Doctor of Philosophy (PhD)
Civil & Environmental Engineering Department
Engineered anaerobic bioreactors (ABR) constructed from mixed media and sand can biodegrade high concentrations of volatile organic compounds (VOCs). Sustainable treatment of benzene, toluene, ethylbenzene, and xylenes (BTEX), chlorinated ethenes and ethanes were used to investigate the use of engineered ABRs, while also analyzing the system performance of a full-scale ABR system. Experimentations conducted on environmental and biological factors that affect ABR system performance was conducted through serum bottles, columns, and reactor studies.
Column and reactor ABR systems were designed to treat VOCs via biodegradation in groundwater with varying terminal electron acceptors (TEAs). Laboratory-scale column ABRs were constructed to treat BTEX compounds while simultaneously adjusting the TEA processes in the bed between methanogenic and sulfate-reducing conditions. Analysis of the groundwater showed that amending the contaminated water with sulfate lead to higher percentages of degradation of BTEX. Experimentations showed that sizing of a full-scale ABR treatment bed would be controlled by benzene due to the lower removal efficiency and lower required discharge limits.
A two-phase pilot-scale ABR system was operated through the use of sequential anaerobic/aerobic ABRs to reductively dechlorinate 1,1,1-trichloroethane (TCA) to chloroethane (CA), followed by aerobic oxidation of CA. Two duplicate reactors operated in parallel in an up-flow mode were prepared for aerobic treatment studies of CA. Pure oxygen was supplied through a porous silastic tube under pressure with a pure oxygen gas cylinder. Investigations concluded that complete mineralization of chloroethane was observed in the effluents from the aerobic zone of the ABR system. During both studies, TEA changes were confirmed by using a 16S rRNA assessment of microbial populations within the ABR beds, which indicated a shift in bacteria and/or archaea to a more effectual degrading community structure.
Two full-scale ABR beds were analyzed for system performance through two sampling trips to the ReSolve, Inc. Superfund Site. Groundwater samples were collected along the length of both ABRs for analysis of chlorinated ethenes and ethanes, while suspended and attached bacteria samples were collected via groundwater and core sampling. Data collected from the Site determined that the ABRs displayed consistent losses of chlorinated ethenes and ethanes, with the exception of minor CA accumulation in the ABRs in 2014, with CA degradation occurring in 2015, showing that the system performance improved over the course of the year.
Pipkin, Leslie Michele, "Enhancing the Performance of Anaerobic Bioreactors for the Biological Degradation of Volatiles Organic Compounds in Groundwater Using Alternate Electron Acceptors" (2017). LSU Doctoral Dissertations. 4106.