5
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Tl
o
/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Issue 30
TTz/'s /55Me o/Technology News and Trends highlights methods for harnessing energy from
renewable resources to reduce remediation costs and minimize the environmental footprint
left by remediation technologies. These methods currently are used to generate virtually no-
cost electrical power for low-energy remediation systems, to "polish " remediation following
aggressive baseline technologies, or to serve as baseline technologies addressing moderate
contaminant concentrations. Incorporation of renew able energy resources early in remediation
planning can significantly reduce long-term cleanup costs and allows site managers to evaluate
environmental tradeoffs of potential remedies.
Solar Power Recirculates Contaminated Ground Water
in Low-Energy Bioreactor
A pilot-scale recirculation bioreactor has
operated at "Landfill 3" on Altus Air Force
Base (AFB), OK, since late 2003 to address
a hotspot of volatile organic compounds
(VOCs) in ground water residing in fractured
clay and weathered shale. A solar-powered
pump operating in the system's extraction/
collection trench recirculates ground water
through the 10,000-ft3 bioreactor and into the
aquifer to generate high-carbon leachate and
enhance VOCbiodegradation. Since startup,
the system has transferred approximately
1,300 mVyr of organic carbon-enriched
leachate from the bioreactor into the aquifer.
Ground water recirculation through the
bioreactor has achieved a 98% reduction in
trichloroethene (TCE) concentrations within
the bioreactor and a 90-97% reduction in
plume toxicity in hotspot wells between the
bioreactor cell and the extraction trench.
Prior to project startup, TCE concentrations
in the hotspot were 19 mg/L, and the plume
extended nearly 1,100 yds downgradient of
the landfill. The bioreactor was constructed
immediately upgradient of hotspot wells
in a 30- by 30-ft excavation extending 11
feet below ground surface (bgs). During
excavation, landfilled materials were removed
and disposed offsite as non-hazardous waste.
The cell was backfilled with a 1:1 mixture of
sand and organic mulch consisting of
municipally-obtained woody material and
cotton-gin trash, an inexpensive and locally
available byproduct of the cotton industry. At
the top of the cell a ground-water distribution
(irrigation) system operates between two layers
of geotextile fabric. The entire cell is capped
with two feet of soil and a native grass cover.
The bioreactor relies on recirculation of ground
water from downgradient of the hotspot,
which is located in the shallow aquifer 10-18
feet bgs. Ground water collected in a 2-ft-
wide by 30-ft-long trench extending 18 feet
bgs is recirculated through the bioreactor by a
single solar-powered pump. Contaminant
degradation is monitored through a network
of 18 wells.
The site's remote location and average solar
radiation of 4-5 kWh/m2/day prompted
investigation of solar power early in the project
planning process to reduce construction and
energy costs associated withlong-termpumping.
The selected photovoltaic (PV) array
comprises four single-crystal silicon panels,
each capable of delivering 50 watts to the pump
through a simple control box. The panels are
mounted in series on a single frame oriented
due southard angledforrrmimum sun exposure
during winter months (Figure 1).
A 3-inch-diameter submersible pump, designed
specifically for solar applications, is suspended in
[continued on page 2]
May 2007
Contents
Solar Power
Recirculates
Contaminated Ground
Water in Low-Energy
Bioreactor page 1
Wind Turbine Cost
Study Shows Need
for Redesigned
Ground-Water
Remediation Systems page 2
DOE Uses No/Low-
Energy Approaches
for Long-Term
Remediation page 4
Sustainability Metrics
Used to Evaluate
Remedial Actions page 5
CLU-IN Resources
Environmentally sustainable
cleanup technologies commonly
include phytoremediation,
bioremediation, and monitored
natural attenuation but increas-
ingly involve modifications to
conventional technologies
relying on passive rather than
active mechanisms. Information
about other no- or low-energy
remediation technologies is
available in the U.S. EPA's
"Technology Focus" on CLU-IN
(http://cluin.org/techfocus/).
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycted fiber
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[continued from page 1]
a sump installed in the extraction trench.
The pump produces 2-3 gal/min during
peak sunlight hours but does not operate
overnight or during low sunlight,
maintaining an average ground-water
flow rate of 928 gal/day. Ground-
water velocity between the bioreactor
cell and the extraction trench likely
increased from the estimated area-
wide velocity of 0.1-1.2 ft/day due to
hydraulic mounding in the bioreactor. In
this case, downgradient water quality
data suggest that some recirculated ground
water may have bypassed the extraction
trench, potentially due to the shallow depth
and limited length of the trench and the
intermittent, low-rate nature of pumping.
The solarunit, pump, and auxiliary equipment
operated without breakdown and required
little maintenance over three years of
operation; the lifespan of the PV system is
estimated at 20 to 30 years. Capital costs
for the pump, controller, and PV array were
low, totaling approximately $2,300. Energy
cost savings achieved by the solar-powered
system are estimated at less than $1,0007
year but significantly higher savings were
realized by avoiding construction of electric
lines to connect to the local utility grid.
Though no enhancements to the Altus PV
system are required, its performance suggests
that similar applications at other sites could
easily increase PV capacity through use of a
solar tracking device or larger PV array.
Evaluation of the bioreactor performance
indicates dissolved organic carbon
concentrations increased from less than
6 mg/L priorto startup to 120 mg/L in shallow
wells and 30 mg/L in deeper wells. Increased
concentrations of c/s-l,2-dichloroethene, vinyl
chloride, and ethene further indicate
reductive dechlorination of TCE occurs in
the bioreactor, and phospholipid fatty acid
analysis shows a predominance of the
anerobic bacteria required for this process.
To achieve more complete reductive
dechlorination of TCE, a semi-soluble
carbon substrate and a bioaugmentation
culture were added to the bioreactor last fall.
Results of the bioreactor's initial two-year
demonstration, including details on the solar-
powered pumping system, are documented
in a final technical report to be released this
summer from the Environmental Security
Technology Certification Program (ESTCP)
(http://www.estcp.orgX The Air Force Center
for Environmental Excellence (AFCEE)
Figure 1. Semi-arid conditions at Altus
AFB contribute to solar radiation as high
as 5-6 kWh/m2/day during summer months.
anticipates significantly increased use of solar
as well as wind energy to power low-energy
remediationsy stems suchasbioreactors across
the Department of Defense (DOD) complex,
particularly in remote locations where
utility-grid connection is cost prohibitive.
Dyess AFB, anactivebaseinAbilene, TX,
recently converted the facility's entire
operation to exclusive use of wind energy,
and the Massachusetts Military Reservation
is investigating the use of a 660-kW wind
turbine to powerthe site's extensive ground-
water cleanup program.
Contributed by Jim Gonzales, AFCEE
(james.gonzales&.brooks.af.mil or
210-535-4255), Roger Wilkson, Air
Education and Training Command
(roger.wilkson&.randolph.af.mil). and
Jason Bidgood, Parsons
(jason. bidgood(a),parsons. com or
303-831-8100)
Wind Turbine Cost Study Shows Need for Redesigned Ground-Water Remediation Systems
University of Missouri-Rolla researchers
recently evaluated the economic and
environmental benefits of a 10-kW wind
turbine powering a ground-water
circulation well (GCW) at the former
Nebraska Ordnance Plant (NOP)
Superfund site in east-central Nebraska.
The project's first phase involved retrofit
installation and use of a grid inter-tie
system whereby electricity is provided by
the turbine during favorable weather.
The local electric utility powers the
turbine during unfavorable weather.
Environmental benefits of the conversion
included a potential reduction of
greenhouse gases associated with fossil-
fuel-generated electricity. When compared
to utility-only operation, monthly emissions
of carbon dioxide averaged 32% less during
the grid inter-tie phase.
In late 2006, the second project phase
converted the wind turbine system to
off-grid operation powering the GCW
submersible pump. Utility power was
required for the remaining GCW
components to meet energy demands during
mid-winter low temperatures. Though
estimated carbon dioxide emissions during
off-grid operation were higher than those
of the grid inter-tie phase due to cold
weather, monthly emissions averaged 24%
less than during utility-only operation.
The NOP site is located in an area with
winds averaging 6.5 m/s, which the DOE
considers suitable for wind turbine
applications (Wind Energy Resource
Atlas of the United States). The GCW
submersible pump extracts contaminated
water from the aquifer for above-ground
air stripping to remove TCE. After
treatment, ground water recharges the
aquifer through a different well interval.
[continued on page 3]
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[continued from page 2]
As part of this project, researchers
evaluated the performance of the selected
10 kW-rated wind turbine as installed on a
30-meter tower. Electricity was delivered
from the turbine to the GCW through a
single circuit breaker, which eased the
system's retrofit for power from an
alternative energy source. The grid inter-
tie system configuration resulted in monthly
energy generation ranging from 500-1,000
kWh.
Although the same wind turbine was used
for both study phases, an off-grid battery
system was added for the second phase
to store energy produced by the turbine.
Production capacity of the grid inter-tie
operating mode was rated at 7.5 kW, but
was 25% lower for the off-grid mode due
to reduced efficiency of the energy storage
system. As a result, stored energy allowed
the turbine to fully power only the 230-
volt, three-phase submersible pump,
which accounted for approximately one-
third of the GCW's total demand.
Additional modifications allowed the GCW
to operate either through exclusive use of
utility power or through intermittent use
of the wind turbine to power the
submersible pump, supplemented by utility
power for remaining GCW components.
Economic benefits of the wind turbine were
evaluated through several measures.
Statistical comparisons were conducted on
comparable data collected when the GCW
relied on: (1) exclusively utility power, (2)
combined utility and grid inter-tie wind
power, or (3) combined utility power plus
off-grid wind power or utility power alone
(Figure 2). Results indicated that average
daily energy consumption from utilities
decreased 26% during the 17 months when
the turbine operated in grid inter-tie mode.
During two cold periods of the 6-month
off-grid operation, the cost of heating the
GCW to prevent freezing and associated
decreases in submersible pump efficiency
contributed to significantly higher demand
for utility power.
Capital recovery was analyzed to evaluate
whether NOP utility-cost reductions could
offset wind turbine costs. Net capital costs
were estimated at $41,000 for the inter-tie
turbine system and $3 9,000 for the off-grid
system, including turbine installation and
utility connection. Based on a GCW rate of
5.7 million liters of ground water treated
each month, the annual energy saved by
the turbine in grid inter-tie mode was
estimated at $1,100. Results suggested that
less than 50% of the grid inter-tie system
cost would be recovered over 20 years.
Net cost of the off-grid system, however,
would be recovered in 14 years if the GCW
were significantly modified to function
without incurring any utility costs. System
modifications would focus on freeze-
proofrngthe GCW by automatically draining
the system to accommodate intermittent
operation during winter. Additional savings
for an off-grid system would be achieved
by using an alternate, low-energy treatment
technology such as bioremediation.
A total TCE mass of 50.6 kg, averaging
2.99 kg/month, was removed through air
stripping during the 17-month grid inter-tie
operational phase. The average TCE mass
removed during the six-month off-grid
phase was 2.53 kg/month. Over both
phases, a combined total of 90.2 million
liters of ground water were treated
without any net loss of ground water to
the aquifer. The average reduction in
carbon dioxide emissions during treatment
was estimated at 437 kg/month during
the grid inter-tie phase and 317 kg/month
during the off-grid phase, as compared
to a potential emission of 1,600 kg/month
during utility-only operations.
Final results suggest that wind turbines
can be used to reduce operation and
maintenance (O&M) costs for long-term
ground-water remediation systems
such as pump-and-treat (P&T) while
significantly reducing carbon dioxide
emissions. Although the study indicates
that retrofit of existing GCWs with a wind
turbine system is not cost effective, it
shows that an off-grid system may be
cost-competitive for a new GCW
specifically designed to operate without
utility power. Results also illustrate the
need for wind-turbine GCW designs to
accommodate cold weather conditions.
Contributed by Curt Elmore, Ph.D.,
University of Missouri-Rolla
(elmoreac(q)umr. edu or 573-341-6784)
and Dave Drake, U.S. EPA Region 7
(drake, dove(q)epa. gov or 913-551-
7626)
Grid inter-tie
wind turbine
plus utility dataset
Off-grid
wind turbine
plus utility
dataset
Figure 2. Mid-winter
utility power
consumption was
lowest during inter-tie
wind turbine operation
of the retrofit GCW
supporting NOP air
stripping.
Jan-02
Jan-03 Jan-04 Jan-05 Jan-06 Jan-07
Months with Comparable Flow Rates (1.9 to 2.5 Us)
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DOE Uses No/Low-Energy Approaches I or Long-Term Remediation
The U.S. Department of Energy (DOE)
increasingly uses passive soil vapor
extraction (PSVE) and DOE laboratory
developments, such as the MicroBlower™
and "GeoSiphon™," to address sites
requiring long-term treatment. Use of these
no/low-energy technologies at the Savannah
River Site (SRS) significantly reduced
electricity and fossil-fuel energy
consumption/costs and demonstrates their
ability to reduce the footprints of
remediation strategies on the environment.
PSVE, also known as barometric pumping,
uses natural venting cycles between the
atmosphere and subsurface to extract
contaminants from soil. When atmospheric
pressure at the ground surface is higher
than subsurface soil gas pressure, airflows
downward through wells into the
subsurface. When pressure at the surface
is lower than subsurface, air flows from
the wells to the atmosphere. As a result, a
vadose-zone well crossing these pressure
differentials can remove gaseous-phase
VOCs from the subsurface without use of
a mechanical pump and associated power
sources. Prior to atmospheric discharge,
extracted vapors may require relatively low-
cost treatment such as carbon adsorption.
PSVE commonly is used to inject air into
soil to stimulate bioremediation.
The SRS and Hanford Site currently use
PSVE as a polishing technology to remove
VOCs from permeable soil. At SRS, for
example, 52 PSVE wells across three
separate areas have operated over the
past 10 years. Combined, these systems
have removed nearly 1,000 Ibs of
tetrachloroethene (PCE) and 400 Ibs of
TCE. In addition, vapor concentrations
and gas-plume footprints have decreased
significantly. Although rates of contaminant
mass removal are declining due to reduced
concentrations of contaminants, the PSVE
systems are expected to continue operating
until soil cleanup targets are met. Results
at both SRS and Hanford confirm that
PSVE is best applied where target
contaminants are in the unsaturated zone, and
is most effective in coarse soil with high
permeability or in soil layers separated from
the atmosphere by a confining unit or by
depth.
SavannahRiver National Laboratory (SRNL)
researchers are investigating PSVE
enhancements such as wind turbine-
powered vacuum pumps to increase system
efficiency and further reduce cleanup costs
and environmental impacts of remediation.
One of the simplest methods for increasing
efficiency involves integration of a simple
one-way checkvalve capable of interrupting
airflow into PSVE wells when atmospheric
pressures reverse. Direct attachment of a
control valve such as the BaroBall™ to the
well casing at ground surface permits
extraction of contaminants during reduced
barometric pressure, while eliminating
undesirable dilution caused by reinjectionof
clean air during periods of high barometric
pressure. This type of valve may be used in
other applications to inject air and/or nutrients
into the subsurface for enhanced
bioremediation, to control or confine
movement of a subsurface gas-phase plume
in the vadose zone, or to passively transfer
solar-heated, water-saturated air into the
subsurface for enhanced volatilization.
The MicroBlower™ is another no/low-energy
technology used to remove VOCs from the
subsurface. This system consists of a small 12-
or24-VDCvacuumblower connected directly
to a wellhead for extracting
or injecting gases into the
vadose zone. PV panels or
small wind generators
typically supply electricity
to power the system,
enhancing its potential for
use in remote locations. Abattery bank can
be used for reserve power when sun or wind
is inadequate. Deployment is made easier
by the system's small pump, approximately
4 inches high by 3 inches wide (Figure 3).
TenMicroBlower systems currently operate
at SRS, each removing 0.1 to several
pounds of solvent from the subsurface
each week. The cost of materials is
estimated at $1,500 per system, with
minimal installation and O&M expenses.
Performance results indicate that reliability
of a MicroBlower system depends on a
pump lifespan of approximately one year.
Additional tests were conducted at SRS to
evaluate the feasibility of GeoSiphon, a
passive technology employing a siphon
made of HOPE tubing to induce ground-
water flow from the target portion of an
aquifer toward a treatment cell. Once
primed, the upward arm of the siphon
draws water from the treatment cell,
inducing ground-water flow towards the
cell. The treatment cell consists of an 8-ft
diameter well containing approximately 25
tons of granular cast iron that abiotically
reduces chlorinated VOCs (CVOCs) to
ethene, ethane, methane, and chloride ions.
The downward arm discharges treated
water to the Savannah River.
Three siphon configurations were
tested using l/i- to 2-inch HOPE tubing
[continued on page 5]
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[continued from page 4]
on engineered and non-engineered
grades extending 223 to 1,032 feet on
different slopes of the test site. All
configurations on engineered grades
maintained continuous, consistent
siphon flow. When needed, an
automatic, solar-powered vacuum
pump was used for passively
recharging the system's air chamber
to remove gas bubbles.
The GeoSiphon shows potential for
significantly improving implementation of
permeable reactive barriers (PRBs) due to
its ability to increase and direct the flow of
water, resulting in less intrusive, less costly,
and more efficient deployment compared
to funnel-and-gate or continuous PRBs.
DOD has documented designs, costs, and/
or performance results of natural pressure-
driven passive bioventing at these DOE sites
as well as DOD sites under the ESTCP
(http://www.estcp.orgX Both agencies
anticipate additional remediation studies
to investigate innovative methods for
harnessing renewable energy from other
natural resources such as ocean tide and
geothermal forces.
Contributed by Brian Riha, SRNL
(brian.riha&srnl.doe.gov or 803-725-
5948) and Brian Looney, Ph.D., SRNL
(brian 02. looney&srnl. doe, gov or
803-725-3692)
Sustainability Metrics Used to Evaluate Remedial Actions
Savannah River National Laboratory
(SRNL) researchers are developing tools
to evaluate the need to power new or
existing remediation systems with
renewable energy sources. The tools
employ Sustainability metrics for
assessing energy demand and storage
along with characteristics of the site and
contaminants. Early evaluation of these
parameters can reduce the footprints of
many aggressive cleanup technologies.
which are now recognized increasingly as
secondary impacts of environmental
contamination. It can also help identify risk
transfer across environmental media and
associated regulatory programs.
This strategy was demonstrated last year
for a Savannah River Site (SRS) P&T
system operating since 1996 to treat TCE-
contaminated ground water. Following
extraction, ground water is treated by a
70-gpm air stripping system and ultimately
discharged to the Savannah River. Average
TCE concentrations in treatment influent
decreased from 600 u,g/L to 40 u,g/L after
eight years of P&T operation. These
dissolved CVOC concentrations (<50
u,g/L or <0.0045% solubility) mark the
point at which media-specific benefits of
baseline technologies such as P&T and
in-situ chemical oxidation typically begin
to be outweighed by increased burdens
transferred to other environmental media.
otherwise known as the onset of collateral
environmental damage.
Common ground-water remediation
goals such as hydraulic containment of
contaminants, attainment of maximum
contaminant levels, contaminant mass
removal, risk reduction, and contaminant
flux reduction do not reflect
environmental burdens posed by cleanup
technologies. Typical goals also do not
reflect the value of in-situ environmental
resource services such as drought
buffering, prevention of land surface
subsidence, protection against salt-water
intrusion, and maintenance of ecological
diversity. Accordingly, the SRNL study
evaluated Sustainability goals considered
only minimally at the time of remedy
selection:
> Resource conservation measured by
"water intensity," or the amount of
water necessary to remove one pound
of contaminant,
> Energy efficiency measured by the
amount of energy needed to remove
one pound of contaminant, and
> "Carbon intensity" estimating the
amount of CO2 emitted for each
pound of contaminant treated, based
on power industry standards.
During the first six months of air
stripping operations, 100,000-500,000
gallons of ground water were removed
for every pound of TCE removed.
Influent contaminant concentrations over
the following seven years were more
moderate, decreasing from 100 u,g/L to
40 u,g/L. Water intensity during that
period increased to 3,000,000 gallons per
pound of contaminant removed. As of
early 2006, TCE concentrations persisted
at levels eight-fold higher than the 5 u,g/L
cleanup target.
Forecasts estimate that influent
concentrations of TCE after 20 more
years of P&T operation would still be 15
u,g/L (three times the cleanup goal) and
[continued on page 6]
Contact Us
Technology News and Trends
is on the NET!
View, download, subscribe,
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Technology News and Trends
welcomes readers' comments
and contributions. Address
correspondence to:
John Quander
Office of Superfund Remediation
and Technology Innovation
(5102P)
U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Ave, NW
Washington, DC 20460
Phone:703-603-7198
Fax:703-603-9135
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-06-009
May 2007
Issue No. 30
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Presorted Standard
Postage and Fees Paid
EPA "
Permit No. G-35
Official Business
Penalty for Private Use $300
Figure 4. Modeling shows a growth of
collateral environmental impacts
associated with long-term operation of
dilute ground-water plumes.
[continued from page 5]
water intensity would increase to 9,000,000
gal/lb. The remediation system's carbon
intensity also would increase exponentially
to an estimated 50,000 Ibs of CO2 for
each pound of contaminant removed,
significantly increasing the rate of risk
transfer from ground water to the
atmosphere (Figure 4).
Recent studies by the Interstate
Technology and Regulatory Council, the
National Research Council, and other
government organizations recommend
addressing the diminishing environmental
returns of aggressive remediation
technologies by:
01
700
600
500 -
400 -
300 -
8 200
111
o
100 -
0 -
Air Stripper Influent Concentration
TCE Forecast
Water Consumption
COo Emissions
Maximum Contaminant Level
10
- 6
- 4
- 2
- 0
LU
O
E
=3
Q_
10 15 20
Elapsed Time (Years)
25
30
- 100
- 80
- 60
a:
O
" 40 Jj
jj
- 20
- 0
Evaluating collateral damages such as
energy use and loss of environmental re-
sources early in remediation planning.
Establishing alternative metrics for
tracking collateral impacts during active
remediation, and
Developing new economic models us-
ing sustainability metrics to balance
natural resource damages with resource
restoration.
SRNL will continue developing innovative
strategies for minimizing collateral damage
during remediation polishing. Potential
methods involve harnessing new forms of
renewable energy and leveraging prevalent
site conditions with natural processes.
Contributed by Ralph Nichols, SRNL
(ralph. nichols&srnl. doe, gov or
803-725-5228)
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment techniques and
technologies. The Agency does not endorse specific technology vendors.
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