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/A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Issue 54
772/5 wrae of Technology News and Trends (TNT) provides site-specific updates about
innovative cleanup technologies and methods described in past issues. Recent work at these
sites involved testing materials to improve technology performance, integrating advanced
equipment to improve field and project management efficiencies, and developing "lessons
learned" to aid technology applications at other sites.
Enhancement of Anaerobic Mulch Bioreactor Involves Emulsified
Vegetable Oil and Iron and Sulfate Amendments
Funded by the Environmental Security
Technology Certification Program
(ESTCP), a pilot-scale, recirculating,
anaerobic mulch bioreactor was installed
in 2003 at the Altus Air Force Base (AFB)
"Landfill 3" in Oklahoma to address a
hotspot of chlorinated volatile organic
compounds (VOCs) within a larger
groundwater plume. [For more
information, see the May 2007 issue of
TNT.] The Air Force Center for
Engineering and the Environment
(AFCEE) and Altus AFB have since
performed two enhancements, both of
which involved injecting reagents directly
into the bioreactor to improve
performance. These enhancements have
shown success in reducing chlorinated
VOC concentrations within water entering
the bioreactor matrix by up to 99% with
reduced accumulation of dechlorination
byproducts. However, results of the second
enhancement are still being analyzed.
The first enhancement involved injecting
emulsified vegetable oil (EVO) and a
microbial bioaugmentation culture into the
subsurface bioreactor in October 2006.
The purpose was to replenish the soluble
organic carbon content and improve
degradation of the trichloroethene (TCE)
dechlorination products, specifically
dichloroethene (DCE) and vinyl chloride
(VC). EVO was selected as the liquid
organic substrate due to its relatively low
cost (less than $2/lb of premixed emulsion)
and persistence in the subsurface. From
February 2004 to July 2006, the
bioreactor yielded total chlorinated VOC
efficiency of 75% to 96% and total TCE
removal efficiency of 97% to >99%.
Following the 2006 bioenhancement, total
chlorinated VOC removal efficiencies
(measured in January and July 2007) were
99% and 66%, respectively, and TCE
removal efficiencies were 98% and 99%,
respectively. The lower total chlorinated
VOC removal efficiency in July 2007 may
have been due to an influx of new TCE
mass into the bioreactor as a result of
higher-than-normal precipitation and water
table in June 2007.
In January 2010, the solar-powered
submersible pump that recirculated
contaminated groundwater through the
bioreactor was replaced. The new
Grundfos 11SQF2 submersible solar-
powered pump recirculates groundwater
at a rate of 2-4 gpm during peak sunlight
hours and maintains an average flow rate
of approximately 2.5 gpm each day.
The second enhancement was performed
during a five-day period from May to June
2010. A combination of EVO and iron/
sulfate amendments was injected into the
bioreactor to supplement biotic VOC
degradation by also enhancing abiotic
[continued on page 2]
July 2011
Contents
Enhancement of
Anaerobic Mulch
Bioreactor Involves
Emulsified Vegetable
Oil and Iron and
Sulfate Amendments page 1
EPA Analyzes
Superfund Remedy
Trends Over Recent
Years page 2
Sediment Cleanup
Remedy for Lower
Fox River Reaches
25% Construction
Completion page 3
EZVI Injection Field
Test Leads to Pilot-
Scale Application page 4
CLU-IN Resources
The U.S. Environmental Protec-
tion Agency (EPA) Technology
Innovation and Field Services
Division now offers a Passive
Samplers focus area on the
CLU-IN Website. The area
describes sampler compo-
nents and operation, target
analytes, costs, advantages,
limitations, and application
examples for no-purge devices
categorized as thief (grab),
diffusion (equilibrium), or
integrating (kinetic) samplers.
Visit the new focus area
through: www.clu-in.org/
characterization/technologies/.
To learn about other new CLU-IN
resources as they become
available, subscribe to EPA's
monthly TechDirect news service
at: www.clu-in.org/techdirect/.
Recycled/Recyclable
Printed with Spy^anola Ink 01 paper ll
contains at least 50% recycled fiber
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[continued from page 1]
degradation. Research suggested that this
mixture of organic and inorganic
amendments could stimulate production
of reactive iron sulfide (FeS) minerals
capable of degrading chlorinated VOCs
abiotically through biogeochemical
transformation. The objective of
introducing iron and sulfate was to obtain
a target FeS concentration in the bioreactor
backfill of approximately 3,000 mg/kg,
measured as acid volatile sulfide.
Design calculations for the iron and
sulfate injection indicated that an FeS
concentration of 3,000 mg/kg should
abiotically reduce influent TCE
concentrations by at least 70%. This
calculation assumes an influent TCE
concentration of 1,210 |J,g/L (based on
July 2007 data), an average residence
time of 7.5 days, and a conservative
TCE degradation rate of 0.53 moles
per day of TCE when exposed to 1.0
mole of FeS in contact with 1.0 liter
of pore water.
Approximately 3,600 pounds of ferrous
sulfate were mixed with 300 gallons of
buffered EVO and 7,200 gallons of
native groundwater were pumped from
the nearby extraction trench sump. The
mixture was pressure-injected into the
subsurface bioreactor via four
temporary, 4-foot-long injection screens
driven to the bottom of the bioreactor,
approximately 11 feet below ground
surface (bgs) and about 5 feet below
the water table.
The recirculation system was temporarily
deactivated prior to the injection.
Recirculation was then delayed for several
weeks following inj ection to allow the EVO
substrate to sorb to the bioreactor matrix.
The delay also allowed the injected sulfate
to be biologically reduced to hydrogen
sulfide. The intended outcome was for the
sulfide to react with ferrous iron to
precipitate reactive FeS minerals within
the bioreactor and immediately
surrounding aquifer matrix.
Preliminary evaluation of groundwater
quality data collected from October 2010
to May 2011 from monitoring wells
screened within the bioreactor indicates that
concentrations of TCE have remained
below 5 |J,g/L, relative to influent
concentrations of TCE as high as 1,200
|J.g/L. hi May 2011, the average reduction
in the concentration of c/s-l,2-DCE within
the bioreactor was 90% relative to the
influent concentration, and average
concentrations of VC relative to the influent
concentration remained stable. These data
potentially indicate that biogeochemical
degradation may be occurring because
abiotic degradation of TCE generally does
not produce intermediate dechlorination
compounds. Samples of bioreactor material
are currently being analyzed for mineral
content to evaluate the formation of iron
sulfide minerals.
Similar to other anaerobic bioremediation
applications, the Landfill 3 bioreactor's
effectiveness is expected to depend on
longevity of the organic substrate and
maintenance of highly anaerobic
conditions conducive to degradation of
chlorinated VOCs. The 2010 EVO
injection was designed to sustain the
desired biogeochemical conditions for a
minimum of 12-18 months-sufficient
time to facilitate and sustain formation
of reactive iron-sulfide minerals.
The cost of amendment injections
totaled approximately $30,000, including
material and shipping costs of $7,300
for the EVO product and $4,900 for the
iron and sulfate amendment. Between
January 2010 when the bioreactor
recirculation pump was replaced and
May 2011, approximately 450,000
gallons of water were recirculated
through the bioreactor. The final data from
this pilot-scale demonstration will be
combined with results from AFCEE
demonstration projects being conducted
at other Air Force bases to assess
whether amendment injection to enhance
abiotic biogeochemical transformation of
VOCs is a technically viable and cost-
effective approach. AFCEE anticipates
release of a final cost and performance
report in early 2012.
Contributed by Doris Anders, Ph.D.,
U.S. Army Environmental Command,
(doris.anders(a)us.armv.mil). J. Seb
Gillette, Ph.D., AFCEE
(John, sillette. 1 (a)us. af.mil or 210-395-
8440), John Hicks and Bruce Henry,
Parsons (iohn.hicks(a)parsons.com or 303-
764-1941)
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[continued from page 2]
2005-2008 decision documents, one or
more of five treatment technologies
were involved in nearly 98% of the in
situ remedial projects for contaminated
groundwater (Figure 1). For more
information about the cleanup trends and
EPA observations, see the Superfund
Remedy Report (13th edition, September
2010; EPA-542-R-10-004), available at
www.clu-in.org/asr.
Permeable
Reactive Barrier
Air Sparging
Phytoremediation
Figure 1. Of the five most
technologies for
groundwater treatment
projects, bioremediation and
chemical treatment
accounted for approximately
51% and 31%, respectively.
Sediment Cleanup Remedy for Lower Fox River Reaches 25% Construction Completion
Addressing sediment containing
polychlorinated biphenyls (PCBs) in a
39-mile stretch of the Lower Fox
River near Green Bay, WI, has
involved an integrated approach of
dredging, multiple cap designs, and
natural recovery [see October 2008
TNT]. This approach has been used
since 2008 to accommodate varying
depths and concentrations of
contaminants as well as restrictive
site conditions such as in-water
navigational structures, steep
shorelines, and nearby commercial
facilities. Project design calls for
capping a total of 880 acres and
dredging approximately 4 million yd3
of contaminated sediment, the largest
sediment remediation project in the
United States. Cleanup was achieved
at one of the site's five operable units
(OUs) in 2009, and completion at
another OU is expected later this year,
based on a site-specific cleanup goal
of 1 ppm and a surface weighted
average concentration goal of 0.25 ppm.
Since dredging began in 2004,
EPA Region 5 and the Wisconsin
Department of Natural Resources
(WDNR) have worked with cleanup
contractors to explore ways to
streamline field operations and
improve dredging efficiency. One
significant improvement was the
integration of a global positioning
system (GPS) with the relatively small
(2-foot) cutterhead used for high
production dredging (Figure 2). Use of
this precision tool helped assure
dredging of the targeted sediment with
PCB concentrations exceeding 1 ppm.
Another improvement involved
introduction of a supplemental, 8-inch
hydraulic dredge equipped with a Vic-
Vac™ suction dredge head. Focusing
this smaller dredging unit on the
sediment that remained after cutterhead
pass-through was found to be more
efficient in dredging areas with thin
layers of PCB-contaminated sediment
overlaying hard-pan clay. To reduce use
of petroleum products in the field and
associated toxicity in the event of spills,
vegetable oil-based hydraulic fluids are
now used routinely in the dredging and
auxiliary equipment.
Implementation of these methods led
to larger dredging volumes of the
targeted sediment; approximately
620,000 yd3 were dredged in 2009 and
740,000 yd3 in 2010. Sediment with
PCB concentrations exceeding the 1
ppm threshold but less than 50 ppm
were transferred to a hazardous waste
management facility located 30 miles
from the site. A relatively small
sediment volume (less than 5% of the
total) with PCB concentrations of 50
ppm or more will be transferred to a
TSCA-approved disposal facility
(regulated by EPA under the Toxic
[continued on page 4]
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[continued from page 3]
Substances Control Act) located several
hundred miles away in Michigan.
Cap construction based on three
primary design configurations has
been completed on 290 acres of
contaminated sediment, about 33% of
the total required. In OU1, where
capping was completed in 2009, a
total of 221 acres were capped with
an average 12-inch-thick layer of
mixed sand and gravel. At an
additional 37 acres of OU1 where
dredging had occurred but residual
contamination remained, selected
areas were covered with 3-9 inches
of clean sand.
Long-term monitoring of areas
achieving the cleanup goals began in
early 2010, with a focus on
quantifying risk reduction in fish and
surface water as well as sediment.
Monitoring results at OU1 show that
PCB concentrations in tissue of
walleye as the primary ecological
indicator species had decreased 73%
when compared to the 1990-2003
baseline, at which time 3 of 79 walleye
(4%) exhibited concentrations below
0.05 ppm. In 2010, 24 of 27 walleye
(89%) from OU1 had concentrations
less than 0.05 ppm, resulting in an
average PCB concentration of 0.03 ppm.
Monthly analysis of the OU1 water
column during 2010 showed a PCB
concentration substantially lower than
pre-remedial (1998) concentrations.
Even greater PCB reductions were
observed when compared to the 5-9 ng/L
range measured in 2007, when dredging
had already begun; as with most
contaminated sediment dredging
projects, the contaminant concentrations
temporarily increased due to water
turbulence. Additionally, OU1 sediment
surface samples indicated an average
PCB concentration of 0.25 ppm,
substantially lower than the pre-
remedial (1998) concentrations.
Similar monitoring steps will be
conducted at each capped area
approximately two years and four
years after construction completion
and every five years thereafter until
cleanup goals are achieved. Based on
the past three years of progress, EPA
Region 5 anticipates completion of cap
construction and sediment dredging in
2017. To date, project costs total over
$300 million, including dredging,
dewatering, waste disposal, and cap
installation.
Contributed by Jim Hahnenberg, EPA
Region 5 (hahnenberg.iames(a)epa. gov
or 312-353-4213)
EZVI Injection Field Test Leads to Pilot-Scale Application
Testing and monitoring of emulsified
zero-valent iron™ (EZVI) injections
were conducted at Cape Canaveral
Air Force Station's Launch Complex
34, FL, from 2002 to 2005 to evaluate
the technology's efficacy in enhancing
reductive dechlorination by increased
dissolution of dense nonaqueous-phase
liquid (DNAPL) [see September 2005
TNT]. Results from the small field test
showed an average 71% reduction of
TCE concentrations in groundwater
wells (at a depth of approximately 8
meters bgs) and a 56% reduction in
mass flux. Later in 2005, findings
from the field test were used to begin
a pilot-scale demonstration at the
Marine Corps Recruit Depot in Parris
Island, SC, with a focus on
differentiating the technology's
degradation mechanisms and improving
substrate delivery methods.
As originally developed by the National
Aeronautics and Space Administration
(NASA), EZVI consists of food-grade
surfactant, biodegradable vegetable oil.
water, and nano- or micro-scale iron that
are mixed onsite. The technology relies
on presence of the water and oil to
increase contact between the ZVI
particles and DNAPL and consequently
dissolve chlorinated VOCs. This increased
dissolution of sorbed or trapped DNAPL
allows enhanced reductive dechlorination
to proceed. In addition, the ZVI's
vegetable oil and surfactant components
serve as long-term electron donors for
anaerobic biodegradation.
The pilot-scale demonstration was
conducted at the Depot's Site 45, where
earlier investigations revealed the
presence of source-zone tetrachloroethene
(PCE) DNAPL. Concentrations of the
chlorinated daughter products TCE, cis-
DCE, and VC in the same wells were as
high as 160 mg/L, 180 mg/L, and 13
mg/L, respectively.
The two EZVI delivery methods
found to be most effective in the
Cape Canaveral field test were
evaluated in two side-by-side plots
at Site 45: pneumatic injection using
nitrogen gas to fracture the
subsurface, and direct injection using
a direct-push rig. In the pneumatic
injection plot, which encompassed
51 m3, a total of 2,180 liters of EZVI
containing 225 kg of iron, 856 kg
of corn oil, and 22.5 kg of
surfactant were injected to treat an
estimated 38 kg of VOCs (of which
roughly 38% is attributed to DNAPL).
The EZVI was injected using a
bottom-up injection procedure in
eight locations between 2.13 and
5.64 meters bgs. Approximately 121
liters of EZVI "daylighted" by
migrating up the area's former
investigation borings to the ground
surface.
[continued on page 5]
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[continued from page 4]
In the adjacent 11-m3 plot, 572 liters
of EZVI containing 59 kg of iron, 225
kg of corn oil, and 5.9 kg of
surfactant were directly injected into
four locations at depths of 1.83-3.66
meters, to treat an estimated 155 g
of VOCs. Approximately 19 liters of
injected EZVI daylighted during
injection. Both delivery methods
involved EZVI containing iron in the
form of nano-scale particles.
Based on visual observation of soil
cores at 17 test plot locations.
pneumatic injection achieved a 2.1-
meter radius of influence (ROI).
while direct injection reached a
smaller ROI of 0.89 meters. The
cores also suggested that EZVI in
both plots was not as evenly
distributed throughout the target
treatment interval as desired, likely
due to viscous fingering of the
DNAPL or preferential flow paths.
Results suggest that pneumatic
injection may be well suited to a
relatively large source zone (with a
high volume of contaminants), while
direct injection may be better suited
to a smaller source zone.
Sampling of downgradient wells
2.5 years after injection indicated
that decreased PCE and TCE
concentrations highly correlated to
increases in degradation products
including ethene (Figure 3). Nine test-
plot soil cores collected from ground
surface to a depth of 6.1 meters bgs
were used to evaluate VOC mass
distribution, and measurements of
soil porosity, bulk density, and the
fraction of organic carbon were
performed on selected soil samples
to refine the VOC mass estimates. By
March 2009, total VOC mass in the
pneumatic injection plot had
decreased approximately 86%, from
the estimated 38 kg to 5 kg. Based
on soil and groundwater sample
analyses, treatment resulted in an
200 400 600 800 1000
Days Since June 1, 2006, Baseline Monitoring
1200
Figure 3. VOC concentrations in groundwater of one representative
monitoring well at Site 45 illustrate the typical spike in PCE and TCE
degradation products (cis-DCE and VC) that occurred after EZVI
treatment concentrations. Increasing generation of methane
(degradation of EZVI) and ethene (degradation of cis-DCE) over the
same nenoc
degradation rather than dissolution or migration.
estimated 63% reduction in the sorbed
and dissolved phases and 93% reduction
in the PCE DNAPL mass. Integral
pump tests in downgradient wells and
groundwater sampling along multilevel
transects for the pneumatic injection
pilot showed that mass flux decreased
more than 85% for both PCE and TCE
and significantly increased (145-
2,271%) for ethene.
VOC degradation via biological
processes was suggested by significant
increases in dissolved sulfide, volatile
fatty acids, and total organic carbon.
Concurrently, significant decreases in
dissolved sulfate and pH were
observed. Dissolved oxygen levels
remained below 2 mg/L prior to and
after injection. Although microbial
analysis was not performed for the
source area, earlier study at another
Site 45 groundwater plume area with
similar lithology and hydrology
revealed the presence of microbes
(Dehalococcoides sp.) known to
degrade cis-DCE and VC to ethene.
A more recent (2010) microcosm
study conducted jointly by Nankai
University, Rice University, and
Carnegie Mellon University shows no
deleterious effect of nano-scale ZVI
on the abundance of bacterial species
such as Dehalococcoides.
Ongoing work includes evaluating
transformation and mobility of the
[continued on page 6]
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-11-003
July 2011
Issue No. 54
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
[continuedfrom page 5]
injected nano-scale ZVI through
analysis of solids sampled from
monitoring wells and from long-term
monitoring of soil cores. A variety of
analytical methods such as x-ray
diffraction and x-ray absorption
spectroscopy are being used to
determine the presence of associated
corrosion products, as an indicator of
the material's toxicity to ecosystems.
Purchasing costs for the nano-scale
iron used at Site 45 totaled
approximately $14,000, at a unit cost
of $28/pound from a Japanese
vendor. Additional detail about cost and
other aspects of the demonstration.
which was funded by EPA and the U.S.
Department of Defense ESTCP, is
available in the September 2010
ESTCP Cost and Performance
Report: Emulsified Zero-Valent
Nano-Scale Iron Treatment of
Chlorinated Solvent DNAPL Source
Areas (ER-200431). The report
includes a cost model and description
of potential cost drivers for other
sites, along with a summary of
implementation issues, advantages.
and limitations of the technology.
Contributed by Chunming Su, Ph.D.,
EPA National Risk Management
Research Laboratory
(su. chunming(a),epa.gov or 580-
436-8638) and Jacqueline Quinn,
NASA Kennedy Space Center
(Jacqueline, w. quinn(q),nasa. gov or
321-867-8410)
Contact Us
Technology News and Trends
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Suggestions for articles may
be submitted to:
JohnQuander
Office of Superfund Remediation
and Technology Innovation
U.S. Environmental Protection Agency
Phone:703-603-7198
quander.iohn@.epa.qov
Innovative Examples
EPA's Technology Innovation and
Field Services Division continues to
build a series of databases with
project profiles on topics such as
alternative landfill covers,
phytotechnology, chemical oxidation,
nanotechnology, and Triad. Access
the online site-specific profiles at:
www.clu-in.org/databases/.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative characterization and treatment
techniques or technologies. The Agency does not endorse specific technology vendors.
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