ELECTRODE ASSISTED SOIL WASHING

Contaminants in soils containing a high percentage of silt- and clay-s ized particles typically are strongly adsorbed and very difficult to r emove. However, a newly patented Electrode Assisted Soil Washing (EASW ) process appears to be effective in removing petroleum hydrocarbons ( gasoline, diesel, crude oil, etc.), chlorinated hydrocarbons, and heav y metals [7] from contaminated soils made up of a high percentage of c lay and silt. The EASW process produces a washed soil material that me ets site-specific regulatory requirements which allow the washed soil to be returned to the site without further treatment. Furthermore, the contaminated water generated by the process can be treated with stand ard biological methods. The EASW process can be used alone, or it can be used in combination with other soil-washing methods. In the latter case, the EASW process is particularly effective in the treatment of c ontaminated fines streams generated by other soil-washing techniques. The results of bench-scale batch tests with EASW used for washing petr oleum hydrocarbons and pentachlorophenol contaminated soils will be di scussed in this paper. Contaminant removal efficiencies of the EASW pr ocess, based on the difference between the contaminant concentrations in the feed soil and the washed soil, were above 99%. The performance of the EASW process in removing pentachlorophenol from soil was benchm arked against a commercially available process and found to be competi tive.