Ex-situ remediation that separates fine, contaminant-bearing soil particles from coarser, cleaner particles by physical and chemical processes (screening, attrition scrubbing, hydrocycloning, froth flotation). Reduces the volume of soil requiring further treatment or disposal.
Soil washing exploits the tendency of organic and metal contaminants to concentrate on fine particles (silt, clay) and on organic matter. Excavated soil is processed through screens, scrubbers, and hydrocyclones that separate the coarse, lightly contaminated sand and gravel fraction from a much smaller, heavily contaminated fine fraction. The coarse fraction can often be returned to the site; the fines go to thermal treatment, stabilization, or landfill.
Volume reduction of 60 to 90 percent is common at sites with favourable particle-size distribution. Performance is poor at sites dominated by silt and clay, where the cleaner fraction is small and the residual fines remain a problem. Soil washing is widely used in the Netherlands, Germany, and the United Kingdom, and is paired with thermal treatment of the recovered fines as the destruction step.
Also known as: soil washing, soil scrubbing.
Heavy Metals (Arsenic, Mercury, Chromium, Lead): treatment approach
Regulated inorganic trace elements — including arsenic, mercury, hexavalent chromium, lead, cadmium, and nickel — that are toxic at parts-per-billion to parts-per-million levels, do not biodegrade, and are managed by immobilization, physical separation, or valence-state conversion.
An ex-situ soil treatment process that heats contaminated soil to volatilize and separate organic contaminants from the soil matrix, after which the liberated vapors are captured and treated, usually in a high-temperature oxidizer.
A thermal desorption configuration where the heat source contacts the soil directly inside the rotary unit, delivering high heat-transfer efficiency and supporting higher treatment temperatures.
A thermal desorption configuration where heat is conducted through the wall of the treatment vessel without combustion gases contacting the soil, producing a concentrated, lower-volume vapor stream suitable for condensation and recovery.
Treatment that heats contaminated soil and groundwater in place, typically with electrical resistance, thermal conduction, or steam injection, to volatilize and recover contaminants without excavation. Used where excavation is impractical or where the contaminant zone sits beneath active infrastructure.