5
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/A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Issue 49
of Techno logy News and Trends describes selected field applications of new
materials, advanced equipment, and various material dispersion methods for treating con-
taminated soil and groundwater.
August 2010
Argonne National Laboratory Examines an Integrated Carbon and
ZVI Source for In Situ Chemical Reduction
The U.S. Department of Energy's Argonne
National Laboratory initiated a field study in
late 2007 at a former grain storage facility
near Centralia, KS, to evaluate the efficacy
of combining carbon and micro-scale zero
valent iron (ZVI) filings in a single injection
material to achieve in situ chemical reduction
(ISCR) of volatile organic compounds
(VOCs). The study examined the material's
ability to remediate subsurface soil and a
shallow groundwater plume hotspot, the
impacts of heterogenous geology on
treatment, and optimal methods for delivering
the carbon/ZVI material. Concentrations of
carbon tetrachloride (CT), as the primary
contaminant of concern, have decreased more
than 99% in groundwater within most of the
study area as a result of ISCR treatment.
The U.S. Department of Agriculture's
Commodity Credit Corporation (USDA/CCC)
used CT as grain fumigant at this facility
from 1949 until 1971, when the facility
was decommissioned. Elevated CT
concentrations were discovered during
Argonne's 2002-2004 site investigation,
which was triggered by detection of CT at a
local private well by the Kansas Department
of Health and Environment as part of the
USDA/CCC Private Well Sampling
Program. Argonne's site investigation and
2005-2006 monitoring, on behalf of
USDA/CCC, revealed CT concentrations
of 202-219 ng/kg in source-area vadose
zone soil at depths of 30-40 feet below
ground surface (bgs) and 221-1,138 ug/L in
three groundwater hotspots in and near the
source area. The groundwater plume is
restricted to a single, vertically and laterally
heterogenous shallow aquifer located 40-60
feet bgs and with a groundwater flow
averaging less than 0.06 ft/day.
A 45- by 75-foot treatment area was
established in the vicinity of the hot spot with
highest CT concentrations, and 15 injection
points were installed across the area at 15-
foot spacing. To establish a pre-injection
baseline, vertical-profile soil coring and VOC
sampling were conducted at 4- to 40-foot
depths in four locations of the test area. Soil
sampling indicated CT concentrations
exceeded 100 ug/kg at two locations in close
proximity within an upgradient corner of the
test area. Baseline groundwater sampling was
conducted at nine locations within and
surrounding the target test area.
Sampling results indicated that CT
was heterogeneously distributed with
concentrations ranging from 16 ug/L to
1,285 ug/L within the proposed test area. In
addition, a high concentration of CT (up to
2,646 Hg/L) was identified in an area
downgradient of the proposed injection
locations. The injection points were adjusted
accordingly to maximize coverage of CT
contaminated zones. Baseline concentrations
of chloroform (CF), as a byproduct of CT
degradation, were generally less than 104 ug/L.
A high ratio of CF to CT was assumed to
indicate CT reductive degradation processes.
Injections were performed from November
26 through December 5,2007, using a direct-
push rig to achieve a minimum pressure of
[continued on page 2]
Contents
Argonne National
Laboratory
Examines an
Integrated Carbon
and ZVI Source for
In Situ Chemical
Reduction page 1
Combined
Cryogenic
Compression and
Condensation
Process Used for
Hydrocarbon
Recovery page 3
Ohio EPA Tests
TCE Reduction
Capacity of
Nanoscale
Metal-Silica Hybrid
Materials page 4
Sustainable
Remediation
Conference page 6
CLU-IN Resources
The Nanotechnology
issue area of CLU-IN lists
resources on field results,
potential applications, and
human health or environ-
mental considerations
concerning the use of
nanoscale particles and
materials for site remediation.
Learn more or suggest
additional resources through:
www.clu-in.org/issues.
Recycled/Recyclable
Printed with Spy^anola Ink 01 paper ll
contains at least 50% recycled fiber
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[continued from page 1]
300 psi. To reach different areas of the
treatment zone, the carbon and ZVI were
administered in two forms: (1) a fine-
grained solid slurry; and (2) a liquid
formulated as aqueous solution containing
soluble food-grade organic carbon and
dissolved iron.
To treat vadose zone soil at depths of 20
to 40 feet bgs, the carbon and ZVI
material was injected as a fluid at seven
injection points. A total of 3,650 pounds
of liquid material diluted with water (at a
ratio of 11:89) was delivered. At these
seven points, a total mass of 1,300 pounds
of the solid carbon/ZVI was administered
as thin slurry (14%) to reach depths of
40-50 feet bgs.
Delivery of the material in both liquid and
solid forms helped assure sufficient
distribution in a vadose zone target area
encompassing approximately 18,000 ft3 of
low permeability soil. The saturated zone
was treated through injection of a thicker
20% carbon/ZVI slurry targeting
approximately 67,500 ft3; a total of 5,300
pounds of carbon/ZVI was injected at 14
points to depths of 50-60 feet.
Injected fluid emergence with no apparent
pattern was observed at ground surface
and in pre-existing borings at distances
ranging from less than 1 foot to more
than 25 feet from the source injection
point. This day lighting indicated probable
movement of the fluids/slurry along
preferred vertical and lateral migration
pathways within the subsurface, indicating
heterogeneous lithologic conditions that
could possibly limit uniform delivery.
To validate injection, direct-push soil
coring was conducted within two
weeks after the last injection.
Continuous cores were collected to
depths of 2-60 feet bgs at 3, 5, and 11
feet from the injection point with the
highest CT concentrations in soil prior to
treatment. Residual carbon/ZVI slurry was
observed in some core intervals.
To further evaluate reductive reaction in
vadose zone soil, vertical-profile soil
sampling for VOC analysis was conducted
nine months later at 2-foot intervals
adjacent to the pre-injection, vertical-profile
sampling location with the highest pre-
injection concentration in soil. The results
demonstrated almost complete removal of
CT in the top 33 feet of vadose zone soil,
where concentrations had declined from
219 ng/kg to below 6.3 ng/kg. In the
remaining lower 7 feet of the vadose zone,
near or in the capillary zone above the
shallow aquifer, CT had decreased from
122 ng/kg to less than 62 ng/kg.
Early post-injection groundwater sampling
was conducted at nine additional monitoring
wells installed shortly thereafter. Sample
results showed a 96-99% reduction in CT
concentrations in the treatment area within
one month of the injections, with the
exception of two wells at the edge of the
treatment area. A 20-70% reduction was
observed at most sampling points within
90 feet of the 45- by 75-foot test area.
Changes in dissolved oxygen (DO) and
oxidation reductionpotential (ORP) in most
of the treatment area over time indicted
that ISCR by way of the carbon/ZVI
injections produced extremely reducing,
oxygen-depleted conditions in groundwater.
Within one month after the injections,
DO levels decreased from a pre-injection
concentration of 2.9-83 mg/L to below
1 mg/L and ORP decreased from
approximately -70 mV to less than -500
mV A less reduced environment in one
portion of the test area, with DO levels
greater than 1 mg/L and ORP of -189 to
-222 my may be attributed to the presence
of a pre-existing well that provided
preferential conduits for the injection
fluids, consequently interfering with
localized distribution of the injected material.
Test-area groundwater monitoring for
VOCs was conducted at quarterly
intervals until 2008 and semi-annually
thereafter. CT transformation appeared
to occur most quickly in the initial period
of reductive reaction and was followed
by gradual decline of accumulated CF
(Figure 1). Consistent results at all
injection-area monitoring locations
suggested that carbon/ZVI material
delivery was sufficient for treatment
within the injection area at the selected
injection spacing, despite heterogeneity
in lithology and CT distribution.
Different CT changes were observed at
the edge of the injection area afterthe initial
spike in CT transformation (Figure 2). In
the five-month post-injection monitoring
event, CT concentrations had increased
while CF concentrations continued to
decrease, which indicated that material
delivery may have been insufficient to
quickly reach all edges of the plume.
Monitoring results from September 2008
to April 2010 indicate that the plume has
slowly reacted, likely due to ongoing
biological reductive dechlorination.
[continued on page 3]
2,500
0) 2,000
1,500
ou 1,000
500
750
600
450
300
150
,0
o
_o
6
Figure 1.
Representative
sampling results
from groundwater
in the injection
area indicated CT
degradation and
CF accumulation
began immediately
Oct 07 Mar 08 Aug 08 Jan 09 Jun 09 Nov 09 Apr 10
Sampling Date
injection at the
Centralia site.
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3,500
edge of injection area
Oct 07 Mar 08 Aug 08 Jan 09 Jun 09 Nov 09 Apr
Sampling Date
o
10
Figure 2. High CT concentrations and low CF concentrations in representative
samples from groundwater at the edge of the injection zone suggested that
outer portions of the plume were untreated.
[continued from page 2]
To evaluate long-term effectiveness of the
ISCR treatment, groundwater sampling
will continue on a semi-annual or annual
basis. Pending Argonne's completed
evaluation, the USD A/CCC will determine
if this technology will be applied in full-
scale remediation at the Centralia site or
other USD A/CCC sites.
Contributed by Eugene Yan, PhD
(eyan&anl.gov or 630-252-6322)
and Lorraine LaFreniere, PhD
(lafreniere(q).anl.gov or 630-252-7969),
Argonne National Laboratory, and
Caroline Roe, USDA/CCC
(caroline.roe(q)M>dc.usda.gov or
202-720-9964)
Combined Cryogenic Compression and Condensation Process Used for Hydrocarbon Recovery
EPA Region 6 is implementing an
innovative technology to collect and
condense vapor from soil vapor extraction
(SVE) and air stripping systems used to
treat contaminated groundwater at the
State Road 114 Superfund site in
Levelland, TX. The technology uses
cryogenic compression and condensation
equipment to recover contaminant vapor
as a liquid for potential recycling or
resale. Since startup of groundwater
treatment in August 2009, project
revenue gained by resale of recovered
hydrocarbon has offset nearly 70% of
the SVE system's electricity costs.
The State Road 114 site encompasses a
former 64-acre refinery where liquid
wastes were disposed in unlined pits and
commingled processing materials were
spilled between 1939 and 1954. The
Texas Department of Health detected
1,2-dichloroethane (1,2-DCA) in 1990
while collecting samples from a well
now operated by an onsite farmers
co-operative. Investigations identified a
1.2-mile groundwater plume and
approximately 717,000 ft2 of light non-
aqueous phase liquid (LNAPL) with a
median thickness of 0.5 feet. Contamination
extends to 28 Ogallala Aquifer wells used
for residential, public water supply, and
commercial purposes.
Cleanup goals were set at the maximum
contaminant level (MCL) of 5 |j,g/L for
both DCA and benzene in drinking water.
170 |j,g/L for vanadium, and 10 [ig/L for
arsenic. Initial cleanup work involved
extending municipal water supply lines
to affected residences and businesses
and excavating 3,600 yd3 of contaminated
soil followed by onsite waste burial.
Designs for the groundwater treatment
system included the cryogenic
compression and condensation equipment
as a means to collect and condense
offgas from both the SVE well network
and air stripping system. The —
cryogenic process relies on
regenerative adsorption to
recover VOCs as hydrocarbon
material (re-condensation
vapors) that is immediately stored in
two 6,500-gallon fiberglass-reinforced
polyethylene tanks (Figure 3) and
subsequently polished by filtration
through granular activated carbon
(GAC). A fuel tanker transports the
recovered hydrocarbon to a fuel facility
where it is mixed with oil blend stock to
produce a low-grade fuel (similar to
gasoline) ultimately traded as a
commodity on the open market.
The groundwater extraction and
restoration system includes 21 onsite
and offsite extraction wells, 4 wells
for injection of treated water, and 62
SVE wells for preventing or minimizing
further migration of contaminants
[continued on page 4]
Figure 3. Cryogenic equipment, a
zeolite wheel concentrator, and
LNAPL storage tanks are staged
adjacent to the State Road 114
treatment plant.
'In;
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[continued from page 3] substrate that is permanently bonded
from the contaminant source, including with a mix of hydrophobic zeolite and
LNAPLs. Upon extraction, groundwater other inorganic compounds capable of
is pumped through arsenic and adsorbing VOCs from the effluent air
manganese treatment units with stream. The concentrator turns several
chemical metering systems for metal revolutions per hour, transporting VOC-
flocculation. The process stream is laden zeolite into the regeneration zone
then directed through two filter media and returning regenerated zeolite to the
vessels to two air stripping units, where surface for continued VOC adsorbtion.
chemical feed pumps equipped with an The selected zeolite wheel concentrator
injection quill and static mixer add an can handle a capacity of 2,600-7,000
anti-scaling agent to the stream. A scfm of VOC-laden air.
defoaming agent also is added to reduce
. , . Sequential steps in the cryogenic
foam within the air strippers.
collection/condensation process involve:
The air stripping system consists of (1) drawing the soil gas and delivering it
two 6-tray,400-gpm units operating in to the air compressor through use of
parallel at a total rate of 400 gpm. Each positive displacement blowers; (2)
unit consists of a skid-mounted separating entrained liquids at a water
stripping tower, a 30-hp fan blower for knockout tank from which the liquids are
aeration, and a 7.5-hp centrifugal diverted to the groundwater treatment
discharge pump. Before discharge to system; (3) compressing process air to
the atmosphere, air stripping off-gas is approximately 150 psi; (4) removing water
treated by a zeolite wheel concentrator vapor from the process stream at air-to-
rotor. The zeolite wheel concentrator air heat exchangers that cool the vapor
uses a corrugated mineral fiber stream to approximately 40°F; (5)
Revenue from Hydrocarbon Recovery vs. SVE System Electricity Consumption
$64,786B
$53,520^^
$46,72^ ,,$44,5,7
E 'IU,UUU -7* T^^ZrfqRq
| $36,157*^ £222— -+WW
Q 30000 *^ --^$3*^18
$27,022 a^ ..^-^128,1 30
's' ^4*1)24,885
1QOOO ^— $21.490
$18,331 .•'^--*r$ 18,929
Xjrm554
1«™ -
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[continued from page 4]
EPA investigations discovered a 2,600-
by 1,600-ft groundwater plume of
trichloroethene (TCE) and its breakdown
products, c/s-l,2-dichloroethene and vinyl
chloride. In the vicinity of past industrial
operations, the TCE concentration reached
a high of 1,500 |J,g/L. The plume is located
approximately 60-120 feet below ground
surface (bgs) in a sand and gravel aquifer
with a groundwater flow rate of 0.5 ft/day.
Earlier laboratory testing at the College
of Wooster, OH, indicated that the
silica-based material would absorb and
expand like a sponge when coming into
contact with hydrophobic materials,
including TCE and its degradation
products, while excluding water, salts,
and non-toxic metals. By adding
nanoscale iron to the silica material,
absorbed TCE molecules within the
swollen matrix are degraded through
reductive dechlorination to ethane gas
and chloride ions that are expelled from
the silica matrix as benign materials.
The swelling and dechlorination process
continues as the natural flow of
groundwater brings additional TCE into
contact with the reactive matrix.
Laboratory tests also indicated 1 kg of the
silica complex embedded with nanoscale
iron could reduce 30-56 kg of TCE prior
to exhaustion of the reactive nanomaterials,
depending on concentration loads and flow
rates. Longitudinal studies determined the
silica matrix to be a stable material that
created no hazardous products, and soil
tests showed no evidence of its interference
with soil composition or plant growth.
The first injection at Penn-Michigan was
performed on July 21, 2009, through use
of a direct push rig. Due to its high
hydrophobicity, the iron-silica matrix
was injected in a sodium lauryl sulfate
slurry to facilitate uniform distribution
across a target radius of 15 feet. A total of
12 kg of the fine (200-3 50 mesh) powder
was injected in one borehole at depths
of 59, 64, and 69 feet bgs upgradient of
an area of groundwater contamination with
TCE concentrations ranging from 300 to
1,000 ng/L.
A fluorescent tracer was embedded in some
of the silica-based material and injected
concurrently with the iron-silica material in
order to monitor the travel distance of the
slurry across the test area. Post injection soil
sampling indicated the slurry had traveled
farther than the desired 15-foot radius, as
evidenced by tracer material in soil 24 feet
downgradientof the injection location. Eight
soil borings within the test area indicated the
matrix slurry had dispersed to an area larger
than anticipated, spreading to a total volume of
52,000 ft3 instead of the targeted 14,000 ft3.
Groundwater was sampled over two months
at six monitoring wells surrounding the
injection point at distances of 7-15 feet.
Results one month after the injection
showed TCE concentrations 10-90% lower
than pre-injection concentrations. Seven
months later, groundwater sampling at four
of the six wells showed TCE concentrations
had rebounded slightly, with TCE
concentration reductions varying from 0 to
61%. The absence of TCE degradation
products in groundwater suggested that
TCE was fully degraded by the iron-silica
matrix. Offsite groundwater sampling 21
feet downgradient of the injection site
showed a TCE concentration of 597 |J,g/L,
a 40% reduction from the initial 1,000 |j.g/L.
The data suggest that the temporary TCE
rebound was caused by 3 inches of
Figure 5. During the second phase of
injection testing at Penn-Michigan,
approximately 15 gallons of silica slurry
was administered over 12 hours.
rainfall that occurred between August
20th and September 3rd. The presence
of iron that had not completely reacted
with contaminants within the silica
complex allowed the TCE reduction
process to continue.
A second injection was administered in
January 2010 to test an alternate
formulation of nanometals, at a separate
onsite location with TCE concentrations
of 250-620 ng/L (Figure 5). The injectant
consisted of 27 kg of nanoscale material
consisting of 10% iron (%w/w) and
0.3-1% palladium (%w/w) embedded in
the silica matrix. Test-area groundwater
sampling in April yielded TCE
concentrations of 200-500 \ig/L, a 20-
50% reduction from pre-injection levels.
Overall results indicated the palladium
formula performed comparably to the
earlier iron-based media.
Results from both phases of Ohio EPA's
field test suggested that delivery of
material to the target zone was a limiting
factor in implementation of this
innovative technology (Figure 6). Due to
its hydrophobic nature, the material did
not easily distribute throughout the aquifer.
The cost of iron-silica material for the first
injection was approximately $18,000, and
slightly higher material costs were incurred
for the palladium formula used in the
second injection. Ohio EPA and vendor
demonstration funds for monitoring,
direct-push, and laboratory work were
supplemented by an advanced
engineering award the vendor received
from the National Science Foundation.
A third trial was initiated by the vendor in
late July 2010, using a newly developed
injection probe. The probe is approximately
6 feet in length (in contrast to the 14-inch
probe previously used) and contains
[continued on page 6]
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-10-004
August 2010
Issue No. 49
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
5 400
Onsite Historical TCE Average
Concentration: 1,180 ug/L
Distance from
Injection Point
Figure 6. Lower rates of TCE reduction over recent months suggest
that replenishment of the iron-silica material is warranted.
[continued from page 5]
additional injection holes to facilitate
more even distribution of the silica-
based material. The trial also involved
injection of a higher volume (57 kg) of
material to blanket the treatment area
more thoroughly. If results of the latest
trial are successful, Ohio EPA will
evaluate this technology in late 2010 to
determine its full-scale potential at the
Perm-Michigan site.
Contributed by Chris Osborne, Ohio EPA
(chris. osborne(q)epa. state, oh. us or 740-
380-5258), Paul Edmiston, PhD, College
ofWooster (pedmiston&wooster. edu or
330-263-2113), and Deanna Pickett, ABS
Materials (d.pickett@absmaterials.com or
614-257-8943)
Contact Us
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Sustainable Remediation Conference
The University of Massachusetts Amherst
andU.S. EPA will hold the International
Conference on Sustainable Remediation
2011: State of the Practice on June 1-3,
2011, in Amherst, MA. Presentation
abstracts may be submitted by
November 1, 2010, at: www.umass.edu/
tei/conferences/SustainableRemediation/.
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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