What Does Air Sparging Mean?
Air sparging, also known as in-situ air stripping or in-situ volatilization, is the process of injecting air into a contaminated zone to allow volatile and semi-volatile contaminants to transfer from the water to the air bubbles. The bubbles move up to the vadose zone where a soil-venting system captures the contaminated air stream.
The addition of oxygen to the soil and contaminated water also acts as a nutrient to the bacteria present and helps in the biodegradation of contaminants present in and above the water table.
Trenchlesspedia Explains Air Sparging
Air sparging is used in conjunction with soil vapor extraction (SVE) to allow the air bubbles to carry the contaminants in the vapor phase to remove them. The vapor plume migration takes place when the SVE system with the help of extraction wells creates a negative pressure in the unsaturated zone.
It enhances the movement of contaminants and oxygenation in the sub-surface increasing the rate of extraction of the contaminants. Though air sparging is very useful in targeting localized contaminated zones, it also has some limitations.
Studies show that air injected in water-saturated media does not move through the entire medium as bubbles, rather move in channels that comprise a fraction of the cross-section of the zone, limiting its efficiency.
Another limitation is in places where overlying the target zone are low-permeability zones, obstructing the air from passing into the vadose zone thus preventing capture by the SVE.