Bioaugmentation and Biostimulation for Dissolved Plume Treatment at Facility 60600

摘要

Biostimulation and bioaugmentation techniques are being applied to treat a dissolved halocarbon plume at Facility 60600 on Cape Canaveral Air Force Station (CCAFS), Florida. The 20 acre plume consists primarily of cis-1,2-dichloroethene (cis- DCE) and vinyl chloride, with remnants of trichloroethene (TCE) and tetrachloroethene in the suspect source area. The plume's distal end approaches the Banana River Lagoon, an Outstanding Florida Water with a zero degradation standard. The U.S. Air Force and its regulatory Partnering Team established objectives of reducing the dissolved contaminant levels to: (1) mitigate the long-term potential for releases to the lagoon and (2) restore the groundwater resource. Bioremediation was the selected strategy because it was compatible with implementation in the highly developed industrial area at the head of the plume and with the sensitive ecological zone at its toe. The local environmental chemistry and native microbial population were assessed prior to technology selection. While specific degraders were present, nutrient deficiencies were identified that may have contributed to slow conversion from DCE and vinyl chloride to non-toxic products. This information guided selection of amendments and the decision to bioaugment a portion of the site. Application of vegetable oil and nutrients (to supply nitrogen and phosphorus), supplemented by bioaugmentation, was implemented at Facility 60600 in the second half of 2006. Vegetable oil, monoammonium phosphate (MAP) and KB-1? Dechlorinator (a strain of Dehalococcoides ethenogenes (Dhc)) were injected into the area where cis-DCE concentrations were > 10,000 μg/L, vinyl chloride was > 4,000 μg/L and TCE or tetrachloroethene concentrations were > 1,000 μg/L. Encircling that area, where cis-DCE concentrations were > 4,000 μg/L, MAP only was added. Post-treatment groundwater monitoring showed a significant increase in Dhc populations in the area where MAP only was added. Approximately one year after the initial treatment event, MAP was again applied, with bioaugmentation at select locations. Between the two events, 31,000 gallons of vegetable oil and 3,100 pounds of MAP were injected hydraulically into an area of approximately 63,500 s.f. Over either a 20–30 or 25–45 ft. Below ground surface (bgs) interval. A total of 270 liters of KB-1? Was slipstreamed in with the vegetable oil and nutrient injections. Performance monitoring results have shown both cis-DCE and vinyl chloride levels across the area initially treated with vegetable oil, MAP and KB-1? Reduced by orders of magnitude. In monitoring wells through the axis of the treatment areas, post-treatment cis-DCE now fluctuates near its cleanup target level of 70 μg/L, down from a maximum