vapor extraction (SVE), also known as "soil
venting" or "vacuum extraction", is an in-situ remedial
technology that reduces concentrations of volatile constituents
in petroleum products adsorbed to soils in the unsaturated (vadose)
zone. In this technology, a vacuum is applied through wells near
the source of contamination in the soil. Volatile constituents of
the contaminant mass "evaporate" and the vapors are drawn
toward the extraction wells. Extracted vapor is then treated as
necessary (commonly with carbon adsorption) before being released
to the atmosphere. The increased air flow through the subsurface
can also stimulate biodegradation of some of the contaminants, especially
those that are less volatile. Wells may be either vertical or horizontal.
In areas of high groundwater levels, water table depression pumps
may be required to offset the effect of upwelling induced by the
SVE is quicker
than cleanup methods that rely on natural processes to do the work.
In general, the wells and equipment are simple to install and maintain.
And it can reach greater depths than methods that involve digging
up soil. SVE is effective at removing many types of pollution that
can evaporate. It can also be used with other methods to clean up
other types of pollution as well. SVE works well under many types
of conditions. SVE is often chosen to clean up Superfund sites.