Site Demonstration of Terra-Kleen Response Group's Mobile Solvent Extraction Process

The U.S. EPA's Superfund Innovative Technology Evaluation (SITE) Program evaluated a pilot-scale solvent extraction process developed by the Terra-Kleen Response Group (TKRG). This process uses a proprietary solvent, or mixture of solvents, to extract organic contaminants from solids. A pilot-scale evaluation was conducted at Naval Air Station North Island (NASNI), near San Diego, CA, on soils which were contaminated with polychlorinated biphenyls (PCBs) and other organic substances. Five tons of soil with an average PCB concentration of 144 mg/kg were excavated, homogenized, and equally distributed to five extraction vessels. Eleven extraction cycles were used to produce a treated soil with an average PCB concentration of 1.71 mg/kg on a dry weight basis (98.8% removed). Oil and Grease (O&G) removal efficiencies were found to be 65.9%. This low O&G removal efficiency was attributed to solvent/solute relationships. Initial concentrations of hexachlorodibenzofuran (HxCDF) in soils averaged 0.697 jig/kg. Following solvent extraction, no HxCDFs were detected (<0.117 fxg/kg) in soil samples. A fullscale solvent extraction system was operated at a site in Stockton, California. Pesticides were extracted from 500 tons of contaminated soil using 19 extractors, each 20 cubic yards in volume. Three extraction cycles produced solids with <0.093 mg/kg residual pesticide (>99% removed). These results demonstrate that the TKRG's solvent extraction process is effective in removing organic contaminants from soils.