Application of nonionic surfactant-enhanced in situ flushing to a diesel contaminated site

Surfactant-enhanced in situ flushing was performed to remediate soil and groundwater at a diesel contaminated area, which had been used as a military vehicle repair area in Korea for 45 years. A pilot-scale site (4 m×4 m×4 m) was selected within the contaminated area for in situ flushing; the selected site was composed of heterogeneous sandy and silt-sandy soils, with an average hydraulic conductivity (K) of 2.0×10−4 cm/s. Two percent of sorbitan monooleate (POE 20) was mixed with uncontaminated groundwater and five pore volumes of solution (three pore volumes of surfactant solution and two pore volumes of groundwater alone) were flushed to remove diesel from the site. The effluent TPH (total petroleum hydrocarbon) concentration with surfactant solution flushing increased to 1761 mg/L, which was over 200 times higher than the average concentration with only groundwater flushing. A total of 48 kg of TPH (about 88% of the initial TPH) was removed from the pilot site with five pore volumes of 2% sorbitan monooleate solution flushing; this total was more than 75 times the amount that was removed when flushing with water alone (less than 640 g). All of the extracted solution was treated by means of a chemical treatment process, which included the use of a dissolved air flotation system to lower the concentration of solution below 5 mg/L and the treated solution was then disposed of in a nearby sewage drain.