Search

An anaerobic membrane bioreactor (AnMBR) treated domestic sewage at 15 °C under different hydraulic retention time (HRT) conditions (6, 12, 16, and 24 h). Propidium monoazide (PMA)-PCR excluded microorganisms without intact cell membranes, focusing on the viable microbial community in anaerobic digestion. The results showed that the 6-hour HRT had poor treatment performance: low chemical oxygen demand removal efficiency (below 80%) and high mean trans-membrane pressure and flux (15 kPa and 9.4 L/(m 2 h)). Comparatively, PMA-PCR combined with next-generation sequencing improved the identification of microbial changes compared to conventional 16S rRNA gene sequencing. HRT influenced microorganisms in the hydrolysis and acid-production stages, including carbohydrate-degrading bacteria such as Bifidobacterium and Prevotella 1. Remarkably, a comparison with an AnMBR at 25 °C showed Proteobacteria to be the main cause of membrane fouling in the low-temperature AnMBR, with most operational taxonomic units negatively correlated with HRT and solids retention time., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The anaerobic membrane bioreactor (AnMBR) has gained huge attention as a municipal wastewater (MWW) treatment process that combined high organics removal, a low sludge yield and bioenergy recovery. In this study, a 20 L AnMBR was set up and operated steadily for 70 days in temperate conditions with an HRT of 6 h and a flux of 12 LMH for the treatment of real MWW, focusing on the behavior of the major elements (C, N, P and S) from an elemental balance perspective. The results showed that the AnMBR achieved more than 85 % COD removal, a low sludge yield (0.081 gVSS/gCOD removed ) and high methane production (0.31 L-CH 4 /gCOD removed ) close to the theoretical value. The elemental flow analysis revealed that the AnMBR converted 77 % of the influent COD to methane (57 % gaseous and 20 % dissolved) and 6 % of the COD for sludge production. In addition, the AnMBR converted 34 % of the total carbon to energy-generated carbon, and only 3 % was in the form of CO 2 in the biogas for further upgradation, which was in line with the concept of carbon neutrality. Since little nitrogen or phosphorus were removed, the permeate was nutrient-rich and further treatment to recover the nutrients would be required. This study illustrates the superior performance of the AnMBR for MWW treatment with a microscopic view of elemental behavior and provides a reference for implementing the mainstream AnMBR process in carbon-neutral wastewater treatment plants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Two anaerobic membrane bioreactors (AnMBRs) equipped with different membrane pore size (0.4 or 0.05 µm) were operated at 25˚C and fed with domestic wastewater. The hydraulic retention time (HRT) of the reactors was shortened. The microbial communities of the two AnMBRs were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT. The predominant Archaea was an aceticlastic methanogen Methanosaeta. The composition of hydrogenotrophic methanogens changed with the HRTs: the population of Methanobacterium was higher for longer HRTs, whereas the population of unclassified Methanoregulaceae was higher for shorter HRTs. The Anaerolineae, Bacteroidia and Clostridia bacteria were dominant in both of the reactors, with a combined relative abundance of over 55%. The relative abundance of Anaerolineae was proportional to the biogas production performance. The change in the population of hydrogenotrophic methanogens or Anaerolineae can be used as an indicator for process monitoring. The sum of the relative abundance of Anaerolineae and Clostridia fluctuated slightly with changes in the HRT in both AnMBRs when the reactor was stably operated. The co-occurrence analysis revealed the relative abundance of the operational taxonomic units belonging to Anaerolineae and Clostridia was functionally equivalent during the treatment of real domestic sewage. A principal coordination analysis revealed that the changes in the microbial community in each reactor were consistent with the change of HRT. In addition, both the HRT and the stability of the process are important factors for maintaining microbial community structures., (Copyright © 2021. Published by Elsevier B.V.)

Sludge yield and suspended solid are important factors concerned in the anaerobic treatment of municipal wastewater. In this study, a large pilot-scale anaerobic membrane bioreactor (AnMBR) was constructed for effectively treating real municipal wastewater at an ambient temperature of 25 °C. The sludge yield and the degradation of influent suspended solids were evaluated during the long-term operation of the AnMBR. This reactor with 5.0 m 3 effective volume is the largest one-stage submerged AnMBR that has ever been used to treat municipal wastewater. During the long-term operation of 217 days, this AnMBR obtained excellent COD and BOD 5 removal efficiency over 90%. Stable biogas production was also successfully obtained from treating municipal wastewater. The sludge yield of the AnMBR was approximately 0.19-0.26 g MLSS g -1 COD removed for the treatment of real municipal wastewater. The shortest SRT of the AnMBR was calculated as 29 days for an HRT of 6 h at an empirical MLSS of 10 g L -1 . While the influent suspended solid (SS) contained in the municipal wastewater was completely removed by the AnMBR, only 57%-66% of the influent SS was degraded. The rest of influent SS was directly converted to MLSS instead of being degraded. The AnMBR maintained a stable membrane filtration using a hollow-fiber membrane with a total area of 72 m 2 , realizing a flux of 2.75-17.83 LMH, and the mean transmembrane pressure (TMP) was 0.9-23.5 kPa. An online chemical backwash cleaning system helped to lower the TMP timely using sodium hypochlorite and citric acid when the TMP increased rapidly and reached the rated limit of membrane. This is the first report on demonstrating the successful operation and detailed performance of a large pilot-scale AnMBR applied to the treatment of real municipal wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A submerged anaerobic membrane reactor (SAnMBR) was employed for comprehensive evaluation of sewage treatment at 25 °C and its performance in removal efficiency, biogas production and membrane fouling. Average 89% methanogenic degradation efficiency as well as 90%, 94% and 96% removal of total chemical oxygen demand (TCOD), biochemical oxygen demand (BOD) and nonionic surfactant were obtained, while nitrogen and phosphorus were only subjected to small removals. Results suggest that SAnMBRs can effectively decouple organic degradation and nutrients disposal, and reserve all the nitrogen and phosphorus in the effluent for further possible recovery. Small biomass yields of 0.11 g mixed liquor volatile suspended solids (MLVSS)/gCOD were achieved, coupled to excellent methane production efficiencies of 0.338 NLCH 4 /gCOD, making SAnMBR an attractive technology characterized by low excess sludge production and high bioenergy recovery. Batch tests revealed the SAnMBR appeared to have the potential to bear a high food-to-microorganism ratio (F/M) of 1.54 gCOD/gMLVSS without any inhibition effect, and maximum methane production rate occurred at F/M 0.7 gCOD/gMLVSS. Pore blocking dominated the membrane fouling behaviour at a relative long hydraulic retention time (HRT), i.e. >12 hours, while cake layer dominated significantly at shorter HRTs, i.e. <8 hours.

Membrane fouling poses a great challenge for practical application of the promising anaerobic membrane bioreactor (AnMBR) process treating organic wastes and wastewater. The integration of electrically conductive membrane with AnMBR process is an innovative practice for simultaneously enhancing pollutants removal and fouling mitigation. This review presents an overview on electro-conductive membrane enabled electrochemical anaerobic membrane bioreactor (AnEMBR) process, with the focus on the fabrication and modification of conductive membranes, process performance enhancement, and antifouling properties. With the assistance of various organic polymeric, inorganic and composite conductive membranes, the AnEMBR can be steadily applied for municipal and industrial wastewater treatment, showing enhanced pollutants removal and methane production as well as reduced fouling propensity. The improved organics removal and biogas production are due to electrochemically improved selectivity, enrichment of electroactive bacteria as well as altered methanogenic pathways. Since the conductive membranes can serve as the anode or cathode, the bio-electrochemically induced fouling control mechanisms are mainly attributed to sludge properties modification, in-situ hydrogen gas generation and scouring, electrostatic repulsion, direct and indirect electro-oxidation. Future perspectives include high-quality electrodes development, value-added resource recovery, emerging contaminants removal as well as advanced modelling and system analysis, which will promote large-scale implementation of the AnEMBRs for low-carbon wastewater treatment. [Display omitted] • Electrochemical AnMBR process enhanced pollutants removal and fouling control. • Fabrication and modification of conductive membranes are important in AnEMBRs. • Enriching electroactive microbes and altering methanogenic pathway are observed. • Bio-electrochemical effects, sludge modification and H 2 generation mitigate fouling. [ABSTRACT FROM AUTHOR]

The stable operation of the partial nitritation and anammox (PN/A) process is a challenge in the treatment of low-strength ammonia wastewater like sewage mainstream. This study demonstrated the feasibility of achieving stable operation in the treatment of 50 mg/L ammonia wastewater with a micro granule-based PN/A reactor. The long-term operation results showed nitrogen removal efficiencies of 71.8 ± 9.9% were stably obtained under a relatively short hydraulic retention time (HRT) of 2 h. The analysis on the physicochemical properties of the granules indicated most of the granules were in a size in a range of 265–536 μm, and the elementary composition of the granules was determined to be CH 1.61 O 0.61 N 0.17 S 0.01 P 0.03. The microbial analysis revealed Candidatus Kuenenia stuttgartiensis anammox bacteria and Nitrosomonas- like AOB were the two most dominant bacteria with 27.6% and 10.5% abundance, respectively, both of which formed spatially syntrophic co-immobilization within the micro-granules. The ex-situ activity tests showed the activity of NOB was well limited through DO regulation in the reactor. These results provide an alternative PN/A process configuration for low-strength wastewater treatment by sustaining microstate granules. Optimization of the nitrogen sludge loading rate and DO regulation are important for the successful performance. Graphical abstract Image 1 Highlights • High anammox activity was reached in a micro-granule reactor with 50 mgN/L influent. • The reactor succeeded stable operation and 72 ± 10% nitrogen removal at a short HRT 2 h • Anammox-AOB co-immobilizing in micro-granules kept efficient PN/A. [ABSTRACT FROM AUTHOR]

[Display omitted] • Real municipal wastewater was treated at 15–25 °C by a SAnMBR at HRT 6 h. • COD removal efficiencies of 90% and BOD removal efficiencies of 92% were obtained. • Electric energy could generate 2.27 kWh/d from biogas in a 10000 m3/d plant. • Trans-membrane pressure and fouling risks were high under the low temperature. • Populations of functional microbes had significant relations with the temperature. A submerged anaerobic membrane bioreactor (SAnMBR) was used in the treatment of real municipal wastewater at operation temperatures ranging from 15 °C to 25 °C and hydraulic retention time (HRT) of 6 h. The treatment process was evaluated in terms of organic removal efficiency, biogas production, sludge growth and membrane filtration. During long-term operation, the SAnMBR achieved chemical oxygen demand removal efficiencies of about 90% with a low sludge yield (0.12–0.19 g-VSS/g-COD rem) at 20–25 °C. Approximately 1.82–2.27 kWh/d of electric energy was generated during the wastewater treatment process at 20–25 °C, 0.67 kWh/d was generated at 15 °C. The microbial community analysis results showed that microbial community was dominated by aceticlastic methanogens, coupled by hydrogenotrophic methanogens and a very small quantity of methylotrophic methanogens. It was also shown that the stabilization of the microbial community could be attributed to the carbohydrate-protein degrading bacteria and the carbohydrate degrading bacteria. [ABSTRACT FROM AUTHOR]

• A pilot-scale SAnMBR-PN/A plant was successfully applied for real municipal wastewater treatment. • The overall COD and total nitrogen removal efficiencies were 95.1% and 81.7%, respectively. • The biogas yield rate was 0.09 NL L−1 of treated wastewater with a methane content of 80%. • Denitrification occurred in PN/A unit, enhancing overall COD and nitrogen removal. A novel municipal wastewater treatment process towards energy neutrality and reduced carbon emissions was established by combining a submerged anaerobic membrane bioreactor (SAnMBR) with a one-stage partial nitritation-anammox (PN/A), and was demonstrated at pilot-scale at 25 °C. The overall COD and BOD 5 removal efficiencies were 95.1% and 96.4%, respectively, with 20.3 mg L−1 COD and 5.2 mg L−1 BOD 5 remaining in the final effluent. The total nitrogen (TN) removal efficiency was 81.7%, resulting 7.3 mg L−1 TN was discharged from the system. The biogas yield was 0.222 NL g−1 COD removed with a methane content range of 78–81%. Approximately 90% of influent COD was removed in the SAnMBR, and 70% of influent nitrogen was removed in the PN/A. The denitrification which occurred in the PN/A enhanced overall COD and nitrogen removal. The successful operation of this pilot-scale plant indicates the SAnMBR-PN/A process is suitable for treating real municipal wastewater. [ABSTRACT FROM AUTHOR]