Bioslurping
Description
Bioslurping
combines elements of bioventing and vacuum-enhanced pumping of
free-product to recover free-product from the groundwater and soil, and to bioremediate soils. The bioslurper system uses
a ÒslurpÓ tube that extends into the free-product layer. Much like a straw in a
glass draws liquid, the pump draws liquid (including free-product) and soil gas up the tube in the same process
stream. Pumping lifts light non-aqueous phase liquids (LNAPLs), such as oil, off the top of the water
table and from the capillary fringe (i.e., an area just above the
saturated zone, where water is held in place
by capillary forces). The LNAPL is brought to the surface, where it is
separated from water and air. The biological processes in the term
ÒbioslurpingÓ refer to aerobic biological degradation of the hydrocarbons when air is introduced into the
unsaturated zone. This is akin to bioventing, a technology described separately.
When free-product removal activities are completed, the bioslurping system is
easily converted to a conventional bioventing system to complete the
remediation.
Limitations
and Concerns
Bioslurping
is less effective in tight (low-permeability) soils. The greatest limitation
to air permeability is excessive soil moisture. Optimum soil moisture is very
soil-specific. Too much moisture can reduce air permeability of the soil and
decrease its oxygen transfer capability. Too little moisture will inhibit microbial
activity.
Low
temperatures slow remediation.
The
system has difficulty establishing a vacuum on deep, high permeability sites.
A
fluctuating water table could create saturated soil lenses, which are difficult
to aerate.
Since
the fuel, water, and air are removed from the subsurface in one stream, mixing
of the phases occurs. These mixtures may require special oil/water separators
or treatment. Air emissions from the bioslurper system often require treatment
before discharge. Bioslurper systems may extract large volumes of water that
may need to be treated prior to discharge.
Accurate
placement of extraction is a key to the success of
bioslurping.
Applicability
Bioslurping
is used to remediate soils contaminated by fuel, as well as groundwater
contaminated with fuel LNAPLs. It can help to remediate soils contaminated with
nonhalogenated volatile organic compounds (VOCs)
and semi-volatile organic compounds (SVOCs). It is
applicable at sites with water tables greater than 30 feet.
Technology
Development Status
Bioslurping
is a commercially available technology.
Web
Links
http://www.frtr.gov/matrix2/section4/4-35.html
http://www.estcp.org/documents/techdocs/CU-9908BioslurperUGuide-final.pdf
http://www.afcee.af.mil/resources/technologytransfer/programsandinitiatives/bioslurping/index.asp
http://www.estcp.org/documents/techdocs/CU-9908.pdf
http://www.clu-in.org/download/toolkit/slurp_o.pdf
Other
Resources and Demonstrations
See
technology description for Bioventing.
See
http://www.estcp.org/Technology/ER-9908-VFS.cfm