Technical and economic evaluation of anaerobic membrane bioreactors for municipal wastewater treatment
[eng] Anaerobic membrane bioreactor (AnMBR), which is a combination of membrane separation and anaerobic digestion, is an emerging biotechnology for municipal sewage treatment. The application of AnMBRs in the mainline of wastewater treatment plants (WWTPs) can provide several advantages compared wi...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/185994 |
| Acceso en línea: | https://hdl.handle.net/2445/185994 http://hdl.handle.net/10803/674315 |
| Access Level: | acceso abierto |
| Palabra clave: | Bioreactors Reactors de membrana Digestió anaeròbia Osmosi Depuració d'aigües residuals Serveis públics Membrane reactors Anaerobic digestion Osmosis Purification of sewage Public utilities |
| Sumario: | [eng] Anaerobic membrane bioreactor (AnMBR), which is a combination of membrane separation and anaerobic digestion, is an emerging biotechnology for municipal sewage treatment. The application of AnMBRs in the mainline of wastewater treatment plants (WWTPs) can provide several advantages compared with conventional activated sludge processes, such as no aeration requirements, biogas production and reduction in the sludge management costs. However, despite these advantages, mainstream AnMBR application still presents challenges, whose resolution requires considering both technical and economic aspects. The goal of this thesis is to evaluate the technical and economic implications of implementing AnMBRs for municipal sewage treatment. Specifically, the thesis covered the techno-economic implications of two main topics: (i) forward osmosis (FO) pre- concentration before AnMBR, and (ii) plant-wide impact of AnMBR implementation in a WWTP. In the first part of this thesis, the techno-economic effects of combining FO and AnMBR technologies have been evaluated. First, a lab-scale mesophilic AnMBR operated at pre- concentration factors of 1, 2, 5 and 10 achieved chemical oxygen demand (COD) removal efficiencies above 90% for all the conditions. The differences between the soluble COD concentration of the permeate and digester suggested that membrane biofilm contributed to COD removal efficiency. Second, the techno-economic analysis of combining FO, reverse osmosis (RO) and AnMBR was conducted. The results showed that the wastewater treatment cost of the FO-RO+AnMBR system ranged between 0.80 and 1.40 € per m3 of wastewater treated. A sensitivity analysis illustrated that FO fluxes above 10 L m-2 h-1 (LMH) would improve the economic competitiveness of the FO-RO+AnMBR system. Finally, the impact of the draw solute and FO membrane material on the economic balance of this system was evaluated. The membrane material had a high impact on the economic balance since thin film composite (TFC) membranes substantially reduced the net cost when compared with cellulose triacetate (CTA) membranes. Conversely, the draw solute featured a moderate impact on the net cost. CH3COONa and CaCl2 were the most economically favourable draw solutes for CTA membrane, whereas MgCl2 was the most economically favourable draw solute for TFC membrane. In the second part of this thesis, the plant-wide impact of implementing AnMBRs in WWTPs has been evaluated. First, the effect of specific gas demand (SGD) and flux on membrane performance and process economics of granular AnMBRs was analysed. SGD and membrane flux impacted membrane fouling, but they did not impact organic matter rejection. The economic evaluation of granular AnMBRs showed that the most competitive strategy for fouling control relied on operating the membrane at normalised fluxes and SGDs of 7.8 LMH and 0.5 m3 m-2 h-1, respectively. Second, the economic feasibility of implementing mainstream AnMBR in a WWTP was evaluated for five different WWTP layouts. The results showed that the net treatment cost ranged between 0.33 and 0.43 € m-3 (100-1200 mg COD L-1) for WWTP layouts combining AnMBR, degassing membrane, primary settler and anaerobic digester. However, when partial nitritation-anammox and chemical phosphorus precipitation were included for nutrients removal, the net treatment cost increased from 0.33-0.43 to 0.51-0.56 € m-3. Finally, the techno-economic implications of co-digesting food waste with sewage sludge in the sidestream anaerobic digester of an AnMBR-WWTP were analysed. Co-digestion reduced the net cost of the sludge line when the nutrients backload was treated in the mainstream. However, when the nutrients backload was treated in the sidestream with partial nitritation-anammox and struvite crystallisation, the electricity revenue did not offset the additional costs of these two processes. The results also indicated that biosolids disposal cost represented the highest cost contributor in the sludge line of an AnMBR- WWTP. |
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