Abstract
Groundwater contamination by cis-1,2-dichloroethylene (cis-DCE) is widespread as a result of transformation from tetrachloroethylene or trichloroethylene in natural environments. Under anaerobic conditions, cis-DCE can be biotransformed via reductive dechlorination to ethylene, which is an environmentally acceptable product. In order to develop anaerobic cis-DCE-dechlorinating enrichment cultures, five anaerobic reactors fed cis-DCE (0.46 mg·l-1) with either acetate, propionate, glucose, yeast extract or hydrogen as a primary substrate (100 mgCOD·l-1) were semicontinuously operated at 25°C. Among the five reactors, only acetate-fed reactor was unable to sustain dechlorination. Other four reactors developed to enrichment cultures capable of dechlorinating cis-DCE to ethylene at high rates. In propionate-fed, glucose-fed and yeast -extract-fed cultures, cis-DCE was almost completely dechlorinated to ethylene in four days, while dechlorination in hydrogen-fed culture was somewhat unstable. These results suggest that organic substrates which produce hydrogen during their anaerobic metabolism serve as effective electron donors for reductive dechlorination of chlorinated ethylenes. Dechlorination was sustained even in cultures fed cis-DCE with low concentrations (10 mgCOD·l-1) of primary substrate, although steady-state conditions were not achieved Results of this study suggest that anaerobic bioremediation can be used for cleanup of groundwater contaminated by chlorinated ethylenes.
