Title: DCE/VC Stall Tool (Web Tool) 
Resource Type: web links 
Producers or distributor NAVFAC 
Author / Producer Type: Agency, regulator or other governmental or inter-governmental body 
Web link for product information: http://www.ert2.org/DCE/tool.aspx  
EUGRIS Keyword(s): Contaminated land-->Remediation options-->In situ treatment technologies
Short description: . The ability of microorganisms to transform chlorinated solvents to innocuous end products enabled the development of in situ bioremediation as a remedial strategy; however, complete dechlorination of perchloroethene (PCE) and trichloroethene (TCE) to innocuous end products (e.g., ethene and ethane) is not always observed. When the reductive dechlorination process is incomplete, levels of dichloroethene (DCE) and/or vinyl chloride (VC) can build up over time in groundwater. This process is referred to as DCE/VC stall, and it can limit the ability of a bioremediation approach to meet cleanup goals and obtain site closure. The purpose of this training tool is to provide remedial project managers with the information necessary to recognize DCE and/or VC stall. A video graphic can be played that explains reductive dechlorination of PCE and TCE to DCE, VC, and ethene. This tool also explores the biological and/or environmental causes of DCE/VC stall, along with potential solutions. Reductive dechlorination of PCE and TCE to DCE appears at most sites where the redox potential in the aquifer is sufficiently reducing (e.g., iron to sulfate reduction), but at some sites, conditions for complete reductive dechlorination of PCE or TCE to ethene are not present, and degradation stalls at DCE and/or VC. Three basic requirements must be met to form a complete reductive dechlorination pathway: sufficient electron donor (a fermentable carbon source), appropriate redox potential (strongly reducing conditions) in the aquifer, and microbial communities capable of complete dechlorination of PCE to ethene. 
Submitted By: Professor Paul Bardos WhoDoesWhat?      Last update: 01/11/2011

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