Dense Nonaqueous Phase Liquids (DNAPLs)

In Situ Flushing

Halogenated Alkenes

This page presents case studies of in situ flushing used to address chlorinated solvents and chlorinated intermediates within the class of Halogenated Alkenes.

Chlorinated Solvents: Case Studies

Aquifer Monitoring Shows Complex-Sugar Flushing Increases Potential for Enhanced Biodegradation
W.J. Blandford, T. Boving, and R. Wade.
Technology News and Trends, Issue 25, p 2-4, July 2006

In 2002, aquifer flushing was conducted at the Naval Amphibious Base Little Creek in Virginia Beach, VA, to remove DNAPL. The flushing system employed a solution containing cyclodextrin (CD) to increase solubility and removal efficiency of chlorinated solvents. The extracted CD solution was treated through air stripping and reused in a subsequent flushing event. Over the monitoring period, aqueous concentrations of 1,1-DCE, 1,1,1-TCA, and TCE within the injection zone decreased 38, 81, and 94%, respectively.

Cyclodextrin-Enhanced In Situ Removal of Organic Contaminants From Groundwater at Department of Defense Sites. Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP) Project CU-0113, 101 pp, 2004

Cyclodextrins are nontoxic, modified sugars that form complexes with hydrophobic pollutants, such as TCE. During this 4-month flushing demonstration, about 32.5 kg TCE and 1,1,1-TCA, plus an estimated 3 kg of 1,1-DCE and an unknown amount of other contaminants were removed, a total DNAPL volume of ~30 liters. This demonstration also compared the performance of a conventional air stripper and a pervaporation system.

Design of a Field Scale Project for Surfactant Enhanced Remediation of a DNAPL Contaminated Aquifer
Brown, Chrissi Lynn, Ph.D. dissertation, University of Texas, 471 pp, 2004

The primary objective was to develop and apply engineering methods, especially flow and transport modeling using UTCHEM, the University of Texas CHEMical flood simulator, to optimize the removal of contaminants (TCE, PCE, 1,1,1-TCA) using surfactant-enhanced aquifer remediation (SEAR). Field surfactant floods and tracer tests were conducted at OU2 in Hill AFB, which allowed validation of the test design methodology, including the value of simulation in this process. The simulations accurately predicted tracer breakthrough times, tracer peak times and concentrations, and performance of the tracer 'tail' or concentration decline critical for moment analysis and DNAPL volume determination. The simulations also were critical in determining the appropriate injection and extraction rates, injection concentrations, and time required for each segment of the test. Surfactant was injected successfully in the field. The field test resulted in 98.5% DNAPL recovery and a reduction in TCE concentration in the produced water from 900 mg/L down to 10 mg/L at the end of the test.

In Situ Flushing: Technology Status Report
D.S. Roote.
Ground-Water Remediation Technologies Analysis Center (GWRTAC). TS-98-01, 212 pp, 1998

Contains brief overviews of field applications of in situ flushing for a variety of contaminants, including DNAPLs.

Case Studies: PCE

Building 25, Morale, Welfare and Recreation (MWR) Dry Cleaners, Camp Lejeune Marine Corps Base, Camp Lejeune, NC
Federal Remediation Technology Roundtable (FRTR), Cost and Performance Case Study Database.

Surfactant-enhanced aquifer remediation (SEAR) and surfactant/cosolvent flushing were applied to a 20- by 30-ft test zone to a maximum depth of 20 ft to address PCE. An estimated 92-96% of the DNAPL swept by the surfactant flood was removed; however, the surfactant flood did not sweep a significant portion of the DNAPL due to permeability reduction associated with a downward-fining depositional sequence that kept the surfactants from reaching all of the DNAPL. The nature and impact of geologic contacts and/or transition zones need to be evaluated further.

Controlled Release, Blind Test of DNAPL Remediation by Ethanol Flushing
Brooks, M.C., M.D. Annable, P.S.C. Rao, K. Hatfield, J.W. Jawitz, W.R. Wise, A.L. Wood, and C.G. Enfield.
Journal of Contaminant Hydrology 69:281-297(2004)

A DNAPL source zone was established within a sheet-pile isolated cell through a controlled release of PCE to evaluate DNAPL remediation by in situ cosolvent flushing. Ethanol was used as the cosolvent, and the main remedial mechanism was enhanced dissolution based on the phase behavior of the water/ethanol/PCE system. Over a 40-day period, 64% of an initial mass of 83 L of PCE was removed by flushing the cell with a solution of 70% ethanol and 30% water; however, tracer results suggest that some PCE was inaccessible to the ethanol solution, which led to the inefficient PCE removal rates observed. Longer abstract.

Cosolvent Flushing Pilot Test Report: Former Sages Dry Cleaner
Florida Department of Environmental Protection, 58 pp, 1998

This report summarizes the results of the cosolvent (alcohol) flushing pilot test conducted at the former Sages Dry Cleaner Facility to remediate PCE DNAPL.

Final Cost and Performance Report for Surfactant-Enhanced DNAPL Removal at Site 88, Marine Corps Base Camp Lejeune, North Carolina
L. Yeh (NFESC), et al. 105 pp, 2001

In-Situ Alcohol Flushing of a DNAPL Source Zone at a Dry Cleaner Site
J.W. Jawitz, R.K. Sillan, M.D. Annable, P.S.C. Rao, and K. Warner.
Environmental Science & Technology, Vol 34 No 17, p 3722-3729, 2000

A pilot-scale field test of in situ alcohol flushing for enhanced solubilization and extraction of a PCE source zone was conducted at a former dry cleaner site located in Jacksonville, FL. Alcohol flushing successfully removed a substantial volume (62 to 65%) of the DNAPL, although evidence indicated that continued alcohol flushing would have resulted in a greater NAPL removal effectiveness.

Technical Report for Surfactant-Enhanced DNAPL Removal at Site 88, Marine Corps Base Camp Lejeune, North Carolina
Environmental Security Technology Certification Program (ESTCP), 114 pp, 2001

Prior to surfactant flooding, free-phase PCE DNAPL removal operations were conducted over a period of about 60 days. During this period, an estimated 30-60 gallons of free-phase DNAPL were removed. Later, during the 143-day SEAR demonstration, approximately 76 gallons of PCE DNAPL were removed from this site as a result of both enhanced solubilization and enhanced mobilization of DNAPL.

Tracer Techniques for DNAPL Source Delineation and In-Situ Flushing Techniques for Enhanced Source Removal: Pilot Scale Demonstrations at the Dover National Test Site
M.C. Brooks, M.D. Annable, S.C. Rao. NTIS: ADA410848, 293 pp, 2001

A study was performed to evaluate the performance of innovative tracer techniques for DNAPL characterization and in situ cosolvent and surfactant flushing for DNAPL removal at the Dover National Test Site, Dover AFB, DE. The project involved controlled releases of up to 100L of perchloroethene (PCE) into test cells for each remedial technology. After the PCE release, two partitioning tracer tests were conducted: one before and another after the remedial test. The first remedial demonstration involved cosolvent flushing and the second, surfactant flushing. This report focuses on the four partitioning tracer tests and the cosolvent flushing demonstration.

Abstracts of Journal Articles

Field Demonstration of Surfactant-Enhanced Solubilization of DNAPL at Dover Air Force Base, Delaware
J. Childs, E. Acosta, M.D. Annable, et al.
Journal of Contaminant Hydrology, Vol 82 Nos 1-2, p 1-22, 5 Jan 2006

Long Term Multilevel Monitoring of the Mass Discharge of Chloroethenes Following Ethanol Flushing at Former Sages Drycleaning Site
G.H. Brown, M.D. Annable, J.W. Jawitz, and J. Cho (Univ. of Florida, Gainesville); R.K. Sillan (LFR, Inc., Tallahassee, FL).
Eos, Transactions of the AGU, Vol 87 No 52, Abstract H11C-1280, 2006

Pilot-Scale Demonstration of Surfactant-Enhanced PCE Solubilization at the Bachman Road Site. 1. Site Characterization and Test Design
L.M. Abriola, C.J. Drummond, E.J. Hahn, et al.
Environmental Science & Technology, Vol 39 No 6, p 1778-1790, 15 Mar 2005

Pilot-Scale Demonstration of Surfactant-Enhanced PCE Solubilization at the Bachman Road Site. 2. System Operation and Evaluation
C.A. Ramsburg, K.D. Pennell, L.M. Abriola, et al.
Environmental Science & Technology, Vol 39 No 6, p 1791-1801, 15 Mar 2005

Case Studies: TCE

Cyclodextrin-Enhanced Vertical Flushing of a Trichloroethene Contaminated Aquifer
W.J. Blanford, M. Barackman, T.B. Boving, E. Klingel, and M. Brusseau.
Ground Water Monitoring and Remediation. p 58-66, 2000

In Tucson, AZ, a pilot-scale test of a ground-water flushing remediation technology was conducted in a source zone of a TCE-contaminated Superfund site. The pilot test involved injecting a 20% HPCE (hydroxypropylbeta-cyclodextrin, a complexing sugar) solution into the upper screened interval of a dual-screened vertical circulation well and extracting it from the lower screened interval. TCE concentrations increased by a factor of three in the presence of the cyclodextrin pulse compared to concentrations obtained during previous water flushing.

Field Test of Cyclodextrin for Enhanced Flushing of Multicomponent Immiscible Liquid Contamination: Comparison to Water Flushing
J. McCray, K. Bryan, R. Cain, G. Johnson, W. Blanford, and M. Brusseau.
Innovative Subsurface Remediation: Field Testing of Physical, Chemical, and Characterization Technologies. Oxford University Press, ACS Symposium Series #725, ISBN: 0-8412-3596-1, p 136-152, 1999

In a pilot-scale field experiment to compare the relative effectiveness of soil flushing with a cyclodextrin solution against flushing with plain water, the investigators concluded that more than 350 pore volumes of water flushing would be required to remove the amount of TCE achieved by flushing with 8 pore volumes of cyclodextrin solution.

In-Situ Decontamination of Sand and Gravel Aquifers by Chemically Enhanced Solubilization of Multiple-Compound DNAPLs with Surfactant Solutions: Phase 1-Laboratory and Pilot Field-Scale Testing and Phase 2-Solubilization Test and Partitioning and Interwell Tracer Tests
U.S. DOE, Washington, DC. DOE/MC/29111-01, 625 pp, 1997

This report describes lab and field feasibility testing of in situ flushing at DOE's Paducah Gaseous Diffusion Plant using a 1% micellar-surfactant solution, sorbitan monooleate (approved by the FDA as a food-grade additive), to solubilize TCE DNAPL.

Well Injection Depth Extraction (Wide) Soil Flushing. Innovative Technology Summary Report
U.S. DOE, Ohio Field Office, Ashtabula Environmental Management Project, Ashtabula, OH. DOE/EM-0577, 30 pp, 2001

Abstracts of Journal Articles

Overcoming the Effects of Heterogeneities in DNAPL Source Zone Remediation

Describes the use of large-scale surfactant foam floods to overcome geological heterogeneities and remove TCE DNAPL at Hill Air Force Base.