Implementation of Bioaugmented Enhanced Anaerobic Dechlorination in a High-Groundwater-Velocity, Low-Organic Carbon Source Area(ABSTRACT)

摘要

Physical inhibitions to bioremediation include certain ranges of hydraulic conductivity of the groundwater system. When low, hydraulic conductivity limits the practical distribution of treatment chemicals and when high, decreases residence time in the treatment zone and constrains the ability to induce and sustain a thorough treatment environment spatially and temporally. The effect of high hydraulic conductivity on the implementation of bioremediation was evaluated at a site where bioaugmented enhanced anaerobic dechlorination was implemented as the groundwater remedy. The site was characterized as having a naturally high groundwater velocity (500 feet per year) and loworganic carbon content (less than 1 milligram per liter). Groundwater was impacted by tetrachloroethene, trichloroethene and 1,1,1-trichloroethane and thorough mass destruction throughout the plume was critical to success; pockets of limited treatment were not an acceptable outcome given the risk factors at the site. Site hydrogeology can be summarized as having a relatively shallow (14 feet below ground surface) water table and high rate of groundwater flow in a relatively thin water-bearing zone. Sulfate reduction was anticipated to be the primary control on the utilization of carbon. The native population of D. ethenogenes was tested and found to be not sufficiently robust to complete the dechlorination process without bioaugmentation. Local regulatory conditions prevented the use of groundwater recirculation as a design technique, limiting available approaches to overcome the physical constraints on effective bioaugmentation.