Grantee Research Project Results
1999 Progress Report: Investigation of the Entrapment and Surfactant Enhanced Recovery of Nonaqueous Phase Liquids in Heterogeneous Sandy Media
EPA Grant Number: R825409Title: Investigation of the Entrapment and Surfactant Enhanced Recovery of Nonaqueous Phase Liquids in Heterogeneous Sandy Media
Investigators: Abriola, Linda M. , Pennell, Kurt D. , Dane, Jacob H.
Institution: University of Michigan , Auburn University Main Campus , Georgia Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period: November 1, 1996 through October 31, 1999
Project Period Covered by this Report: November 1, 1998 through October 31, 1999
Project Amount: $449,938
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Objective:
The primary objectives of this research project are to: (1) investigate the influence of scale and formation heterogeneity on the entrapment and surfactant-enhanced recovery of nonaqueous phase liquids (NAPLs) in two-phase sandy aquifer systems, and (2) refine and validate numerical simulators that may be used for the design and prediction of surfactant-enhanced aquifer remediation (SEAR) performance at the field scale.Progress Summary:
Progress has been made in each of the four task areas: (1) measurement of fundamental fluid properties, solubilization capacities, and completion of one-dimensional column experiments for the quantification of dissolution rate limitations; (2) refinement and adaptation of numerical models for two-phase NAPL migration and entrapment, and for surfactant-enhanced recovery; (3) experimental measurement of NAPL infiltration and entrapment processes in small- and large-scale two-dimensional tanks; and (4) experimental and numerical investigation of surfactant-enhanced solubilization of perchloroethylene (PCE) in two- dimensional sand tanks.Fundamental parameters, including density, viscosity, and interfacial tension, were measured for PCE and surfactant/cosolvent solutions. The addition of cosolvents to the surfactant formulations was considered to modify the density of the flushing solutions and to evaluate the influence of cosolvents on solubilization kinetics and recovery efficiency.
A series of one-dimensional column experiments were conducted to measure the solubilization of PCE by different surfactant/cosolvent solutions and to quantify the influence of rate-limited solubilization on PCE recovery efficiency in porous media. Column effluent PCE concentrations were well below equilibrium values indicating rate-limited interphase mass transfer. Results showed that initial steady-state column effluent PCE concentrations decreased with increasing pore-water velocity, and decreased with decreasing ethanol concentration. Initial steady-state effluent concentrations were used to develop mass transfer correlations for flowing systems as a function of pore-water velocity. PCE concentrations in elution peaks following flow interrupts were found to increase with increasing duration of flow interruption and to increase with increasing ethanol concentration. Mass transfer correlations also were developed for flow interrupt conditions as a function of flow interrupt duration.
Experiments in large-scale, highly monitored two-dimensional laboratory sand tanks were conducted to investigate the impact of macroscale heterogeneities on two-phase NAPL migration and entrapment. The macro-heterogeneities were observed to impart considerable influence on the PCE migration pathway. PCE was not observed entering the low permeability zones, but instead it was flowing around and pooling over the sand lenses. A series of partitioning tracer experiments were conducted to obtain information about the PCE saturation.
The influence of surfactant-facilitated interfacial tension reduction on PCE infiltration pathways and entrapment was investigated in a series of laboratory experiments in smaller scale sand tanks. At large interfacial tensions, the PCE did not penetrate the low permeability lenses, and instead pooled on top and flowed laterally around the lenses. At reduced interfacial tensions, PCE migration pathways additionally depended on the soil entry pressure of the lens for the specific pore fluid.
The effects of rate-limited micellar solubilization and subsurface layering on PCE recovery by 4 percent Tween 80 plus 5 percent ethanol were evaluated in two two-dimensional box studies. The cosolvent solution containing 5 percent ethanol was selected for this portion of the research, primarily due to considerations for neutral buoyancy SEAR. Good PCE recovery was obtained in both surfactant flush experiments, typically ranging between 65?70 percent in about 7?8 pore volumes. In some experiments, density override of the surfactant solution was visually observed, leading to some bypassing of the PCE pools.
A numerical model has been developed that is capable of simulating two-phase flow processes (aqueous-gas or aqueous-organic) and constituent transport for a variable number of phase constituents. The model can account for sorption; biodegradation; nonequilibrium interphase partitioning among the aqueous, gas, organic, and solid phases; and surfactant-enhanced solubilization processes. The model has been used to simulate NAPL infiltration and surfactant flush experiments in the laboratory sand tanks. In general, good agreement with measured results has been obtained. The degree of accuracy, however, depends on the ability to characterize fluid and soil properties, including the mass transfer coefficients and soil heterogeneity.
Future Activities:
Future work will focus on the continued enhancement of the numerical simulation model enhancement and its application to the analysis of the sand tank experiments. The numerical model will be used to simulate enhanced solubilization experiments in which ethanol was used to obtain neutral buoyancy effects. Numerical simulations will be used to study tracer experiments conducted in the large sand tank system.Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 23 publications | 5 publications in selected types | All 4 journal articles |
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Rathfelder KM, Abriola LM, Taylor TP, Pennell KD. Surfactant enhanced recovery of tetrachloroethylene from a porous medium containing low permeability lenses: 2. Numerical simulation. Journal of Contaminant Hydrology 2001;48(3-4):351-374. |
R825409 (1998) R825409 (1999) R825409 (Final) |
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Taylor TP, Pennell KD, Abriola LM, Dane JH. Surfactant enhanced recovery of tetrachloroethylene from a porous medium containing low permeability lenses: 1. Experimental studies. Journal of Contaminant Hydrology 2001;48(3-4):325-350. |
R825409 (1999) R825409 (Final) |
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Supplemental Keywords:
groundwater, soil, sediment, adsorption, chemicals, toxics, PCBs, solvents, DNAPL, surfactants, remediation, cleanup, restoration, surfactant-enhanced aquifer remediation, SEAR, engineering, geology, environmental chemistry, mathematics, modeling, analytical, measurement methods., RFA, Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Remediation, Environmental Chemistry, HAPS, Chemistry, Fate & Transport, Hazardous Waste, Hazardous, Environmental Engineering, SEAR technology, fate and transport, fate and transport , NAPL, contaminant transport, surfactant enhanced aquifer remediation, transport contaminants, dual energy gamma radiation system, chemical contaminants, pump and treat systems, geochemistry, saturated porous media, ecological impacts, hazardous chemicals, assessment methods, heterogenous sandy media, NAPLs, porous mediaProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.