BIODEGRADATION OF CHLORINATED ETHENES BY NATURALLY OCCURING MICROBES IN WETLAND SOILS

The biotransformation of several chlorinated ethenes or CEs (1,1-dichloroethene, trans 1,2- dichloroethene, cis- 1,2 dichloroethene or DCE and vinyl chloride or VC) under various electron accepting conditions is investigated at bench-scale by using enrichment cultures obtained from a shallow soil core collected from a local wetland. The anaerobic microbial enrichment cultures were capable of degrading CEs using nitrate or sulfate as electron acceptors. The results indicated that the DCEs and VC were degraded under nitrate-reducing conditions. The microcosms were frequently amended with nutrient solution and 200 mg L-1 yeast extract (carbon source). Further, the degradation of 1,1-DCE; trans-DCE; cis-DCE and VC were also observed in aerobic condition in slurry microcosms prepared with wetland-soil, and without addition of a carbon substrate, where DCEs or VC may have served as sole carbon source and oxygen as a terminal electron acceptor. The biodegradation of various CEs under sulfate reducing condition is still under investigation. The rate constants of degradation for the above CEs appear to vary among the conditions studied, as the removal rate of a particular CE was slower under nitrate-reducing conditions compared to aerobic conditions in analogous systems.