Minquan Jin's dissertation
by
Minquan Jin, Ph.D.
University of Texas at Austin, 1995
Supervisors: Gary A. Pope
Kamy Sepehrnoori
The objectives of this research were to identify and evaluate environmentally
acceptable surfactants that could be used for surfactant enhanced aquifer remediation
and to develop a partitioning tracer test method for the detection, estimation, and
remediation performance assessment of subsurface nonaqueous phase liquids.
First, a systematic approach for selection of surfactants for the remediation of
nonaqueous phase liquid contaminated subsurface was developed. The approach entails
the observations of the classical Winsor type phase behavior of the
surfactant-water-tetrachloroethylene mixtures in calibrated test tubes. The basic
observations consist of how many and what type of phases form, how fast equilibrium
is approached, and how much tetrachloroethylene is solubilized. The mixtures of
sodium diamyl, sodium dihexyl and sodium dioctyl sulfosuccinates were found to yield
both Winsor Type I and Type III phase behavior based on the diamyl or dihexyl to
dioctyl sulfosuccinate ratio and calcium chloride concentration, which are ideal
properties for enhancing the solubility of tetrachloroethylene and lowering the
interfacial tension to mobilize the residual tetrachloroethylene phase.
The effectiveness of these sodium sulfosuccinate mixtures were then tested in sand
column experiments to recover trapped residual tetrachloroethylene. The results of
these column experiments show that the selected surfactants have the capacity to
simultaneously enhance the aqueous solubility of tetrachloroethylene and to mobilize
tetrachloroethylene as a separate phase and remove more than 99% of residual
tetrachloroethylene from sandpack columns.
The mobilization of trapped residual nonaqueous phase liquid was investigated from
theoretical and experimental perspectives. A trapping number which combines the
effects of buoyancy and viscous forces was derived. This trapping number option was
implemented in UTCHEM, a three-dimensional chemical flood simulator developed at The
University of Texas at Austin. From a practical perspective, the trapping number
provides a basis for assessing the potential for dense nonaqueous phase liquid
mobilization during surfactant remediation operation and minimizes the possibility of
the uncontrolled downward migration of mobilized dense nonaqueous phase liquids into
uncontaminated parts of the aquifer.
The most important contribution of this research is the development of a new
partitioning interwell tracer test method for detection, estimation, and remediation
performance assessment purposes. The method can be used in both saturated and
unsaturated soils contaminated by either light or dense nonaqueous phase liquids.
The key elements that need to be considered when designing and interpreting a
field-scale tracer test are discussed. Validation of this technique is illustrated
by both laboratory column experiments and numerical simulation results. Finally, the
design of two field partitioning interwell tracer tests, an unsaturated zone
partitioning interwell tracer at the site of the Chemical Waste Landfill at Sandia
National Laboratories and a saturated zone partitioning interwell tracer in an
isolation test cell within Operable Unit 1 at Hill Air Force Base in Utah is
presented.
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