COMPLETE DECHLORINATION OF TETRACHLOROETHYLENE BY USE OF AN ANAEROBIC CLOSTRIDIUM BIFERMENTANS DPH-1 AND ZERO-VALENT IRON

A laboratory test was conducted to examine the combined effect of an anaerobic Clostridium bifermentans DPH-1 and addition of zero-valent iron (Fe-0) on the reductive dechlorination of tetrachloroethylene (PCE). In addition, the dechlorination of cis-1,2-dichloroethylene (cDCE) produced from PCE was examined using Fe-0. The cDCE produced was completely dechlorinated to non-toxic end products, mostly, ethylene by a subsequent chemical reductive process. Production of ethylene was dramatically increased with increase of initial cDCE concentration in the range of 10.3 mu M to 928 mu M (1.0-90 mg 1(-1)) and the velocity constant was calculated to be 0.38 day(-1). On the other hand, the combined use of strain DPH-1 and Fe-0 showed the most significant effect on the initial PCE dechlorination, but cohesion of Fe-0 was found to inhibit the dechlorination rate of PCE. It is thought that phosphoric acid iron contained in a medium forms film on the surface of iron particle, so oxidation of iron is inhibited.