Enhanced In Situ Biodegradation of PCE Following Electrical Resistance Heating at a DNAPL Source Area
Area of Concern (AOC) 607 is a former dry cleaner at the Charleston Naval Complex (CNC). During the RCRA field investigation (RFI), soil and groundwater were found to be impacted by tetrachloroethene (PCE). PCE concentrations in groundwater as high as 42,000 mircograms per liter (μg/L) were detected. During a nine-month period, an area defined by monitoring wells with PCE concentrations greater than 2,000 μg/L was treated using electrical resistance heating (ERH). Initial monitoring conducted during the cooling period indicated that a dissolved plume remained in some portions of the treatment zone at concentrations greater than several thousand μg/L. The ratio of biodegradation daughter products to PCE in groundwater was significantly greater than prior to implementation of ERH. To evaluate whether the reductive dechlorination (RD) process could be enhanced, the team implemented an enhanced reductive dechlorination (ERD) pilot study. A soluble substrate was periodically injected into two injection wells in the portion of the original treatment area at which VOC concentrations in groundwater were greatest and downgradient groundwater was monitored to assess the impact on RD. The pilot study indicated a significant enhancement of the RD process.