Harnessing membrane segregation of polysaccharide-degrading strains to mitigate fouling in membrane bioreactors: Insights from bacterial community ecology and metabolomics.

Anaerobic/oxic/anoxic-membrane bioreactor process coupled with polyaluminum chloride for simultaneous nitrogen and F- removal in semiconductor wastewater, and membrane fouling mitigation: Performance and mechanism.

Development of membrane bioreactor using biopolymer recovered from corncob waste for tannery wastewater treatment.

Hollow Fiber Membrane Bioreactors (HFMBs) support mammalian cell culture at high cell density by enabling effective transport of nutrients, gases and metabolites to/from cells and by offering high membrane surface area-to-bioreactor volume ratios, scalability and flexibility in design. A recent study showed that shell-and-tube HFMBs with cells in the extracapillary space (ECS) for medicine may be designed to mimic the bone architecture for bone tissue engineering (TE). A more transport-efficient HFMB, the BRx-HFMB, consists of a 3D stack of alternating cross-woven mats of microporous and gas-permeable hollow fiber membranes with cells in the ECS and medium flowing inside the membranes. This design was shown to support the culture of a large mass of densely packed cells with high oxygen and nutrient metabolic demands similar to bone cells. Its biomimicry and rationale for good performance are poorly characterized, hindering exploitation of its characteristics for bone TE. Herein, we report the architectural and biomimetic characterization of pore/void distribution in the ECS of laboratory BRx-HFMBs using non-invasive non-destructive micro-computed tomography and advanced image analysis to minimize artifacts. The results suggest that the ECS pore architecture and specific surface area of BRx-HFMBs mimic those of bone tissue, favoring cell migration around, and adhesion on, membranes at clinical cell densities. The membrane network architecture enables cell perfusion with medium, and membranes act as spatially distributed oxygen sources promoting oxygen transport through the cell construct over longer distances than in static bioreactors. This supports the use of BRx-HFMBs to develop cellular models of bone tissue for drug testing and precision medicine.

Toward energy-efficient algal-bacterial membrane bioreactors: Metagenomic evidence for intermittent aeration-driven carbon reallocation and fouling control

Enhancing separation performance of gravity-driven membrane bioreactor via membrane packing density optimization: Comprehensive insights from biological responses and hydrodynamic insights

Carbon cloth-mediated direct interspecies electron transfer effect on the intensification mechanism of high-load codigestion dynamic membrane bioreactors.

Membrane fouling is a major impediment to the widespread application of membrane bioreactors (MBRs) for water treatment. In recent years, the electro-conductive membrane bioreactor (E-MBR) has demonstrated efficacy in mitigating membrane fouling. The application of a negative potential to the electro-conductive membrane promotes electrostatic repulsion, effectively displacing negatively charged extracellular polymeric substances (EPS) away from the membrane surface. However, given the established vital role of quorum sensing (QS) in membrane fouling development, the interference of the negative potential on QS-mediated EPS secretion and biofilm formation has been largely overlooked. Herein, we found that the negative potential applied to the electro-conductive membrane could effectively suppress the QS process, thereby inducing the in situ quorum quenching (QQ) effect. The application of negative potential significantly reduced the levels of the signal molecule C14-HSL as well as EPS. Metagenomic analysis indicated that the relative abundance of the "signal transduction mechanism" pathway was suppressed, and the functional genes encoding C14-HSL receptor proteins belonging to "LuxR family" was downregulated in the cake layer of E-MBR. Density functional theory calculations and molecular dynamics simulation results revealed that the application of negative potential enhanced the electrostatic repulsion between the membrane and C14-HSL and induced the conformational changes of the LuxR protein, which synergistically induced the in situ QQ effect. This study provides a novel perspective on the antifouling mechanism in E-MBR.

The treatment of landfill leachate is a significant environmental challenge because of its high concentration of resistant organic pollutants that are difficult to remove using conventional methods. This study aimed to remove resistant organic matter from the membrane bioreactor effluent (MBR) of leachate through the use of advanced oxidation processes. The catalytic effect of transition metals (Fe2+, Zn2+, Cu2+, Mn2+, Ni2+, and Co2+) was evaluated, where peracetic acid (PAA) was used as the oxidant. Among the applied processes, the highest pollutant removal was obtained by Fe2+/PAA, Co2+/PAA, and Mn2+/PAA processes. The Box-Behnken design was used for parameter optimization of these processes. The initial pH, catalyst dose, and oxidant dose were independent variables, whereas COD and UV254 removal efficiencies were system responses. Regression models describing COD and UV254 removal through Fe2+/PAA, Co2+/PAA, and Mn2+/PAA processes were developed, and the data obtained were analyzed by analysis of variance. Under the optimum conditions for the Fe2+/PAA process (pH: 3.13, Fe2+: 0.233 mM, PAA: 2.25 mM), the COD and UV254 removal were 86.1% and 87.5%, respectively. For the Co2+/PAA process under optimum conditions (pH: 3.93, Co2+: 0.298 mM, PAA: 2.16 mM), the COD and UV254 removal were 80.2% and 86.0%, respectively. For the Mn2+/PAA process under optimum conditions (pH: 3.12, Mn2+: 0.299 mM, and PAA: 2.22 mM), the COD and UV254 removal were 84.0% and 84.8%, respectively. These results showed that the optimized transition-metal-catalyzed PAA processes provide a highly efficient approach for the advanced treatment of real leachate MBR effluent.

A membrane-anchored nanoscale zero-valent iron bio-interface enhances interspecies electron transfer in anaerobic membrane bioreactors.

ABSTRACT This study assessed fouling of waste sugarcane bagasse ash-based ceramic membranes (SBA-CMs) in a sequential batch reactor (SBR)-anaerobic membrane bioreactor (AnMBR) treating low-strength wastewater (total chemical oxygen demand, tCOD∼180 mg/L). The system was operated at a hydraulic retention time of 18 h and permeate flux of 14.9 L/m2 h. Different SBA-CMs were screened, followed by testing the effect of varying mixed liquor suspended solids (MLSS) on filtration performance and long-term system performance using the optimal SBA-CM and MLSS concentration. Single-layer SBA-CM with no coating (pore size 8.6 μm, porosity 46%) displayed 50% lower filtration resistance (1.1 × 1012 /m) compared to two-layer coated SBA-CMs. Higher MLSS (5 g/L) was associated with higher transmembrane pressure, and unstable flux; 2.5 g/L MLSS proved to be optimal. Stable flux was sustained over 64 days by applying fouling control measures, viz., filtration-relaxation, backflushing, and physical cleaning. FTIR, SEM, and particle size analysis of the membrane surface deposits identified extracellular polymeric substances, colloids, and micro-and macroparticles as key components of the fouling layer. The total filtration resistance indicated both surface deposition (50%, 1.7 × 1012 /m) and pore blockage (40%, 1.4 × 1012 /m) as key fouling mechanisms. Statistical analysis further indicated F/M ratio (ρ = −0.43) and MLSS (ρ = 0.38) showed relatively strong associations with fouling rate compared to EPS content and composition (ρ ≈ 0.19–0.33). Overall, this study demonstrates the optimal operation conditions and provides insights into the fouling behaviour of an SBA-CM-equipped AnMBR treating low-strength wastewater.

Fouling mitigation in membrane bioreactors via strategic dopamine-nanoparticle incorporation: Tailored modifier type and distribution.

Differential stability and adaptive recovery of two-stage partial nitritation-anammox system treating pilot-scale food waste-derived anaerobic membrane bioreactor permeate.

Malic acid, a four-carbon dicarboxylic acid, represents a top value-added chemical from biomass and important building-block molecule for various industrial chemical processes. Currently, however, it is primarily produced from petrochemicals via an unsustainable process with high greenhouse gas intensity. Alternatively, malic acid can be produced from renewable biomass sugars via anaerobic fermentation by engineered Escherichia coli. While inorganic carbon (Ci) serves as an essential co-substrate in this carbon-negative process, its typical delivery methods suffer from several key limitations. To address these, we systematically developed a hollow fiber membrane (HFM) bioreactor for direct and efficient delivery of CO2 gas in a bubbleless manner. A kinetic model for predicting CO2 mass transfer rates to the HFM bioreactor was first developed and used to identify process conditions where rates of Ci delivery closely match those of biological demand, thereby minimizing wasteful oversupply. Ultimately, using a CO2 delivery pressure of 2.5 psig and 8 fiber HFM (4.93 m-1 specific surface area), a maximum malic acid titer of 38.2 ± 0.4 g/L was achieved at a yield of 0.94 ± 0.01 g-malic acid/g-glucose; both comparable to the performance of a conventional E. coli batch fermentation wherein (bi)carbonate salts were directly supplied, albeit with ~50% less CO2 off-gassing from the headspace. By enabling direct and efficient CO2 delivery while achieving greater overall carbon efficiency, the HFM bioreactor represents a promising and more sustainable design for malic acid bioproduction.

Performance and microbial community dynamics of an internal circulating photogranular membrane bioreactor for synthetic mariculture wastewater treatment under different hydraulic retention times.

ABSTRACT Membrane bioreactor (MBR) has attracted widespread attention owing to its unique membrane separation technology and high treatment efficiency. However, conventional MBRs struggle to remove pollutants with different oxygen requirements (e.g. nitrogen removal) in a single bioreactor, and the cost of membrane fouling control remains high. To address these challenges, this study devised an integrated gas-lift cross-flow Membrane Bioreactor (GL-CF-MBR), that possesses unique oxygen supply conditions and a cross-flow circulation pattern. Chemical analysis, 16S rRNA sequencing and transmembrane pressure (TMP) monitoring were employed to systematically evaluate the performance in terms of pollutant removal efficiency, microbial community composition and metabolic pathways, and membrane fouling behaviour. Results showed that the effluent concentrations of COD, NH₄⁺-N, and TN reached 25.58, 0.50, and 14.31 mg/L, respectively, meeting the Class 1A discharge standards of China's “Discharge standard of pollutants for municipal wastewater treatment plants’ (GB 18918-2002). Molecular biological analysis confirmed that, compared with the inoculated sludge, the Chao1 index and Observed species index increased by 37.32% and 30.94%, respectively. Moreover, denitrifying genera such as Rhodobacter and SC-I-84 were enriched in the system, and key functional genes involved in carbon and nitrogen metabolism were predicted. Owing to the unique flow field of the reactor, the time to reach a critical TMP surge for membrane modules installed in the scouring zone was delayed by 65.4% compared with those installed in the turbulent zone. The reactor promotes simultaneous pollutant removal and fouling mitigation, and its promising low operating cost provides a theoretical reference for practical engineering applications.

Biofouling control by quorum quenching bacteria in membrane bioreactors for high strength wastewater treatment with doubled flux.

Feedforward fouling control guided by online UV and fluorescence spectral early warning for low-energy operation of membrane bioreactor.

Maximizing nitrogen removal in a membrane bioreactor (MBR) via a swing-basin and dissolved oxygen reduction configuration: A bio-inspired machine learning optimization approach

The mutual impacts of climate change and wastewater treatment: Critical review of challenges and solutions