Feasibility investigation for monitored natural attenuation of a shallow chlorinated solvent plume at the former Naval Training Center, Orlando, Florida
Ramaley, Seth Bullock
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A two layer site-conceptual model is proposed to explain the attenuation of chlorinated solvents at the NTC, Orlando site. Microcosm biodegradation experiments investigated the rates and extent of Perchloroethylene (PCE), Trichloroethylene (TCE), and Dichloroethylene (DCE) degradation by indigenous microbial communities in NTC, Orlando site sediments. Microcosms amended with different carbon substrates (acetate, lactate, corn oil, molassess, a polylactate ester HRC[reg], and yeast extract) were used to determine if in-situ biodegradation could be enhanced and implemented in the clean up plan for the site. The biodegradation experiments consisted of both batch vials and continuously stirred bioreactor vessels containing site sediment and site groundwater. Provided with extra carbon sources, the chloroethenes were dehalogenated to ethene. Degradation patterns suggest dehalorespirating processes are responsible for biodegradation in the source zone and co-metabolic processes exist away from the source zone. Biodegradation was enhanced by the additions of carbon sources in both the surface and deep sediments, with the best results obtained by using amendments of acetate or lactate with yeast extract. The results of this laboratory feasibility study warrant a scale up field test for enhanced bioremediation as a remedial technology for the site.