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/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
February 2006
Issue 22
Pilot-Scale Bioreactive PRB Removes Metals from
Ground-Water Plume Within One Year
The South Carolina Department of Health and
Environmental Control (SCDHEC) recently
completed a field-scale pilot study on the use
of an in-situ sulfate-reducing bioreactor/
permeable reactive barrier (SRBR/PRB) to
address metals contamination in ground water
at the Stoller Chemical Site in Jericho, SC. The
SRBR/PRB contains common biomaterial such
as coastal hay, woodchips, and livestock manure
that encourages growth of sulfate-reducing
bacteria, thereby passively treating influent
ground water. The study evaluated the
technology's effectiveness based on
achievement of maximum contaminant levels
(MCLs) within the SRBR/PRB, hydraulic
performance of the system, longevity of such a
passive system, presence or absence of
plugging from aluminum hydroxide or metallic
precipitates, constructability, and potential cost
savings.
Past fertilizer manufacturing operations at the
site resulted in low pH and metals contamination
in a shallow aquifer 2-18 ft below ground surface
(bgs) that overlies a clay confining unit of
variable thickness. Primary metals of concern
are cadmium, copper, nickel, manganese and
zinc, and to a lesser extent, aluminum and iron.
Sampling and analysis indicated that the metals
have not migrated to the aquifer below the clay
unit. The 900-ft-long contaminant plume extends
from the site northward, across North Creek to
Caw Caw Swamp. Migration of the excess
dissolved metals in the plume was greatly
enhanced by the area's high oxidation/reduction
potential (ORP) of approximately 300 mV. As a
result, a 22-gpm interim pump and treat system
began operating in 2002 to address the source
area, which is located approximately 400 ft
upgradient of the pilot project. Based on the
soil's effective porosity of 0.26 and an average
gradient of 0.012 ft/ft, the average linear ground-
water velocity for the aquifer while undergoing
treatment is estimated to be 0.36 ft/day.
SRBR/PRB technology employs sulfate-
reducing bacterial reactions that generate
sulfide ions. These combine with dissolved
metals to precipitate sulfide compounds and
bicarbonate, which raises the effluent pH to a
neutral 5.0-6.0. The bioreactive medium
includes limestone to provide bicarbonate
alkalinity and to buffer initial pore water
solutions against pH drops associated with
fermentation. Earlier studies showed that
sulfate-reducing bacteria such as Desulfovibrio
account for less than 1% of the total bacterial
community needed in an effective in-situ
bioreactor.
A six-month bench-scale evaluation was
conducted in five test cells at the Stoller site in
early 2004. Metals-impacted ground water from
an existing monitoring well was added to each
cell, which were filled with different ratios of
reactive materials. Results indicated 99.3-99.8%
removal of metals. Construction of the pilot-
scale system began soon afterward in mid 2004.
Prior to excavating the barrier trench, ground-
water screening using direct-push technology
was conducted to ensure SRBR/PRB
placement within and perpendicular to the
contaminant plume. Reinforced-steel sheet piling
was installed in the subsurface in a 21-by-11.5-ft
rectangular configuration extending 15 ft bgs.
Six clusters of three monitoring points (at depths
of 6.5-7.5, 8.5-9.5, and 10.5-11.5 ft bgs) were
installed in the trench prior to its filling.
[continued on page 2]
Contents
Pilot-Scale Bioreactive
PRB Removes Metals
from Ground-Water
Plume Within One Year page 1
ZVI-Clay Soil Mixing
Treats DNAPL Source
Area at 35-Foot Depth page 3
ERH Pilot Project
Removes 48 Tons of
PCA DNAPL Within
Six Months page 4
Thermo-Chemical
Process Converts
Contaminated Sediment
to Clean Construction
Material page 5
CLU-IN Resources
The U.S. EPA's Technology
Innovation and Field Services
Division continuously updates
CLU-IN's Technology Focus, an
online compilation of "bundled"
information on 19 categories of
remediation technologies
including bioreactor landfills,
permeable reactive barriers,
electrokinetics, soil washing/
mixing, soil vapor extraction,
and thermal desorption. An
overview of each bundled
category is provided, along with
associated guidance, case
studies, and listings of addi-
tional resources. Technology
Focus is available at
http://www.cluin.org/techfocus.
Recycled/Recyclable
Printed with Soy/Canola Ink or paper that
contains at least 50% recycled fiber
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[continued from page 1]
Based on the bench-scale results, the selected
reactive media consisted of amixture of 32.4%
(by volume) coastal hay, 19.3% hardwood
chips, 19.3% softwood chips, 16.6% saw
dust, 7% limestone, 5.5% horse manure, and
0.4% cement kiln dust. The media were mixed
onsite, emplaced in the trench, compacted
to within 1.5 ft of ground surface, saturated
with plume ground water, and incubated for
33 days. The sheet-pile walls then were
removed to allow natural ground-water flow
through the completed 10-ft-wide PRB.
Ground-water flow was enhanced by the
higher permeability of the reactive media.
Loading of the trench occurred at a rate of
2.7 gal/day/ft2, and an estimated 554 gal of
ground water flowed through the barrier each
day thereafter. Hydraulic monitoring was
performed within and outside the treatment
area, and no significant changes in water
levels, hydraulic gradient, or hydraulic
conductivity were noted during the study
period.
Two core samples of the barrier media from
the upgradient side of the trench were
collected after one year of treatment. Visual
inspection showed saturation and blackening
of the biomass, but the coastal hay and wood
chips, which accounted for 71 % of the original
biobarrier volume, appeared intact and
without significant structural degradation.
Approximately 5% of the organic material,
primarily the manure, had been consumed.
The lack of evidence of gypsum or aluminum
hydroxide precipitation suggested that
barrier plugging had not occurred.
Examination of the barrier core samples with
a scanning electron microscope revealed no
visible precipitates. Analysis of particle
surfaces with an electron microprobe,
however, comfirmed the presence of metals
Figure 1. Ground water sampled from a
monitoring well approximately 10ft
downgradient of the bioreactive barrier
showed a 72-96% decrease in all six
metals of concern at the Stoller site
within one year.
I
on the surface of the media near the base of
the aquifer.
In addition to the 18 monitoring points within
the wall, three upgradient and five
downgradient monitoring points were used
for routine testing of target metal
concentrations and of ground-water
parameters such as pH, ORP, conductivity,
and temperature. Seven ground-water
sampling rounds were conducted between
August 2004 and July 2005. Sample data
suggested that the geochemical conditions
inside the trench mimicked the conditions
observed in the bench-scale tests. Pore water
pH was consistently 5.5-7.0, and reducing ORP
conditions consistently were conducive to
bacterial sulfate reduction (< -200 mV).
Ambient ground-water temperatures initially
warmed due to incubation prior to removal of
the sheet piling but cooled to background
conditions over a period of weeks after removal
of the sheet piling.
Additional testing was conducted to evaluate
the treatment system's impact beyond the
study area and on other environmental media.
The absence of fecal coliform bacteria in any
of the five downgradient monitoring points
indicated that the use of manure as a reactive
medium did not induce viable colonies of fecal
coliform in the aquifer after one year of
treatment. To evaluate potential air emissions,
a photoionization/flame ionization detector and
a four-gas air monitor were used to evaluate
the headspace of each monitoring point.
Results showed no detrimental emissions of
methane, hydrogen sulfide, methane,
hydrogen sulfide, or carbon monoxide.
As expected, metal concentrations in the
trench met MCLs and achieved the remedial
goal of a 90% reduction in metals of concern.
Time series graphs derived from data
collected at one downgradient monitoring
point (representing a mixture of treated
effluent from the wall and contaminated water
in place) demonstrate an approximate 84%,
96%, and 72% reduction of cadmium, copper,
and zinc, respectively (Figure 1).
The long-term effectiveness and longevity
of the SRBR/PRB will depend on factors
such as the rate of ground-water flow
through the trench, influent ground-water
characteristics, and quantity of organic
matter supplying total organic carbon. A
lifespanof 12-16 years currently is projected.
Development of a feasibility study is
underway for two scaled-up biobarriers that
address offsite portions of the plume and
replace the existing pump and treat system.
SCDHEC estimates that use of the sulfate-
reducing PRB will achieve a $ 1 -2 million
savings over the cost of expanding the pump
and treat system for the downgradient
portion of the plume. If the entire pump and
treat system is replaced, cost savings of
several million dollars are anticipated due to
a significant reduction in operation and
maintenance costs that currently average
approximately $400,000/yr.
Contributed by Judy Canova, SCDHEC
(canovajmdhec.sc.gov or 803-896-4046)
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ZVI-Clay Soil Mixing Treats DNAPL Source Area at 35-Foot Depth
Over the past several years, Colorado State
University (CSU) collaborated with private
industry to develop a technology that
involves in-situ admixing of contaminated
soil, granular zero-valent iron (ZVI), and clay
using conventional soil mixing equipment. A
full-scale application of this technology was
conducted in 2002 at a former nylon
manufacturing facility in Martinsville, VA,
where carbon tetrachloride (CT)
concentrations averaged 4,000,000 (Ig/kg.
Post-treatment soil analyses indicated 99%
removal of CT and total chlorinated volatile
organic compounds (C VOCs) after one year
of treatment. Field tests also showed that
treatment significantly reduced soil
permeability and thereby limited the release
of remaining contaminants into ground water.
The treatment area comprised a 70-by-100-ft
source area with 8,000 yd3 of soil initially
containing an estimated 20 tons of CT. The
area is underlain by 15-20 ft of alluvium
overlying 10-20 ft of saprolite that grades to
bedrock at approximately 35 ft bgs. During
soil mixing, boulders were encountered at a
depth of 25 ft in a small portion of the treated
interval and subsequently excavated.
Mixed soil columns were constructed using
a crane-mounted drill system equipped with
an 8-ft-diameter soil auger. A clay /water grout
was combined onsite with granular ZVI, and
the mixture was blended with subsurface soil
through multiple auger passes. A total of 76
mixed soil columns extending 35 ft bgs were
created over 10 weeks.
Treatment required approximately 225 tons
of ZVI as a reactive medium and 340 tons of
kaolin clay as a stabilizing agent. Target
amounts of ZVI varied from 2 to 6 lbs/ft3 soil,
with higher amounts added in contaminant
hot spots. After mixing, the upper 5 ft of
treated soil were remixed with Portland cement
to improve load-bearing capacity. An asphalt
cap was constructed over the entire treatment
area six months later.
Twenty soil cores from the treated interval
were collected and analyzed the following
year and again in 2004. Samples were analyzed
for CT and potential daughter products,
including chloroform (CF), methylene chloride
(MC), chloromethane (CM), tetrachloroethene
(PCE), and trichloroethene (TCE). After one
year of treatment, the average concentration
of CT in soil had decreased from 4,000,000 |lg/
kg to 210 (Jg/kg (Figure 2). Concentration
increases in most daughter products,
particularly MC, indicated that ZVI-mediated
reductive dechlorination had occurred. Rates
of daughter compound production were
found to depend on factors such as
amenability to ZVI reaction and sorption in
the soil matrix. Contaminant concentrations
detected in the second annual sampling event
indicated that the reaction had apparently
ceased or slowed.
To characterize the remaining iron, granular
iron was magnetically separated from soil
obtained during the second annual sampling
event. Laboratory analysis indicated that most
of the granular iron mass remained, and a batch
study confirmed that it was still capable of
degrading chlorinated compounds. These
results suggest that the remaining contaminant
mass is irreversibly adsorbed in the soil matrix
and consequently unavailable for reaction or
migration through downgradient water.
Permeability of the aquifer was measured at
10"3 to 10"2 cm/s prior to treatment. Post-
treatment samples collected from one mixed
soil column at depths of 10, 20, and 30 ft
showed an average permeability of 2.9 x 10"7
cm/s, indicating a permeability reduction of
four to five orders of magnitude. This
reduction suggested that ground-water flow
selectively bypassed the treated interval and
allowed for containment of the contaminant
mass, an increase in contaminant residence
Figure 2. Mixing of contaminated soil
with ZVI and clay at the Martinsville
manufacturing facility achieved greater
than 99% mass depletion ofCT and
formation of low levels of related
daughter pro ducts.
time, and a reduced inflow of competing
oxidative agents.
Implementation of this technology requires
sufficient overhead space to operate the
mixing equipment and remove buried
obstructions. Completed applications
suggest that soil mixing technologies such
as this can be used at depths reaching 100 ft
bgs but are most effective at depths less than
40 ft bgs. Costs for construction (including
equipment, materials, and labor) were
estimated at $80/yd3 of treated soil at the
Martinsville site. Similar ZVI-clay projects
were initiated last year at Camp Lejeune, NC,
and Arnold Air Force Base, TN. CSU's
ongoing ZVI-clay research focuses on
improving post-treatment soil strength and
enhancing methods for performance
monitoring. The U.S. EPA's National Risk
Management Research Laboratory (NRMRL)
plans to further evaluate the technology's
performance as part of a technology
demonstration anticipated by the federal
interagency Remediation Technology
Development Forum.
Contributed by Robert Puls, EPA NRMRL
(puls. robert&epa. gov or 580-436-8543),
Mitchell Olson, CSU
(mitcello(a)engr.colostate.edu or 970-491-
8720), and Tom Sale, Ph.D., CSU
(tsale(q),engr. colostate.edit or 970-491-
8413)
10,000,000
1,000,000
100,000
10,000
1,000
100
I Pre-Application
I 1-Yr Post Application
I 2-Yr Post Application
nn mi
CT CF MC PCE TCE
Compound
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ERH Pilot Project Removes 48 Tons of PGA DNAPL Within Six Months
Li 2003-2004, the U.S. Navy deployed in-
situ three-phase electrical resistance heating
(ERH) technology on a pilot scale to evaluate
the technology's success in treating
DNAPL at Site 89 of the Marine Corps Base
Camp Lejeune, NC. Though high
concentrations of 1,1,2,2-tetrachloroethane
(PCA) and TCE previously were removed
fromunsaturated soil using low-temperature
thermal desorption, additional treatment was
needed to address the separate-phase
DNAPL encountered at depths of 5-19 ftbgs.
Results from the pilot will be used to evaluate
methods of addressing additional areas of
DNAPL throughout the site.
Three hydrostratigraphic units comprise the
treatment interval of 5-26 ft bgs: fine- to
medium-grained sand with interbedded silt
and clay layers from grade to about 8-15 ft
bgs; a discontinuous layer of clay with fine
sand or silt at 8-18 ft bgs; and a lower clay
combined with calcareous sand and shell or
fossil fragments. Hydraulic conductivity
within the interval decreases with depth from
10"3 cm/s to 10"6 cm/s, and the water table is at
an average depth of 3 ft bgs.
A network of 15 monitoring wells was
established throughout the area to monitor
treatment performance and detect any
undesired contaminant migration. Seventeen
horizontal vapor extraction wells were installed
in the area and covered by a unique 10,000-ft2
impermeable and thermally insulated cap. Due
to the anticipated volume of contaminants and
extensive base activity surrounding the site, all
collected vapors were treated using a catalytic
oxidizer followed by a caustic wet scrubber.
In-situ treatment of the unsaturated zone
employed three-phase electricity delivered to
an array of 91 electrodes in an area of!5,900ft2.
Each electrode was vented and installed with
the dual capability of extracting vapors and
ground water for hydraulic control in order to
mitigate lateral and downward migration of
DNAPL into the aquifer.
Active heating of the entire treatment area
began after a two-month period of gradual
heating of the area's "floor" and "walls." VOC
contaminant recovery was observed
immediately after system start-up and continued
while temperatures increased. After four months
of active heating, subsurface target
temperatures of 100°C were reached in both soil
and ground water, and substantial contaminant
recovery still was occurring (Figure 3).
The system continued to operate another two
months, when analytical sampling indicated
that the average concentration of PCE had
decreased from 992 mg/L to 0.9 mg/L in ground-
60000
water samples taken from shallow treatment-
area wells. Upon system shutdown, the
average concentration of PCA in soil had
decreased from 2,351 ug/kg to less than 1 ug/
kg. Similarly, concentrations of TCE as a PCE
degradation product had decreased from an
average of 1,148 ug/kg to less than 1 ug/kg.
Analysis of contaminant concentrations
throughout the treatment period indicate that
the VOC extraction rate increased from an
average of 2 Ibs/day upon system startup to
200-440 Ibs/day after three months of
operation. Removal then began declining to
a final rate of approximately 10 Ibs/day, at
which point ground-water and soil sampling
within the treatment area indicated a 99% VOC
reduction in both media.
Quantitative sampling of the vacuum system
influent determined that more than 48,000
pounds of VOCs were removed as a result of
electrical resistance heating, at a calculated
cost of $41/lb. Soil and ground-water
monitoring detected no air emissions at the
project borders or migration of contaminants
from the treatment area. Based on these results,
the U.S. Navy will consider use of electrical
resistance heating to treat additional DNAPL
areas at Camp Lejeune.
Contributed by Dan Hood, U.S. Navy
(daniel. r.hood(a)navy.mil or 757-322-
4630), Gena Townsend, U.S. EPA Region 4
(townsend.gena(q),epa. gov or 404-562-
8538), and Ron Kenyan, Shaw Group
(ronald. kenyon(a)shawgrp. com or
770-663-1453)
Figure 3. Rates of VOC removal from
the upper vadose zone at Camp Lejeune's
Site 89 increased exponentially during
the third month of electrical resistance
heating.
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Thermo-Chemical Process Converts Contaminated Sediment to Clean Construction Material
The New Jersey Department of
Transportation's Office of Maritime
Resources (NJ DOT/OMR) and U.S. EPA
Region 2 recently completed Phase 1 of a
full-scale pilot test on the use of an ex-situ
thermo-chemical process (Cement-LockŪ)
for decontamination and beneficial use of
dredged sediment from the New York and
New Jersey Harbor. The full-scale test has
been in design and construction since 2001
as part of ongoing efforts to treat dredged
material containing a wide range of harbor
contaminants. This phase was designed to:
> Process a bulk quantity of navigational
sediment in a technology-specific dem-
onstration plant;
> Demonstrate the mechanical operation
and trouble-shooting capability of the
plant's systems;
> Demonstrate the technology's effective-
ness in treating organic and inorganic
contaminants;
> Show destruction rather than transfer-
ence of organic contaminants;
> Determine leachability of the treated sedi-
ment;
> Demonstrate the treated material's quali-
fications for beneficial use under state
regulations, and
> Educate the public on sediment decon-
tamination issues.
The full-scale pilot results demonstrate that
the processed sediment meets the state's
residential direct-contact cleanup criteria for
soil and is suitable for use as construction
fill. The NJ DOT/OMR and EPA Region 2
currently are evaluating recommendations
for Phase 2 of the project, which will employ
the thermo-chemical process to treat up to
400 yd3 of sediment over a three-week period
later this summer.
Phase 1 testing included treatment of
approximately 400 yd3 of navigational
sediment dredged by the U.S. Army Corps
of Engineers from the Stratus Petroleum site
in upper Newark Bay, NJ. The sediment was
screened to -1A inches, mechanically
dewatered onsite, and then transported to
the demonstration facility in Bayonne, NJ.
The sediment was blended with mineral
modifiers typically used in cement
manufacturing and the mixture was auger-
screw fed into a natural-gas-fired rotary kiln,
where it was heated for one hour at a
temperature of 1,83 5° F. Thermal treatment
successfully destroyed complex
contaminants such as polychlorinated
biphenyls (PCBs), dioxins, and polynuclear
aromatic hydrocarbons and converted the
mixture into innocuous components. Volatile
metals such as mercury were captured in an
activated carbon bed.
Decontamination operations using this
technology have been conducted in both
slagging and non-slagging modes. In
slagging mode, the dredged material with
added modifiers melts completely during
travel through the kiln. Upon exiting the kiln,
the melt is quenched with water, and the
cooled material takes a non-crystalline form
comprising thin, black, glassy strands
("Ecomelt"). The glassy product can be
ground into a fine powder and blended with
Portland cement to yield construction-grade
cement. Independent laboratory testing on
the construction-grade cement yielded a
compressive strength of 5,190 psi, which
exceeds ASTM requirements (3,480 psi) for
blended cement. Under non-slagging
processing mode, the sediment is converted
into a larger-grained aggregate material
("EcoAggMat") that can be used as clean
fill or as partial replacement for sand in mortar.
Over a 17-day period in early 2005, the
Bayonne plant processed sediment at a rate
of approximately 1,000 Ibs/hr, or 0.5 y d3/hr,
in non-slagging mode. A total of
approximately 80 yd3 of the sediment/
modifier mixture was processed, which
yielded about 53 tons of the remediated
aggregate product. Earlier slagging-mode
trials on approximately 20 yd3 of the
sediment/modifier mixture produced
approximately two tons of the glassy product,
with large clinkers or slag accounting for the
material balance.
EPA's Superfund Innovative Technology
Evaluation (SITE) Program conducted a
broad range of environmental tests to
characterize the end products and confirm
that organic contaminants were destroyed
during thermo-chemical processing at the
Bayonne plant. Testing of the aggregate
product by the toxicity characteristic
leaching procedure (TCLP), synthetic
precipitation leaching procedure, and
multiple extraction procedure indicated no
leaching of metals above the state's ground-
water quality criteria. TCLP tests also
detected no priority elements in leachate
from the glassy product.
Plant emission rates for semi-volatile organic
compounds and target compounds such as
PCBs met the state's air quality permit limits,
and 99% of the toxicity equivalency from
PCBs, dioxins, and furan congeners in the
sediment was destroyed during treatment.
Comparison of mercury emission rates
against concentrations of mercury entering
[continued on page 6]
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Solid Waste and
Emergency Response
(5102G)
EPA 542-N-06-001
February 2006
Issue No. 22
United States
Environmental Protection Agency
National Service Center for Environmental Publications
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[continued from page 5]
the plant's activated carbon bed showed a
99% collection efficiency, which exceeds the
state's air permit requirement of 70% for
mercury.
Due to processing difficulties common in
plant startups and shakedowns of this type,
continuous and sustained operations for
processing all of the targeted 400 yd3 proved
difficult. Process enhancements will be
implemented prior to initiating Phase 2 of
the project, with focus on increasing the
consistency of sediment feeding, improving
the control of sediment and modifiers during
treatment, and increasing the rates of slag
discharge from the system's rotary kiln. It is
also anticipated that co-processing of
contaminated sediment with other materials
containing high calorific values, such as
petroleum wastes and shredded tires, would
reduce fuel costs and improve process
economics.
Based on these results, the NJ Department of
Environmental Protection anticipates approval
of the Cement-Lock aggregate to be used as
clean fill at a South Keamy, NJ, site undergoing
remediation. Researchers estimate that
sediment processing costs for a large-scale
commercial thermo-chemical plant would be
similar to those of alternate options for
sediment disposal in the harbor, which average
$35/yd3.
Contributed by Eric Stern, U.S. EPA Region
2 (stern.eric(q),epa.gov or 212-637-3806),
Scott Douglas, NJDOT/OMR
(scott.douglas(a)dot.state.nj.us or 609-530-
4773), and Michael Mensinger, Gas
Technology Institute
(mike.mensinger(a)gastechnology.org or
847-768-0602)
Errata
Please note corrections to the article
entitled "Tree-Core Analysis Brings
Savings to Site Assessments" as
published in the November 2005
issue of Technology News and
Trends. The U.S. Geological Survey,
rather than the U.S. Department of
Agriculture, pioneered the tree-coring
approach for site assessment. Also,
all measurements involving "jag"
(microgram) units were printed
erroneously as "mg" (milligram)
units. The Technology News and
Trends editorial staff apologizes for
any inconvenience this may have
caused.
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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