KINETICS OF CHLORINATED ETHYLENE DEHALOGENATION UNDER METHANOGENIC CONDITIONS

Kinetics were determined for methanogenic activity and chlorinated eth ylene dehalogenation by a methanol-enriched, anaerobic sediment consor tium. The culture reductively dechlorinated perchloroethylene (PCE) to trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinylchlorid e (VC), and ethylene and ethane. The absence of methanol or the additi on of 2-bromoethanesulfonic acid in the presence of methanol suppresse d both methanogenic activity and dechlorination. In contrast, acetate production continued in the presence of 2-bromoethanesulfonic acid. Th ese results suggest that dechlorination was strongly linked to methane formation and not to acetate production. A kinetic model, developed t o describe both methanogenesis and dechlorination, successfully predic ted experimentally measured concentrations of biomass, methane, substr ate, and chlorinated ethylenes. The average maximum specific dehalogen ation rates for PCE, TCE, 1,1-DCE, and VC were 0.9 +/- 0.6, 0.4 +/- 0. 1, 12 +/- 0.1, and 2.5 +/- 1.7 mu mol contaminant/ g . DW/day, respect ively. This pattern for dechlorination rates is distinctly different t han that reported for transition metal cofactors, where rates drop by approximately one order of magnitude as each successive chlorine is re moved. The experimental results and kinetic analysis suggest that it w ill be impractical to targeting methanol consuming methanogenic organi sms for in situ groundwater restoration. (C) 1995 John Wiley & Sons, I nc.