Effectiveness of complex organic electron donors with respect to PCE dechlorination is investigated.

"The primary goal of this research was to determine the ability of a culture taken from a bulk-aerobic fluidized-bed reactor (FBR) to dechlorinate tetrachloroethylene (PCE) under anaerobic conditions when provided with an electron donor and nutrient source. Subsequent objectives examined the effects of toluene, 1,1,1-trichloroethane (TCA), and chloroform (CF) on the dechlorination of PCE."--Abstract.

The introduction of synthetic organic chemicals into the environment during the last few decades has given rise to major concern about the ecotoxicological effects and ultimate fate of these compounds. The pollutants that are considered to be most hazardous because of their intrinsic toxicity, high exposure level, or recalcitrant behavior in the environment have been placed on blacklists and other policy priority lists. The fate of synthetic compounds that enter the environment is mainly determined by their rate of biodegradation, which therefore also has a major effect on the degree of bioaccumulation and the risk of ecotoxicological effects. The degree and rate of biodegradation is also of critical importance for the feasibility of biological techniques to clean up contaminated sites and waste streams. The biodegradation of xenobiotics has thus been the subject of numerous studies, which resulted in thousands of publications in scientific journals, books, and conference proceedings. These studies led to a deeper understanding of the diversity of biodegradation processes. As a result, it has become possible to enhance the rate of degradation of recalcitrant pollutants during biological treatment and to design completely new treatment processes. At present, much work is being done to expand the range of pollutants to which biodegradation can be applied, and to make treatment techniques less expensive and better applicable for waste streams which are difficult to handle.

Tetrachloroethylene (PCE) and trichloroethylene (TCE) are among the most frequently detected ground water contaminants at industrial sites, including many DoD facilities. Due to the high cost and uneven performance of traditional remediation technologies, monitored natural attenuation is emerging as a new technology for ground water remediation of pollutants such as these. In addition, there is growing interest in active remediation technologies that employ abiotic minerals. PCE and TCE are susceptible to reductive dechlorination by microorganisms as well as reduced minerals such as iron sulfide (FeS). Unlike biological reductive dechlorination, which often results in accumulation of harmful intermediates such as cis 1,2-dichloroethylene (cis-DCE) and vinyl chloride (VC), abiotic mineral-mediated dechlorination of PCE and TCE tends to result in complete transformation to non-toxic products such as acetylene. To more accurately apply natural attenuation and other remediation technologies, a greater understanding of the geochemical factors affecting the rates of purely abiotic reductive dechlorination of PCE and TCE is needed. Additional tools are also needed to determine whether or not abiotic reductive dechlorination is occurring at a particular site, and its relative importance compared to microbial dechlorination under a variety of geochemical conditions.