Long-term AS/SVE for petroleum removal in low-permeability Piedmont saprolite

A 3.5-year pilot test of air sparging/soil vapor extraction (AS/SVE) was ca rried out to determine whether the heterogeneity of the Piedmont saprolite would allow adequate soil vapor velocities and effective vapor-phase extrac tion rates for petroleum hydrocarbon (PHC) remediation. The objectives were to compare: (1) the effectiveness of pulsed SVE versus pulsed AS/SVE opera tion; (2) benzene, toluene, ethylbenzene, and xylene (BTEX) versus PHC remo val; and (3) biological versus physical removal of PHC. Stack exhaust gas, SVE wells, and soil vapor probes were monitored for total combustible hydro carbons (TCH), BTEX, O-2, CO2, temperature, and flow rate using handheld me ters and gas chromatography. The majority of contaminant recovered was remo ved from the vadose zone via SVE. BTEX and TCH were both effectively remove d from the more-permeable and highly contaminated unsaturated-saturated zon e interface. Bioremediation accounted for 23% of total removal. Overall, th e AS/SVE system physically removed an estimated 18,800 kg of PHC and 5,300 g of BTEX with an average rate of 70 kg d(-1) and 0.4 g d(-1), respectively , which was consistent with other AS/SVE studies in sandy media.