Laboratory Studies of Air Stripping of VOC-Contaminated Soils

Bench-scale laboratory experiments were conducted to evaluate the effectiveness of air stripping for in situ remediation of benzene-contaminated soils. Several parametric studies were performed to evaluate the effect of soil grain size, air injection flow rate, and air inlet temperature on the benzene recovery efficiency. An increase in soil grain size produced a significant increase in benzene recovery efficiency especially during the early stages of air injection. After 2 h of treatment, an increase in soil grain size from D50 = 0.31 mm to D50 = 1.20 mm resulted in an increase in benzene recovery efficiency from 49 to 65%. When the air-flow rate was increased from 5 l/min to 10 l/min, the benzene recovery efficiency increased from 56 to 70% after 4 h of venting operation. Maximum recovery of benzene was reached after approximately 37 h of soil venting at a flow rate of 5 l/min and after approximately 24 h at a flow rate of 10 l/min. Preheating the air to 45°C at the inlet resulted in an increase in recovery efficiency from 70 to 90% after 5 h of air stripping.