Soil washing and post-wash biological treatment of petroleum hydrocarbon contaminated soils

A laboratory scale study was conducted to investigate the treatability of petroleum contaminated soils by soil washing and subsequent biological treatment of the different soil fractions. In addition to soils obtained from contaminated sites, studies were also performed on soils contaminated in the laboratory. Soil washing was performed using a bench-scale soil washing system. Washing was carried out with simultaneous fractionation of the bulk soil into sand, silt and clay fractions. Cleaning efficiencies due to soil washing ranged from 60 to 81% for different soils. After washing, the finer soil particles (silts and clays) were found to possess higher concentrations of adsorbed hydrocarbons, thus requiring further treatment. Distribution of n-alkanes was studied to obtain a better understanding of contaminant redistribution and mass transfer during washing.