REDUCTIVE DECHLORINATION OF CHLOROALKENES IN MICROCOSMS DEVELOPED WITH A FIELD CONTAMINATED SOIL

Static microcosms were constructed with a low organic carbon content, field-contaminated soil containing (in mumol/kg wet soil) tetrachloroe thylene (PCE; 69. 1), trichloroethylene (TCE; 18. 1) and cis-1,2-dichl oroethylene (cDCE; 2.3). Incubation at 20-degrees-C resulted in reduct ive dechlorination of PCE and TCE to cDCE under both sulfate-reducing and fermentative/methanogenic conditions. Low levels of vinyl chloride (VC) were also produced. Addition of electron donors (such as ethanol , acetate and lactate) was necessary for reductive dechlorination to o ccur. However, less than 0.25% of the electron equivalents potentially made available by the electron donor(s) were actually used for the de chlorination of the target chlorinated alkenes. More than 99% of the s oil PCE was dechlorinated in less than 200 days of incubation under ei ther sulfate-reducing or methanogenic conditions when external electro n donors were added to these microcosms. Nitrate reduction conditions led to a much lower rate and extent of PCE dechlorination.