In situ, field-scale evaluation of surfactant-enhanced DNAPL recovery using a single-well, ``push-pull'' test Page: 4 of 19
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Nonaqueous phase liquids (NAPLs), which include a variety of common petroleum fuels
and chlorinated solvents, are groundwater contaminants at many DOE sites. In the subsurface, a
portion of the NAPL (called residual NAPL) may become trapped in the pore space by capillary
forces. Conventional treatment technologies typically are ineffective in removing residual NAPL
because the slow rate of dissolution and low aqueous solubility of many NAPLs limit their removal
by extraction pumping. One approach for increasing the effectiveness of NAPL removal is to inject
surface-active-agents (surfactants) to enhance NAPL solubilization. Surfactant-enhanced DNAPL
recovery involves the use of injected surfactants to increase the solubility and/or mobility of
DNAPL in the subsurface in order 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, sorption,
precipitation, as well as ion exchange, which affect the transport and phase behavior of injected
surfactants. An innovative new site-characterization technology termed the single-well, "push-
pull" test method was used for this study. This technology has been the recent subject of
development at Oregon State University because it can be 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 overall goal of this project was to further develop the single-well, "push-pull" test
method as a feasibility-assessment and site-characterization 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 were:
(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
(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 trichloroethene (TCE),
(3) to demonstrate the utility of the developed test method for performing site
characterization and feasibility studies for surfactant-enhanced DNAPL recovery systems
in the field.
The project was a collaborative research effort between the Departments of Civil
Engineering and Environmental and Molecular Toxicology at Oregon State University (OSU).
The project was interdisciplinary and designed to utilize the scientific skills, experimental
systems, and analytical capabilities available in each department.
To address the three objectives, the research plan combined controlled intermediate-scale
laboratory experiments in unique physical aquifer models with a parallel series of pilot-scale
field experiments in existing monitoring wells at a TCE-contaminated field site. The physical
models were constructed in the shape of a circular arc ('piece of pie') to represent the alternating
diverging/converging radial flow field near a well during the injection and extraction phases of a
push-pull test. Intermediate-scale, push-pull test experiments (as opposed to studies in small
scale batch reactors or columns) were selected for this project because spatial and temporal
information on surfactant sorption, precipitation, and ion exchange in the vicinity of a monitoring
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Istok, J. D. & Field, J. A. In situ, field-scale evaluation of surfactant-enhanced DNAPL recovery using a single-well, ``push-pull'' test, report, October 1, 1999; Idaho Falls, Idaho. (digital.library.unt.edu/ark:/67531/metadc709476/m1/4/: accessed June 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.