Air sparging (AS) is an in situ remedial technology that reduces concentrations of volatile constituents of petroleum products that are adsorbed to soil particles and dissolved in groundwater. This technology, which is also known as "in situ air stripping" and "in situ volatilisation," involves the injection of contaminant-free air into the subsurface saturated zone, enabling a phase transfer of hydrocarbons from a dissolved state to a vapour phase. The air is then vented through the unsaturated zone.

Air sparging is most often used together with soil vapour extraction (SVE), but it can also be used with other remedial technologies. When air sparging is combined with SVE, the SVE system creates a negative pressure in the unsaturated zone, via the extraction wells, to control the vapour plume migration thereby ensuring control and capture of contaminated vapours.

Suitability

Air sparging can be used to effectively reduce concentrations of volatile organic compounds (VOCs) commonly found in petroleum products. Air sparging is generally considered to be more applicable to the lighter constituents of petrol (e.g., benzene, ethylbenzene, toluene, and xylene [BTEX]), because they readily transfer from the dissolved to the gaseous phase. Air sparging is therefore less applicable to heavier petroleum products such as diesel and kerosene. Appropriate use of air sparging often requires that it is combined with other remedial methods (e.g., SVE or pump-and-treat).

Stratified or highly variable heterogeneous soils typically create the greatest barriers to successful air sparging. Both the injected air and the stripped vapours will always travel along the paths of least resistance (coarse-grained zones).  Therefore only experienced contractors, such as ourselves, should design and install these systems to ensure that contaminant plumes are contained and remediated and not pushed off-site.

Please call or e-mail to discuss the applicability of this technique to one of your sites.