CLEANING EXCAVATED SOIL USING EXTRACTION AGENTS - A STATE-OF-THE-ART REVIEW

In response to the RCRA Hazardous and Solid Waste Amendments of 1984 prohibiting the continued land disposal of untreated hazardous wastes, the U.S. Environmental Protection Agency (EPA) has instituted a research and development program for new technologies to treat RCRA and Superfund wastes. As part of this research program, technologies applicable to cleaning excavated soils were reviewed. This report reviews the state-of-the-art of soil cleaning technologies and their applicability to Superfund sites in the United States. The review includes Superfund site soil and contamination characteristics; as well as soil washing technologies, their principles of operation, and process parameters. The technical feasibility of using soil washing technologies at Superfund sites in the United States is assessed. Contaminants are classified as volatile, hydrophilic, or hydrophobic organics; PCBs; heavy metals; or radioactive material. Soils are classified as either sand, silt, clay, or waste fill. Three generic types of extractive treatments are identified for cleaning excavated soils: water washing augmented with a basic or surfactant agent to remove organics, and water washing with an acidic or chelating agent to remove organics and heavy metals; organics-solvent washing to remove hydrophobic organics and PCBs; and air or steam stripping to remove volatile organics. Although extraction of organics and toxic metal contaminants from excavated sandy/silty soil that is low in clay and humus content has been successfully demonstrated at several pilot-plant test facilities, extraction from clay and humus soil fractions is more complicated and requires additional pilot-scale testing before application at Superfund sites.