Laboratory studies of steam stripping of lnapl-contaminated soils

Bench-scale laboratory experiments were conducted to evaluate the effectiveness of steam injection for in situ remediation of soils contaminated by light nonaqueous-phase liquids (LNAPLs). Several parametric studies were performed with various combinations of soils, LNAPLs, and steam injection conditions. An increase in steam injection pressure produced a significant increase in LNAPL recovery efficiency. An increase in steam injection pressure from 12.4 to 44.8 kPa resulted in increased LNAPL recovery efficiency from 86 to 95% after one pore volume of steam injection. Higher steam injection pressure yielded maximum LNAPL recovery efficiency in significantly less time and required a smaller amount of steam than at low pressure. An increase in soil grain size or an increase in grain-size-distribution slope resulted in increased LNAPL recovery efficiency. The final LNAPL residual saturation was approximately 0.5% for coarse-grained soils and 1.8% for soils with finer grain sizes. Soils with finer grains required more time for treatment than soils with coarser grains. Steam injection experiments with No. 2 heating oil and with jet fuel showed no significant variation in steam front propagation, temperature profile, and maximum LNAPL recovery efficiency. The LNAPL residual saturation after steam injection was essentially independent of the starting LNAPL saturation.