Effects of air-injection pressure on airflow pattern of air sparging

Abstract

Air sparging is a remediation technology for treating soil/groundwater contaminated with volatile organic compounds (VOCs). VOC removal during air sparging is rendered less effective, because of the random formation of air channels, creating preferential paths for airflow, thus, limiting remediation to these channels, referred to as a zone of influence (ZOI). Pulsation is a popular method used to improve the effectiveness of air sparging through cyclic operation, with the hope air channels would form elsewhere. Pulsation makes air sparging more time-consuming. This paper studies the effects of one cycle of pulsation and air pressure on airflow pattern and presents the laboratory study to investigate the effects of initial and further increases in the injected air’s pressure on airflow pattern within a glass-bead medium used as a medium analogous to the soil. Digital images of airflow patterns were collected; these images show a larger radius of influence (ROI) and ZOI due to the initial air-pressure increase, especially when a higher overburden pressure (i.e., the stress due to the partially saturated layer on top of the saturated soil-simulant layer) exists above the water-saturated zone. Further air-pressure increases seem to have no measurable effect on the ROI and the shape of the ZOI.