In Situ Bioremediation of Chlorinated Solvent Source Areas with Enhanced Mass Transfer

This report provides the demonstration results for enhanced mass transfer of chloroethenes from dense non-aqueous phase liquid (DNAPL) to groundwater during in situ bioremediation (ISB) at the Fort Lewis Logistics Center East Gate Disposal Yard (EGDY). Enhanced mass transfer can occur as a direct result of biological anaerobic reductive dechlorination (ARD), or simply due to the physicochemical interaction of the electron donor itself and the nonaqueous contaminant(s). Increased mass transfer from DNAPL to groundwater through the latter mechanism by addition of certain electron donors, such as sodium lactate or whey powder, has been demonstrated to increase contaminant bioavailability and thereby rates and extents of biological degradation via ARD in both laboratory and field-scale studies (U.S. patents 6,783,678; 7,045,339; and 7,141,170). This technology is referred to as Bioavailability Enhancement Technology (trademark), or B.E.T. (trademark). This demonstration provided rigorous documentation of the electron donor (whey) concentration-dependence of enhanced mass transfer of chlorinated solvents in a source area for the first time in a field study. It was also observed that ARD occurred concurrently with the enhanced mass transfer and resulted in rapid source strength reduction. The original document contains color images.