United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102W)
EPA542-K-94-Q06
April 1995
&EPA
In Situ Remediation
Technology Status
Cosolvents
(Report:
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
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EPA542-K-94-006
April 1995
In Situ Remediation Technology Status Report:
Cosolvents
U.S. Environmental Protection Agency
Office of Solid Waste and Emergency Response
Technology Innovation Office
Washington, DC 20460
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Acknowledgements
The authors would like to thank all the researchers and technology developers described in this report for
their assistance in its preparation. We especially would like to thank A. Lynn Wood of the EPA R.S. Kerr
Environmental Research Laboratory for reviewing the draft document and making valuable suggestions
for improvement.
For more information about this project, contact:
Rich Steimle
U.S. Environmental Protection Agency (5102W)
Technology Innovation Office
401M Street, SW
Washington, DC 20460
703-308-8846
Notice
This material has been funded by the United States Environmental Protection Agency under contract
number 68-W2-0004. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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Foreword
The purpose of this document is to describe recent field demonstrations, commercial applications, and
research on technologies that either treat soil and ground water in place or increase the solubility and
mobility of contaminants to improve their removal by pump-and-treat remediation. It is hoped that this
information will allow more regular consideration of new, less costly, and more effective technologies to
address the problems associated with hazardous waste sites and petroleum contamination.
This document is one in a series of reports on demonstrations and applications of in situ treatment
technologies. To order other documents in the series, contact the National Center for Environmental
Publications and Information at (513) 489-8190 or fax your request to NCEPI at (513) 489-8695. Refer to
the document numbers below when ordering.
EPA542-K-94-003 Surfactant Enhancements
EPA542-K-94-004 Treatment Walls
EPA542-K-94-005 Hydrofracturing/Pneumatic Fracturing
EPA542-K-94-006 Cosolvents
EPA542-K-94-007 Electrokinetics
EPA542-K-94-009 Thermal Enhancements
Walter W. Kovalick, Jr., Ph.D.
Director, Technology Innovation Office
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Contents
Introduction .
Purpose and Process ....
Technology Needs
Technology Description .
Ongoing or Future Demonstrations
University of Florida and R.S. Kerr Environmental Research Laboratory
Current Research
Rice University
General References 6
Abbreviations
BTEX = Benzene, Ethylbenzene, Toluene, Xylene
CERCLA = Comprehensive Environmental Response, Compensation, and Liability Act
DNAPL = Dense Non-Aqueous Phase Liquid
DOE = Department of Energy
PAH = Poly-Aromatic Hydrocarbons
PCE = Tetrachloroethylene
RCRA = Resource Conservation and Recovery Act
SITE = Superfund Innovative Technology Evaluation Program
SVE = Soil Vapor Extraction
SVOC = Semi-Volatile Organic Compound
TCA = 1,1,1-Trichloroethane
TCE = Trichloroethylene
TPH = Total Petroleum Hydrocarbon
VOC = Volatile Organic Compound
in
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IV
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Introduction
Purpose and Process
This document describes the development and application of in situ solvent enhancement as a technology
to remove contaminants from soils and ground water at waste disposal and spill sites. The activities
described include research, demonstrations, and field applications of the technology.
Information in this report was obtained from computerized databases such as the Dialog Information
Services, the Environmental Protection Agency's (EPA) Vendor Information System for Innovative
Treatment Technologies (VISITT), and EPA's Alternative Treatment Technologies Information Center
(ATTIC). Information also came from publications such as EPA's Superfund Innovative Technology
Evaluation (SITE) Profiles and the Department of Energy's (DOE) Office of Technology Development
Program Reports. This information was supplemented with telephone interviews with representatives of
federal agencies, academic research centers, and hazardous waste remediation consulting firms. In some
cases, the data concerning the performance of the technology were provided by the technology vendor.
Technology Needs
Treatment of aquifers contaminated by non-aqueous phase liquids (NAPLs) by traditional pump-and-treat
systems has proven impracticable. NAPLs have very low solubility in water and tend to exist as pockets at
the subsurface location to which they have migrated. They dissolve slowly, leading to very slow rates of
removal by pumping. To improve this performance, new technologies are being developed to mobilize or
solubilize these pockets.
Environmental professionals are acknowledging the limitations of pump-and-treat techniques to clean
ground water contaminated with organic solvents. Excavation of contaminated soil is another option.
However, this can be very expensive if a large volume of soil is affected because the soil still needs to be
treated.
Technology Description
In situ solvent flushing involves injecting a solvent mixture (e.g., water plus amiscible organic solvent
such as alcohol) into either the vadose zone, the saturated zone, or both to extract organic contaminants.
Cosolvent flushing can be applied to soils or ground water to solubilize either the source of contamination
or the contaminant plume emanating from it. The cosolvent mixture is injected upgradient of the
contaminated area. The solvent with the dissolved contaminants is extracted downgradient and treated
above ground. Physical barriers may be installed to prevent uncontrolled migration of solvent and
contaminants.
Cosolvents can promote contaminant removal in two ways. The first is by increasing the apparent
solubility of the contaminant in water, which improves the mass removal per pore volume. The second is
by reducing interfacial tension between the water and the contaminant, which may result in direct
mobilization of NAPLs. Cosolvents that microbes can use as substrates may have the added advantage of
promoting bioremediation if they are used at nontoxic levels.
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Researchers also are exploring the effect of the inclusion of cosolvents in other types of remediation. A
methanol/water cosolvent has been shown to improve the supercritical CO 2 extraction of DDT from soil
and cosolvents added to potassium permanganate (KMnO4) improved the degradation (by oxidation) of
the common dense non-aqueous-phase liquids trichloroethylene and perchloroethylene.
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Ongoing or Future Demonstrations
Hill Air Force Base, Utah
University of Florida and R.S. Kerr Environmental Research Laboratory
Description of Demonstration: EPA is funding, through a cooperative agreement with the University of
Florida, a field test of in situ solvent extraction at Hill AFB in Utah.
The water table at the site has declined in the past few years due to drought conditions, so researchers will
raise the water table to the top of the contaminant zone before injecting an ethanol/water mixture into the
gravelly sand in a 3 meter by 5 meter test cell to solubilize the light non-aqueous phase liquid (LNAPL).
Contamination in the test bed is predominantly jet fuel with some pesticides and chlorinated solvents
mixed in. There were multiple sources of contamination: fire training site and chemical waste pits. The
LNAPL mixture occurs as a coating on particles and as globules in pore spaces in the ground water and
above it in the vadose zone.
Wastes Treated: BTEX (jet fuel), pesticides, VOCs, SVOCs
Status: Initial site characterization has been completed. Researchers will begin injecting the cosolvent
mixture in March 1995. The injection and extraction process will last for one month. A report of the
findings is scheduled for late 1995.
Preliminary Results: None yet.
Future work at this site
A project to study the use of solvents to promote mobilization of residual organic phase was recently
funded as was a comparative study on the effectiveness of cosolvents, surfactants, air and steam to extract
contaminants at this site.
Future work at another site
At a site not yet selected, researchers will evaluate cosolvent-enhanced mobilization and solubilization
under different hydrogeological conditions and for different waste mixtures.
Contact:
A. Lynn Wood
U.S. Environmental Protection Agency
R.S. Kerr Environmental Research Laboratory
P.O. Box 1198
Ada, OK 74820
405-436-8552
References:
Augustijin, D.C.M. and Rao, P.S.C. "Enhanced Removal of Organic Contaminants by Solvent Flushing."
ACS Symposium Series (submitted), 1995.
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Augustijin, D.C.M.; Dai, D.; Rao, P.S.C.; and Wood, A.L. "Solvent Flushing Dynamics in Contaminated
Soils." In Transport and Reactive Processes in Aquifers. T.H. Dracos and F. Stouffer (eds.).
Balkema/Rotterdam/Brookefield, 1994.
Augustijin, D.C.M.; Jessup, R.E.; Rao, P.S.; and Wood, A.L. "Remediation of Contaminated Soils by
Solvent Flushing". Journal of Environmental Engineering, 120 (1) Jan/Feb 1994, p 42-57.
Rao, P.S.C.; Lee, L.S.; and Wood, A.L. Solubility, Sorption, and Transport of Hydrophobic Organic
Chemicals in Complex Mixtures. U.S. Environmental Protection Agency, EPA/600-M-91-009, March
1991.
Wood, A. Lynn; Bouchard, D; Brusseau, M; and Rao, P.S.C. "Cosolvent Effects on Sorption and
Mobility of Organic Contaminants in Soils." Chemosphere, 21 (4-5) 1990, p 575-587.
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Current Research
Removal of Gasoline from Sandy Aquifer Material
Rice University
Description of Research: Researchers studied the use of cosolvents and surfactants for the removal of
residual aviation fuel from aquifer material from a U.S. Coast Guard base in Traverse City, Michigan.
Alcohols at 20% concentration did not mobilize the contaminants from the soil column. 2-Propanol
mobilized the contaminant at 50% concentration while 50% methanol showed little effect.
Wastes Treated: BTEX
Contact:
Dr. Mason Tomson
Rice University
PO Box 1892
Houston, TX 77251
713-527-6048
Fax: 713-285-5203
Reference:
Kan, A.T.; Tomson, M.B.; McRae, T.A. "Enhanced Mobilization of Residual Aviation Gasoline in Sandy
Aquifer Material by Surfactant and Cosolvent Flush," Proceedings of the 203rd American Chemical
Society National Meeting, San Francisco, California, April 1992.
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General References
Boyd, G.R. and Farley, K.J. "NAPL Removal from Groundwater by Alcohol Flooding: Laboratory
Studies and Applications." In Hydrocarbon Contaminated Soils and Groundwaters: Analysis, Fate,
Environmental and Public Health Effects, and Remediation. P. Kostecki, E. Calabrese, and C. Bell (eds.).
Ann Arbor, MI: Lewis Publishers, 1992.
Brandes, D. and Farley, K.J. "Importance of Phase Behavior in Remediation of Dense Nonaqueous Phase
Liquid (DNAPL) Contaminated Aquifers by Alcohol Flooding. "Proceedings of Spectrum '92, Nuclear
and Hazardous Waste Management, International Topical Meeting, Boise, Idaho, 1992.
Broholm, K. and Cherry, J.A. "Enhanced Dissolution of Heterogeneously Distributed Solvents Residuals
by Methanol Flushing—A Field Experiment." Transport and Reactive Processes in Aquifers. Draces and
Stouffer (eds.), Balkema/Rotterdam/Brookefield, 1994.
Brusseau, M.L. Complex Mixtures and Groundwater Quality. U.S. Environmental Protection Agency,
EPA/600/S-93/004, September 1993.
Dooley, K.M.; Ghonasgi, D.; Knopf, F.G.; Gambrell, R.P. "Supercritical CO2-Cosolvent Extraction of
Contaminated Soils and Sediments." Environmental Progress. 9 (4) 1990, p 197.
Farley, J.A. "Technical Feasibility and Conceptual Design for Using Supercritical Fluid to Extract
Pesticides from Aged Soil." Remediation. 4 (3) 1994, p 301.
Palmer, C.D. and Fish, W. Chemical Enhancements to Pump-and-Treat Remediation. U.S. Environmental
Protection Agency, EPA/540/S-92/001, September 1992.
Rixey, W.G.; Johnson, P.C.; Deeley, G.M.; Byers, D.L.; and Dortech, I.J. "Mechanisms for the Removal
of Residual Hydrocarbons from Soils by Water, Solvent, and Surfactant Flushing." In Hydrocarbon
Contaminated Soils and Groundwater: Analysis, Fate, Environmental and Public Health Effects, and
Remediation. P. Kostecki, E. Calabrese, and C. Bell (eds.). Ann Arbor, MI: Lewis Publishers, 1992.
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