Demonstration of Bioaugmentation at Kelly AFB: Cost & Performance Report

Chlorinated ethenes such as tetrachloroethene (PCE) and trichloroethene (TCE) are some of the most common groundwater contaminants found at Department of Defense (DoD) facilities. In addition to their common presence, these compounds are persistent under most natural geochemical conditions at these contaminated sites. Remediation of these sites through biodegradation of the chlorinated ethenes is a promising alternative at many of the sites. Reductive dechlorination is the primary pathway for biodegradation of chlorinated solvents. With this pathway, the chlorine atoms on the ethenes are sequentially replaced by hydrogen atoms through a biologically-mediated process. Generally, the hydrogen is generated through fermentation of an electron donor. Although many microorganisms are capable of mediating the reductive dechlorination process, only Dehalococcoides ethenogenes is known to completely reduce PCE and TCE to ethene. Unfortunately, D. ethenogenes is not present at all choroethenecontaminated sites and the reductive dechlorination process stalls at cis-1,2-dichloroethene (c- DCE). Under conditions such as these, the application of enriched cultures containing D. ethenogenes or closely related microorganisms is used to complete the reductive dechlorination process. The primary objective of the demonstration was to determine if complete reductive dechlorination could be stimulated through the introduction of a culture known to contain halorespiring bacteria. Secondary objectives involved testing the robustness of the applied culture by depriving it of electron donor and adding sulfate to the system. Samples were collected at a frequency and analyses were performed to evaluate the objectives of the demonstration. The results of the chemical analyses indicated that the complete dechlorination was achieved through the addition of the microbial culture. The original document contains color images.