3 concentrations and a decrease in acetate concentration, the degree of CH3CCl3 dechlorination decreased. Both packed-bed reactor studies and batch experiments with bromoethanesulfonic acid, an inhibitor of m ethanogenesis, demonstrated the involvement of methanogens in CH3CCl3 transformation. Batch experiments with molybdate showed that sulfate-r educing bacteria in the packed-bed reactor were also able to transform CH3CCl3. However, packed-bed reactor experiments indicated that sulfa te reducers only had a minor contribution to the overall transformatio n in the packed-bed reactor.