Soil treatment for remediation of heavy metal contaminated soils

A novel soil treatment process for the removal of metals from industrially contaminated soils has recently been developed. The process consists of units for soil segregation, metals extraction, and water treatment. The project was awarded funding under the federal-provincial Demonstration of Site Remediation Technology (DESRT) program and from the Science Council of BC and has been proven at the bench scale and is ready for on-site pilot scale demonstration. A number of soils and chelating agents have been tested at a bench scale to demonstrate the process. High metals removal efficiencies were observed for arsenic, barium, cadmium, cobalt, chromium, coppper, lead and zinc. Optimal conditions for the soil tested involved using the chelating agent NTA under highly acidic pH conditions at 70°C. The metals removal efficiencies varied widely depending on the soil used. The metals laden aqueous stream generated in the process was effectively treated using a high density sludge water treatment system. The economics of the process appear to be competitive with the primary remediation option of excavation and landfilling. The cost to clean-up contaminated soil is dependent upon the ability to segregate the uncontaminated fraction from the contaminated soil, as well as on the soil type and the nature of contamination.