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Interactions between Biological and Abiotic Pathways in the Reduction of Chlorinated Solvents
Citation:
Brown, R., J. Mueller, A. Seech, J. K. Henderson, AND J. T. WILSON. Interactions between Biological and Abiotic Pathways in the Reduction of Chlorinated Solvents. Remediation Journal. John Wiley & Sons, Ltd., Indianapolis, IN, 20(1):9-20, (2009).
Impact/Purpose:
Purpose - observing abiotic reductive processes for the remediation of chlorinated solvents
Description:
While biologically mediated reductive dechlorination continues to be a significant focus of chlorinated solvent remediation, there has been an increased interest in abiotic reductive processes for the remediation of chlorinated solvents. In situ chemical reduction (ISCR) uses zero valent iron (ZVI) based technologies such as nano-scale iron and bimetallic ZVI, as well as naturally occurring reduced minerals incorporating dual valent iron (DVI), such as magnetite, green rust and iron sulfides that are capable of dechlorinating solvents. A more recent area of development in ISCR has been in combining biological and abiotic processes. There are several ways in which biological and abiotic processes can be combined. First, the interaction between the two may be “causative”. For example, AFCEE’s BiRD (biogeochemical reductive dechlorination) technology combines a mulch barrier with hematite and gypsum to create an iron-sulfide based reducing zone. Biodegradation under sulfate reducing conditions produces sulfide which combines with the hematite to form iron sulfides. As such, the BiRD technology is “causative;” the biological processes create reducing minerals. The biological generation of other reducing minerals such as magnetite, siderite and green rust is feasible and is, with magnetite, observed in nature at some petroleum sites. A second type of interaction between abiotic and biotic processes is “synergistic”. For example biological processes can enhance the activity of reduced metals/minerals. This is the basis of the EHC® ISCR technologies, which combine ZVI with a (slowly) degradable carbon substrate. This combination rapidly creates buffered, strongly reducing conditions which result in more complete solvent degradation (i.e., direct mineralization). The extent and level of reducing activity commonly observed are much greater when both the carbon substrate and the ZVI are present. When the carbon substrate is expended the reducing activity due to ZVI alone is much less. The understanding of biogeochemical processes and their impact on abiotic processes is still developing. As that understanding develops, new and improved methods will be created to enhance VOC destruction.
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INTERACTIONS BETWEEN BIOLOGICAL AND ABIOTIC PATHWAYS IN THE REDUCTION OF CHLORINATED SOLVENTS
Abstract