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- Bioslurping
- Use of vacuum-enhanced pumping to recover light, non-aqueous
phase liquid (LNAPL) and initiate vadose zone remediation
through bioventing. In bioventing, air is drawn through the
impacted vadose zone via extraction wells equipped with low
vacuums to promote biodegradation of organic compounds.
- Bioremediation - Enhanced
microbial degradation of organic constituents by which complex
organic compounds are broken down to simpler, usually less toxic
compounds through aerobic or anaerobic processes. Often
incorporates either augmentation of current microbial
populations or supplementation of nutrients to enhance existing
populations.
- Air Sparging
- Injection of gas (usually air or oxygen) under pressure into
wells installed within the saturated zone to volatilize
contaminants dissolved in groundwater, present as non-aqueous
phase liquid, or adsorbed to the soil matrix. Volatilized
contaminants migrate upward and are removed upon reaching the
vadose zone, typically through soil vapor extraction. Most
applicable for volatile organic contaminants in relatively
moderate to high permeability geologic materials.
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Blast-Enhanced Fracturing - A technique used at sites
with fractured bedrock formations to improve the rate and
predictability of recovery of contaminated groundwater by
creating "fracture trenches" or highly fractured areas through
detonation of explosives in boreholes (shotholes).
Blast-enhanced fracturing is distinguished from hydraulic or
pneumatic fracturing in that the latter technologies do not
involve explosives, are generally conducted in the overburden,
and are performed within individual boreholes.
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- Directional
Wells - Encompasses horizontal wells. Trenched or
directly drilled wells installed at any non-vertical inclination
for purposes of ground-water monitoring or remediation.
Especially useful when contaminant plume covers a large area and
has linear geometry, or when surface obstructions are present.
This technology can be used in the application of various
remediation techniques such as ground-water and/or non-aqueous
phase liquid extraction, air sparging, soil vapor extraction,
in situ bioremediation, in situ flushing,
permeable reactive barriers, hydraulic and pneumatic fracturing,
etc.
- Ground-Water
Recirculation Wells - Encompasses in situ
vacuum, vapor, or air stripping, in-well vapor stripping,
in-well aeration, and vertical circulation wells. Creation of
ground-water circulation "cell" through injection of air or
inert gas into a zone of contaminated ground-water through
center of double cased stripping well which is designed with
upper and lower double screened intervals. Injection of air
creates "airlift pumping system" due to density gradient,
causing ground-water with entrained air bubbles to rise and
partition volatile contaminants from dissolved to vapor phase.
Water exits upper screen beneath a divider, where vapors are
drawn off through annular spaces between well casings by vacuum
pump, and ground-water re-enters the contaminated zone, where it
is again drawn into the stripping well. In this manner,
ground-water is re-circulated through the stripping well until
remediation goals are met. Several commercial types of in-well
vapor stripping exist which strive to make the general process
most efficient, or to use the process to enhance bioremediation
or metals fixation by taking advantage of the circulation cell
development. Most applicable to volatile organic contaminants;
modifications of the basic remedial process are proposed for
application to semi-volatile organic compounds, pesticides and
inorganics. May be used in unconfined or confined aquifers;
process has been applied to geologic materials of wide ranging
permeability.
- Hydraulic
and Pneumatic Fracturing - Techniques to create
enhanced fracture networks to increase soil permeability to
liquids and vapors and accelerate contaminant removal.
Especially useful for vapor extraction, biodegradation and
thermal treatments. Hydraulic fracturing involves injection of
high pressure water into the bottom of a borehole to cut a
notch; a slurry of water, sand and thick gel is pumped at high
pressure into the borehole to propagate the fracture from the
initial notch. The gel biodegrades, leaving a highly permeable
sand-filled lens that may be up to 60 feet in diameter.
Pneumatic fracturing involves injection of highly pressurized
air into consolidated sediments to extend existing fractures and
create a secondary fracture network. Most applicable for
unconsolidated sediments or bedrock.
- In Situ
Flushing - Also known as injection/recirculation or in
situ soil washing. General injection or infiltration of a
solution into a zone of contaminated soil/groundwater, followed
by downgradient extraction of groundwater and elutriate
(flushing solution mixed with the contaminants) and above ground
treatment and/or re-injection. Solutions may consist of
surfactants, cosolvents, acids, bases, solvents, or plain water.
Any variety of configurations of injection wells, directional
wells, trenches, infiltration galleries and extraction wells or
collection trenches may be used to contact the flushing solution
with the contaminated zone. Excellent understanding of the
hydrogeologic regime for potential projects is essential; best
applied to moderate to high permeability soils. May be used for
variety of organic contaminants, including non-aqueous phase
liquid; may have application to some inorganic contaminants.
- In Situ
Stabilization/Solidification - Also known as in situ
fixation, or immobilization. Process of alteration of organic or
inorganic contaminants to innocuous and/or immobile state by
injection or infiltration of stabilizing agents into a zone of
contaminated soil/groundwater. Contaminants are physically bound
or enclosed within a stabilized mass (solidification), or their
mobility is reduced through chemical reaction (stabilization).
Excellent understanding of the hydrogeologic regime for
potential projects is essential; best applied to moderate to
high permeability soils; may be used for variety of organic and
inorganic contaminants.
- Permeable
Reactive Barriers - Encompasses passive barriers,
passive treatment walls, treatment walls, or trenches. An
in-ground trench is backfilled with reactive media to provide
passive treatment of contaminated ground-water passing through
the trench. Treatment wall is placed at strategic location to
intercept the contaminant plume and backfilled with media such
as zero-valent iron, microorganisms, zeolite, activated carbon,
peat, bentonite, limestone, saw dust, or other. The treatment
processes which occur within the treatment wall are typically
contaminant degradation, sorption or precipitation. Applicable
to wide range of organic and inorganic contaminants; choice of
media for treatment wall is based on specific contaminant.
Hydrogeologic setting is critical to application; geologic
materials must be relatively conductive and a relatively shallow
aquitard must be present to provide a "basement" to the system.
Ground-water flow should have a high degree of preference, and
ground-water quality must support the desired reaction without
imposing additional loading of the reactive media or creating
undesirable by-products.
- Thermal
Enhancements - Use of steam, heated water, or radio
frequency (RF) or electrical resistance (alternating current or
AC) heating to alter temperature-dependent properties of
contaminants in situ to facilitate their mobilization,
solubilization, and removal. Volatile and semi-volatile organic
contaminants may be vaporized; vaporized components then rise to
the vadose zone where they are removed by vacuum extraction and
treated. Steam best applied to moderate to high permeability
geologic materials; RF and AC heating may be applied to low
permeability, clay-rich geologic materials as the clay will
preferentially capture the RF or AC energy. Excellent
understanding of hydrogeologic conditions essential for all
applications. May be used for variety of organic contaminants
and non-aqueous phase liquid; may have application to some
inorganic contaminants.
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Treatment Train
- the sequential use of unique remediation technologies to treat
the same volume of contaminated soil or groundwater.
- Intrinsic
Bioremediation - Natural, non-enhanced microbial degradation
of organic constituents by which complex organic compounds are
broken down to simpler, usually less toxic compounds through
aerobic or anaerobic processes. For environmental application,
documentation that current biodegradation rates are sufficient
to control or degrade a contaminant plume or zone without
creation of unacceptable risk to human health or the environment
must be demonstrated.
- Monitored
Natural Attenuation - Encompasses intrinsic
bioremediation. Reliance on a variety of physical, chemical,
or biological processes (within the context of a carefully
controlled and monitored site cleanup approach) that, under
favorable conditions, act without human intervention to reduce
the mass, toxicity, mobility, volume, or concentration of
contaminants in soil or groundwater.
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Phytoremediation - The general use of plants to
remediate environmental media in situ. Includes rhizofiltration
(absorption, concentration, and precipitation of heavy metals by
plant roots), phytoextraction (extraction and accumulation of
contaminants in harvestable plant tissues such as roots and
shoots), phytotransformation (degradation of complex organic
molecules to simple molecules which are incorporated into plant
tissues), phytostimulation or plant-assisted bioremediation
(stimulation of microbial and fungal degradation by release of
exudates/enzymes into the root zone), and phytostabilization
(absorption and precipitation of contaminants, principally
metals, by plants). May or may not involve periodic harvesting
of plants, depending upon method utilized. Applicable to a wide
range of organic and inorganic contaminants; most appropriate
for sites where large volumes of ground-water with relatively
low concentrations of contaminants must be remediated to strict
standards. Most effective where ground-water is within ten feet
of the ground surface, and soil contamination is within three
feet of the ground surface.
- Treatment Train
- the sequential use of unique remediation technologies to treat
the same volume of contaminated soil or groundwater.
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