Air Sparging Design Paradigm

Abstract

Air sparging generally involves the injection of air into an aquifer through vertical or horizontal wells. In situations where contaminant vapor recovery is necessary (e.g., as required by regulation, or in situations where vapor migration could cause adverse impacts), air sparging systems are coupled with soil vapor extraction (SVE) systems. Historically, practitioners have installed air sparging systems to: (1) treat immiscible contaminant source zones at or below the capillary fringe; (2) remediate dissolved contaminant plumes; and (3) provide barriers to prevent dissolved contaminant plume migration. Air sparging systems are also now being incorporated into novel aquifer bioremediation schemes for the delivery of other gases (e.g., oxygen, hydrogen, propane), and they have also been used as a means of improving air distribution for bioventing applications targeting near-capillary fringe soils. Some practitioners implement a variation of air sparging that they term biosparging. In practice, the term biosparging is frequently used to refer to air sparging systems when the intent is to operate without an SVE system. The helium air recovery tests discussed above can be used to quantify the efficiency of vapor capture during combined IAS and SVE operation, and can provide valuable insight to the areal distribution of IAS treatment zones. The ease and speed with which these tests can be conducted and interpreted makes them well suited for IAS pilot tests (even 1-day tests). The helium tests can also be conducted on full-scale systems already in operation to confirm that SVE system performance meets project goals. In addition, the tests can be easily repeated, which allows system parameters to be modified and the impact of those modifications to be quickly assessed. The three case histories presented here were chosen to represent the kinds of conclusion that can be drawn from the tests.