ENHANCED ANAEROBIC BIODEGRADATION OF VINYL-CHLORIDE IN GROUND-WATER

The enhanced biotransformation of vinyl chloride (VC) under anaerobic conditions was studied using static microcosms and a flow‐through column packed with soil from a study site. Vinyl chloride was found to be resistant to transformation in the static microcosms in five months of incubation; however, 89% of the vinyl chloride that was dissolved in the water was transformed when the microbiota in the columns was stimulated with a mixture of nutrients. In the presence of nutrients such as methane, methanol, ammonium phosphate and phenol, the main products of biotransformation were nonchlorinated organics such as methane and ethylene. Sodium acetate, added to the water and soil, did not enhance the biotransformation of VC because acetate‐utilizing bacteria were not found at the study site and none developed in soil sample after the 21 d allowed for adaptation. Four biodegradation mechanisms of vinyl chloride under anaerobic conditions were recognized in this study: (a) reductive dechlorination to ethylene; (b) mineralization to methane; (c) formation of chloromethane, probably followed by methane formation; and (d) bio‐oxidation to CO2, where acetate and citrate were added. A pseudo‐first‐order rate constant of 1.01 × 10−3 months−1 and a t1/2 of 57.2 years were calculated for the disappearance of vinyl chloride in soil and water microcosms under anaerobic conditions, without bioenhancement. Copyright © 1990 SETAC