Reductive dechlorination of chlorinated solvents in groundwater: A case study

An experiment was conducted, in which a carbohydrate solution (molasses) was injected into groundwater wells at a site impacted with chlorinated VOC, e.g., perchloroethylene and trichloroethylene (TCE), to create strongly anaerobic and reducing conditions that might cause Enhanced Reductive Dechlorination (ERD). Concentrations of TCE decreased in wells PTW-1, PTW-2, MW-HP-1S, and GP-104 while daughter products, primarily cis-l,2-dichloroethylene, vinyl chloride, and ethylene increased in concentration. Based on the field data and TOC results, the in-situ reactive zone had encompassed monitoring points PTW-1, PTW-2, and MW-HP-IS, and was the catalyst for the ERD of TCE. There was more evidence from the analysis of field data and biogeochemical indicators that supported the occurrence of anaerobic and reducing conditions, as well as ERD at the site. These include: low dissolved oxygen (< 1 mg/L) and REDOX (< 0 mv) concentrations, reduced nitrate and sulfate, and increased nitrite and sulfide concentrations. Methane concentrations increased continually, suggesting that the environment could have approached and achieved methanogenic conditions.