Reductive transformation of tetrachloroethylene to ethylene and ethane by an anaerobic filter

Tetrachloroethylene (PCE) is one of the most common groundwater contaminants in Japan. PCE can be completely dechlorinated to ethylene (ETY) and ethane (ETA) by anaerobic microorganisms in the presence of a suitable electron donor. This study was conducted to examine the feasibility of using an anaerobic filter for the degradation of PCE in a bioremediation process. Laboratory-scale anaerobic filters were operated at 25°C using ethanol as the electron donor. Rapid start-up of the reactors was achieved by using anaerobic completely PCE-dechlorinating enrichment cultures as the inoculum. During the continuous operating periods, low concentrations (2.8 mg/L) of PCE were almost completely dechlorinated to ETY and ETA at hydraulic retention times of 49-15 hours with 100 mgCOD/L of ethanol. PCE concentrations as high as 80 mg/L was dechlorinated to ETY with a relatively low supply (200 mgCOD/L) of ethanol. Results of this study suggest that the anaerobic filter system is a feasible bioremediation process for the cleanup of groundwater which is contaminated by chlorinated ethylenes.