EPA-542-N-03-002
TECH TRENDS
Ground Water Currents
A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Issue 5
March 2003
Landfill Bioreactor Demonstration Underway in Yolo County, CA
Monitoring results gathered over the past
six years show that controlled bioreactor
operations in demonstration cells at the
municipal landfill in Yolo County, CA, are
accelerating anaerobic bioremediation of
solid waste. Field data suggest that waste
settlement in the bioreactor is occurring
approximately 12% faster than in the control
cell where conventional landfilling
technology is employed. As a result, the
demonstration was expanded in 2002 to
address large-scale enhanced bioremedia-
tion using both anaerobic and aerobic
processes.
The Yolo County bioreactor depends upon
the controlled circulation of liquid
(containing leachate and ground water)
throughout the waste material. This process
increases the rate of microbial activity, thus
decreasing the time required for waste
stabilization and decomposition. The
technology offers:
4 Generation of renewable energy
through an accelerated production of
recoverable landfill gas;
4 Elimination of fugitive emissions of
methane gas, a byproduct of anaerobic
composting;
< Improved opportunities for treatment
and onsite use of leachate; and
4 Increased landfill capacity and life.
Due to enhanced waste stabilization, the
bioreactor process is anticipated to decrease
post-closure maintenance requirements. In
addition, the technology provides greater
opportunity for landfill "mining," whereby
the composted fraction is removed and used
for an alternative daily cover in other landfill
modules at the site.
Two 100-ft-square by 40-ft-deep demonstra-
tion cells (an enhanced bioreactor cell and a
control cell), each containing about 9,000 tons
of non-hazardous solid waste, were
constructed at the landfill in!995. The base
of each cell was constructed with a gravel
operations layer over geotextile, a drainage
net, a 60-mil HDPE geomembrane composite
li ner, and a 2-foot layer of compacted clay. In
the enhanced cell, a second liner system was
added below the primary liner to capture any
potential leakage. The depth to the water table
in the area ranges seasonally between 4 and
1 5 ft below ground surface.
To facilitate liquid additions, the waste
surface of each cell was constructed with 14
infiltration trenches filled with shredded tires.
The trenches are approximately 3 ft wide, 10
ft long, and 5 ft deep. A 3-in perforated PVC
pipe was placed vertically at the bottom of
each trench, and water was injected through
each pipe from a leachate distribution
manifold. Liquid is added to the system
continuously to maintain a moisture content
of 50-65% within the waste.
Two perforated, 4-in vertical wells in each cell
coEect gas within the waste and through the
permeable layer of shredded tires. Gravel
surrounds one of the vertical wells, while
shredded tires (encased in mesh wire)
surround the second. To accommodate the
increasing height of waste as it was placed in
[continued on page 2]
. Environmental Protection Agency
Contents
Landfill Bioreactor
Demonstration
Underway in Yolo
County, CA page 1
Enhanced
Bioremediation Used
for Hazardous Wastes
in SRS Soil page 2
DNAPL Treatment
Demonstration
Completed at Cape
Canaveral page 4
Chemical Amendment
Reduces Metal
Contamination at
Former Fertilizer
Facility page 5
More About Alternative
Landfill Approaches...
...is available in a new series of
profiles highlighting alternative
cover design concepts (such as
evapotranspiration covers and
capillary barrier covers) that man-
ipulate water balance principles
to minimize the infiltration of water
to waste. On-line users may
search the site profiles, update
existing profiles, or submit new
treatment profiles to EPAis
Technology Innovation Office.
The series is available from the
CLU-IN website (www.cluin.org).
. library
Recycled/Recyclable
-------
[continued from page 1]
the demonstration cells, well heights were
increased as needed. Both cells are
monitored for moisture, temperature, and
pressure by 112 sensors wired to a
continuous data logger.
Performance data confirm that waste
degradation in the bioreactor cell should
occur in 5-10 years, in contrast to the
30-100 years required in a conventional
landfill. By reducing the overall pollutant
load (leachate and landfill gas) early in the
life of the landfill, the risk of ground-
contamination caused by leachate and
landfill gas seepage from an aging,
defective, or damaged liner likely has
decreased significantly. Recent data
indicate that the bioreactor has reached a
waste settlement rate of 15.8%, while the
control unit reached slightly less than 3.8%.
(Figure 1). These results are confirmed by an
increase in the total volume of methane gas
that was generated; 240% more methane gas
was generated by the enhanced cell than by
the control cell.
Cumulatively, the enhanced bioreactor has
generated 1.54 standard cubic feet of methane
per dry pound (scf/lb) of waste, while the
control cell has produced 0.64 scf/lb. This
production increase suggests more favorable
economics for operation of a gas-to-energy
conversion facility associated with abioreactor
unit than with a conventional landfill.
In April 2002, the demonstration was expanded
to investigate both anaerobic and aerobic
decomposition of waste in a 12-acre module
containing 220,000 tons of solid waste. The
module contains a 9.5-acre anaerobic cell
similar to the initial bioreactor, and a 2.5-acre
aerobic cell equipped with a vacuum system
for drawing air through the landfill. Aerobic
operations are expected to degrade
significant waste fractions such as ligneous
(woody) materials that cannot be degraded
anaerobically. Additional information on the
technical and regulatory aspects of this
"Project XL" initiative is available from the
U.S. EPA at www.epa.gov/projectxl. The
U.S. Department of Energy and the
California Energy Commission has provided
funding for this project.
Contributed by Ramin Yazdani, Yolo
County/Planning and Public Works
Department (530-666-8848 or
ramin.yazdani@yolocounty.org)
Bioreactor and Control Cell Average Settlement
-A- Control Cell
— Bioreactor Cell
Figure I. Over six years of
treatment, the bioreactor
demonstrated a 4-fold increase in
waste settlement tit the Yolo Countv
Central Landfill.
Time (date)
Enhanced Bioremediation Used for Hazardous Wastes in SRS Soil
In late 2002, the U.S. Department of Energy
(DOE) completed treatability studies on the
effectiveness of soil amendments for
enhancing biodegradation of pesticides and
polychlorinated biphenyls (PCBs) in soil at
the Savannah River Site (SRS) in Aiken, SC.
Amendments consisting of carbon and
nitrogen sources such as molasses and animal
manure were applied through windrowing
techniques. Study results indicate that all
contaminants of concern decreased to
concentrations below the treatability study
goals following 3-6 months of treatment.
The field studies were conducted in
treatment areas adjacent to the SRS "CMF
Pits" waste site, which contains sever
unlined pits that were used until 1979 for tta
disposal of solvents, pesticides, and lighting
components. Due to the detection o
[continued on page 3
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DNAPL Treatment Demonstration Completed at Cape Canaveral
In 1997, the Interagency DNAPL
Consortium initiated side-by-side field
evaluations of in-situ chemical oxidation
(ISCO), six-phase heating (SPH), and steam
injection/extraction (SI/E) for treating
trichloroethene (TCE) dense non-aqueous
phase liquid (DNAPL) at Cape Canaveral,
FL (see July 2001 Ground Water Currents
[www.cluin.org]). Final demonstration
results indicate that these technologies
likely destroyed, captured, or removed
84-97% of the total TCE DNAPL.
The former Cape Canaveral launch site
encompasses extensive areas of TCE
DNAPL due to the past use of TCE solvent
for rocket engine flushing and equipment
cleaning. Three 50-by-75-ft treatment cells
were constructed at the site in a side-by-
side setting that allowed for technology
evaluations under a single set of conditions.
Treatment efficiencies of the three
technologies tested were estimated by
analyzing pre- and post-remediation soil
cores taken from the saturated zone at
depths of 5-45 ft below ground surface.
In the ISCO ceE, pre-treatment data indicated
atotalTCEmassof6,100kgwim5,OOOkgof
TCE present as DNAPL. The mass of total
TCE following treatment decreased to 1,100
kg with 800 kg of TCE DNAPL. Spatial data
showed good distribution of the oxidant
(potassium permanganate) throughout the cell,
with the exception of a corner of the cell in the
vicinity of a building. Post treatment data
indicated that TCE declined sharply in patterns
consistent with the oxidant distribution.
Data from the SPH cell indicated a pre-
treatment total TCE mass of 11,300 kg with
10,500 kg of TCEDNAPL. The post-treatment
total TCE mass in this cell was 1,100 kg with
300 kg TCEDNAPL. Approximately 1,950kg
of TCE vapor and a small amount of TCE
degradation products (together accounting for
approximately 17% of the total TCE) were
recovered aboveground during SPH
operations. The amount of TCE remaining in
the cell following treatment (approximately
10%), plus that recovered by the vapor
extraction system, accounted for approximately
27% of the total TCE estimated to be present
before treatment. The unaccounted mass of
TCE may be attributed to:
4 Erroneous mass estimates for TCE;
< Escape of extracted TCE into the vapor
treatment system prior to measurement;
4 Escape of TCE vapor emissions into thi
atmosphere;
4 Lateral subsurface migration of TCE
beyond the cell boundaries; and/or
< In-situ TCE destruction by hydro-
pyrolysis oxidation or other reactions.
Based on thermocouple data and onsite
characterization of the three lithologic zones
within the demonstration area, vapor and
contaminated ground water appeared to
migrate laterally beyond the SPH cell. Lateral
migration of shallow ground water beyond
the cell was found to increase as a result of
heavy rainfall during the test. Additionally,
displacement of contaminated ground water
in the adjacent ISCO cell caused by
potassium permanganate injection may
have contributed to contaminated ground-
water transport from the SPH cell.
Data from the SI/E test cell indicated a pre-
treatment total TCE mass of 10,400 kg with
9,300 kg of TCE DNAPL. Following
treatment, the total TCE mass had decreased
to 1,500 kg with 1,000 kg TCE DNAPL. To
avoid contaminant migration beyond the test
cell, hydraulic control was implemented by
[continued on page 5]
Cleanup Efficiencies
Total TCE
TCE DNAPL
ISCO
SI/E
SPH
Figure 3. Estimated cleanup
efficiencies during the Cape
Canaveral DNAPL demonstration
ranged from 827c to 97%.
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[continued from page 4]
injecting steam in the center of the cell and
extracting vapor and ground water from
recovery wells located along the cell
perimeter. Thermocouple data verified that
most of the cell was heated sufficiently to
vaporize the TCE, with minimal temperature
increases beyond the cell boundary. More
than 3,962,000 gallons (11 pore volumes) of
ground water were pumped from the recovery
wells during the test. The use of recovery
wells positioned along the cell perimeter,
where ground water from outside of the cell
also was captured, contributed to the high
volume of water pumped from the wells.
Cleanup efficiencies for total TCE mass and
TCE DNAPL were determined for the three
technologies tested (Figure 3). Analysis
indicated an SUE cost of $ 134, SPH cost of
$ 164, and ISCO cost of $234 for each kg of
TCE removed or destroyed. Costs per cubic
meter of material treated were estimated at
$ 152 for SPH, $265 for ISCO, and $283 for
SMI It is anticipated that these costs may
be lowered through additional system
design optimization and in large-scale
applications benefiting from economy of
scale. The Interagency DNAPL Consortium
will issue a comprehensive report on this
demonstration in 2004. Additional
information about the consortium's
activities is available at www.getf.org/
dnapl.
Contributed by Thomas Holdsworih,
U.S. EPA (513-569-7675 or
holdsworth.thomas@epa,gov); Jackie
Quinn, NASA (321-867-8410); Thomas
Early, Oak Ridge National Laboratory
(865-576-2103); and Laymon Gray,
Florida State University (850-644-
5516)
Chemical Amendment Reduces Metal Contamination at
Former Fertilizer Facility
Remediation efforts at a former fertilizer-
manufacturing site illustrate the challenges
posed by metal contamination in saturated
soil. Several technologies were evaluated
over the past three years at the 2.5-acre
Former Ashepoo Phosphate/Fertilizer
Works site near Charleston, SC. Treatment
technologies that were considered
sequentially and field-tested in various
degrees included: (1) a permeable reactive
barrier (PRB); (2) in-situ, high-pressure
injection of chemical amendment; (3) in-situ,
low-pressure chemical injection; and (4)
solidification/stablization. Significant
concentration reductions for the primary
metals of concern (arsenic and lead) in soil
and ground water were achieved only
through a solidification/stabilization
involving excavation of contaminated soil,
mechanical mixing with amendment, and
backfilling with treated soil.
The Ashepoo site is located in lowlands
between the Ashley and Cooper Rivers. It
is underlain by 1-8 feet of low-strength fill
and debris above 14-28 ft of loose permeable
sand resting on low-permeability clay; the
water table is approximately 4 ft below
ground surface. The fertilizer manufacturing
process used at Ashepoo between the mid
1800s and the 1960s involved dissolution of
phosphate rock (containing trace levels of
naturally-occurring arsenic) with sulfuric acid
in lead-lined vats. Dissolved lead and arsenic
were found at concentrations up to 18 mg/L
and 220 mg/L, respectively. Additionally, the
pH of ground water was as low as 0.4 standard
units, which is a common result of fertilizer
manufacturing practices used in the past.
In 1999, a PRB was selected as the preferred
remedy for the site. Pre-design investigations,
however, found the remedy was not
appropriate due to unfavorable hydrogeologic
conditions. Field tests to evaluate the
potential of in-situ stabilization/solidification
by chemical amendment began in 2000.
Remediation goals for lead and arsenic
stabilization required that concentrations of
arsenic and lead in the leachate of unsaturated
soil be less than 5.0 mg/L. Remediation goals
for arsenic and lead concentrations in ground
water at a point downgradient of the
contaminant source area were less than 0.050
[continued on page 6]
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[continued from page 2]
solvents in ground water, the pits were
excavated, backfilled, and covered by a low-
permeability cap in 1984. Surface soil in the
adjacent "ballast area," where material was
staged during excavation, was found to
contain PCB concentrations of 0.005-5.52
mg/kg and pesticide (such as DDT)
concentrations of 0.001 to 235 mg/kg.
The presence of the herbicide Silvex
precluded incineration as a remedial option
for the contaminated soil. As a result, field
studies were initiated to evaluate
bioremediation enhanced through
micronutrient amendments applied by
windrow turning equipment (the
Microenfractionator™). Aggressive turning
of the windrow provided the increased mass
transfer and homogenization needed to
promote biological reactions.
Surface soil in the treatment areas, which
was used in the treatability studies, consists
of clayey sand with rocks and pebbles. In
previous studies, the soils were found to
be highly consolidated, low in pH, nutrient
deficient, and low in microbial diversity.
Ground water is located 90 ft below ground
surface.
Field studies involving cycled aerobic and
anaerobic processes were conducted in two
treatment areas. Each area contained
approximately 600 yd3 of contaminated soil in
four 15-by-125-ft windrow treatment cells
(Figure 2). One to two equipment passes were
made twice each week to mix the windrows
and stimulate microbial activity. Anaerobic
conditions were established by adding organic
material and sufficient water to maintain a
moisture content of 18%.
Nutrients were added to the soil to ensure
sufficient concentrations of boron, calcium,
cobalt, copper, iron potassium, magnesium,
manganese, molybdenum, phosphorous,
sulfur, and zinc. These additions helped to
maintain microbial enhancing conditions, i.e.,
a temperature of 95-105°F and a pH of 5-8.5.
Study results indicated that treatment
beginning with an aerobic process required
up to six months for completion, while
treatment initiated by an anaerobic process
reduced the time to three months.
Aerobic, heterotropic, and pseudomonad
plate counts taken one month after treatment
indicated that the microbial population within
the windrows had increased by three orders
of magnitude. Most significantly, study results
showed concentration reductions reaching
90% for organochlorine compounds such
as DDT. Findings also suggested that the
technology was optimized by sustaining a
saturated moisture content, cycling aerobic
and anaerobic conditions, balancing the
carbon/nitrogen ratio by molasses and
manure addition, and ensuring thorough
blending of the amendments with the
contaminated soil.
It is anticipated that enhanced
bioremediation will be used to remediate
approximately 5,000 yd3 of contaminated
soil remaining at the CMP Pits. At an
estimated implementation cost of $400 per
cubic yard of treated soil, this technology
is expected to realize an SRS cost savings
of approximately $12.5 million. Additional
studies are underway at Clemson University
to investigate the mechanisms responsible
for anaerobic and aerobic bioremediation
occurring at the site. In May 2003, DOE will
issue the final treatability study report.
Contributed by Karen Adams, U.S. DOE
(803-725-4648 or karen-
m.adams@srs.gov) and Ron Beul,
Westinghouse (803-952-6451 or
ronald. beul@srs. gov)
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Solid Waste and
Emergency Response
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EPA 542-N-03-002
March 2003
Issue No. 5
First Class Mail
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[continued from page 5]
mg/L and 0.015 mg/L, respectively.
Approximately 1,500yd3 of unsaturated soil
and 60,000 yd3 of aquifer required treatment.
The amendment selected for use at Ashepoo
(EnviroBlend®) is based on pH
neutralization and buffering, reduction/
oxidation, lead-complexation, and arsenic
adsorption/co-precipitation. Excess acid
neutralization capacity was added to the
process to provide for long-term pH control
of the treated soil mass. Pilot tests were
conducted to assess technologies for
introducing the chemicals to the aquifer.
The first injection test used pneumatic
fracturing and liquid atomized injection of
slurried chemicals under high pressures and
low liquid flow rates. The low strength of
the backfill and soil and the anthropo-
morphic preferential flow paths, however,
caused injectate to discharge at the ground
surface. The second pilot test involved
hydraulic fracturing and direct, low-pressure
injection of slurry at a rate of 10-15 gpm. This
approach improved delivery of the slurry to
soil but the in-situ distribution of chemicals
was insufficiently uniform.
Successful treatment results finally were
achieved through excavation of unsaturated
soil and direct mechanical mixing with dry
chemicals using a specialized Lang rotary mixer.
Full-scale application of this technology began
in February 2002 and was completed nine
months later.
Quality control of the aquifer soil treatment
was monitored through a porewater screening
process followed by ground-water sampling
from 20 temporary wells. Based on these
results, six monitoring wells were placed in the
aquifer at locations downgradient of the treated
backfill. Post-treatment median arsenic and
lead concentrations in ground water from the
six wells were 92 and 98% lower, respectively,
than pre-treatment median concentrations. The
maximum post-treatment lead concentration
was 0.028 mg/L, with approximately 70% of
the samples meeting the lead concentration
target. The maximum post-treatment arsenic
concentration was 0.68 mg/L, with about
25% of the samples meeting the arsenic
target.
Geochemical evaluations, including
modeling, suggest that arsenic
concentrations may decrease further as
carbon dioxide produced by treatment
reactions degasses from the aquifer.
Monitoring of the treated aquifer and the
downgradient compliance point will
continue through 2008.
Contributed by Craig Zeller, U.S. EPA/
Region 4 (404-562-8827 or
zeller.craig @epa.gov), Christina Straib,
URS Corp (713-914-6502 or
christina.staib@urscorp.com), and
Bernd Rehm, RMTInc (608-662-5108 or
bemd. rehm @ rmtinc. com)
EPA is publishing this newsletter as a means of disseminating useful Information regarding innovative and alternative treatment techniques and
The Baimcv does not endorse specific technology vendors.
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