Enhancing Natural Attenuation through Bioaugmentation with Aerobic Bacteria that Degrade cis-1,2-Dichloroethene
GEOSYNTEC CONSULTANTS ATLANTA GA
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Monitored natural attenuation MNA and enhanced in situ bioremediation EISB remedies hold the promise of reducing the costs associated with the cleanup of Department of Defense DoD sites impacted by chlorinated solvents. However, there are many DoD sites where tetrachloroethene PCE and trichloroethene TCE are undergoing only partial dechlorination to cis-1,2-dichloroethene cDCE, even when sufficient electron donor is present either because of the absence of required bacteria Dehalococcoides or aerobic conditions. Under SERDP sponsorship ER-1168, a novel aerobic bacterium Polaromonas sp. strain JS666 that uses cDCE as a sole carbon and energy source was isolated and characterized Coleman et al., 2002a,b. Since it requires no exotic growth factors, JS666 is a promising bioaugmentation culture for aerobic sites where cDCE is recalcitrant. The microorganism will grow and thrive where oxygen and cDCE are co-located, and JS666 also degrades 1,2- dichloroethane DCA and cometabolizes TCE and vinyl chloride VC. Ideal groundwater conditions for JS666 include dissolved oxygen DO levels between 0.01 mgL and 8 mgL low ionic strength conductivity 15 milliSiemens per centimeter mScm a pH of 6.5 to 8 and relatively low concentrations of TCE, 1,2-DCA and VC 500 gL. The goal of this first field demonstration was to evaluate the effectiveness of JS666 in biodegrading cDCE. The demonstration was conducted at Site 21, St. Julien s Creek Annex in Chesapeake, Virginia. This site had several relatively well-characterized groundwater plumes of chlorinated volatile organic compounds VOCs primarily cDCE, TCE and VC, appropriate site conditions, and a suitable on-site support network. In the vicinity of the pilot test area, groundwater flow is towards the west. Shallow groundwater typically ranges from 2 to 7 ft below ground surface bgs.
- Organic Chemistry