Remediating Ground Water with Zero-Valent Metals: Chemical Considerations in Barrier Design |
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| Authors: | Paul G Tratnyek Timothy L Johnson Michelle M Scherer Gerald R Eykholt |
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| Institution: | Paul G. Tratnyek;is an associate professor in the Department of Environmental Science and Engineering at the Oregon Graduate Institute (P.O. Box 91000, Portland, OR 97291;e-mail: tratnyek@ese.ogi.edu). He received his Ph.D. from the Colorado School of Mines in 1987. Tratnyek served as a National Research Council postdoctoral fellow at the U.S. Environmental Protection Agency Laboratory in Athens, Georgia, during 1988 and as a research associate at the Swiss Federal Institute for Water Resources and Water Pollution Control (EAWAG) from 1989 to 1991. His research has involved remediation with zero-valent iron metal since he joined the University of Waterloo Solvents-in-Groundwater Research Programme in 1992. Timothy L. Johnson;is currently a postdoctoral associate at the Oregon Graduate Institute (Department of Environmental Science and Engineering, P.O. Box 91000, Portland, OR 97291) studying the effects of ligands on dechlorination by zero-valent iron. He was a DOE energy research fellow from 1993 to 1995 and received an AGWSE graduate student fellowship in 1994. Michelle M. Scherer;is currently a doctoral candidate at the Oregon Graduate Institute (Department of Environmental Science and Engineering, P.O. Box 91000, Portland, OR 97291) using electrochemical techniques to probe the reaction of chlorinated solvents with zero-valent iron. Scherer has an M.S. in environmental engineering from the University of Connecticut and received an AGWSE graduate student fellowship in 1995. Gerald R. Eykholt;is assistant professor in the Department of Civil and Environmental Engineering at the University of Wisconsin, Madison (Madison, WI 53706). His prior position was as staff scientist at General Electric Corporate Research and Development, Schenectady, New York. Eykholt received his M.S. and Ph.D. degrees from the University of Texas, Austin. |
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| Abstract: | To gain perspective and insight into the performance of permeable reactive barriers containing granular iron metal, it is useful to compare the degradation kinetics of individual chlorinated solvents over a range of operating conditions. Pseudo first-order disappearance rate constants normalized to iron surface area concentration (kSA) recently have been reported for this purpose. This paper presents the results of further exploratory data analysis showing the extent to which variation in kSA is due to initial halocarbon concentration, iron type, and other factors. To aid in preliminary design calculations, representative values of kSA and a reactive transport model have been used to calculate the minimum barrier width needed for different ground water flow velocities and degrees of halocarbon conversion. Complete dechlorination of all degradation intermediates requires a wider treatment zone, but the effect is not simply additive because degradation occurs by sequential and parallel reaction pathways. |
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