Sequential anaerobic/aerobic degradation of tetrachloroethylene in a soil enrichment culture.

Abstract

An enrichment culture taken from a contaminated site could efficiently degrade tetrachloroethylene (PCE) under a sequential anaerobic/aerobic condition. Under an anaerobic condition using citrate as a carbon source and yeast extract as a nutritional requirement, the enrichment culture could transfer 60 μM of PCE nearly stoichiometrically to cis-1, 2-dichloroethylene (cis-DCE) via trichloroethylene (TCE) within 3 days. A solution of 19.6% H2O2 was added atfinal concentration of 1.0% (v/v) to change the anaerobic condition of medium to aerobic one. Under the aerobic condition, more than 80% of cis-DCE accumulated was co-metabolized by indigenous phenol degrading bacteria in the enrichment culture. During the co-oxidation in the aerobic condition, all of phenol (125 mg/liter) added were completely consumed and population of phenol degrading bacteria was increased. The degradation of cis-DCE was affected by H2O2 (0.1-2.0% (v/v) ) and phenol (0-250 mg/liter) concentrations, indicating that the optimum doses of H2O2 and phenol are very important to lead successful co-metabolisms of less chlorinated ethylenes under aerobic conditions. The results from this research suggested that the sequential anaerobic/aerobic biostimulation would be viable as a cost-effective and safe bioremediation technique for degradation of PCE and less chlorinated metabolites. But it should need thorough investigation of microbial populations and their interactions for degrading chlorinated ethylenes under anaerobic and aerobic environments of contaminated sites.