Effect of Activated Sludge Bioselector Designs on Estrogen-Degradation Kinetics

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PI: H. David StenselProposal Number: CBET-106744Institution: University of WashingtonTitle: Effect of Activated Sludge Bioselector Designs on Estrogen-Degradation KineticsEstrogens are known endocrine disruptor compounds (EDC) that can affect aquatic life at concentrations as low as 0.35 ng/L. A main source of aquatic estrogen contamination is wastewater treatment plant (WWTPs) effluents. Estrogens enter the WWTP through normal human water use. In order of their EDC potency these estrogens are 17á-ethynyl estradiol (EE2, a synthetic estrogen), 17â- estradiol (E2), estrone (E1) and estriol (E3). Biological degradation is a primary estrogen removal mechanism at WWTPs and EE2 is degraded much slower than E1 and E2. Prior work by the research team found that heterotrophic bacteria play a major role in estrogen biodegradation even when grown on a wide range of organic substrates. Laboratory experiments with three bioreactors fed synthetic feed showed that EE2, E1 and E2 degradation kinetics varied among reactors configured for anaerobic/aerobic sequenced treatment, which selects for phosphorus accumulation organism; anoxic/aerobic sequenced treatment, which selects for facultative organisms; and aerobic treatment. The anaerobic and anoxic selector designs are also important for biological nutrient removal (BNR) systems, commonly used today. Critical questions for this research are: (1) will similar relative degradation kinetics for the different microbial populations (anaerobicaerobicanoxic) occur when treating actual municipal wastewater versus synthetic, (2) how will microbial populations compare within the selector designs, and (3) can EE2-degrading bacteria be identified for study in pure culture. Parallel bench scale reactors similar to those described above for the three configurations treating municipal primary effluent will be integrated with mechanistic modeling and advanced molecular and microbial techniques to address biodegradation kinetics of estrogens at relevant ng/L concentrations. Specific research goals include: (1) Evaluate the effect of selector/BNR process designs on estrogen removal performance; (2) compare the EE2, E1, and E2 degradation kinetics in the different reactor configurations; (3) characterize the microbial populations for the different selector designs through terminal restriction fragment length polymorphism (T-RFLP), (4) determine if the fraction of estrogen-degrading biomass is higher for the bioreactors with higher specific estrogen degradation rates, and (5) evaluate estrogen degradation ability of microbial isolates obtained from the study bioreactors (including anaerobic and anoxic selectors). The results will be incorporated into a comprehensive estrogen/activated sludge model based on the International Water Association ASM1 and ASM2d models. The estrogen/ASM1 model has been completed by us by applying the industry GPS-X software. Similar work will be done with the ASM2d model, which includes enhanced biological phosphorus removal. The models include free and conjugated forms of E1, E2 and EE2, deconjugation and biodegradation kinetics, possible production of E1 from E2 degradation, and liquid-solids partitioning of estrogens.The intellectual merit of the project is its transformational approach, which integrates modeling the fate of a micropollutant in a biological process with a fundamental co-substrate mechanism, bioselector design effects, and microbial composition based on molecular methods. A second potential far reaching benefit will be the development of pure cultures capable of EE2 degradation under condition similar to WWTP for future kinetic and genetic studies, and development of qPCR primer sets for monitoring select EE2-degrading heterotrophs in WWTP facilities.The broader impacts of the project are benefits to society by providing a basis to optimize WWTP biotreatment design to minimize estrogen release to the environment. Direct educational benefits include the training of graduate students, and participation of undergraduate researchers. Increased participation by underrepresented groups will be realized through established University of Washington programs and continued partnership with the UW, College of Engineering Office of Diversity.