TECH TRENDS
A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Mulch Biowall Used toTreatTCE-ContaminatedGround Water
1 he U.S. Air Force Center for
Environmental Excellence (AFCEE)
completed pilot-scale testing of a
permeable reactive biowall in August
2000 at Offutt Air Force Base (AFB) near
Omaha, NE. Field tests were conducted
to determine the efficacy of organic mulch
as an electron donor for promoting
biological reductive dechlorination of
ground water contaminated with
trichloroethene (TCE). Performance data
indicated that the biowall is a low-
maintenance, cost-effective, in-situ
treatment wall technology. Based on these
results, a full-scale 500-ft biowall was
installed at Offutt AFB in July 2001.
The pilot test took place at a site used
between 1942 and 1945 to manufacture
military aircraft. The resulting ground-water
contamination consists of a 3,000-ftplume
with TCE concentrations reaching 2.2 mg/
L. Soil in the area comprises alluvial silt
and clay, with ground water located
approximately 6 ft below ground surface.
Hydrologic testing indicated that the
underlying 30-ft aquifer has an average flow
velocity of 84 ft/yr, a gradient of 0.01 ft/ft,
and a hydraulic conductivity of 3.5 ft/day
Mulch was selected as the electron donor
for the biowall due to evidence of reductive
dechlorination under an adjacent
agricultural field where the soil contains a
high level of naturally occurring organic
carbon. The low costs associated with
obtaining mulch also were considered.
Mulch was generated onsite using shredded
trees and leaves, and mixed with coarse
sand in a 50:50 ratio to enhance the
permeability and stability of the biowall.
Using a continuous trencher, a 1 ft-thick
wall was installed and filled simultaneously
to a length of 100 ft and depth of 23 ft.
Two upgradient, four downgradient, and
two control wells were sampled in five
events during the 31-month pilot test.
Sampling results indicated depressed
oxygen concentrations and oxygen-
reduction potentials due to the
consumption of organic matter and
oxygen by aerobic bacteria. Nitrate and
sulfate levels also declined. Methane
production was observed, providing
further evidence of the establishment of
reducing conditions. Over 31 months of
treatment, the mean TCE removal 20 ft
downgradient of the biowall was
approximately 70% (Figure 1).
Upgradient TCE concentrations were
variable (0.3-2.1 mg/L), but downgradient
TCE concentrations were consistently
between 0.2 and 0.6 mg/L. The ratio of
c/5-dichlorothene (DCE), a degradation
byproduct, to TCE downgradient of the
wall increased by a factor of 820 after 5
months of treatment. This ratio
subsequently dropped as cis-DCE was
converted to vinyl chloride, ethene, and
ethane. The control plot showed no
decrease in TCE concentrations.
Demonstration findings suggest that this
technology is appropriate at sites with
shallow (less than 8 ft) ground water and
biowalls extending less than 30 ft below
[continued on page 2]
AboutThis Issue
This is the first issue of Technology
News and Trends, a technology
newsletter for environmental
professionals published by EPA's
Technology Innovation Office (TIO).
Technology News and Trends
is replacing Tech Trends and
Ground Water Currents-~T\O's
technology newsletters for the past
10 years. The new newsletter
features a combination of articles
on innovative, in-situ technologies
for the characterization and
treatment of soil, sediment, and
ground water. TIO welcomes
your suggestions for news features
and articles for Technology News
and Trends. (See page 5 for how
to contact us.)
Contents
Mulch Biowall Used to
Treat TCE-Contaminated
Ground Water page 1
Full-Scale
Bioremediation of
Organic Explosive-
Contaminated Soil page 2
Treatment of Chlorinated
Organics Using Injected
Zero-Valent Iron Powder page 3
DOE Evaluates Vertical-
Melt Vitrification of
Radioactive Mixed Waste page 5
Technology Comparisons
Conducted on LNAPL page 6
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[continued from page 1]
toll-Scale Bioremediation of Organic
Explosiue-ContaminatedSoil
ground surface. Costs for installing the
Offutt AFB biowall were approximately
$140-360/linear ft. If not generated onsite
(at no cost), mulch for applications at other
sites is estimated to cost approximately
$20/yd3. Additional performance data for
this technology will be collected over the
next two years during full-scale operations
at Offutt AFB. Prior studies by others
indicate that a mulch-based biowall will
last approximately 10 years.
AFCEE plans to construct a 500 ft-long,
25 ft-deep mulch biowall at Altus AFB,
OK, later in 2002, and is seeking
implementation of this technology at two
additional Air Force sites.
Contributed by James Gonzales, AFCEE
(210-536-4324 or James. gonzales@
brooks.af.mil); Jerry Hansen, AFCEE
(210-536-4353 orjerry.hansen@
brooks.af.mil); Philip Cork, Offutt AFB
(402-294-7621 or philip.cork@
offutt.af.mil); and Carol Aziz,
Groundwater Services Inc. (713-522-
6300 or ceaziz@gsi-net.com)
Li August 2001, the U.S. Army Corps of
Engineers (USAGE) initiated full-scale
bioremediation of 6,000 yd3 of organic
explosive-impacted soil at the Iowa Army
Ammunition Plant (IAAP). Daramend®
bioremediation was selected due to its low
soil bulking, effectiveness in the presence
of elevated heavy metal concentrations,
and potential cost savings over alternative
technologies. Following treatment over
an 8-week period, RDX, HMX, and TNT
concentrations were reduced by 98.9%,
92.4%, and 93.7%.
Production of conventional ammunition
at the IAAP, located near Burlington in
southeast Iowa, began in 1941. Past
operations resulted in soil and ground-
water contamination through the
discharge of wastewater containing
explosives and explosive byproducts, and
through open burning and land disposal
of production wastes. Soil at the site is
characterized as clayey glacial till
amenable to bioremediation. Currently,
no technology is in place to address the
site's contaminated ground water.
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10 15 20
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Daramend bioremediation involves the
generation of repeated and sequential
anoxic and oxic conditions through the
application of organic amendments and
powdered iron at low doses (0.5-2% by
weight). The amendments are formulated
with the specific particle size distribution
and nutrient profile needed to create
optimal microbiological conditions in the
soil. This technology can be applied in-situ
to surface soils when contamination does
not extend beyond the upper 2-3 ft. For
deeper contamination zones, ex-situ
applications are employed through a land
treatment or aerated windrow process.
Land treatment typically is less expensive
than aerated windrows; however, windrows
often require less space.
Contaminated soil at the IAAP was
excavated and treated ex-situ in two high-
density, polyethylene-lined land treatment
units identified as Trench 6 and Trench 7.
These trenches contain 5,500 yd3 and 500
yd3 of unprocessed soil, respectively.
Amendments were applied to the soil
surface and blended to a depth of 2 ft using
a tractor-driven rotary tilling system, which
helped to achieve uniform amendment
distribution and increased soil aeration.
Water then was applied to reach the target
soil moisture content of 42% (dry weight).
These steps were repeated in 7- to 10-day
treatment cycles. Five treatment cycles
were conducted in Trench 6, while six
cycles were required for Trench 7 due to
higher initial contaminant concentrations.
Treatment progress was monitored with an
immunoassay field test kit measuring the
combined concentration of RDX and
[continued on page 3]
Figure 1. Over 31 months of treatment at
Offutt AFB, the mean TCE removal was
approximately 70%.
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Figure 2. Following Daramend
bioremediation treatment, RDX
concentrations in soil at the IAAP
decreased more than 93%.
[continued from page 2]
HMX, and verified through laboratory
analysis (Figure 2). RDX served as the
driving contaminant in this application due
to its high initial concentration (819-2,270
mg/kg) relative to its remedial goal (53 mg/
kg). Following treatment, RDX
concentrations ranged from 3 to 32 mg/
kg, while the mean concentration was
reduced by almost 99% (from 1,530 to 16.2
mg/kg). Similarly, the mean concentration
of HMX was reduced by 92.4% (from
1,112 to 84.5 mg/kg), and the mean TNT
concentration was reduced by 93.7% (from
95.8 to 6.1 mg/kg). Concentrations of other
contaminants, including biodegradation
intermediates, also were reduced to levels
below remedial goals in the 20 zones that
were sampled. An estimated 42,000
pounds of explosive compounds were
treated by the process.
The treatment cost for full-scale
bioremediation at the IAAP was $ 167/yd3,
excluding costs for soil excavation or
construction of the land treatment units.
This compares favorably with alternative
treatment technologies such as composting
or thermal treatment. Daramend
bioremediation has been applied
successfully at other U.S. Department of
Defense installations, including the Joliet
Army Ammunition Plant, the Yorktown
Naval Weapons Station, and the
Hawthorne Army Depot
Contributed by Kevin Howe, USAGE/
Omaha District Office (402-221-7185 or
kevin. m. howe@usace. army, mil); David
Raymond, Grace Bioremediation
Technologies (905-273-5374 or
david. raymond@adventustech. com); and
Scott Marquess, U.S. EPA/Region 7
(913-551-7131 or
marquess. scott@epa. gov)
2500-,
E 2000-.
c
o
c
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[continued from page 3]
The depth to ground water, which reaches
80 ft below ground surface, exceeds the
depth at which a PRB could be installed
and maintained cost-effectively. Direct
injection also allowed treatment of ground
water below existing utility structures and
a shallow subsurface that was suspected
of containing unexploded ordnance.
The Ferox process employs a driven
casing/nozzle system or open borehole to
create an in-situ, iron-enriched zone of soil
above or below the ground-water table.
Using potable water and ZVI powder, the
slurry is fed into the nitrogen gas stream,
which atomizes the water and iron particles
to produce a fine mist. This transformation
results in dispersal of the iron powder
within the subsurface over significant
horizontal distances using relatively low
injection pressures (Figure 3).
In the field, two overlapping treatment zones
were installed: a 3,000 sq-ft source-area
treatment zone exhibiting TCE
concentrations in ground water as high as
72 mg/L, and a 450- by 60-ft downgradient
treatment zone. By applying the injections
in 3-ft intervals using a downhole packer
system, a total of 125 slurry injection events
occurred at pressures ranging from 60 to
120 psig.
During injections, the influence of
atomized iron powder was observed as far
as 35 ft from the point of injection. No
effect was observed at any of the nearby
manufacturing buildings or buried utility
lines. On several occasions the injected
atomized slurry encountered unidentified
old boreholes, which resulted in slurry
appearing at the ground surface. Such an
encounter halted the injection event until
the old borehole was grouted or sealed with
a pneumatic packer.
Quarterly ground-water sampling at the
MSFC over the past 1.5years shows that TCE
concentrations in ground water at the MSFC
decreased from apre-injection level of 72,800
ug/L to a post-injection level of 2,500 ug/L.
Ongoing reductive dechlorination is
evidenced further by increased concentrations
of chloride (from 3.29 to 44.4 mg/L) and cis-
1,2-dichloroethene concentrations (from 100
ug/L to 9,900 ug/L) within the source zone
wells.
Contributed by Amy Keith, NASA (256-
544-7434 or amy.keith@msfc.nasa.gov);
John Liskowitz, ARS Technologies (732-
296-6620 orjjl@arstechnologies. com);
and Bill McElroy, CH2MHUI (352-335-
5877 or bmcelroy@ch2m.com)
pneumatic injection
module
Ferox injection
trailer
-B-
overburden
atomized ZVI slurry
in gas stream
Figure 3. The injected Ferox™
process slurry produces a fine
mist that disperses Iron powder
within the subsurface.
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DOE EualuatesVertical-Melt Vitrification of Radioactive Mixed Waste
1 he U. S. Department of Energy (DOE)
National Energy Technology Laboratory
is evaluating a non-traditional in-situ
vitrification (ISV) technology for treating
radioactive mixed waste at the Los
Alamos National Laboratory (LANL) in
New Mexico. This technology, known as
GeoMelt™, involves the melting of
subsurface soil through the use of
vertically oriented planar melts
established between two pairs of
electrodes. Initial seismic tomography
data and continued site monitoring since
ISV completion in April 2000 indicate
that the vitrified waste at LANL is
contained successfully within a 25- by 15-
ft monolith. The monolith extends from
8 to 26 ft below grade, which is
considerably greater than depths achieved
through conventional ISV melts.
This ISV approach differs significantly
from traditional ISV, which typically
melts a soil matrix in a "top-down"
sequence with a horizontally oriented
melt established at or near ground surface
between four electrodes. In contrast to
top-down ISV, the vertical melt provides
a taller, narrower melt and improved
control of melt progression. Two separate
vertical melts begin in the subsurface,
forming parallel melt planes that grow
together horizontally during the treatment
process to form a single monolith of the
targeted treatment volume. In comparison
with conventional top-down ISV, this
subsurface approach uses approximately
30% less electrical power and decreases
exposure potential for workers.
DOE's Subsurface Contaminants Focus
Area sponsored the GeoMelt
demonstration in cooperation with the
Western Environmental Technology
office of DOE. The demonstration took
place at LANL's technical area 21, which
contains three absorption beds located in a
welded volcanic tuff matrix. Operations
were conducted in a portion of a single
absorption bed. From the 1940s to the early
1960s, the absorption beds received liquid
effluent primarily from a radioactive
laundry facility and intermittently from
nearby laboratory and research facilities.
Soil sampling indicated the presence of
plutonium 239/240 in concentrations
reaching 525 pCi/g. Other contaminants
within the absorption beds included
radionuclides (americium, cesium,
strontium, and uranium) and heavy metals
(cadmium, chromium, copper, and lead).
The demonstration commenced with the
injection of a graphite-based mixture into
the subsurface to form two vertical planes
of melt starter material between two pairs
of electrodes. Based on the local geology,
an injection target depth of 9-12 ft below
grade was established prior to the melt.
Joule-heated melting occurred over a 21-
day period, reaching a depth of 25 ft.
During this period, the melting process
operated for approximately 14 days at a
power input averaging 2 megawatts.
Melting operations were interrupted for 11
days while cavities of unsubsided
overburden material were collapsed using
vibratory equipment, but continued again
without difficulty. Off-gases were
contained within a hood covering the
treatment area and drawn to a treatment
system. Laboratory and field evaluations
of the off-gas and treatment system showed
no radiological contamination.
Due to the insulating properties of the
surrounding volcanic tuff, cooling of the
monolith has occurred more slowly than
anticipated. From an initial temperature
over 2,000°F, the top surface of the
monolith cooled to 700°F within six
months, 300°F after 12 months, and 100°F
after 24 months. DOE is conducting
additional analysis of the vitrified
monolith in 2002 to verify that target
compounds were incorporated into the
melt and uniformly distributed. In
addition, leaching tests will be performed
to ensure that contaminants are
immobilized within the glass matrix. By
producing a final waste form that is more
resistant to physical, chemical, and
weathering changes, non-traditional ISV
appears to provide an alternative to
contaminant solidification or stabili-
zation.
Contributed by Marja Springer, LANL
(505-665-7112 or marja@lanl.gov);
and Gordon Huddleston, MSE-
Technology Applications, Inc. (406-
494-7382 or hudgj@mse-ta.com)
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Technology ComparisonsConducted on INAPL
In collaboration with several universities
and federal interagency programs, EPA's
National Risk Management Research
Laboratory (NRMRL) is evaluating
technologies for treating ground water
contaminated with light nonaqueous
phase liquid (LNAPL). Side-by-side
comparisons of nine technologies
employing various remedial agents have
been conducted since 1996 at Hill Air
Force Base (AFB) near Ogden, UT. Tests
were conducted in 3- by 5-m hydraulically
isolated treatment cells containing a
complex mixture dominated by fuel
components but containing solvents,
polychlorinated biphenyls, and pesticides.
Traditional pump and treat methods were
compared against:
• Cosolvent solubilization
(low molecular-weight alcohols)
• Cosolvent mobilization
(high molecular-weight alcohols)
• Surfactant solubilization
(hydrophilic fluids)
• Surfactant mobilization
(hydrophobic fluids)
• Surfactant micro-emulsion
(surfactants and alcohol cosolvents)
• Macro-molecule emulsion
(cyclodextrin)
• Steam injection
• Air sparging and venting
• In-well aeration
Based on the evaluation results, Hill AFB is
considering full-scale alternatives that will
begin during 2002. In Situ Enhanced
Source Removal (EPA/600/C-99/002),
which is available from NRML at
www.epa.gov/ada/research/featured.html,
provides a comprehensive summary of
these technology evaluations.
For more information, contact Dr. Carl
Enfleld, NRMRL (513-569-7489 or
enfield. carl@epa. gov)
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NewsandTrends
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EPA 542-N-02-003
July 2002
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