Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
The Scenic Highway area of the PetroProcessors of Louisiana, Inc. (PPI) Superfund site located near Baton Rouge, LA, has groundwater contaminated with a variety of chlorinated alkanes (e.g., 1,2-dichloroethane, 1,2-dichloropropane) and alkenes (e.g., trichloroethene and vinyl chloride). In March 2009, a field-scale pilot test was conducted to evaluate the efficacy of injecting diluted agricultural feed grade molasses into the groundwater in an effort to stimulate in-situ reductive dechlorination of these chlorinated contaminants. Because H2 plays an important role as an electron donor in the metabolism of reductively dechlorinating bacteria, in support of the pilot-scale effort, experiments described in this thesis were conducted to better understand the biological hydrogen production potential of the microbial populations from contaminated groundwater at the site. As a means of evaluating the capacity of microbial populations derived from the site to produce H2 as a potential renewable energy source, additional experiments were carried out to evaluate the rate and yield of hydrogen production using molasses as a feedstock. Batch-mode experiments carried out in a laboratory-scale bioreactor inoculated with groundwater from the PPI site revealed that molasses was rapidly fermented with concomitant H2 production at all pH values tested (ranging from 4.5 to 7.5). In the batch tests, a pH of 5.5 resulted in the highest total production H2 with a net yield of 1.47 mol-H2¬/g-glucose. H2 production rates at higher pH values (6.5 and 7.5) decreased over time due to homoacetogensis and methanogenesis. At a pH of 4.5, H2 production was characterized by lower production rates lasting for a longer period of time. The microbial consortia developed during batch-mode experiments were subsequently employed in continuous-flow (CSTR) experiments to further evaluate the effects of pH on the rate, yield, and stability of H2 production. As with batch-mode experiments, the highest H2 production rate (averaging 8.86 L/L/d over a two-month interval) and yield (1.93 mol-H2/mol-glucoseconsumed) was obtained at pH 5.5. In short-term experiments, supplying elevated concentrations of 1,2-dichloroethane in the bioreactor feed was found to have a slight positive effect on H2 production rate and yield.
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Narez, Hector, "Hydrogen Production from Molasses Using Chlorinated Alkane-contaminated Groundwater as an Inoculum" (2010). LSU Master's Theses. 3852.
Moe, William M.