In Situ Air Stripping Overview

Remediation of contaminated soil and groundwater has traditionally meant the bulk removal of the contaminated media for treatment or controlled disposal. In situ air stripping focuses on the develop-
ment of innovative solutions that can be used to replace the tradi-
tional pump-and-treat or excava-
tion systems. Using air stripping, contaminants are extracted as vapor, reducing the treatment facilities needed to handle the large bulk of groundwater remov-
ed by pump-and-treat, and the energy requirements for pumping groundwater to the surface for treatment, and alleviating the potential need to dispose of the pumped groundwater.

In situ air stripping, as demonstrat-
ed at the Savannah River Site, is based on a simple mass transfer process using horizontal injection and vacuum extraction wells. Two subparallel horizontal wells are used: air is injected under pressure into the lower horizontal well (be-
low the water table); air bubbles through the saturated zone, con-
tacting dissolved, adsorbed, and/or separate phase contaminants, and into the vadose zone (the zone above the water table). Finally, the air and vapors are collected by the upper horizontal gas extraction well. During the process, contami-
nants are volatilized into the air stream and exit the subsurface through the upper horizontal well. The use of horizontal wells may provide better contact with con-
taminated subsurface strata than vertical wells.