Air sparging involves the injection of compressed air into the saturated zone, where air bubbles strip volatile organic compounds (VOCs) from groundwater by promoting volatilisation. The air emerges in the vadose zone, where it often stimulates in situ biodegradation of organic contaminants. Biosparging builds on this principle, optimising air movement to enhance biodegradation processes directly.
The system typically uses sparging wells with screens installed below the water table. It can be applied to both strip volatile contaminants and stimulate microbial conversion, with simultaneous treatment of the vadose zone possible when air emerges from the saturated zone. To manage emissions, soil vapour extraction (SVE) is often paired with sparging. While basic air sparging is effective for removing VOCs, it also promotes biodegradation of a broader range of contaminants, depending on site conditions.
However, air sparging faces challenges, particularly in controlling air flow pathways in the subsurface. Geological variability, such as soil permeability differences, can cause preferential air channels, reducing treatment efficiency. Techniques such as intermittent air injection, pressure control, and bubble size management can mitigate these issues. In low-permeability soils, creating permeable reactive zones can extend its application.
The process is most effective in permeable aquifers and can be enhanced by ozone injection to oxidise persistent contaminants. However, it is less suitable for low-permeability soils, highly soluble VOCs, and heterogeneous strata, where uneven air distribution limits effectiveness.
Air sparging is used to treat VOCs, semi-volatile organic compounds (sVOCs), polycyclic aromatic hydrocarbons (PAHs), pesticides, and certain toxic elements. It supports both contaminant extraction and transformation, reducing pollution risks for future generations. Despite its advantages, regulatory challenges may arise due to concerns over fugitive emissions and operational difficulties.