Biological Treatment of Mixed SVOCs Including 1,2,3-trichloropropane and 1,4-Dioxane

Groundwater in three separate transmissive zones at the site of a former chemical production plant in Mississippi contains several volatile and semi-volatile organic compounds (VOCs and SVOCs) in the parts per million (ppm) range. The pilot test was conducted on water with up to 140 ppm 2-chloroethanol, 70 ppm bis(2-chloroethoxy)methane (BCEM), 21 ppm 1,2-dichloroethane (DCA), 13 ppm ethylene glycol, 11 ppm 1,2,3-Trichloropropane (1,2,3-TCP), 3.4 ppm 1,4-dioxane, and minor (<1.0 ppm) concentrations of bis(2-chloroethyl)ether (BCEE) and minor concentrations of several other organics and VOCs. Dense non-aqueous phase liquids (DNAPLs) are present in two distinct areas of the upper aquifer, consisting of varying concentrations of the contaminants of concern (COCs). Hydrochloric acid was used in the former plant’s production processes, with historic releases resulting in depressed groundwater pH as low as 3.5, and dissolved iron concentrations as high as 400 ppm. An interim groundwater pump and treat system has been operating at the site, providing hydraulic containment of the impacted groundwater plume as well as pretreatment prior to discharging to a publicly owned treatment works (POTW). Both aspects of the planned remedy require a reliable treatment system with a high degree of COC removal.