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MNA of Metals and In Situ Bioremediation
Citation:
WILKIN, R. T. AND R. G. FORD. MNA of Metals and In Situ Bioremediation. Presented at The Federal Remediation Technologies Roundtable (FRTR) Meeting, Washington, DC, November 15, 2007.
Impact/Purpose:
To present information at the Federal Remediation Technologies Roundtable (FRTR) Meeting.
Description:
Monitored Natural Attenuation (MNA) is a frequently applied remediation option for organic contaminants in groundwater, especially fuel hydrocarbons and chlorinated compounds. Current lines of research examine whether or not MNA is more broadly applicable to inorganic contaminants, including metals, metalloids, and radionuclides. Indeed, in situ bioremediation approaches for treating inorganic contaminants attempt to strategically enhance either the rate or the capacity of naturally occurring processes in order to impact the solubility, reactivity, and toxicity of contaminant species. However, there are recognized technical distinctions between organic and inorganic contaminants. These distinctions, which relate to attenuation mechanisms and site characterization requirements, need to be considered in order to adequately select and monitor the performance of MNA as a component of a groundwater remedy. Technical distinctions between the applications of MNA for cleanup of organic versus inorganic contaminants are discussed in the 1999 OSWER Directive. The directive emphasizes that attenuation of inorganic contaminants is often due to sorption onto immobile aquifer solids. Furthermore, it is acknowledged that inorganic contaminants that are attenuated via sorption will persist in the subsurface. Thus, developing a site-specific technical basis for MNA as a component of the cleanup action will necessitate determination of the mass transfer process(es) leading to immobilization or degradation of the contaminant within the boundaries of the groundwater plume. The EPA is preparing a series of documents that address the technical basis for selection of MNA as a component of a remedy for cleanup of inorganic contaminants in groundwater. These documents provide an overview of the technical basis for natural attenuation of inorganic contaminants as well as site characterization requirements for application to specific non-radionuclides and radionuclides in groundwater. Emphasis is placed on characterization of immobilization and/or degradation processes that may control contaminant attenuation, in addition to analytical approaches to assess performance characteristics of the MNA remedy. In these documents, a tiered analysis process is adopted to provide a means to screen sites for MNA that is anticipated to be most effective because it prioritizes and limits the data that are needed for decision making at each screening step.
URLs/Downloads:
MNA OF METALS AND IN SITU BIOREMEDIATION
FEDERAL REMEDIATION TECHNOLOGIES ROUNDTABLE