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EVALUATION AND ANALYSIS OF MICROSCALE FLOW AND TRANSPORT DURING REMEDIATION
Citation:
Yortsos, Y. C., K. Shing, AND J S. Cho*. EVALUATION AND ANALYSIS OF MICROSCALE FLOW AND TRANSPORT DURING REMEDIATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-99/022, 1999.
Impact/Purpose:
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Description:
The design of in-situ remediation is currently based on a description at the macroscopic scale. Phenomena at the pore and pore-network scales are typically lumped in terms of averaged quantities, using empirical or ad hoc expressions. These models cannot address fundamental remediation issues at the pore and pore network scales, including: The emplacement in-situ of the contaminant NAPL, and the displacement patterns; the mass transfer of the contaminant from the NAPL to the groundwater to a sparging fluid, and of the remedial agents to the NAPL; and possible microscale flow instabilities during injection of a remedial fluid. The objective of this work is to obtain a fundamental understanding by conducting theoretical, experimental and computational pore-scale studies. Emphasis is placed at the pore network scale. Use of this information can be incorporated in macroscopic simulators to provide fundamentally correct expressions for the various coefficients or parameters, currently treated empirically. The theoretical findings are compared with findings from experiments in glass micromodels and Hele-Shaw cells. Specific tasks of the work described include: 1. The determination of immiscible displacement patterns that develop during seepage of NAPLs in the groundwater or during air sparging of contaminated groundwater. 2. The pore-scale study of the mass transfer from a trapped NAPL to an injected remedial fluid. 3. A sensitivity analysis of the effective mass transfer coefficient on parameters such as the flow rate and the pattern geometry. 4. Studies of pore-scale instabilities developing during miscible displacements in porous media, particularly when non-monotonic viscosity profiles are involved. 5. The up-scaling of the information obtained to the macroscopic scale. 6. Finally, the comparison of theoretical predictions with experimental results obtained in etched-glass micromodels and Hele-Shaw cells in order to validate and improve the theoretical models. The research described here is expected to improve the fundamental understanding of remediation processes, to help in the more accurate design of remediation projects, to assess in the screening of new or proposed remediation techniques and to help in the design of new ones. More generally, the research will contribute to the advancement of the state of the science in pollution abatement.