Co-metabolism Biodegradation of Tetrachloroethylene under Different Groundwater Conditions

Tetrachloroethylene (PCE) is one of the most common contaminants in groundwater. The microorganism treatment method has the advantages of low cost and no secondary pollution. PCE can only be biodegraded under reducing conditions, and most research aimed at PCE biodegradation under methanogenic conditions and few under relatively weak reducing conditions, such as denitrifying, iron reducing, sulfate reducing. Trichloroethylene (TCE) biodegradation under different groundwater conditions, including denitrifying, iron reducing, sulfate reducing, mixing electron acceptors and natural groundwater condition, was studied with batch experiments and is described in this paper. The results show that the iron reducing condition is the best condition for PCE biodegradation, followed by natural groundwater condition with PCE removal efficiencies of 91.34% and 84.71% respectively. PCE is transformed to TCE quickly, and to dichlorethane (DCE) eventually. PCE biodegradation is in accordance with the first order kinetic equation. It is difficult to achieve PCE biodegradation in denitrifying, sulfate reducing and mixing electron acceptor conditions, and the degradation product is TCE only, where most PCE is removed by volatilization. PCE biodegradation is promoted by the existence of ferric iron, while it is inhibited by the high concentration of nitrate and sulfate.