Membrane enhanced A/B staged biological processes to harvest energy and reuse municipal wastewater

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Recently, a paradigm shift is emerging in wastewater industry, considering it from a waste stream that needs to be disposed of, to a valuable resource from which to produce reusable water, generate energy and recover other valuable resources. A benchmarking energy study published by Water Environmental Research Foundation concluded that municipal wastewater could contain approximately ten times the energy needed to treat it. Yet, most wastewater treatment practices currently being employed are very energy-intensive because of the necessity to supply a large amount of oxygen for biodegradation. Similarly, technological advance provides great potential to recover non-renewable phosphorous from municipal wastewater economically. The goal of this study is to develop and optimize membrane enhanced A/B staged biological process (MeA/B) that can maximize energy recovery, while providing the opportunities to recover other valuable resources and reuse wastewater. Stage-A bioreactor consisting of an anaerobic zone ahead of aerobic zone offers distinct features: 1) to maximize the conversion of organic matter in wastewater into biomass through bioflocculation because of extremely short SRT, 2) to minimize excessive sludge decay to reduce the oxygen demand for biodegradation, and 3) to produce phosphorous-rich biomass, thereby, providing an opportunity to recover it from the supernatant of subsequent sludge digesters. Further synergistic benefits could be realized by incorporating membrane aerated biofilm reactor (MABR) process as Stage-B treatment. The bubbleless aeration of MABR could achieve extremely high oxygen transfer efficiency. The effective removal of organic matter by Stage-A bioreactor also helps control serious sludge clogging problem within Stage-B membrane modules. Extensive experiments will be conducted to examine the feasibility of MeA/B system in terms of effluent quality, sludge production and phosphorous removal. Emphasis will be placed on Stage-A A/O process by identifying key factors affecting the bioflocculation of biomass, characterizing the fundamental interactions between the microbial ecology and process performance and, developing the strategies to improve sludge settleability. As well, the performance of MABR process will be assessed by characterizing the biofilm attached onto membrane surface and measuring oxygen transfer rate and nitrification efficiency. Finally, a series of experiments will be performed to quantify the biological stoichiometric and kinetic parameters. The collected data are then used as model inputs to modify and calibrate a new integrated process model.If successful, this project will provide Canadian municipalities and private water industry with an energy-producing wastewater treatment process in addition to the potential for water reuse and phosphorous recovery. As well, the research will provide a better understanding of the biofloculation of sludge and establish the linkage between microbial community ecology and process performance in short SRT bioreactors. This project will also result in effective strategies to improve sludge settleability. The process models developed from this research can aid in designing and optimizing membrane enhanced A/B staged biological processes when used in practice. Finally, this project will provide training opportunities for 3 PhD students, 3 MSc students and 1 post-doctoral fellow who are now in high demand because of rapid expansion of water industry in Canada.