United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-00-002
March 2000
Issue No. 35
Ground Water Currants
^ter Treatment
CONTENTS
Federal Roundtable
Proposes National
Action Plan for
DNAPL
Source Reduction Pg. 1
The Role of Microbes
in Remediation
with Fe° Pg. 2
Well Head Monitoring
Technology
Verification Pg. 3
About this Issue
This issue highlights multi-
agency efforts to accelerate
the development and
implementation of innovative
DNAPL remediation
technologies, research into
increasing the effectiveness of
permeable reactive barriers,
and development and
implementation of innovative
site characterization and
remediation technologies.
Federal Roundtable
Proposes National Action
Plan for DNAPL Source
Reduction
by Jim Cummings, U.S. EPA
Technology Innovation Office
The Federal Remediation Technolo-
gies Roundtable has developed a
national action plan for accelerating
the development and implementation
of innovative technologies for
remediating Dense Non-Aqueous
Phase Liquids (DNAPLs) in ground
water. DNAPLs are present at 60-70
percent of Superfund National
Priorities List (NPL) sites. Due to
their complexity, including the
numerous variables influencing their
fate and transport in the subsurface,
the ultimate path taken by DNAPLs
can be difficult to characterize and
predict. As a consequence, DNAPLs
can be a significant limiting factor in
site remediation.
The Roundtable is an interagency
group that undertakes cooperative
efforts to promote greater application
of innovative technologies for site
cleanup. Its members include the
U.S. EPA, the U.S. Departments of
Defense (DoD), Energy (DOE) and
Interior (DOI), the U.S. Geological
Survey (USGS) and the National
Aeronautics and Space Administration
(NASA).
The Plan
The focus of the new initiative is on
sites contaminated with free DNAPL
product at which current technologies
(particularly pump and treat systems)
take too long to meet national needs.
The ultimate goal of the action plan is to
develop a national model for technology
development programs that reduces the
development cycle from about 10 years
to 3 to 5 years. The plan calls for a
coordinated effort to determine what
the nation needs to solve the current
DNAPL source term problem and
keep the focus on solving that problem.
The Roundtable has identified three
technology classes as having potential
to greatly augment, if not replace, pump
and treat systems, the most common
DNAPL remediation methods. These
are on in situ thermal, surfactant
flushing, and chemical oxidation. Initial
work under the action plan will focus on
these processes.
To accelerate the development and
implementation of innovative DNAPL
remediation technologies, the plan
proposes collaborative efforts among
federal agencies, private sector
vendors, and responsible parties in
research and development, technology
demonstrations, and full-scale
technology deployment. In addition, an
expert panel will provide technical input
and review of activities and results.
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Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
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Research and Development
The objective of the research and
development portion of the action
plan is to identify and address critical
issues hampering commercialization
of innovative DNAPL remediation
technologies. DOE and the University
of California Berkeley are coordinat-
ing collection of input from federal
agencies, private sector researchers,
and technology vendors about areas
of potentially beneficial research,
relevant ongoing research activities,
and future plans. In addition, agen-
cies with research support programs
are being asked to include areas of
potentially beneficial research in their
individual solicitations. These areas
include: characterization and perfor-
mance assessment; process factors
and monitoring; scale of effective
testing/application; and a number of
issues specific to the three initial-
focus technologies.
Outreach
The action plan includes implementa-
tion of a variety of activities to
encourage collaboration and dissemi-
nate information. These include:
• Preparing and maintaining an up-
to-date, Internet-based descrip-
tion of ongoing research and
development, proposed demon-
stration projects, and full-scale
deployments;
• Developing an ongoing program to
actively solicit private sector
partners;
• Scheduling seminars and workshops
to facilitate information exchange
and audio/video conferences to
discuss results of demonstrations;
and
• Preparing and distributing hard-
copy and Internet-based versions
of lessons learned from each
demonstration and application.
For more information about the
National Action Plan for DNAPL
Source Reduction, contact Jim
Cummings of EPA (703-603-7197)
or Skip Chamberlain of DOE (301-
903-7248).
Role of Microbes in
Remediation with Fe°
Reactive Barriers
G.F. Parkin, P.J. Alvarez, MM.
Scherer, andJ.L. Schnoor,
University of Iowa
Experiments conducted at the
University of Iowa have shown
microbes can play an important role
in enhancing the treatment of ground
water using permeable reactive
barriers (PRBs). Increasingly, PRBs
made of zero-valent iron (Fe°) are
being used to treat ground water
contaminated with reducible pollut-
ants such as chlorinated solvents,
nitrate, chromium, uranium, munitions
wastes, and pesticides. These same
pollutants also can be degraded by a
variety of anaerobic bacteria. Using
anaerobic bacteria together with Fe°
PRBs can increase the rate and extent
of transformation of some common
contaminants. In addition, the combina-
tion can produce more environmentally
benign end products and perhaps
remove Fe oxides and hydrogen (H2)
gas bubbles that can reduce the reactiv-
ity of the PRB.
Reductive treatment with Fe° is driven
by the oxidation of Fe°, which releases
electrons:
Fe°
Fe2
2r
These electrons can then be used to
transform reducible pollutants. For
example, both carbon tetrachloride
(CC14) and chromate (CrO4~) can be
reduced by Fe°:
CC14 + H+ + 2e- -> CHC13 + Cl
CrO/- + 8H+ + 3e- -> Cr3+ + 4H O
4 2
The electrons can also be used to
reduce water-derived protons to make
hydrogen gas (H ), the overall
reaction being written as:
Fe° + H2O -> Fe2+ + 2OFf
H
2(g)
Hydrogen gas is an excellent energy
source for a wide variety of anaerobic
bacteria. Removal of H by these
microbes increases the rate of Fe°
corrosion and thus the production of
more FL .. This stimulates microbial
2(g)
reduction of target pollutants and the
further degradation of some dead-end
products that accumulate during abiotic
reduction by Fe°. Microbes can also
remove the FL , layer from the Fe°
2(g) J
surface enhancing the reactivity of Fe°.
Microbial consumption of H2 gas
bubbles can also enhance barrier
permeability and potentially enhance
the treatment efficiency of a barrier
through reductive dissolution of Fe +
oxides. Such biogeochemical interactions
may enhance the performance of bioaug-
mented Fe° barriers under most
commonly encountered hydraulic regimes
and redox conditions.
Over the past five years, the University of
Iowa team has investigated a variety of
pollutants and experimental conditions.
The team has demonstrated that bioaug-
menting Fe° with a methanogenic
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enrichment increased the rate and extent
of chloroform (CF) and carbon terra-
chloride (CT) transformation. Column
studies with CF, CT, PCE, and 1,1,1-
TCA have shown that the process is
sustainable and that the choice of
microbial seed plays an important role.
A variety of batch and column experi-
ments with nitrate as a secondary
contaminant have shown that bioaug-
mentation with mixed cultures and pure
cultures of denitrifying bacteria results in
production of nitrogen gases. Abiotic
reduction of nitrate yields primarily
ammonia, which is an undesirable end
product. These studies and others have
demonstrated the importance of Fe°
source and surface area, microbial seed,
andpH.
Experiments with mixtures of contami-
nants have shown that bioaugmentation
of PRBs with bacteria offers promise
when more than one contaminant is
present. More complete dechlorination
occurred when the Fe° was bioaug-
mented. Batch experiments with
mixtures of CT, Cr 6,+and nitrate showed
that bioaugmentation reduced competi-
tion by these pollutants for active sites
on the Fe° surface.
Bioaugmenting Fe° in microcosms and in
flow-through columns showed enhanced
rate and extent of removal of RDX
(hexahydro -1,3,5 -trinitro-1,3,5-
triazone). In abiotic Fe° reactors,
undesirable heterocyclic breakdown
products were found. In bioaugmented
Fe° reactors, these products were not
detected.
The University of Iowa team has begun
to assess whether microbes colonize the
Fe° surface in field PRBs. Scanning
electron microscopy of samples from a
PRB treating a chlorinated solvent
plume shows microbial colonization of
the surface. Fluorescent in situ hybrid-
ization of samples from a PRB treating a
uranium plume showed the presence of
more microbes within the barrier than
either upgradient or downgradient from
the PRB. The role of these microbes
has yet to be ascertained.
In summary, research at the University
of Iowa has demonstrated the potential
advantages of bioaugmenting Fe°
barriers for the removal of a wide
variety of redox-sensitive contaminants.
Results also indicate that performance
of these barriers might be enhanced by
the participation of indigenous microbes.
The effects of these biogeochemical
interactions on the long-term perfor-
mance of PRB systems remains to be
determined.
For additional information about the
University of Iowa studies on
bioaumentation of Fe° PRB systems,
contact Gene Parkin, Ph.D, PE. at
(319) 335-5655 or References used
to prepare this article are listed on the
CLU-IN website at www.clu-in.org/
pub 1.htm.
Well-Head Monitoring
Technology Verification
by Eric Koglin, U.S. EPA National
Exposure Research Laboratory, and
Dan Powell, U.S. EPA Technology
Innovation Office
Five well-head monitoring technologies
for measuring volatile organic com-
pounds (VOCs) in water have been
tested over the past four years under the
U.S. EPA's Site Characterization and
Monitoring Technologies (SCMT) Pilot.
The SCMT Pilot is one of 12 Environ-
mental Technology Verification (ETV)
programs designed to verify the perfor-
mance of commercial-ready
environmental technologies.
For these tests, EPA partnered with the
U.S. Department of Energy's (DOE's)
Sandia National Laboratories to demon-
strate the well-head monitoring
technologies at DOE's Savannah River
Site (SRS) near Aiken, SC, and
McClellan Air Force Base near
Sacramento, CA.
Three technologies based on gas
chromatography were tested:
• Electronic Sensor Technology's
surface acoustic wave detector
(EST Model 4100),
• Sentex Systems, Inc.'s
microargon ionization and elec-
tron capture detector (Sentograph
Plus II), and
• Perkin-Elmer Photovac's dual
capture photoionization and
electron capture detector (Voy-
ager).
The demonstration included one
technology based on gas chromatog-
raphy/mass spectrometry:
• Inficon, Inc.'s gas quadrupole
mass spectrometer (HAPSITE).
In addition, a single technology based
on photoacoustic infrared monitoring
was tested:
• Innova Air Tech Instruments'
pressure wave (sound) detector
(Innova Type 1312 Multi-Gas
Monitor).
For each technology, performance
indicators such as correlation coeffi-
cients, false positives, false negatives,
and sample throughput were evaluated.
This information is tabulated below.
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[continued from page 3]
Complete verification reports for these
technologies are available through the
ETV Web site at www.epa.gov/etv.
Under the SCMT Pilot, a total of 29
innovative technologies have been tested
and verified. For more information,
contact Eric Koglin (EPA/National
Exposure Research Laboratory) at 702-
798-2432 or e-mail koglin.eric@
epa.gov, or Dan Powell (EPA/Technol-
ogy Innovation Office) at 703-603-7196
or e-mail powell.dan@epa.gov; or visit
the Internet at www.epa.gov/etv.
Highlights of Weil-Head Monitoring Technology Demonstration
False Positives for
Correlation 16 Blank Samples/
Coefficient at SRS Number of False Negatives/PE Sample Throughput
(greater than or Calibrated Samples at SRS (number of
Technology equal to 100 ug/L) Compounds (10ug/L) samples/hour)
EST Model 41 OO
Sentograph Plus II
Voyager
HAP SITE
Innova Type 1312
O.969 O/31 6/1 0 2-3
O.9O7 O/19 1/8 2
O.83O 6/24 4/1 0 1-3
O.996 8/38 5/11 2.5
O.984 3/5 1/2 1-2
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