Effect of pulsed air injection during in-situ air sparging for groundwater remediation

Air sparging column experiments were conducted using coarse sand and fine sand subjected to both continuous and pulsed air injection in order to determine the effectiveness of pulsed air injection when compared to continuous air injection. For this study, the soil samples were saturated with a known concentration of benzene solution. Compressed air was then injected into the soil column under pre-selected pressure and flow rates. Three injection regimes were used: continuous air injection, pulsed air injection with a period of two hours, and pulsed air injection with a period of six hours. During testing, benzene concentration profiles were measured in the soil at different time intervals by sampling pore water from sampling ports and analyzing using gas chromatography(GC). This study demonstrated that pulsed air injection did not offer any appreciable advantages over continuous injection in tests using the coarse sand; however, pulsed air injection led to substantial reductions in system operating time for tests performed in fine sand. Therefore, pulsed air injection systems may lead to more efficient and fiscally attractive remediation programs for the application of in-situ air sparging to finer sandy soils.