Laboratory and Field Scale Bioremediation of Tetrachloroethene (PCE) Contaminated Groundwater

Bioremediation studies were conducted at a tetrachloroethene contaminated site located in Manhattan Kansas. A former dry cleaning facility was in operation for 30 years. Shallow and deep aquifers down gradient from contaminated site were found to be contaminated with PCE and it s degradation products all above their Maximum Contamination Limits (MCL s). PCE concentration in groundwater at the pilot study area was about 15 mg/L (ppm) in the deep zone and 1 mg/L in the shallow zone. Lab scale microcosms were prepared with different nutrients like soy oil methyl esters (SOME), yeast extract (YE), glucose, lactate, methanol and cheese whey for biostimulation experiments, and commercially available KB-1 bacterial culture was used to bioaugment PCE degradation. Biostimulation of the natural ground water and soil microflora did not completely degrade PCE as cis-DCE (c-DCE) accumulated in the sample. Bioaugmented microcosms containing YE and SOME created reducing conditions for KB-1 culture, resulting in ~ 90% dechlorination of PCE. Cheese whey microcosms with concentrations of (0.01% to 0.025%) reduced PCE, while 0.05% cheese whey and higher inhibited the KB-1 culture. This inhibition was due to a drop of pH that inhibited the bacterial culture activity. At pilot study area, tracer studies were conducted to monitor the direction and velocity of groundwater before during and after remediation experiments. Several nutrient feeding events took place during biostimulation and bioaugmentation. Results indicate that complete degradation of PCE occurred when KB-1 culture containing Dehalococcoides bacteria was introduced under anaerobic conditions. The total chlorinated ethenes (CEs) decreased by about 80% in the pilot study area due to bioremediation. Biodegradation of CEs continued for a long term (several months) after the addition of nutrients.