Author: David A. Sabatini
Publisher:
ISBN:
Category : Dense nonaqueous phase liquids
Languages : en
Pages : 18

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 212

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Due to the limitations of conventional groundwater remediation technologies, innovative methods have been sought to enhance the removal of recalcitrant compounds such as trichloroethylene (TCE) and tetrachloroethylene (PCE), which are frequently trapped in the subsurface as dense nonaqueous phase liquids (DNAPLs). Surfactant-Enhanced Aquifer Remediation (SEAR) is one such method, which has been adapted from enhanced oil recovery techniques used by the petroleum industry. It involves sweeping a surfactant solution across the DNAPL-contaminated portion of the aquifer. The surfactants accomplish rapid removal of the DNAPL contaminant by greatly increasing its effective aqueous solubility and by reducing the interfacial tension between the DNAPL and water phases. In field demonstrations conducted to date, up to 99% removal efficiencies have been achieved with just three pore volumes of surfactant followed by water flooding. In a typical remediation scheme, surfactants are used to remediate DNAPL source areas and complement the use of other technologies, such as conventional pump- and -treat systems, for removing the dissolved-phase plumes that are associated with DNAPL source areas. Currently, simple options for remediating DNAPL source areas are limited. Residual DNAPL in an aquifer acts as a continual source of contamination to the groundwater, and site closure cannot be achieved unless the source is removed. This surfactant-based technology will be more cost-effective than conventional pump-and-treat systems and will provide for a more rapid site cleanup.

Author: Konstantinos Kostarelos
Publisher:
ISBN:
Category : Soil remediation
Languages : en
Pages : 660

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"The two most important outstanding issues regarding surfactant enhanced aquifer remediation of DNAPL [Dense Nonaqueous Phase Liquids] sites are the risk of downward migration of the DNAPL to lower, uncontaminated groundwater or underlying clean aquifers and the impact of aquifer heterogeneity. The first of these problems has been addressed and solved by this research. The main objective was to prevent vertical migration of microemulsion (and thus dense contaminants) when using surfactant solutions to recover DNAPLs from the subsurface and still remove essentially all of the DNAPL with a reasonable amount of surfactant. When surfactant solution solubilizes DNAPL, the resulting microemulsion is denser than the surrounding fluid and thus tends to migrate downward. Unless a good capillary barrier exists below the DNAPL, vertical migration can cause contamination of clean groundwater below the DNAPL and should be avoided. Since many sites do not have a known lower confining layer with certainty, this problem needed to be addressed so that surfactant enhanced aquifer remediation could be more widely used and used with acceptable risk and effectiveness. The DNAPLs used in these experiments were trichloroethylene and perchloroethylene. and the surfactant was sodium dihexyl sulfosuccinate. Isopropanol was used in the surfactant solution to lower the density of the microemulsion that formed when the DNAPL was solubilized and has other benefits as well. This approach, termed neutral buoyancy, was used to prevent vertical migration. To test the concept, several major steps were taken. First, a suitable surfactant exhibiting classical Winsor phase behavior was selected. Density measurements were made of the microemulsions formed when the surfactant solution solubilized DNAPL, using various alcohols in the solution. Next, column experiments were done to ensure that the surfactant solution exhibited good behavior when used to recover the DNAPL from a sandpack. Finally, a model aquifer was constructed. and experiments designed and performed. Three tank experiments were made to demonstrate the neutral buoyancy concept. The first experiment was designed so that the microemulsion would exhibit a small degree of vertical migration but would still be recovered by the extraction well of the model. The second experiment was designed with a large degree of vertical migration that would render the microemulsion unrecoverable before it reached the bottom of the tank. The third tank experiment used a neutrally buoyant design to demonstrate that DNAPL can be removed from a coarse sand layer on top of a clean fine sand layer that would not be an adequate barrier for downward migration of microemulsion (and thus contaminant) if it were not neutrally buoyant. The main contribution of this research work was solving the problem of vertical migration of microemulsion so that surfactant solutions could be used at field sites that are not underlain by a capillary barrier. The neutral buoyancy concept was developed and was verified in these experiments"--Leaves v-vii.

Author: Nichole L. Case
Publisher:
ISBN:
Category :
Languages : en
Pages : 224

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 152

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During 1996 and 1997, five separate partitioning interwell tracer tests (PITTs) were conducted as part of two separate surfactant-enhanced aquifer remediation (SEAR) demonstrations targeting DNAPL (primarily TCE) at Operable Unit 2 (OU2), Hill Air Force Base, Utah. These PITTs were used as a DNAPL characterization tool to accurately determine: 1.) the total aquifer volume swept; 2.) the total amount of DNAPL present in the swept aquifer volume; and, 3.) the average residual saturation present. PITTs were conducted before and after each SEAR demonstration to provide remediation performance assessments and were hydraulically controlled without using sheetpile walls. The successful implementation of field-scale PITTs required an engineering design strategy using conventional characterization activities, laboratory studies, and UTCHEM modeling. The volume sampled by each PITT was on the order of an average of 6500 cu ft (14,000 gallon pore volume). Tracer recoveries ranged from 79% to 92%, indicating that, within experimental error, all of the injected tracers were recovered. The method of temporal moments was used to analyze each PITT, and the resulting DNAPL volume estimates were in close agreement with other measurements (e.g. SEAR DNAPL recoveries and core data estimates). Thus, in sandy alluvium, PITTs are very accurate estimators of DNAPL volumes, and provide an excellent characterization and performance assessment tool for DNAPL remediation efforts. Based on the success of these PITTs, the USAF is currently conducting large-scale PITTs to characterize the entire DNAPL source zone at OU2.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309065496
Category : Science
Languages : en
Pages : 301

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Book Description
This book presents a comprehensive, up-to-date review of technologies for cleaning up contaminants in groundwater and soil. It provides a special focus on three classes of contaminants that have proven very difficult to treat once released to the subsurface: metals, radionuclides, and dense nonaqueous-phase liquids such as chlorinated solvents. Groundwater and Soil Cleanup was commissioned by the Department of Energy (DOE) as part of its program to clean up contamination in the nuclear weapons production complex. In addition to a review of remediation technologies, the book describes new trends in regulation of contaminated sites and assesses DOE's program for developing new subsurface cleanup technologies.

Author: Chrissi Lynn Brown
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages :

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 4

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Surfactant enhanced DNAPL recovery involves the use of injected surfactants to increase the solubility and/or mobility of DNAPL in the subsurface to reduce the time and cost required for site remediation. The successful design of a surfactant enhanced DNAPL recovery system requires a quantitative understanding of the competing processes of DNAPL solubilization and mobilization, and sorption, precipitation, and microbial degradation of injected surfactant components. An innovative new site-characterization technology, the single-well, push-pull test method, is currently under development at Oregon State University and has been successfully used in the field to determine a wide range of aquifer physical, chemical, and biological characteristics. A push-pull test consists of the controlled injection of a prepared test solution into a single monitoring well followed by the extraction of the test solution/groundwater mixture from the same well. The type, combination, and concentration of injected solutes is selected to investigate specific aquifer characteristics. The overall goal of this project is to further develop the single-well, push-pull test method as a new site characterization and feasibility assessment tool for studying the fundamental fate and transport behavior of injected surfactants and their ability to solubilize and mobilize DNAPLs in the subsurface. The specific objectives are: (1) to develop a modified push-pull test for use in identifying and quantifying the effects of sorption, precipitation, and biodegradation on the fate and transport of injected surfactants, (2) to use the developed test method to quantify the effects of these processes on the ability of injected surfactants to solubilize and mobilize residual phase trichloroethylene, and (3) to demonstrate the utility of the developed test method for performing site characterization and feasibility studies for surfactant enhanced DNAPL recovery systems.

Author: Jan Schaerlaekens
Publisher:
ISBN:
Category :
Languages : en
Pages : 186

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Author: David A. Sabatini
Publisher:
ISBN:
Category : Language Arts & Disciplines
Languages : en
Pages : 320

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Book Description
Provides a timely and thorough review of surfactant-based remediation technologies. Covers fundamental mechanistic studies to scale-up and process modeling and full-scale field implementation studies. Summarizes the technical, economic, and sociopolitical issues affecting widespread implementation of these technologies. Includes contributions from academic and industrial researchers as well as regulatory personnel.