Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Civil and Environmental Engineering
Zitomer, Daniel H.
Anaerobic biotechnology is viewed as a sustainable alternative to aerobic biotechnology for municipal wastewater recovery. However, anaerobic processes have not been successful in cold climates. Past examples have not been able to meet low organic effluent concentrations, or have failed due to biomass washout resulting from low temperature operation and short hydraulic residence time. Recently, the anaerobic membrane bioreactor (AnMBR) has been shown to achieve low effluent organic concentrations and maintain stable anaerobic biomass. However, shortcomings have included high energy demands for membrane operation and poor understanding of microbial community structures within AnMBRs. This dissertation describes efforts to improve AnMBRs by developing a low energy membrane operation strategy and describes the microbial relationships responsible for organic removal. Two different AnMBR configurations were operated at both 10 and 25oC. The AnMBRs achieved over 94% organic removal with average permeate five-day biochemical oxygen demand (BOD5) concentrations remaining at 10 mg/L or less while treating synthetic or real primary effluent municipal wastewater. The AnMBRs utilized either ceramic or polymeric external tubular membranes that were operated at crossflow velocities (CFV) ranging from 0.018 to 0.3 m/s, which is below the typical CVF range of 2 to 5 m/s. Use of fluidized granular activated carbon (GAC) within the membranes at very low CFV extended membrane run time between cleanings by 55 to 120% and resulted in energy demands of 0.07 to 0.15 kWh/m3, which represents a 98% energy savings compared to historical energy requirements. Additionally, Illumina sequencing and statistical techniques were used to characterize the microbial consortia within each AnMBR. Results indicated a large portion of the microbial communities were composed of only 5 out of over 700 uniquely identified operational taxonomic units. Unique microbial community structures were observed in each bioreactor during synthetic wastewater operation, ostensibly due to selective pressures including bioreactor configuration and temperature. A significant shift in all AnMBR microbial populations was observed when switching from synthetic to real wastewater, suggesting that continual bioreactor seeding with influent wastewater microbiota impacts bioreactor community composition. Sequencing and results of activity assays also indicated that hydrogenotrophic methanogenesis emerged as the dominant pathway in each AnMBR.