In an anaerobic environment, some bacteria utilize chlorinated compounds as alternate electron acceptors for respiration through the process of reductive dechlorination. Through their respiratory process, bacteria sequentially replace chlorines with hydrogen. The biochemical reactions for complete dehalogenation of TCE through ethene are well documented.
Reductive dechlorination reactions for TCE occurs on a 1:1 molar basis (ie. one mole of TCE will be converted to one mole of cis-DCE and so on).
BRT has demonstrated enhanced anaerobic bioremediation of chlorinated solvents in situ. A brief description of a recent successful field deployment of BRT technology at a site with soil and groundwater impacted with chlorinated solvents in Western Pennsylvania follows. Historic site data showed consistent levels of trichloroethylene (TCE) occurring in groundwater. Pump and treat systems were installed over a 10 year span in attempts to remediate the contaminant. This approach proved extremely ineffective as TCE concentration showed very little movement over the same span. To enhance the reductive dechlorination process that was determined to be suitable by BRT analysis, site specific amendments needed to be introduced to the contaminated media. Addition of the hydrogen donating substrate, along with site specific nutrients, provided the hydrogen necessary for dechlorination of the solvents, thereby enhancing the remediation process on site.
The site has shown a clear decrease in TCE concentrations, with concomitant increases in both DCE and VC concentrations, significantly higher than any historical concentrations, followed by decrease in both DCE and VC to drinking water standards. After nine months of remediation, BRT showed degradation of all chlorinated compounds, including daughter products to below detection limits.
Pipe and Tube Plant
Vapor Degreaser Pit
Groundwater and Soil
Pump and Treat – 9 years
Bioinjection of substrate and site specific nutrients