Evaluation of alkaline activated sodium persulfate sustained release rod for the removal of dissolved trichloroethylene

Abstract

The presence of trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) in the subsurface can generate a dissolved phase plume in groundwater. This study developed an alkaline activated sodium persulfate (SPS) sustained release oxidation rod (alkaline SPS SR-Rod) for long-term in situ chemical oxidation accelerated treatment of TCE dissolved from TCE DNAPL, by creating a greater concentration gradient at the TCE DNPL boundary. The dissolution of TCE DNAPL (1 mL) in water (280 mL) generated ~700 mg L^-1, with a volumetric mass transfer coefficient (k_La) of 0.0187 d^-1. The alkaline SPS SR-Rod system had a k_La of 0.013 d^-1 for TCE dissolution at early stage, and thereafter aqueous TCE concentration remained below ~10 mg L^-1 over 60 d of reaction. An SPS SR-Rod life-span of 186 d, for 90% of SPS released from the rod, was estimated. In the soil-water system, aqueous TCE was maintained < 3 mg L^{- 1} throughout the reaction and the soil oxidant demand was determined to be ~4 g-SPS/kg-soil in the alkaline SPS SR-Rod system. These results revealed that the use of the alkaline SPS SR-Rod can be effective as a method of treating dissolved TCE released from DNAPL contamination, and thereby accelerating TCE DNAPL removal.

Keywords: Chlorinated solvent; Controlled release; DNAPL; In situ chemical oxidation (ISCO); Soil and groundwater contamination.