Effect of groundwater flow on remediation of dissolved-phase VOC contamination using air sparging

This paper presents two-dimensional laboratory experiments performed to stu dy how groundwater flow may affect the injected air zone of influence and r emedial performance, and how injected air may alter subsurface groundwater flow and contaminant migration during in situ air sparging. Tests were perf ormed by subjecting uniform sand profiles contaminated with dissolved-phase benzene to a hydraulic gradient and two different air flow rates. The resu lts of the tests were compared to a test subjected to a similar air flow ra te but a static groundwater condition. The test results revealed that the s ize and shape of the zone of influence were negligibly affected by groundwa ter flow, and as a result, similar rates of contaminant removal were realiz ed within the zone of influence with and without groundwater flow. The air flow, however, reduced the hydraulic conductivity within the zone of influe nce, reducing groundwater flow and subsequent downgradient contaminant migr ation. The use of a higher air flow rate further reduced the hydraulic cond uctivity and decreased groundwater flow and contaminant migration. Overall, this study demonstrated that air sparging may be effectively implemented t o intercept and treat a migrating contaminant plume. (C) 2000 Elsevier Scie nce B.V. All rights reserved.