COMPLETE BIOLOGICAL REDUCTIVE TRANSFORMATION OF TETRACHLOROETHENE TO ETHANE

Reductive dechlorination of tetrachloroethene (perchloroethylene; PCE) was observed at 20-degrees-C in a fixed-bed column, filled with a mixture (3:1) of anaerobic sediment from the Rhine river and anaerobic granular sludge. In the presence of lactate (1 mM) as an electron donor, 9-mu-M PCE was dechlorinated to ethene. Ethene was further reduced to ethane. Mass balances demonstrated an almost complete conversion (95 to 98%), with no chlorinated compounds remaining (<0.5-mu-g/liter). When the temperature was lowered to 10-degrees-C, an adaptation of 2 weeks was necessary to obtain the same performance as at 20-degrees-C. Dechlorination by column material to ethene, followed by a slow ethane production, could also be achieved in batch cultures. Ethane was not formed in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis. The high dechlorination rate (3.7-mu-mol . l-1 . h-1), even at low temperatures and considerable PCE concentrations, together with the absence of chlorinated end products, makes reductive dechlorination an attractive method for removal of PCE in bioremediation processes.