Complete dechlorination of tetrachlororethene to ethene in presence of methanogenesis and acetogenesis by an anaerobic sediment microcosm.

An anaerobic consortium taken from brackish sediments, enriched by PCE/CH3OH sequential feeding, was capable of completely dechlorinating tetrachloroethene (PCE) to ethene (ETH). In batch experiments, PCE (0.5 mM) was dechlorinated to ethene (ETH) in approximately 75 h with either CH3OH or H-2 as the electron donor. When VC (0.5 mM) was added instead of PCE it was dechlorinated without any initial lag by the PCE/CH3OH enriched consortium, although at a lower dechlorination rate. In batch tests H-2 could readily replace CH3OH for supporting PCE dechlorination, with a similar PCE dechlorination rate and product distribution with respect to those observed with methanol. This indicates that H-2 production during CH3OH fermentation was not the rate-limiting step of PCE or VC dechlorination. Acetogenesis was the predominant activity when methanol was present. A remarkable homoacetogenic activity was also observed when hydrogen was supplied instead of methanol.