Evaluation of dynamic chemical gradients during the course of trichloroethene remediation using a fermentable substrate

Currently, trichloroethene (TCE) is the most prevalent groundwater contaminant in the United States. In situ bioremediation is an emerging technology for the treatment of chloroethenes, like TCE. Although TCE can be degraded through a variety of microbial processes, field studies indicate that naturally occurring degradation is most frequently incomplete, stalling at the toxic intermediates cis-1,2-dichloroethene and vinyl chloride. Besides a lack of an appropriate microbial population, the exact reason for incomplete dechlorination is unknown; however, it is accepted that a suitable electron donor source is critical for supporting microbial growth, creating strongly reducing conditions, and sewing as a supply of electrons for reductive dehalogenation. In this study, the fermentable substrate, chitin, was evaluated for its ability to support a diverse community of microorganisms capable of complete TCE remediation. To elucidate the complex interactions between chitin fermentation products and reductive dechlorination processes, a set of sacrificial, continuous flow columns were established. The columns were packed with a mixture of chitin and sand, inoculated with an appropriate mixed ̀ulture, and then supplied with a continuous flow of natural, TCE-amended groundwater. Effluent from the columns was collected every 4 - 5 days and monitored for chlorinated ethenes, pH, volatile fatty acids, chloride, and microbial DNA. Pore water and sediment from along the length of the columns was similarly collected every 1 - 2 pore volumes (20 - 40 days). This presentation will highlight the dynamic chemical gradients that were observed over the course of remediation, and forecast the distribution of the associated microbial community, which will be analyzed in future work.