Techno-economic analysis of combining forward osmosis-reverse osmosis and anaerobic membrane bioreactor technologies for municipal wastewater treatment and water production

The economic feasibility of combining forward osmosis (FO), reverse osmosis (RO) and anaerobic membrane bioreactor (AnMBR) technologies for municipal wastewater treatment with energy and water production was analysed. FO was used to pre-concentrate the AnMBR influent, RO for draw solution regeneration and water production, and AnMBR for wastewater treatment and energy production. The minimum wastewater treatment cost was estimated at 0.81 ¿ m-3, achieved when limiting the FO recovery to 50% in a closed-loop scheme, however, the cost increased to 1.01 and 1.27 ¿ m-3 for FO recoveries of 80% and 90%, respectively. The fresh water production cost was estimated at 0.80 and 1.16 ¿ m-3 for an open-loop scheme maximising water production and a closed-loop scheme, respectively. The low FO membrane fluxes were identified as a limiting factor and a sensitivity analysis revealed that FO membrane fluxes of 10 LMH would significantly improve the competitiveness of FO-RO+AnMBR technology

Co-digestion of sewage sludge and food waste in a wastewater treatment plant based on mainstream anaerobic membrane bioreactor technology: A techno-economic evaluation

The implementation of anaerobic membrane bioreactor as mainstream technology would reduce the load of sidestream anaerobic digesters. This research evaluated the techno-economic implications of co-digesting sewage sludge and food waste in such wastewater treatment plants to optimise the usage of the sludge line infrastructure. Three organic loading rates (1.0, 1.5 and 2.0 kg VS m− 3 d− 1 ) and different strategies to manage the additional nutrients backload were considered. Results showed that the higher electricity revenue from co-digesting food waste offsets the additional costs of food waste acceptance infrastructure and biosolids disposal. However, the higher electricity revenue did not offset the additional costs when the nutrients backload was treated in the sidestream (partial-nitritation/anammox and struvite precipitation). Biosolids disposal was identified as the most important gross cost contributor in all the scenarios. Finally, a sensitivity analysis showed that food waste gate fee had a noticeable influence on co-digestion economic feasibilit

Techno-economic analysis of forward osmosis pre-concentration before an anaerobic membrane bioreactor: Impact of draw solute and membrane material

This research investigated the impact of draw solute and membrane material on the economic balance of a forward osmosis (FO) system pre-concentrating municipal sewage prior to an anaerobic membrane bioreactor (AnMBR). Eight and three different draw solutes were evaluated for cellulose triacetate (CTA) and polyamide thin film composite (TFC) membranes, respectively. The material of the FO membrane was a key economic driver since the net cost of TFC membrane was substantially lower than the CTA membrane. The draw solute had a moderate impact on the economic balance. The most economically favourable draw solutes were sodium acetate and calcium chloride for the CTA membrane and magnesium chloride for the TFC membrane. The FO + AnMBR performance was modelled for both FO membrane materials and each draw solute considering three FO recoveries (50, 80 and 90%). The estimated COD removal efficiency of the AnMBR was similar regardless of the draw solute and FO membrane material. However, the COD and draw solute concentrations in the permeate and digestate increased as the FO recovery increased. These results highlight that FO membranes with high permselectivity are needed to improve the economic balance of mainstream AnMBR and to ensure the quality of the permeate and digestate

Impact of permeate flux and gas sparging rate on membrane performance and process economics of granular anaerobic membrane bioreactors

This research investigated the impact of permeate flux and gas sparging rate on membrane permeability, dissolved and colloidal organic matter (DCOM) rejection and process economics of granular anaerobic membrane bioreactors (AnMBRs). The goal of the study was to understand how membrane fouling control strategies influence granular AnMBR economics. To this end, short- and long-term filtration tests were performed under different permeate flux and specific gas demand (SGD) conditions. The results showed that flux and SGD conditions had a direct impact on membrane fouling. At normalised fluxes (J20) of 4.4 and 8.7 L m−2 h−1 (LMH) the most favourable SGD condition was 0.5 m3 m−2 h−1, whereas at J20 of 13.0 and 16.7 LMH the most favourable SGD condition was 1.0 m3 m−2 h−1. The flux and the SGD did not have a direct impact on DCOM rejection, with values ranging between 31 and 44%. The three-dimensional excitation-emission matrix fluorescence (3DEEM) spectra showed that protein-like fluorophores were predominant in mixed liquor and permeate samples (67-79%) and were retained by the membrane (39-50%). This suggests that protein-like fluorophores could be an important foulant for these systems. The economic analysis showed that operating the membranes at moderate fluxes (J20 = 7.8 LMH) and SGD (0.5 m3 m−2 h−1) could be the most favourable alternative. Finally, a sensitivity analysis illustrated that electricity and membrane cost were the most sensitive economic parameters, which highlights the importance of reducing SGD requirements and improving membrane permeability to reduce costs of granular AnMBRs

Advances in anaerobic membrane bioreactor technology for municipal wastewater treatment: A 2020 updated review

The application of anaerobic membrane bioreactors (AnMBR) for mainstream municipal sewage treatment is almost ready for full-scale implementation. However, some challenges still need to be addressed to make AnMBR technically and economically feasible. This article presents an updated review of five challenges that currently hinder the implementation of AnMBR technology for mainstream sewage treatment: (i) membrane fouling, (ii) process configuration, (iii) process temperature, (iv) sewage sulphate concentration, and (v) sewage low organics concentration. The gel layer appears to be the main responsible for membrane fouling and flux decline being molecules size and morphology critical properties for its formation. The review also discusses the advantages and disadvantages of five novel AnMBR configurations aiming to optimise fouling control. These include the integration of membrane technology with CSTR or upflow digesters, and the utilisation of scouring particles. Psychrophilic temperatures and high sulphate concentrations are two other limiting factors due to their impact on methane yields and membrane performance. Besides the methane dissolved in the effluent and the competition for organic matter between sulphate reducing bacteria and methanogens, the review examines the impact of temperature on microbial kinetics and community, and their combined effect on AnMBR performance. Finally, the review evaluates the possibility to pre-concentrate municipal sewage by forward osmosis. Sewage pre-concentration is an opportunity to reduce the volumetric flow rate and the dissolved methane losses. Overall, the resolution of these challenges requires a compromise solution considering membrane filtration, anaerobic digestion performance and economic feasibility

Sustainability assessment of green ammonia production to promote industrial decarbonization in Spain

This article investigates the economic and environmental implications of implementing green ammonia production plants in Spain. To this end, one business-as-usual scenario for gray ammonia production was compared with three green ammonia scenarios powered with different renewable energy sources (i.e., solar photovoltaic (PV), wind, and a combination of solar PV and wind). The results illustrated that green ammonia scenarios reduced the environmental impacts in global warming, stratospheric ozone depletion, and fossil resource scarcity when compared with conventional gray ammonia scenario. Conversely, green ammonia implementation increased the environmental impacts in the categories of land use, mineral resource scarcity, freshwater eutrophication, and terrestrial acidification. The techno-economic analysis revealed that the conventional gray ammonia scenario featured lower costs than green ammonia scenarios when considering a moderate natural gas cost. However, green ammonia implementation became the most economically favorable option when the natural gas cost and carbon prices increased. Finally, the results showed that developing efficient ammonia-fueled systems is important to make green ammonia a relevant energy vector when considering the entire supply chain (production/transportation). Overall, the results of this research demonstrate that green ammonia could play an important role in future decarbonization scenarios.This study has been supported by the Research Spanish Agency (AEI) through the projects REEMEs (PID2021-127028OB-I00) and SUSTDESALT (TED2021-131708B-C21). Additionally, the authors acknowledge the Open Innovation - Research Translation and Applied Knowledge Exchange in Practice through University–Industry Cooperation (OpenInnoTrain) with the grant agreement number (GAN) 823971 (H2020-MSCA-RISE-2018-823971), and the Catalan government (2021-SGR-GRC-00596). J. L. Cortina received support for the research through the “ICREA Academia” recognition for excellence in research funded by the Generalitat de Catalunya.Peer ReviewedPostprint (published version

Potential of anaerobic co-fermentation in wastewater treatments plants: A review

Fermentation (not anaerobic digestion) is an emerging biotechnology to transform waste into easily assimilable organic compounds such as volatile fatty acids, lactic acid and alcohols. Co-fermentation, the simultaneous fermentation of two or more waste, is an opportunity for wastewater treatment plants (WWTPs) to increase the yields of sludge mono-fermentation. Most publications have studied waste-activated sludge co-fermentation with food waste or agri-industrial waste. Mixing ratio, pH and temperature are the most studied variables. The highest fermentation yields have been generally achieved in mixtures dominated by the most biodegradable substrate at circumneutral pH and mesophilic conditions. Nonetheless, most experiments have been performed in batch assays which results are driven by the capabilities of the starting microbial community and do not allow evaluating the microbial acclimation that occurs under continuous conditions. Temperature, pH, hydraulic retention time and organic load are variables that can be controlled to optimise the performance of continuous co-fermenters (i.e., favour waste hydrolysis and fermentation and limit the proliferation of methanogens). This review also discusses the integration of co-fermentation with other biotechnologies in WWTPs. Overall, this review presents a comprehensive and critical review of the achievements on co-fermentation research and lays the foundation for future researc

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 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.[spa] El biorreactor anaeróbico de membranas (AnMBR, por sus siglas en inglés) es una tecnología emergente para el tratamiento de aguas residuales municipales. El AnMBR no requiere de aeración, produce biogás y reduce la producción de fangos en comparación con procesos convencionales de lodos activos. Sin embargo, la aplicación del AnMBR en estaciones depuradoras de aguas residuales (EDAR) es muy limitado, ya que la tecnología debe superar barreras técnicas y económicas antes de una implementación generalizada. El objetivo de esta tesis es evaluar las implicaciones técnicas y económicas de implementar el AnMBR para el tratamiento de aguas residuales municipales. En concreto, la tesis aborda dos temáticas relacionadas con el AnMBR: (i) preconcentración del agua residual municipal mediante osmosis directa (FO, por sus siglas en inglés), e (ii) impacto global de implementar un AnMBR en una EDAR. En la primera parte de esta tesis se ha evaluado la combinación de las tecnologías de FO y AnMBR. El sistema experimental AnMBR alcanzó eliminaciones de demanda química de oxígeno por encima del 90% para el tratamiento de aguas residuales preconcentradas. Un análisis tecno-económico sobre la combinación de la FO, osmosis inversa y AnMBR mostró que el coste de tratamiento osciló entre 0,80 y 1,40 € por m3 de agua residual tratada. Los resultados también mostraron que el material de la membrana de FO tuvo un gran impacto sobre el balance económico del sistema. En la segunda parte de esta tesis se ha evaluado el impacto de implementar un AnMBR en una EDAR. La demanda específica de gas y el flujo de permeado tuvieron un impacto directo sobre el ensuciamiento de la membrana en un sistema AnMBR con fango granular. El análisis tecno-económico de la implementación de un AnMBR en una EDAR mostró que el coste de tratamiento se situaba entre 0,33 y 0,43 € m-3 para configuraciones que combinaron AnMBR, membrana de desgasificación, sedimentador primario y digestor anaeróbico. Finalmente, se determinó que la codigestión de fangos y residuos alimenticios tiene el potencial de reducir el coste de la línea de fangos de una EDAR que utiliza un AnMBR para tratar las aguas residuales

Unravelling the economics behind mainstream anaerobic membrane bioreactor application under different plant layouts

This research evaluated the economic feasibility of anaerobic membrane bioreactor (AnMBR) as a mainstream technology for municipal sewage treatment. To this end, different wastewater treatment plant (WWTP) layouts were considered, including primary settler, AnMBR, degassing membrane, partial nitritation-Anammox, phosphorus precipitation and sidestream anaerobic digestion. The net treatment cost of an AnMBR-WWTP decreased from 0.42 to 0.35 ¿ m-3 as the sewage COD concentration increased from 100 to 1100 mg COD L-1 due to revenue from electricity production. However, the net treatment cost increased above 0.51 ¿ m-3 when nutrient removal technologies were included. The AnMBR and partial nitritation-Anammox were the costliest processes representing a 57.6 and 30.3% of the treatment cost, respectively. Energy self-sufficiency was achieved for high-strength municipal sewage treatment (1000 mg COD L-1) and a COD:SO42--S ratio above 40. Overall, the results showed that mainstream AnMBR has potential to be an economically competitive option for full-scale implementation

Assessing the impact of granular anaerobic membrane bioreactor intensification on treatment performance, membrane fouling and economic balance

Anaerobic membrane bioreactors (AnMBRs) have attracted much attention for mainstream domestic wastewater treatment. However, membrane fouling, operating costs, energy consumption and low filtration flux are important challenges slowing the scale-up of the technology. In this study and for the first time, granular sludge, submerged membrane, no gas sparging and low permeate flux were chosen to mitigate membrane fouling and to improve the energy and economic balance of an AnMBR. A granule-based AnMBR (G-AnMBR) was operated under four organic loading rates (between 0.5 and 1.6 kgCOD.m–3.d–1) with hydraulic retention times ranged from 13.9 to 4.9 h, and instantaneous permeate flux levels (Jp20,inst) ranged from 2.8 to 6.0 LMH to evaluate OLR impact on anaerobic digestion performance, membrane fouling extent and economic balance. Results show that COD removal rates above 83 % were achieved during the four experimental periods. Membrane fouling was directly correlated to the flux and OLR and increased from 0.03 to 2.86 kPa.d–1 as the Jp20,inst increased from 2.8 to 6.0 LMH and the OLR increased from 0.5 to 1.6 kgCOD.m–3.d–1, respectively. In all the periods, macromolecules and colloidal proteins were the major foulants deposited on the membrane. Most of the fouling was reversible and was easily removed by physical cleaning (>97.7 %). A preliminary economic assessment revealed that the permeate flux and OLR are key economic drivers for the G-AnMBR economic balance and allowed to define the satisfactory compromise between membrane purchase and chemical consumption for the long-term control of membrane fouling.Peer ReviewedPostprint (author's final draft