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Arsenic
Chromium VI Dense Nonaqueous Phase Liquids (DNAPLs) 1,4-Dioxane Dioxins Mercury MTBE Perchlorate POPs PCBs TCE Other Contaminants
Treatment Technologies 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 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.
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 Surfactant Enhanced Remediation of a DNAPL Contaminated Aquifer At least two pools of DNAPL (a mixture of TCE, PCE, 1,1,1-TCA, and Freon 113) have been identified in Operational Unit 2 at Hill Air Force Base. Based on the phase behavior experiments, sodium dihexyl sulfosuccinate (MA) was chosen as the surfactant for the Phase I and Phase II field tests. An 11-day Phase I test was conducted in May '96 to (1) quantify the amount of DNAPL within the test area by a tracer test and (2) demonstrate that injection of surfactant can be carried out effectively without causing problems with confinement or plugging. The Phase II test was carried out in July '96 to remove as much as possible of the DNAPL remaining within the test area after Phase I and to demonstrate the effectiveness of the surfactant-enhanced aquifer remediation process by following it with a tracer test to determine the remaining DNAPL saturation.
Contains brief overviews of field applications of in situ flushing for a variety of contaminants, including DNAPLs.
Building 25, Morale, Welfare and Recreation (MWR) Dry Cleaners, Camp Lejeune Marine Corps Base, Camp Lejeune, NC 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.
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.
This report summarizes the results of the cosolvent (alcohol) flushing pilot test conducted at the former Sages Dry Cleaner Facility to remediate PCE DNAPL.
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.
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.
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
Long Term Multilevel Monitoring of the Mass Discharge of Chloroethenes Following Ethanol Flushing at Former Sages Drycleaning Site
Pilot-Scale Demonstration of Surfactant-Enhanced PCE Solubilization at the Bachman Road Site. 1. Site Characterization and Test Design
Pilot-Scale Demonstration of Surfactant-Enhanced PCE Solubilization at the Bachman Road Site. 2. System Operation and Evaluation
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.
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.
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.
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. |