Organic-Based Permeable Reactive Barriers for the Treatment of Heavy Metals, Arsenic, and Acidity - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 149

Recent data have suggested that the cow manure/wood chip/limestone
mixture may be beginning to fail. Reasons for this are unclear although
it may be a result of the wood chips not being able to sustain microbially
mediated sulfate reduction at an adequate rate compared to the cow manure.
Alternatively, groundwater flow velocities may have been significantly faster
in the presence of wood chips, thereby reducing the residence time in the
PRB relative to the pilot PRB without the wood chips. Differences in hydrau-
lic conductivity between the two mixtures using slug tests could not be dis-
cerned with any confidence in the study.
The addition of ZVI in an organic-based PRB system likely better ensures
the removal of arsenic and also, likely enhances the longevity of organic-
based PRB systems by providing a long-term source of H 2 . However, ZVI-
induced pH increases may also promote more clogging of PRB systems,
particularly in the presence of highly mineralized groundwater.
References
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Bouwer, H. and R.C. Rice. 1976. A slug test method for determining hydraulic con-
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Butler, J.J., Jr. 1997. The Design, Performance, and Analysis of Slug Tests . Lewis Publishers,
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Delvin, J.F. 2003. A spreadsheet method for estimating best-fit hydraulic gradients
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