Bioremediation of TCE in Groundwater through Enhanced Reductive Dechlorination

Jacob, Clint*; Weber, Eric; Bet, James
(Landau Associates, Edmonds, WA and The Boeing Company, Seattle WA)

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Trichloroethene (TCE) contaminated groundwater beneath a former aerospace manufacturing building in Auburn, Washington was effectively bioremediated through enhanced reductive dechlorination. TCE is a common chlorinated degreasing solvent and known human carcinogen used by many industries including semi-conductor manufacturers. When released to groundwater aquifers, TCE commonly results in large, persistent groundwater plumes that exceed regulatory cleanup levels and require lengthy and expensive containment and treatment efforts. Bioremediation is a relatively new and innovative approach that can achieve TCE cleanup over a shorter time frame and at a lower cost than conventional cleanup methods. TCE bioremediation is achieved through addition of electron donor substrates to stimulate bacteria present in the aquifer to respire the TCE, resulting in reductive dechlorination through successive breakdown products to carbon dioxide and water. At the Boeing Company’s Auburn facility, a historic TCE release from a former vapor degreaser resulted in a groundwater plume that extended laterally over 8.5 acres and from the water table at 15 ft to approximately 40 ft below grade. Remediation of the release area was completed within one year as a result of two injections of sodium lactate and vegetable oil electron donor substrates. A combined 275,000 gallons of site groundwater amended with 73,000 lbs of sodium lactate and 98,000 lbs of vegetable oil emulsion were injected. Destruction of TCE and associated breakdown products was observed, resulting in a reduction of contaminant concentrations to below federal maximum contaminant levels (MCLs) for drinking water.

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