Two-stage bioreactor to destroy chlorinated and nonchlorinated organic groundwater contaminants

Both chlorinated and nonchlorinated volatile organic compounds are found as common contaminants of groundwater across the nation. Two field-pilot bioreactors successfully treated contaminated groundwater at Robins Air Force Base (AFB). The fluidized-bed bioreactor (FBR) effectively removed >97% of the 1,2-dichlorobenzene (DCB) and >95% of the benzene, toluene, ethylbenzene, and xylene(s) (BTEX) from more than 210,000 gal of contaminated groundwater. The FBR removed 84% of the trichloroethylene (TCE), also found in this groundwater, based on a total mass balance beyond carbon adsorption. Enhanced operational stability was demonstrated for the gas-phase reactor (GPR) with 10 months of continuous operation in the laboratory and 2 months in the field. TCE concentrations in contaminated air entering the pilot GPR were reduced by 75% on average. Capital and operating costs for the FBR system were compared to other treatment options including ultraviolet (UV)-peroxidation, air stripping with carbon adsorption, and wet carbon adsorption. GPR economics were compared to carbon adsorption at two TCE concentrations. These bioreactor systems provide economical, destructive technologies for treating either contaminated water or contaminated air originating from air stripping, air sparging, or soil vapor extraction operations and will be effective remedial options at many sites