(213c) Attenuation of Tetrachloroethylene In Groundwater by Bioremediation

A pilot scale feasibility study was conducted for attenuation of tetrachloroethylene (PCE) contaminated site. PCE concentration in groundwater at the pilot study area was about 15 mg/L (ppm) in the deep zone of the aquifer. Nutrient solutions prepared with different combinations of soy oil methyl esters, cheese whey, yeast extract, lactate and glucose were injected for biostimulation and preconditioning of ground water prior to KB-1 (a consortium of Dehalococcoides) injection. Nutrient solution was injected four times during the first year of the pilot study to supplement microbial growth. During biostimulation, no appreciable degradation beyond dichloroethylene (DCE) was evident. The addition of KB-1, during second nutrient injection, reduced PCE and DCE concentrations in the pilot study area to less than 10 percent of the original levels. Total chlorinated ethene concentrations did not reach the original levels two years after the last nutrient addition. The combination of substrates injected provided both short term and long term supply of nutrients for the microbes. Tracer study results demonstrated that microbial growth decreased ground water velocity during the study, but returned to normal conditions one year after the last nutrient addition.