&EFA
United States
Environmental Protection
Agency
EPA/540/MR-95/500
January 1995
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Unterdruck-Verdampfer-Brunnen Technology (UVB)
Vacuum Vaporizing Well
Roy F. Weston, Inc. / IEG Technologies Corporation
Technology Description: The Weston/IEG UVB technology is
an in situ groundwater remediation technology that combines air-
lift pumping and air stripping to clean aquifers contaminated with
volatile organic compounds. A UVB system consists of a single
well with two hydraulically separated screened intervals installed
within a single permeable zone. The air-lift pumping occurs in
response to negative pressure introduced at the wellhead by a
blower. This blower creates a vacuum that draws water into the
well through the lower screened portion of the well. Simulta-
neously, air stripping occurs as ambient air (also flowing in
response to the vacuum) is introduced through a d'rffuser plate
located within the upper screened section of the well, causing air
bubbles to form in the water pulled into the well. The rising air
bubbles provide the air-lift pump effect that moves water towards
the top of the well and draws water into the lower screened
section of the well. This pumping effect is supplemented by a
submersible pump that ensures that water flows from bottom to
top in the well at a rate of approximately 20 gal/min. As the air
bubbles rise through the water column, volatile compounds are
transferred from the aqueous to the gas phase. The rising air
transports volatile compounds to the top of the well casing where
they are removed by the vacuum blower. The blower effluent is
treated before discharge using granular activated carbon.
The transfer of volatile compounds is further enhanced by a
stripping reactor located immediately above the air d'rffuser. The
stripping reactor consists of a fluted and channelized column that
facilitates the transfer of volatile compounds to the gas phase by
increasing the contact time between the two phases and by
minimizing the coalescence of air bubbles.
Once the upward stream of water leaves the stripping reactor,
the water falls back through the well casing and returns to the
aquifer through the upper well screen. This return flow to the
aquifer, coupled with inflow at the well bottom, circulates ground-
water around the UVB well. The extent of the circulation pattern
Carbon adsorption units
Unsaturated zone
Blower
Well
centerline
Monitoring well
Ambient air
40ft
60ft
85ft
Monitoring well
Inner cluster Vapor Outer cluster
monitoring wells monitoring well monitoring wells
\Saturated zone
x
NOT TO SCALE
Groundwater
intake
Groundwater |
table
Figure 1. The Unterdruck-Verdampfer-Brunnen Technology as demonstrated.
Printed on Recycled Paper
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is known as the radius of influence, which determines the volume
of water affected by the DVB system.
Waste Applicability: The UVB technology, demonstrated from
April 1993 to May 1994 at Site 31, March Air Force Base, CA, has
removed trichloroethene (TCE) and 1,1-dichloroethene (DCE) from
groundwater. The developer claims that the technology can also
clean up aquifers contaminated with other organic compounds,
including volatile and semivolatile hydrocarbons. Additionally, the
developer claims that in some cases the UVB technology is
capable of simultaneous recovery of soil gas from the vadose
zone.
Demonstration Approach: The UVB technology demonstration
evaluated the reduction of TCE and DCE concentrations in the
groundwater discharged from the treatment system, the radius of
influence of the system, and the reduction (both vertically and
horizontally) of TCE and DCE concentrations in the groundwater
within the radius of influence over the course of the pilot study.
The demonstration program objectives were achieved through
collection of groundwater and soil gas samples, as well as UVB
system process air stream samples over a 12 month period. To
meet the objectives, data were collected in three phases: baseline
sampling, long term sampling, and dye tracer sampling. Baseline
and long term sampling included the collection of groundwater
samples from eight monitoring wells, a soil gas sample from the
soil vapor monitoring well, and air samples from the three UVB
process air streams both before UVB system startup and monthly
thereafter. In addition, dye tracer study was implemented to evalu-
ate the system's radius of influence. This study included the
introduction of fluorescent dye into the groundwater and the sub-
sequent monitoring of 13 groundwater wells for the presence of
dye 3 times a week over a 4 month period.
Preliminary Results: Demonstration results indicate that TCE
concentrations were reduced by greater than 94 percent in ground-
water discharged from the system. TCE concentrations were
reduced from a mean of approximately 53 micrograms per liter
(u,g/L) in the system's influent to approximately 3 u,g/L in the
system's effluent. A meaningful estimate of the system's ability to
remove DCE could not be made due to the low (less than 4 jig/L)
influent concentration of DCE.
Based on the results of the dye tracer study, the radius of influence
was estimated to be at least 40ft. Modeling of the radius of influence
by the developer suggests that it may extend to approximately 83 ft;
however, preliminary interpretation of site-specific data obtained
from the demonstration and aquifer testing suggests thatthe radius
of influence may be less than 60 ft.
In general, TCE and DCE in the shallow and intermediate screened
monitoring wells showed a reduction in concentration over the
duration of the pilot study. Concentrations of target compounds in
these zones appeared to homogenize as indicated by the
convergence and stabilization of TCE and DCE levels.
Key findings from the demonstration, including complete analytical
results and an economic analysis, will be published in a Capsule
Report and an Innovative Technology Evaluation Report. These
reports may be used to evaluate the UVB technology as an
alternative method for cleaning upsimilargroundwater contamination
across the country. The results will also be presented in a videotape.
For Further Information:
EPA Project Manager:
Michelle Simon
U.S. Environmental Protection Agency
Office of Research and Development
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7469 FAX: 513-569-7676
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/540/MR-95/500
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