rfCH TRENDS
Ground Water Currants
A newsletter about soil, sediment, and ground-water characterization and remediation technologies
January 2003
Issue 4
Complexing Sugar Removes DNAPL from Aquifer
The U.S. Department of Defense recently
completed a field demonstration using
cyclodextrin, a corn starch-based sugar, to
enhance in-situ removal of dense non-aqueous
phase liquid (DNAPL) at the Naval Amphibious
Base Little Creek (NABLC) in Virginia Beach,
VA. The primary objective of the demonstration
was to determine whethertrichloroethene (TCE)
could be separated from the cyclodextrin
solution above ground, and if the solution could
be reconcentrated to reduce treatment costs.
(The cyclodextrin molecule forms a weak complex
with contaminants such as TCE, thereby
increasing contaminant solubility and removal
efficiency.) Cyclodextrin solution was injected
directly into a TCE-contaminated aquifer. Air
stripping of the extracted cyclodextrin solution
produced an effluent containing TCE
concentrations 99% lower than initial
concentrations and below the maximum
contaminant level (5 ug/L).
An underground neutralization tank and soil
containing DNAPL (primarily TCE) had been
removed near a former plating facility at NABLC
in 1995. Follow-up site investigations revealed
residual DNAPL below the excavation limit, in a
trough approximately 7 mbelow ground surface.
The area comprises a shallow, sandy,
unconfined aquifer underlain by alayer of low-
permeability marine clay. The hydraulic gradient
is shallow, with an average ground-water flow
velocity close to 0.3 m/day.
Pre-treatment sampling indicated an average
aqueous TCE concentration of 15 mg/L. Based
on the screen length, nature of the source zone
area, and porosity of the sandy aquifer, the
treatment zone was estimated to contain
approximately 9,000 liters of water. Based on
preliminary partition tracer test data, 0.5-1%
of this volume consisted of DNAPL.
Eight 4-in wells were installed at NABLC in
orwithinS m of the source zone to depths of
7.5-8 m. Each well reached the uppermost
portion of the clay layer and was screened
across the bottom 1.5 m of the aquifer. This
relatively short screened interval permitted
a focused delivery of cyclodextrin solution
to the lowest, most contaminated part of the
aquifer. The treatment system flushed one
pore volume (P V) of solution (approximately
9,000 liters) per day.
A "line drive" flushing system was initiated
in July 2002 to inject one PV of a 20%
cyclodextrin solution (1,800 kg) into two to
four wells. After passing through the source
zone, the solution was extracted from one to
three downgradient wells, treated, and
reinjected. The distance between injection
and extraction wells ranged from 3 to 6 m.
The initial (combined) flow rate was 6.25
L/min, but the rate decreased sharply over
the first eight days of operation. This
reduction resulted from the mixing of injected
aerated water with anaerobic subsurface
water, which caused ironfouling and ultimate
well clogging. The reduced flow rate did not
allow for sufficient hydraulic control of the
flow field, thereby decreasing cyclodextrin
recovery efficiency and contributing to
dilution of the flushing solution.
The treatment scheme was modified to
employ a multiple-well "push-pull" system.
This method involved cyclodextrin injection
into three wells within the DNAPL source
[continued on page 2]
Contents
Complexing Sugar
Removes DNAPL
from Aquifer page 1
Chitin/Fracturing Used
to Stimulate Microbial
Degradation of
Chlorinated Solvents page 2
Field Tests Conducted
on Use of Potassium
Permangante for In-Situ
Oxidation page 4
Co-Oxidation Used to
Remove PCE DNAPL at
Drycleaner Site page 5
Update on the State
Coalition for
Remediation of
Drycleaners page 6
This Issue Highlights.
...pilot tests that inject various
additives to remediate
contaminated ground water
through in situ-chemical
oxidation, co-oxidation, and
bioremediation.
O*K fl; .:-vP...rv:in":-
fatMM m mtm a~i -*\imi^^
-------
[continued from page 1]
zone. After all cyclodextrin solution was
injected, it was extracted through the same
wells, treated through air stripping, and
stored in commercial holding tanks. The
recovered solution, which contained an
average of 11% cyclodextrin, was used in
the next push-pull cycle by adding 40%
cyclodextrin stock solution to obtain the
appropriate volume of 20% flushing solution
Sampling data collected from a well during
the initial push-pull test (Figure 1) represent
similar results achieved during subsequent
tests involving varied pumping rates and well
constellations over longer durations. From
July through August, approximately 5 kg of
TCE were removed during three push-pull
tests.
Preliminary results indicate that
approximately 50% of the estimated DNAPL
volume in the subsurface was removed
during the demonstration. Onaper-flushing
volume basis, cyclodextrin enhanced
removal of DNAPL 9-12 times more
effectively than a (theoretical) conventional
pump and treat system. Direct field
comparison demonstrated that the push-pull
system outperformed the line drive system
by flushing 48% less cyclodextrin to remove
127% more TCE mass.
Project researchers estimate that the use of
cyclodextrinadds $2,000 - $4,000 perkilogram
of TCE removed through pump and treat
technology. Under the Environmental
Security Technology Certification Program,
which sponsored this demonstration, a
detailed cost and performance assessment
is being developed to compare this
technology with other innovative
technologies for remediating contaminated
ground water and soil.
Contributed by Thomas Boving,
University of Rhode Island/Department of
Geosciences (401-874-7053 or
boving@uri.edu) and Dawn Hayes, Naval
Facilities Engineering Command/
Atlantic Division (757-322-4792 or
hayesdm @efdlant. navfac. navy, mil)
1-4O
130-
• TCE Coned rtuacn
* TCE Mate Pwarwry
2W
Tims
Figure 1. TCE solubility achieved through
cyclodextrin treatment was enhanced 9- to 12-
fold at NABLC when compared to conventional
pump and treat technology.
Chitin/Fracturing Used to Stimulate Microbial Degradation
of Chlorinated Solvents
The National Science Foundation
sponsored a pilot-scale field test of
enhanced bioremediation at the Distler
Brickyard site near Louisville, KY, from
October 2001 to January 2002. The pilot test
technology combined the use of hydraulic
fracturing ("fracing") with anaerobic
bioremediation enhanced by the addition of
chitin, a solid, natural polymeric organic
material consisting of shrimp and crab shells.
The primary objectives of the field test were
to determine if fracing would enhance the
geologic formation's permeability and if the
addition of chitin would impact the aquifer's
geochemistry in ways conducive to
anaerobic reductive dechlorination (ARD).
Field data indicate that active ARD of
trichloroethene (TCE) continues to occur in
the treatment area as a result of chitin/
fracing.
As a result of past waste-handling activities.
ground water at the Distler Brickyard site
contains TCE and c/s-l,2-dichloroethene
(DCE) at concentrations reaching nearly 100
and 500 |J,g/L, respectively. The underlying
stratigraphy consists of approximately 40 ft
of silty-sand and silty-clay overlaying shale
bedrock. The ground-water table is
approximately 30 ft below ground surface
(bgs). Horizontal hydraulic conductivities
range from 10"8 to 10"4 cm/sec. Although
monitoring data indicate that natural
biodegradation via ARD was occurring, the
rate and extent of ARD reactions are limited
by a lack of sufficient electron donor and the
low permeability of the formation. Earlier
laboratory studies conducted by the
University of Illinois at Urbana/Champaign
(UIUC) demonstrated that chitin produces
volatile fatty acids (VFAs) shown to be high-
quality electron donors for ARD.
Hydraulic fracturing was conducted at the
Distler Brickyard through a single borehole
within the contaminant source area, near the
bedrock surface. By injecting sand slurry with
chitin, three sets of highly permeable fractures
were created in the borehole at depths of 25.
33, and 38 ftbgs. Approximately 250 gallons
of the (1:4 ratio) chitin/sand slurry were
[continued on page 3]
-------
[continued from page 2]
delivered into each frac. The borehole
subsequently was completed as a monitoring
well.
The hydrologic system evaluation included
tiltmeter monitoring to measure the
orientation of fractures, pre- and post-fracing
slug tests, and a pumping test. Results
indicated that tracing produced a network of
three permeable zones with a modeled
effective radius of 4 ft for the uppermost frac
(within the silt/sand unit) and 13 ft for the
two lowerfracs (within the silt/clay unit). As
anticipated, the extent of fracture
propagation depended upon the site's
lithology, degree of soil consolidation.
presence and orientation of bedding planes.
and presence of geologic heterogeneities.
Despite the heterogenous propagation of
fractures, the pumping test showed that all
four of the monitoring wells were in direct
hydraulic connection with the fracing well.
Ground-water sampling in the fracing well and
surrounding monitoring wells was conducted
to determine the effect of chitin emplacement
on the electron donor concentrations.
oxidation-reduction (redox) conditions, and
ARD. The breakdown of chitin as an electron
donor was measured by the production of
individual VFAs such as acetate, propionate.
isobutyrate, butyrate, isovalerate, and
formate. Monitoring well data showed that
the dominant VFAs produced from chitin
were acetate and butyrate, which reached
maximum concentrations of greater than 600
and 300 mg/L, respectively. Acetate
concentrations of greater than 200 mg/L
persisted in the treatment cell nine months
following chitin emplacement.
Pilot test results indicated that conditions
became more reducing following chitin
emplacement. Redox conditions were
assessed using concentrations of ferrous iron.
sulfate, and methane. Strong methanogenic
conditions, which are required for successful
ARD, were indicated by the increased
concentrations of methane and ferrous iron
and by the absence of sulfate. Ferrous iron
concentrations increased and sulfate dropped
within the first month after chitin emplacement.
indicating an immediate impact to redox
conditions. Methane concentrations began
increasing steadily approximately two months
after chitin emplacement and reached up to
12,000 ug/L withinnine months.
Concentrations of TCE and breakdown
products c/5-l,2-DCE, vinyl chloride, and
ethene were monitored to further evaluate the
ARD process (Figure 2). Data indicated an
initial decrease in c/5-l,2-DCE following chitin
emplacement, followed by a three-month
rebound. In contrast, ethene concentrations
initially increased but subsequently
decreased. (These trends may be attributed
to higher ground-water levels and dilution
effects.) After nine months, however, cis-1,2-
DCE concentrations dropped below detection
(5 |J,g/L), and a nearly stoichiometric increase
in ethene concentrations was observed.
These results indicate the persistence of ARD
reactions as long as nine months after chitin
emplacement. Overall concentrations of
chloroethene contaminants in the source
area decreased to or below maximum
contaminant levels (MCLs) in three of the
five wells within nine months. TCE and cis-
1,2-DCE concentrations in the remaining
wells decreased from a maximum of 59 ug/L
to 11 ug/L and 450 to 99 ug/L, respectively.
Region 4 of the U.S. EPA, which provided
analytical services and technical assistance.
estimates a cost of $ 140,000 for implementing
this pilot project. Full-scale application of
chitin/fracing technology at the Distler
Brickyard during 2003 will focus on
evaluating the technology's cost-
effectiveness, achieving adequate
distribution of chitin in-situ, and evaluating
the long-term performance of chitin as a
slow-release electron donor for ARD of
chloroethene contaminants in low-
permeability systems.
Contributed by Femi Akindele, EPA
Region 4 (404-562-8809 or
akindele.femi@epa.gov), Kent Sorenson
Ph.D., North Wind Environmental, Inc.
(208-557-7829 or
ksorenson@nwindenv.com), and Jennifer
Martin, North Wind Environmental, Inc.
(317-920-8518 or
jmartin@nwindenv. com)
^ 1 £
Figure 2. Chitin/fracing at the Distler
Brickyard site resulted in significant
break-down of cis-l,2-DCE within
nine months.
Dccct-or 2tH i
Jjl» 2
-------
Field Tests Conducted on Use of Potassium Permangante for In-Situ Oxidation
The U.S. Air Force (USAF) is collaborating
with researchers from the University of
Arizona and Raytheon to study the
effectiveness of large-volume injections of
potassium permanganate (KMNO4) solution
for remediating ground-water contamination
sources. In-situ oxidation (ISO) field studies
were conducted recently at Air Force Plant 44
(AFP 44), located within the Tucson Airport
Area Superfund site in Tucson, AZ, as part of
extensive efforts to remove trichloroethene
(TCE)andl,l-dichloroethene(DCE)fromthe
aquifer as dense non-aqueous phase liquid
(DNAPL). Atwo-square-mile pump and treat
system has operated at the facility since 1987,
and soil vapor extraction (SVE) and dual-phase
extraction systems were added in 1995 for
source control at five former disposal sites.
Based on the field study results, ISO using
KMNO4 will be implemented on a larger scale
in 2003 as a follow-up technology to SVE.
AFP 44 is located in the central part of the
Tucson Basin. The area is underlain by
unconsolidated to semi-consolidated alluvial
basin fill sediments consisting of thin (less
than 20-ft-thick) permeable beds of sand and
gravel separated by thick, low-permeability
beds of sandy clay and clay. Ground water in
the area occurs under semi-confined
conditions at depths of 135-150 ft below
ground surface (bgs). Transmissivities in test
locations are onthe orderof 10,000-50,000 gal/
day/ft.
Two methods of KMNO4 injection were
compared during the study. In August 2001,
15,000 gallons of 2%KMNO4 solution (2,500
Ibs of KMNO4) were injected into the
subsurface in an area known as "Site 2." The
solution was injected into the vadose zone
above a fine-grained unit, 20-30 feet above
the watertable. The injection was designed to
provide a vertical flood allowing the solution
to migrate laterally in the unsaturated
permeable zone along the top of the fine-
Figure 3. Fine-grained clay and silt
prevented complete distribution of
KMnO4 through vertical flooding at
AFP 44 Site 2.
grained unit suspected to contain the DNAPL,
and then downward through this unit and into
the ground water (Figure 3).
Af'Site 3," 12,000 gallons of the solution (2,000
Ibs of KMNO4) were injected directly into the
ground water at depths of 140-160 ft bgs,
within a permeable sand and gravel bed
bounded by low-permeability, fine-grained
units. This injection was intended to provide
a horizontal flood, allowing the solution to
migrate horizontally and to contact the TCE
and DCE DNAPL in the lower portion of the
overlying fine-grained unit.
Nine and twelve wells were used at Sites 2 and
3, respectively, to monitor ground water for
six months. Monitoring parameters included
TCE, DCE, chromium, major anions and
cations, pH, temperature, conductivity, and
oxygen reduction potential. (Chromium
monitoring was performed due to the trace
amounts of chromium present in potassium
permanganate and the possibility of mobilizing
trivalent chromium potentially present in the
aquifer.) The characteristic purple color of
KMNO4 served as the most useful indicator
of its presence; KMNO4 concentrations as low
as 10 mg/L could be detected on color alone.
Movement of KMNO4 solution within the
aquifer was controlled by pumping ground
water from selected wells to induce the flow of
injected solution toward the wells.
Bench-scale testing prior to field injections
indicated that KMNO4 concentrations of 50
mg/L or more could oxidize TCE. To determine
the effectiveness of breakdown reactions
under site conditions, tests were performed
using TCE-contaminated ground water in
columns containing AFP 44 aquifer material
derived from a site core. Testing indicated
that aquifer materials did not inhibit the TCE
breakdown reaction.
Field study results showed that distribution
of the KMNO4 was most effective at Site 3,
where solution was injected directly into the
aquifer and spread through horizontal flow.
Tenofthe 12 wells were impactedbyKMNO4
concentrations greater than 50 mg/L. At
Site 2, however, much of the solution
remained absorbed to the fine-grained unit
above the water table and only three of the
wells were impacted.
Results indicated that all impacted wells
experienced reductions in TCE
concentrations during the period when active
KMNO4 ISO was observed, with some wells
experiencing a 100% reduction. DCE, where
present, also decreased in concentration.
The period of time when the active KMNO4
was present varied among wells, with active
solution residing in some wells for up to six
months. Three months after injection, TCE
[continued on page 5]
KMnOq Infection at Site 2
-------
[continued from page 4]
concentrations in most wells began to
rebound as a result of contaminated ground
water migration into the study area from
upgradient contamination zones. Most of the
impacted wells continued to experience
rebound over the following three months, but
TCE concentrations remained lower than pre-
test concentrations. Average pre-test TCE
concentrations in two benchmark wells at
Site 2 ranged from 900 to 1,200 ug/1, while
average pre-test TCE concentrations in three
benchmark wells at Site 3 ranged from 90 to
475 ug/1 range. Sampling data collected from
these wells 12 months after the injections
indicated concentrations had decreased
approximately 65% at Site 2 and 30-70% at
Site3.
Since previous studies at Site 3 suggested
that full rebound of TCE and DCE
concentrations would occur within 20 days
of injection if no TCE DNAPL had been
oxidized, the extended period of rebound
observed during these field tests indicated
DNAPL was destroyed in the treated areas.
Field results showed that the KMNO4 solution
remained viable in the aquifer for up to six
months, in contrast to the two months
predicted by bench-scale tests. The unusual
persistence of the KMNO4 solution was
attributed partially to the low organic carbon
content of soil at AFP 44. Although bench-
scale tests also suggested that MnO2
precipitation may cause a loss of soil
permeability, no loss was encountered.
Chromium concentrations were found to
decline as KMNO4 was consumed and as
ground water returned to a lower redox
potential.
This study cost approximately $125,000,
including $9,000 for KMNO4. Field
experiences suggest that a similar injection
could be implemented for approximately
$35,000 by eliminating unnecessary field
monitoring and sample analysis. Researchers
concluded that a combination of vertical
flood and horizontal flow injection methods
are needed to remediate the source area
completely.
In December 2002, the USAF initiated an
expanded injection test involving both
vertical and horizontal flooding with KMNO4
solution across the entirety of Site 2, into
both the vadose zone and aquifer. Located
at the upgradient end of the TCE plume,
Site 2 is expected to produce unambiguous
test results due to the absence of TCE-
contaminated ground water migration.
Modifications to the technology will include
vertical flooding using greater volumes of
more dilute solutions injected into multiple
wells.
Contributed by John Doepker, USAF
(937-255-1972 or
john.doepker@wpafb.af.mil) and Timothy
Allen, Raytheon (520-794-9450 or
tjallen@raytheon. com)
Co-Oxidation Used to Remove PCE DNAPL at Orycleaner Site
The Florida Department of Environmental
Protection (FDEP) is conducting pilot tests
to remediate contaminated ground water at a
drycleaning facility in Jacksonville, FL.
Following the limited success of in-situ
chemical oxidation (ISCO) testing at this site.
co-oxidation technology is being tested to
improve remedial effectiveness, reduce
cleanup costs, and accelerate overall cleanup.
As a result of past releases of tetra-
chloroethene (PCE), dense nonaqueous
phase liquid (DNAPL) exists immediately
adjacent to the drycleaning facility in a
source area located 10-15 feet below ground
surface (bgs). The dissolved-phase plume
emanating from the source extends across
an area of approximately 670 by 150 feet. The
site is underlain primarily by sandy soil with
interbedded layers of silt and clay. Within
these units, the measured hydraulic
conductivity is approximately 5 ft/day. The
water table is approximately 6 feet bgs, and
the hydraulic gradient is 0.01 ft/ft.
From September 1999 throughDecember2000,
ISCO tests were conducted by injecting
potassium permanganate (KMnO4) directly
into the DNAPL zone (10-15 ft bgs). Atotal of
4,000 pounds of KMnO4 was injected through
screened wells into the source area during four
3-week events. Results indicated an initial
reduction of dissolved-phase PCE
concentrations, followed by consistent PCE
rebound in source area monitoring wells.
Rebound was attributed to limitations in pore
diffusion and interfacial mass transfer between
the DNAPL and ground water.
The pilot was modified to incorporate in-situ
co-oxidation technology. Co-oxidation was
selected due to its ability to:
< Employ a co-solvent for addressing mass
transport limitations,
4 Reduce the solvent's aqeuous concen-
tration, thereby maximizing the rate of
chemical oxidation,
[continued on page 6]
Contact Us
Technology News and Trends
is on the NET!
View, download, subscribe, and
unsubscribe at:
http://www.epa.gov/tio
http://clu-in.org
Technology News and Trends
welcomes readers' comments
and contributions. Address
correspondence to:
Ann Eleanor
Technology Innovation Office
(5102G)
U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Ave, NW
Washington, DC 20460
Phone:703-603-7199
Fax:703-603-9135
-------
Technology
News and Trends
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-03-001
January 2003
Issue No. 4
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
First Class Mail
Postage and Fees Paid
EPA
Permit No. G-35
Official Business
Penalty for Private Use $300
[continued from page 5]
< Allow for retention of co-oxidant solu-
tion in the aquifer for a short time with-
out the need for hydraulic control.
< Reduce treatment costs for the extracted
fluid, due to destruction of contaminant
once it transfers to the aqueous phase.
and
< Reduce overall remediation costs
through accelerated, in-situ contaminant
destruction.
Co-oxidation testing began at the site in May
2001. This phase of pilot testing involved a
single source-area injection of 1,000 gallons of
co-oxidant solution containing tertiary butyl
alcohol and KMnO4. The solution was
extracted 10 days later and disposed offsite.
Preliminary results from ground-water
monitoring and direct-push soil samples
collected in April 2002 indicated an 80-90%
reduction of source-area DNAPL following co-
oxidation. PCE concentrations in a
representative monitoring well decreased from
pre-treatment levels of 15,000-20,000 ug/L to
less than 750 ug/L.
Testing of alternative co-oxidants is underway
to enhance performance of the process.
Contributed by Doug Fitton, FDEP (850-
245-8927 or douglas.fitton@dep.state.fl.us)
and Kevin Warner, Levine Fricke (850-422-
2555 or kevin.warner@lfr.com)
Update on the State Coalition for Remediation of Drycleaners
For the past four years, the State Coalition for Remediation of Drycleaners has worked to address problems posed by soil and ground-water
contamination at drycleaning sites. It is estimated that contamination exists at more than 25,000 drycleaning sites across the country. Under
sponsorship of the U.S. EPA's Technology Innovation Office, representatives from 11 states with established dry cleaner remediation
programs have joined the coalition to provide a forum for:
< Exchanging information on existing state drycleaner programs,
< Sharing information and lessons learned with states having no drycleaner-specific programs, and
< Encouraging the use of innovative technologies in drycleaner remediation.
More information about the coalition's work, including development of more than 60 site-specific cleanup profiles, is available on the web
at www.drycleancoalition.org.
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.
-------
|