[Dechlorination of chlorinated ethenes under different redox conditions]

Chlorinated ethenes are pollutants in contaminated soil and groundwater, and one of the efficient way to remove them is biodegradation. In this paper, the microbial breakdown of PCE, cis-DCE and VC with initial concentrations of 100 mumol/L were studied under different redox conditions at temperature 20 degrees C. The results showed that in the presence of ferric iron and carbon dioxide, PCE were dechlorinated to TCE (0.26/day) and cis-DCE (0.31/day), respectively. In the presence of fatty acids and without competition from inorganic electron acceptors, all the studied chlorinated compounds were completely dechlorinated to ethenes. However, the degradation rates of cis-DCE and VC (0.04/day) were much lower than that of PCE (0.57/day). Under denitrifying, manganese reducing and sulfate reducing conditions, no degradation of chloroethenes was observed. When the temperature was lowered to 12 degrees C, the activities of dechlorinating microbes were also reduced, nevertheless, the completely reductive dechlorination of chloroethenes still occurred.