Name of Candidate:
Trevor Patrick Needham
February 20, 2019; 2 pm
Abstract: Despite four decades since the ban on new commercial use and production, polychlorinated biphenyls (PCB) continue to persist in the environment with risk to human health and the ecosystem. Monitoring in a Waste Water Treatment Plant (WWTP), reported in this work, shows ongoing releases to the environment through wastewater effluent and biosolids, with evidence of some microbial dechlorination in the collection and treatment systems. Although microbial degradation of PCBs has been observed, these compounds are slow to degrade in the environment and the kinetic bottlenecks are not well understood. The overall objective of this research was to measure PCB anaerobic dechlorination kinetics, understand key bottlenecks, and quantify the effect of black carbon on kinetics.
Prediction of microbial bioremediation of polychlorinated biphenyl (PCB) has been a challenge in the past due to the difficulty in measuring the microbial kinetics at low environmentally relevant concentrations. The experimental design of the kinetic studies in this work relied heavily on a novel passive dosing/passive sampling approach that allowed kinetic measurements at low ng/L dissolved concentrations of PCBs. Kinetics of microbial dechlorination was demonstrated to be controlled by the freely dissolved concentrations in microcosms with or without sediments. The research demonstrates that with a combination of accurate measurement of the freely dissolved concentration in water and an understanding of site-specific partitioning characteristics, it is possible to predict PCB microbial dechlorination in sediments for bioaugmentation or monitored natural attenuation in sediments. Microcosm studies with activated carbon focused on three different sources of anaerobic bacteria consisting of Dehalobium chlorocoercia (DF1), the West Branch Consortium (WBC-2), and anaerobic wastewater sludge from the Back River WWTP. The addition of activated carbon did not result in a statistically significant increase in dechlorination activity in the microbial communities tested.