The Effect of Clay on DNAPL Behavior During Alcohol FlushingEPA Grant Number: R827120
Title: The Effect of Clay on DNAPL Behavior During Alcohol Flushing
Investigators: Hayden, Nancy J.
Institution: University of Vermont
EPA Project Officer: Lasat, Mitch
Project Period: December 1, 1998 through November 11, 2001 (Extended to June 21, 2003)
Project Amount: $375,240
RFA: Exploratory Research - Environmental Engineering (1998) RFA Text | Recipients Lists
Research Category: Sustainability , Land and Waste Management , Engineering and Environmental Chemistry
The overall objective of the proposed research project is to investigate the effect of clays (and clay colloids) on the distribution of dense nonaqueous phase liquids (DNAPLs) in porous media and the subsequent effect on DNAPL dissolution, mass transfer and interfacial phenomena during alcohol flushing. Subsurface environments contaminated with DNAPLs are currently difficult, if not impossible, to remediate using current methods, such as pump and treat. An improved understanding of DNAPL behavior is critical for improving restoration attempts using innovative in-situ methods such as alcohol flushing. The impact of clays and colloidal clay on the behavior of DNAPLs in the subsurface including effects on distribution, dissolution and remediation is unknown.
A unique series of experiments and analyses will be performed at the micro-scale, pore-scale, and column-scale levels to meet the objectives. Both swelling and nonswelling clays will be used in batch, and column experiments. The impact of the amount of clay present will also be investigated. Initial characterization of the clays will include X-ray diffraction, infra-red spectroscopy (IR) and measurements of hydrophobicity, particle size distribution and others. Batch experiments will be used to investigate the effect of clay colloids on interfacial phenomena and dissolution in alcohol solutions. Column studies will be used to determine: pressure-saturation relationships for water-DNAPL systems; permeabilities with and without a residual DNAPL saturation; residual DNAPL saturation and trapping; dissolution; and remobilization of the DNAPL during water and alcohol flushing. Long columns will be used to investigate mobilization on a larger scale. X-ray diffraction, IR and electrophoretic studies will be performed to determine changes in clay characteristics due to interaction of clays with DNAPLs and alcohol solutions. Pore-scale studies will be done to visualize and quantify the effects of clays on pore shape, pore size and DNAPL ganglia size and shape using Environ. Scanning Electron Microscopy (ESEM).
The benefits of this research will be to advance our understanding the effect of clays on interfacial phenomenon, and soil characteristics related to DNAPLs and DNAPL remediation. A fundamental understanding of clay and clay colloids on DNAPL behavior and in-situ DNAPL remediation technologies is currently needed for the further development and application of cost effective environmental restoration techniques. Remediation techniques which address the DNAPL source areas are essential in order to better manage and reduce the risk associated with hazardous waste sites. The results of this research will be disseminated in refereed publications and at national conferences. Additional benefits of this research include enhancing graduate education within the Department of Civil and Environmental Engineering at the University of Vermont (UVM) and providing interaction with Chemistry and Geology (UVM), and MIT's Center for Materials Science.