Laboratory and Modeling Efforts to Refine the use of In Situ Chemical Oxidation for Addressing Residual VOC Plumes on the Savannah River Site

In situ chemical oxidation (ISCO) has been widely used in recent years for the remediation of VOC contaminated soil and groundwater. Among several chemical oxidizing agents injected into the subsurface for ISCO, persulfate has often been selected due to the advantage of being less reactive and longer-lived in the subsurface environment. Through this research, the effect of side reactions occurring during the remediation of a VOC plume at the Department of Energy’s Savannah River Site (SRS) was evaluated using lab-scale experiments as well as a model simulation. Two SRS soils with different mineral and organic compositions were used to study persulfate adsorption and consumption by the oxidation of soil organic matter. A high degree of reversible persulfate sorption was observed for the SRS materials that contained significant Fe oxides and limited organic matter.The consumption of persulfate caused by the oxidation of organic matter for the surface soil material was significant as well. The details of adsorbed persulfate speciation on the soil and oxidation of persulfate are currently under investigation using the PHREEQC geochemical modeling code.