Effects of surfactant injection position on the airflow pattern and contaminant removal efficiency of surfactant-enhanced air sparging.

Abstract

Surfactant-enhanced air sparging (SEAS) is an effective remediation technique for VOCs-contaminated soil. In this study, three types of tests are performed to investigate the effects of the surfactant injection position on the airflow pattern, contaminant removal efficiency, and airflow path control. The three tests are conventional air sparging (CAS), entire SEAS (ESEAS), where the surfactant is incorporated into the entire contaminated soil, and local SEAS (LSEAS), where the surfactant is injected locally at different positions. With increasing distance between the injection position and the central axis, the LSEAS test results approach the results measured in the CAS test. When the surfactant is injected directly at the central axis, a high contaminant removal rate of 89% is obtained, which is even higher than that obtained for the ESEAS test. As the injection position moves away from the central axis, the removal rate decreases. Furthermore, when the injection position is close to the sparging point, the surfactant can successfully control the airflow path. Based on the test results, a critical distance between the surfactant injection position and sparging point exists where high remediation efficiency can be achieved. This optimal surfactant injection position is specific to each contamination site.