Abstract
cis-1,2-Dichloroethylene (cis-DCE) is frequently found as a groundwater contaminant. cis-DCE can be biotransformed via reductive dechlorination to ethylene under anaerobic conditions. We have recently reported a high-rate transformation of cis-DCE to ethylene by anaerobic enrichment cultures. A small part of ethylene was further reduced to ethane. Hydrogen appeared to be the actual electron donor for reductive transformation of cis-DCE in these cultures. In this study, batch experiments were conducted for investigating the mechanism of cis-DCE transformation by these anaerobic enrichment cultures. Hydrogen was used as an electron donor. Addition of 2-bromoethanesulfonate (BES), a specific inhibitor of methanogenesis, did not inhibit reductive dechlorination of cis-DCE. The major organisms utilizing hydrogen were not methanogens but homoacetogens. These results suggest that the dechlorinating organisms were homoacetogens. On the other hand, reduction of ethylene to ethane was inhibited in the presence of BES, suggesting a role of methanogens in this transformation.
Batch experiments examining the biodegradability of tetrachloroethylene (PCE) by these cultures were also conducted and it was found that the cultures were able to transform PCE to ethylene at high rates.
