Bioremediation of Trichloroethylene-Contaminated Sediments Augmented with a Dehalococcoides Consortia

At the Department of Energy's (DOE) Savannah River Site (SRS) in Aiken, SC there are a number of sites contaminated with Chlorinated Ethenes (CE) due to past disposal practices. Sediments from two CE contaminated SRS locations were evaluated for trichloroethylene (TCE) biodegradation through anaerobic laboratory microcosms. The testing included addition of amendments and bioaugmentation of sediments. The anaerobic microcosms were first amended with substrates including acetate, lactate, molasses, soybean oil, methanol, sulfate, yeast extract, Regenesis HRC(R), and MEAL (methanol, ethanol, acetate, lactate mixture). Microcosms were analyzed after biostimulation for 9 months and no significant TCE biodegradation was observed. At 10 months, additional TCE, fresh amendments, and a mixed culture containing Dehalococcoides ethenogenes were added to active microcosms. A significant decrease in TCE concentrations and an increase in biodegradation products cis-dichloroethylene (cDCE) and vinyl chloride (VC) were noted within 2 weeks of bioaugmentation. Microcosms amended with lactate and sulfate showed complete transformation of TCE (3 ppm) to ethene within 40 days after bioaugmentation. Microcosms amended with other substrates - soybean oil, acetate, yeast extract, and methanol - also show enhanced biodegradation of TCE to ethene. Microcosms amended with molasses and Regenesis HRC showed limited TCE transformation. No TCE transformation was seen in killed control microcosms. On the basis of these successful results, plans are underway for field-scale in-situ deployment of biostimulation/bioaugmentation at SRS.