CENSUS – Chlorinated Ethenes
Characterization of sites impacted by chlorinated solvents such as tetrachloroethene (PCE) and trichloroethene (TCE) initially emphasizes determination of contaminants of concern (COCs) and evaluation of site geologic and hydrogeologic conditions. Following this first phase, additional site characterization often focuses on evaluation of attenuation mechanisms including biodegradation to ultimately lead to an effective corrective action. Chemical and geochemical data including the concentrations of contaminants, daughter products, and terminal electron acceptors (dissolved oxygen, nitrate, iron, sulfate, etc.) obtained during site characterization provide the first two lines of evidence to evaluate the feasibility of bioremediation as a remedial alternative. While providing valuable information, both are somewhat indirect approaches to assess biological activity. The most direct avenue to evaluate biodegradation as a treatment mechanism is to directly quantify the microorganisms or biological processes responsible for biodegradation of the contaminants of concern. Following is a breakdown of the CENSUS targets available for evaluating biodegradation of chlorinated ethenes.
CENSUS Targets for Reductive Dechlorination (Analysis of Dehalococcoides, Dehalobacter, Dehalogenimonas and other bacteria capable of reductive dechlorination)
Under anaerobic conditions, PCE can be sequentially dehalogenated through TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC) to ethene via microbially mediated reductive dechlorination. Because ethene is an innocuous end product, reductive dechlorination is an attractive treatment mechanism for PCE/TCE-impacted sites.