Innovative Soil and Groundwater Remediation Alternative
Remediation Technologies, LLC (ART)
Integrated Remediation System
technologies have been implemented at sites worldwide to
remediate contaminated groundwater.
Some of the most commonly used technologies such
as air sparging, vapor extraction and ex-situ
(above-ground) air-stripping are based on physical
removal of contaminants; however, significant
shortcomings are inherent with each method. This
document will briefly present a review of ex-situ air
stripping and air sparging/vapor extraction technologies
along with an evaluation of their strengths and
summary of currently available, in-well air stripping
technologies will also be presented. A description of an innovative technology that combines the
elements of air stripping and air sparging/soil vapor
extraction will be discussed.
Results of laboratory simulation and actual field
implementation of this innovative remediation system
will also be presented.
1.0 Ex-situ Air Stripping
air stripping has been used in conjunction with
pump-and-treat systems to remedy contaminated
groundwater since the 1950s to treat water impacted with
contaminants including petroleum hydrocarbons,
chlorinated hydrocarbons and pesticides.
Pump-and-treat technology is based on extracting
contaminated groundwater from the subsurface for
The characteristics of the contaminants will
dictate the approach selected for the above-ground
treatment for the water.
Air stripping is a technology in which volatile
organics are partitioned from groundwater by greatly
increasing the surface area of the contaminated water
that is exposed to air. This technology is well proven
and has been implemented worldwide.
air stripping towers can be designed to remove up to
99.9% of a contaminant, extracting all of the
contaminated groundwater to the surface has been a
in the subsurface are either adsorbed to the soil in the
vadose zone or may exist in form of free-product on the
groundwater table or at the bottom of the aquifer,
depending on the relative density of the compound.
Another portion will be dissolved in the
the dissolved zone, small droplets of free phase
contamination may be suspended in groundwater.
As a result of groundwater movement and
fluctuation, those droplets become locked in what is
referred to as the “dead zone” or pore spaces that
are not connected. The effects of water flushing as a
result of pump-and-treat remediation are minimal in
treating and cleansing the saturated zone/dead zone.
Accordingly, this may explain why pump-and-treat
technology may require in excess of 30 years to achieve
acceptable clean up levels. Large volumes of water must
be pumped to the surface, treated and properly disposed.
The disposal process requires a long list of
analysis and permits for regulatory compliance.
Considering the extended project life, quarterly
chemical analysis/monitoring, remediation design,
equipment, operation and maintenance – costs and
project management can become unwieldy.
2.0 Air Sparging
sparging is a technology that has been used extensively
in recent years as a result of increased desire to
implement in-situ rather than ex-situ remedial measures.
Air sparging is based on the same physical
removal concept as air stripping. Pressurized air is
bubbled through a contaminated aquifer.
The air travels horizontally and vertically
through the carrying the contaminants to a vapor
Air sparging has several advantages when compared
to pump-and-treat technology, including the following:
All groundwater treatment is performed in-situ
treated at the point of location
Shorter project life
results in significant cost savings
maintenance costs are reduced
May be implemented
for a wider range of subsurface conditions
injection of fresh air in the subsurface resulting in
enhanced biodegradation processes. (Thus another treatment is occurring along with air sparging
to expedite the remediation of the subsurface).
numerous deficiencies are associated with in-situ air
number and magnitude of the shortcomings may vary
depending on site conditions, location and contaminant
With air sparging technology, treatment
may not be as effective since all of the design
parameters are estimated and may be significantly
different from actual values.
Conversely, with an air stripping tower the water
flow rate, contaminant concentrations and tower
dimensions are known.
Therefore, air flow rate to achieve acceptable
removal rates to remedy the water stream can be
The radius of
influence (cleaning zone) depends on the hydraulic
conductivity of the subsurface material. High conductivity soils (e.g. sandy soils) can allow air
bubbles to float vertically shortly after leaving the
sparging point, resulting in a very small radius of
if the hydraulic conductivity is low, the radius of
influence will be larger, but air injection will be
difficult based on the soil type
The radius of
influence is usually assumed based on a pilot test.
It is common to assume that subsurface conditions
at the site are homogeneous. In reality, air flow rate sparged at one point may not be
adequate for another location at the same site
Air sparging technology design and
implementation requires specialized expertise to
minimize the potential for spreading contaminants.
remedial technology that combines the advantages of
air-stripping and air sparging methods that includes in-situ
active treatment (e.g. bioremediation), would be more
effective and ideal.
This technology would compensate for shortcomings
associated with pump-and-treat such as long project life
and costs of water disposal and the deficiencies related
to air sparging such as limited radius of influence and
removal rate. This
technology is discussed below.
3.0 In-well Air Stripping
to create this improved technology were made by Stanford
University (NoVOCTM), and by IEG Technologies
Corporation (Underduck-Verdampfer-Brunnen (UVB)).
The in-well air stripping, an extension of air
sparging technology, involves the creation of a
circulation cell around a well in which groundwater is
the NoVOCTM technology, a blower introduces
air to produce bubbles in a sparging well. The well is
equipped with a deflector plate that separates two
the sparged air encounters the deflector plate, the
bubbles break, re-combine and then re-infiltrate the
vadose zone to be extracted through the upper screen.
With the UVB technology, air-lift pumping occurs
in response to negative pressure induced at the well
head by a blower. Vacuum
draws water into the well through the lower screen. As a
result, air is introduced through a diffuser plate
located within the upper, screened section.
The air bubbles provide air-lift pump effect that
moves water up in the well. A submersible pump is
installed to insure that water flows from bottom to top.
A stripping reactor consisting of fluted and
channeled columns is installed to facilitate transfer of
volatile compounds to the gaseous phase.
the UVB approach may be considered as significant
improvement over the NoVOCTM technology,
major shortcomings remain, including:
The radius of influence of a well is only
based on the water drawn to the well as a result of head
reduction created by vacuum pressure.
Accordingly, the radius of influence is unlikely
to be significant
reactor will require a vault or a large diameter well.
These are difficult to construct, costly, and may
not be feasible in most cases - especially if the
contamination is underneath structures or at an
technologies such as the Density Driven Convection (DDC)
system have been developed.
These technologies utilized the addition of
nutrients to enhance in-situ biodegradation; however,
they are based on the UVB or the NoVOCTM
technologies and maintain their shortcomings.
the next section, an innovative remediation system is
technology is based on proven, accepted techniques and
will be referred to as the “ART
Integrated Remediation System”.
4.0 ART Integrated Remediation System
Remediation Technologies, LLC (ART)
has recently developed and patented an effective,
innovative remedial technology that relies on
well-proven and established concepts.
technology combines in-situ air stripping, air sparging/soil
vapor extraction and enhanced bioremediation in an
innovative wellhead system. The system is designed to accommodate a four inch well and be
very cost effective when compared with other,
stand-alone remediation technologies.
Figure 1 (below) provides a schematic of the well
air sparging component results in lifting the water
lifting of the water in the well causes a net reduction
in head at the well location, which results in water
flowing toward the well.
Vacuum pressure (the vapor extraction component)
is be applied atop of the well point to extract vapor
from the subsurface.
The negative pressure from vacuum extraction
results in water suction that creates additional water
lifting (mounding) and a net lower gradient. This
further enlarges the radius of influence.
submerged pump is placed at the bottom of the well to
recirculate water to the top for downward discharge
through a spray head.
The water cascades down the interior of the well
similar to what occurs in an air stripping tower.
Enhanced stripping via air sparging near the bottom of
the well will occur simultaneously. In essence, the well
will act as a subsurface air stripping tower. In
addition to the air stripping effected by the
pumping/cascading, the pumped, stripped, highly
oxygenated water will flow down well annulus and over
the “mounded” water back in to the aquifer. This
will set up a circulation zone surrounding the well that
will further enhance cleanup.
Effects of the different forces on the
groundwater table in relation to the wellhead technology
are shown in Figure 2 (below).
packing may be placed in a well to increase the
effectiveness of air stripping as shown in Figure 3
most cases, however, in-well packing will probably not
Figure 2 and
In summary, contaminants
are stripped from water as a result of the combined
effects in-well air stripping and in-well air sparging.
The radius of influence/cleaning zone will be
created by a combination of three forces:
Negative gradient as a result of the lifting of
the groundwater caused by air sparging at the bottom of
Additional, negative gradient and water lifting
resulting from the application of vacuum extraction at
the top of the well
Subsurface water circulation surrounding the well
induced by a submersible pump placed at the bottom of
of these different components can be integrated and
installed in a 4-inch groundwater well.
Cost of this technology is in the range of air
sparging technology alone, since the costs of added pump
and piping will be compensated for by the elimination of
a separate vapor extraction point and associated
trenching and construction.
experimentation was necessary to simulate the
effectiveness and utility of the of the ART
Integrated Remediation System. The main objective of the
laboratory simulation was to determine the behavior of
the water when extracted from the bottom of a well and
sprayed back in the same well above the groundwater
to the different forces acting in the same well, it was
not clear whether the pumped water is replaced by water
in the well void, or replaced by water extracted from
the aquifer. Additionally,
it was not clear if the water sprayed atop the water
table remains in the well void or flows away from the
well to be replaced by contaminated water from the
4.2.1 Laboratory Set-up
experimentation included simulation of different forces.
To achieve the objectives, an 85-gallon, glass,
fish tank was filled with a medium-grained, well-graded
sand. The ART
well was constructed of ½ inch, PVC pipe and placed
near the center of the tank.
The well was manually slotted to simulate a
screen. A small, fountain pump with a pumping rate of
approximately 0.2 gallons per minute (gpm) was placed at
the bottom of the well to lift the water approximately
18 inches for spraying near the top of the well. The well also contained a tube placed at its bottom and
connected to an air pump to sparge air at the bottom of
the well. A
fish tank aeration pump with a capacity of approximately
0.2 standard cubic feet per minute (SCFM) was used to
effect the air sparging.
tank was slightly sloped approximately 0.25% to simulate
natural groundwater flow conditions. Four monitoring
wells (MWs) were simulated using ½ inch, PVC pipe and
slotted similar to the in-situ air stripping well.
The first well (piezometer) was placed next to
the air stripping well to measure well conditions since.
This was done because ART well measurements could not be taken due to different tubes and
The second well, MW-1, was located 12 inches
upgradient of the ART well. MW-2 and MW-3
were placed 12 and 24 inches, respectively, downgradient
of the well.
procedures consisted of measuring water levels in the
tank prior to and at different intervals after sparging
and pumping. Water
levels were measured by inserting a small-diameter
wooden dowel in the well and measuring the wetted length
of the sticks. Dedicated
sticks and similar procedures were used for each well to
minimize potential for measurement errors.
Water levels were measured in each monitoring
point prior to starting sparging.
Water levels were also measured following
sparging, at different increments until stabilization,
and following air sparging pumping.
Water levels are shown in the following table in
inches from the bottom of the tank.
Level after sparging only (5 minutes)
Level after Sparging only (10 minutes)
Level after Sparging only (25 minutes)
Level after Sparging & pumping (35 minutes)
4.2.3 Laboratory Simulation
expected, water levels were elevated when sparging
occurrence has been exhibited at thousands of sites. However, the main objective of this experiment was to
determine the behavior of the water sprayed through the
well atop of the groundwater surface.
After starting the submersible
pump, water was visually and clearly observed migrating
away from the ART well at a significant rate.
It was apparent that pumped water does not sink
back into the ART
well, but rather it flows over the vacuum/sparged-induced,
mounded water table and away from the ART
well. The pumped water was observed traveling a
distance of approximately 18 inches away from the well
until water movement was no longer visually detected.
was also observed that water in the vicinity of the well
contained a large number of small bubbles. This appears
to be a result of air sparging and stripping which
significantly increased the air content in the water –
thus elevating dissolved and suspended air that reduced
the water density.
As a result of the water density reduction,
sparged and stripped water was pushed to the surface of
the water table. Further,
the stripped/sparged water was not allowed to sink in
the well but migrated outward, over and down the
higher-density water interface away from the well.
Simultaneous replacement by higher density water from
the well surroundings was also observed in the well.
4.2.4 Laboratory Experiment
laboratory simulation was successful in deriving the
Air stripped water will flow away from the
well and it does not appear to sink back in the same
Air stripped water
has significantly lower density than surrounding water
and will float on the surface and flow down the mounding
water away from well.
The radius of
influence of the air striping well is larger than
initially thought and is in the range of three times the
water column in the well.
can be confidently concluded that the ART
Integrated Remediation System will result in a more
effective remedial process, a shorter project life and
thus lower expenses and a larger radius of influence
than sparging alone.
The air stripping technology appears to be the
most practical, promising and effective to remedy
chemically impacted groundwater, especially hydrocarbon,
chlorinated and recalcitrant compounds.
ART Integrated Remediation System was implemented at an industrial
site in Minnesota where tetrachloroethene (PCE) was
detected in soil and groundwater.
A national environmental consulting firm
installed in-situ soil vapor extraction and groundwater
air sparging systems in 1995 to remedy soil and
groundwater at the site.
As of early 2001, PCE concentrations remained
elevated and it was apparent that remediation had become
was granted to install an ART
Integrated Remediation System on May 17, 2001.
5.1 General Site
facility occupies an area approximately six acres with a
16,000 square feet structure.
An industrial laundry operation was established
at the site in the mid-1970s.
A dry cleaning process was used at the site for
several years. The
topography of the site is relatively flat with a river
located approximately 1,500 feet to the east.
Subsurface soils at the site consist of fine sand
mixed with silt, loam and organic sediments.
5.2 Subsurface Conditions
soil borings and groundwater monitoring wells were
installed at the site in 1994.
PCE was detected at varying depths at several
highest level of PCE in soils was 47,000 ppb. Highest
levels of PCE in groundwater were encountered in MW-2 at
20,000 ppb and have fluctuated throughout the last seven
last sampling round prior to the installation of the ART
Integrated Remediation System detected PCE at 2,700 ppb.
TCE and cis-1,2-DCE were also detected at
concentrations of up to 250 and 110 ppb, respectively.
5.3 ART Integrated Remediation System Implementation
a result of the impending sale of the site, the owner
needed a remedial technology that would provide more
effective results and reduce contamination at the site
to acceptable levels in a shorter period of time, while
controlling additional costs.
The owner selected the ART Integrated Remediation System that was approved by the
consultant and the state regulatory agency.
ART extraction well was installed approximately 18 feet upgradient
of monitoring well MW-2. The well was extended to a
depth of approximately 20 feet below the groundwater
table where a submersible pump was placed.
The general construction details are as shown in
was used as the main monitoring point to gage the
effectiveness of the technology.
Immediately prior to the implementation of ART
Integrated Remediation System alternative, PCE and
dissolved oxygen (DO) concentrations were approximately
2,700 ppb and 1.23 ppm, respectively.
MW-2 was sampled on May 29, 2001, thirteen days
after the implementation of ART
analysis indicated that PCE concentrations were reduced
by approximately 90% to 240 ppb.
DO concentration increased from approximately
1.23 to 9.57 ppm (near saturation). TCE and DCE concentrations were reduced to below detection.
PCE concentration reduction was also exhibited in
wells approximately 70 feet down gradient from the ART
results clearly demonstrate that the ART
Integrated Remediation System is a very effective
technology that was able to jump-start site remediation
and significantly reduce contaminant concentrations over
a period over a relatively short period of time.
Further, the ART
Integrated Remediation System demonstrated that it could
achieve more in a few weeks than air sparging alone had
achieved over a period of several years.
It is anticipated that the ART
system will continue to demonstrate contaminant
reduction over a shorter period of time than that of
can be concluded from the case study/field test and
laboratory simulation that the ART Integrated Remediation System is a very effective remediation
was proved to be significantly more effective than air
sparging. Significant shortcomings associated with air sparging and air
ex-situ air stripping have been eliminated.
technology is based on proven concepts that have been
used with varying levels of effectiveness at thousands
of sites over the years.
When integrated as a technology system, these
concepts were found to be synergistic and far more
effective than past remediation approaches.
the ART System....contact:
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