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 "slurp" 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 "bioslurping" 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.serdp-estcp.org/content/download/3826/60204/file/CU-9908BioslurperUGuide-final.pdf
http://www.serdp-estcp.org/content/download/3823/60180/file/CU-9908-FR-01.pdf
http://www.clu-in.org/download/toolkit/slurp_o.pdf
Other
Resources and Demonstrations
See
technology description for Bioventing.