Graduate Research and Discovery Symposium (GRADS)

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Aeration costs in traditional activated sludge systems are the highest operational cost of wastewater treatment plants and account for approximately 0.75% of the total U.S. energy consumption. In an effort to subset these energy costs, anaerobic wastewater treatment allows for the generation of methane-rich biogas, making a normally energy-intensive process energy-neutral or even energy-positive. Efficient operation of anaerobic processes usually require heating wastewater to mesophilic or thermophilic temperatures, which is not feasible for secondary treatment. Therefore, operating anaerobic bioreactors in cold climate conditions is a challenge. The slow growth of microbes at cold temperatures impacts the efficiency of anaerobic bioreactors causing a need for long solid retention times (SRTs). Anaerobic membrane bioreactors (AnMBR) eliminate sludge washout, increase SRTs, and allow for treatment of wastewater at low temperatures. However, membrane fouling and reliable treatment at low temperatures remain as two primary challenges for AnMBRs. Since the temperature of untreated domestic wastewater (DWW) in the South Carolina ranges from 13 to 27ºC, it is necessary to characterize the performance of AnMBRs for DWW treatment within these ranges of seasonal variation. The performance of the reactor is likely to vary as a result of the changing microbial community that is responsible for converting complex organics in the waste (like carbohydrates, proteins, and lipids) to their end product of methane through a complex series of biochemical reactions. One goal of this study is to evaluate the change in reactor performance as a function of varying bioreactor temperature. Performance is evaluated by monitoring biogas production and chemical oxygen demand (COD) removal. Another goal is to quantify mcrA gene expression in RNA as a function of varying bioreactor temperature. The mcrA gene is a functional gene that has been related to the production of methane by methanogenic communities. The last objective of the study is to establish a relationship between the microbial community structure at different temperatures and the AnMBR performance. This will be done by completing a metagenomic analysis on the communities existing at different temperatures. By further understanding the microbial components and relating them with the performance of the AnMBR, we can better understand the functionality of specific microbial comminutes and therefore better inform, operate, and design anaerobic resource recovery processes for maximum effectiveness.