AIR SPARGING

Air sparging is an in situ remedial technology that reduces concentrations of volatile organic compounds that are adsorbed to soils and dissolved in groundwater. This technology, which is also known as "in situ air stripping" and "in situ volatilization," 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. Oxygen added to contaminated groundwater and vadose zone soils can also enhance biodegradation of contaminants below and above the water table.

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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 (AS) is combined with SVE, the SVE system creates a negative pressure in the unsaturated zone through a series of extraction wells to control the vapour plume migration. This combined system is called AS/SVE.

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In general, air sparging is more effective for constituents with greater volatility and lower solubility and for soils with higher permeability.

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When used appropriately, air sparging has been found to be effective in reducing concentrations of volatile organic compounds (VOCs) found in petroleum products at underground storage tank (UST) sites. Air sparging is generally more applicable to the lighter petrol constituents (i.e., benzene, ethylbenzene, toluene, and xylene [BTEX]), because they readily transfer from the dissolved to the gaseous phase. Air sparging is less applicable to diesel fuel and kerosene. Appropriate use of air sparging may require that it be combined with other remedial methods (e.g., SVE or pump-and-treat). An air sparging system can use either vertical or horizontal orientated sparge wells based on site-specific needs and conditions.

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