Flat Sheet Membrane Bioreactor Research Articles

Water treatment with free-bubbling corrugated sheet MBR

Having previously introduced a new type corrugated-sheet membrane bioreactor (CS-MBR) with slug bubbling, this work investigates its water treatment performance and hydrodynamic optimization under a free bubbling regime. Experiments in parallel were conducted to compare CS-MBR with flat sheet membrane bioreactor (FS-MBR). The transmembrane pressure (TMP) and permeability results indicate that the corrugated sheet membrane has better anti-fouling performance with a final flux after 15 days of operation that was 45 % higher than that of the flat sheet membrane that had been tested in parallel. The analysis results of effluent quality and sludge extracellular polymeric substances (EPS) indicate that the membrane configuration has little impact on the effluent quality and sludge properties in the system. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) revealed the accumulation pattern of foulants on the surface of the corrugated sheet membrane and suggested that the corrugations were the cause of the improved anti-fouling performance. Bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) was extracted from fouling example at membrane surfaces, which was 50 % lower in the CS-MBR than in the FS-MBR. Computational Fluid Dynamics (CFD) simulations showed that channel gap distance of 2– 4 mm combined with 20 m/s nozzle velocity could produce an intense hydrodynamic effect. Based on the traditional free bubbling air usage, total air consumption of this CS-MBR optimal design is expected to save up to 70 % on energy.

A CFD simulation and experimental study: The impact of aerator design on the bubble flow pattern, foulant removal and scouring capability of flat sheet membrane bioreactor (FSMBR)

Membrane fouling is a main drawback of membrane bioreactor systems. Moreover, optimization of influential parameters via practical analyses is tedious and time-consuming. Therefore, the CFD-RSM approach accompanied by experimental results was employed to propose the optimal aerator design. In comparison with the linear nozzles, simulation results proposed that at equal air flow rate, the angular nozzle aerators with 30° toward the surface of the membrane could provide higher amounts of surface tension, air scouring capabilities as well as air volume fraction at a similar air flow. Simulation findings were experimentally validated using a bench-scale MBR system. Obtained results showed that the irreversible fouling ratio to the total fouling ratio for neat membrane was decreased from 62.99 % to 43.97 % for linear and angular nozzles, respectively. This improvement in the nozzle performance was more pronounced for nanocomposite membranes, in which the abovementioned ratio was decreased from 43.44 % to 24.57 %. It is confirmed that the impact of nozzle design on the nanocomposite membrane was 30.48 % higher than that of the neat membrane. Specific aeration demand (SADm) value was decreased from 0.77 to the 0.49 [Nm3/(m2h)] at an equal amount of shear stress and lower inlet velocity, when linear nozzles were replaced by the angular nozzles. The lower SADm and better foulant capability leads to the optimal operation condition and lower energy as well as operating costs.

Superior performance of a membrane bioreactor through innovative in-situ aeration and structural optimization using computational fluid dynamics.

The optimization of membrane bioreactors (MBRs) involves a critical challenge in structural design for mitigation of membrane fouling. To address this issue, a three-dimensional computational fluid dynamics (CFD) model was utilized in this study to simulate the hydrodynamic characteristics of a flat sheet (FS) MBR. The optimization of the membrane module configuration and operating conditions was performed by investigating key parameters that altered the shear stress and liquid velocity. The mixed liquor suspended solids (MLSS) concentration was found to increase the shear stress, leading to a more uniform distribution of shear stress. By optimizing the appropriate bubble diameter to 5mm, the shear stress on the membrane surface was optimized with relatively uniform distribution. Additionally, extending the side baffle length dramatically improved the uniformity of the shear stress distribution on each membrane. A novel in-situ aeration method was also discovered to promote turbulent kinetic energy by 200 times compared with traditional aeration modes, leading to a more uniform bubble streamline. As a result, the novel in-situ aeration method demonstrated superior membrane antifouling potential in the MBR. This work provides a new approach for the structural design and optimization of MBRs. The innovative combination of the CFD model, optimization techniques, and novel in-situ aeration method has provided a substantial contribution to the advancement of membrane separation technology in wastewater treatment.

Evaluation of using a porous medium approach to simulate flat-sheet membrane bioreactors

Abstract The porous medium approach has been applied by others to study the global hydrodynamics in hollow-fiber (HF) membrane bioreactors (MBR). This study explores the usability of the porous medium approach for flat-sheet (FS) MBR and introduces a CFD-based numerical calibration of the porous parameters. Two key modeling strategies are suggested to ensure the pressure prediction accuracy: (1) use SST turbulence model incorporated with an intermittency transition model (SSIT); (2) considerate two-phase flow during the calibration. The results showed that SSIT significantly improved the pressure prediction of the flow between two sheets. Also, unlike HF MBR, the gas phase was observed to be non-negligible during the calibration for FS MBR. The numerically calibrated porous parameters were then applied in a three-dimensional simplified model (SPM), where multiple membrane sheets were treated as one porous zone. The SPM was compared with a realistic model (RM), where all membrane sheets were simulated directly. A similar pressure distribution was observed in both models; however, local flow characteristics (i.e., the acceleration of the flow entering the module zone) were not reflected in the SPM. Hence, it is recommended to use the porous medium approach for global hydrodynamics investigation when the local flow characteristics are not of interest.

Performance of Newly Developed Intermittent Aerator for Flat-Sheet Ceramic Membrane in Industrial MBR System

An intermittent aerator was newly developed to reduce energy costs in a flat-sheet ceramic membrane bioreactor (MBR) for industrial wastewater treatment. Large air bubbles were supplied over a short time interval by the improved aerator technology at the bottom of the flat-sheet membrane. Performance tests for the intermittent aerator were carried out in a pilot system with two cassettes immersed in a membrane tank of the 1-MGD demonstration plant at Jurong Water Reclamation Plant (JWRP) in Singapore. Stable operation was achieved at an average flow of 19–22 LMH with every-2-days MC and peak flow of 27 to 33 LMH with daily MC with reduced air flow for membrane aeration. This indicates that energy costs for membrane aeration can be reduced by using the intermittent aerator. Stable MBR operation with a projected 43% reduction in the overall operating costs could be achieved with an improved aerator together with improved MC regime and membrane cassette.

Aeration pipe design for free bubbling hydrodynamic optimization of flat sheet MBRs

An open-end aerator for free bubbling has been found previously for hydrodynamic effect enhancement. This study is focused, through two modifications, on its further optimization for aeration homogeneity in a commercial flat sheet membrane bioreactor (FSMBR). One relates to the aerators themselves, the other to the central aeration air supply pipe. The aerators are tapered, or to be more precise each one is a frustum i.e. that portion of cone which remains after the upper part has been cut off by a plane parallel to its base. A validated computational fluid dynamics (CFD) model is constructed, hydrodynamic features were predicted for various implementations of the new design. An extensive study found that to achieve a very high degree of uniformity between different aerators for a full-scale FSMBR (160 sheets), the optimal design featured frustum-designed aerators of length 180 mm with the diameter decreasing from 18 to 9 mm at the open end. Each aerator had four top nozzles of diameter 4 mm, and 20 aerators were attached to a pipe of 1760 mm. Based upon this aerator design, the central aeration pipe diameter was optimized, the shear stress was enhanced and corresponding number of effective channel coverage was enhanced by 25–75%.

Simultaneous Enzymatic Cellulose Hydrolysis and Product Separation in a Radial-Flow Membrane Bioreactor.

Hydrolysis is the heart of the lignocellulose-to-bioethanol conversion process. Using enzymes to catalyze the hydrolysis represents a more environmentally friendly pathway compared to other techniques. However, for the process to be economically feasible, solving the product inhibition problem and enhancing enzyme reusability are essential. Prior research demonstrated that a flat-sheet membrane bioreactor (MBR), using an inverted dead-end filtration system, could achieve 86.7% glucose yield from purified cellulose in 6 h. In this study, the effectiveness of flat-sheet versus radial-flow MBR designs was assessed using real, complex lignocellulose biomass, namely date seeds (DSs). The tubular radial-flow MBR used here had more than a 10-fold higher membrane surface area than the flat-sheet MBR design. With simultaneous product separation using the flat-sheet inverted dead-end filtration MBR, a glucose yield of 10.8% from pretreated DSs was achieved within 8 h of reaction, which was three times higher than the yield without product separation, which was only 3.5% within the same time and under the same conditions. The superiority of the tubular radial-flow MBR to hydrolyze pretreated DSs was confirmed with a glucose yield of 60% within 8 h. The promising results obtained by the novel tubular MBR could pave the way for an economic lignocellulose-to-bioethanol process.

Toray Membrane USA partners with M|MBR Systems

Toray Membrane USA Inc (TMUS) and M|MBR Systems LLC, a service provider of flat-sheet membrane bioreactor (MBR) systems, have entered into an exclusive supply agreement covering MBR retrofit applications.

Novel economical three‐stage slug bubbling process in a large‐scale flat‐sheet membrane bioreactor of double deck configuration

AbstractSlug bubbling in single deck flat sheet membrane bioreactor (FSMBR) is effective in controlling membrane fouling. Here the primary focus is on the employment of the slug bubbling method, with its more economical air consumption, to a double‐deck large‐scale FSMBR with 100 membrane plates on each deck. The analysis of a new design concept shows that sufficient hydrodynamic effect could be induced by a novel economical three‐stage slug aeration process of formation‐breakup‐reformation. Computational fluid dynamics simulation was applied to examine both the development of the slug bubble and especially its reformation. It was found that the combination of a gap between two decks of 400 mm with an air velocity of 16 m/s was an optimal condition to achieve good hydrodynamic conditions in both decks. The corresponding SADm is 0.098 Nm3m−2 hr−1, which is a reduction of 66% compared to the most advanced single deck FSMBR.

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost. Different hydraulic retention times (72–24 h) were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewa ter. Field experimental data from the membrane bioreactor, both full-scale (500 m3/d) and pilot (1.0 m3/d), were used to calculate the net present value (NPV), incorporating both capital expenditure (CAPEX) and operating expenditure. The results showed that the tank cost was estimated above membrane cost in the 38.2%, where capital expenditure contributed 24.2% more than operational expenditure. Tank construction cost was decisive in determining the net present value contributed 62.1% to the capital expenditure. The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane, while flux decline was tolerable. The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent. The upgrade to the membrane bioreactor also benefited further treatments by 10.1%–44.7% lower direct investment.

Partial nitrification of piggery wastewater as pre-treatment for anammox process using flat sheet membrane bioreactor

Partial nitrification of piggery wastewater as pre-treatment for anammox process using flat sheet membrane bioreactor

Newly Designed Hydrolysis Acidification Flat-Sheet Ceramic Membrane Bioreactor for Treating High-Strength Dyeing Wastewater.

Cost-effective treatment of dyeing wastewater remains a challenge. In this study, a newly designed hydrolysis acidification flat-sheet ceramic membrane bioreactor (HA-CMBR) was used in treating high-strength dyeing wastewater. The start-up phase of the HA-CMBR was accomplished in 29 days by using cultivated seed sludge. Chemical oxygen demand (COD) removal rate reached about 62% with influent COD of 7800 mg/L and an organic loading rate of 7.80 kg-COD/(m3·d). Chromaticity removal exceeded 99%. The results show that the HA-CMBR has good removal performance in treating dyeing wastewater. The HA-CMBR could run with low energy consumption at trans-membrane pressure (TMP) <10 kPa due to the good water permeability of the flat-sheet ceramic membrane. New strains with 92%–96% similarity to Alkalibaculum bacchi, Pseudomonas sp., Desulfovibrio sp., and Halothiobacillaceae were identified in the HA-CMBR. Microbial population analysis indicated that Desulfovibrio sp., Deltaproteobacteria, Halothiobacillaceae, Alkalibaculum sp., Pseudomonas sp., Desulfomicrobium sp., and Chlorobaculum sp. dominated in the HA-CMBR.

Fluid dynamics in a full-scale flat sheet MBR, an experimental and numerical study.

Fluid dynamics is used for fouling mitigation in membrane bioreactors (MBRs), whereby a proper understanding of the fluid dynamics is of great interest. The influence of fluid dynamics has led to the use of computational fluid dynamics for optimizing MBR systems. In this work, a model has been validated for flat sheet membranes, with use of the Eulerian multiphase method. The model is validated against a comparable setup where the liquid velocities are measured with a laser Doppler anemometer (LDA). Furthermore, the Eulerian multiphase approach is validated against the more numerical direct volume of fluid (VOF) approach with sludge properties for the liquid, resulting in an error between the models of less than 2% for the wall shear stresses. The VOF model further showed that the horizontal components contribute significantly to the total wall shear stresses. The model has been applied to a full-scale setup for studying the effect of deflecting membranes as deflections have been seen in production. Minimizing the deflection of the membrane sheets was crucial to achieve a good operating condition as a deflection of 2 mm in a setup with a gap of 7 mm decreased the wall shear stresses with as much as 40% on average on the specific membrane surface.

The Impact of Mechanically-Imposed Shear on Clogging, Fouling and Energy Demand for an Immersed Membrane Bioreactor.

The impact of the application of mechanically-imposed shear on the propensity for fouling and clogging (or “sludging”—the agglomeration of sludge solids in the membrane channel) of an immersed flat sheet (iFS) membrane bioreactor (MBR) was studied. The bench-scale test cell used contained a single flat sheet fitted with a crank and motor to allow the membrane to be oscillated (or reciprocated) vertically at a low rate (20 RPM). The membrane was challenged with sludge samples from a local MBR installation treating petroleum industry effluent, the sludge having previously been demonstrated as having a high sludging propensity. Sludging was measured by direct visual observation of membrane surface occlusion by the agglomerated solids, with fouling being notionally represented by the rate of transmembrane pressure increase. Results demonstrated membrane reciprocation to have a more beneficial impact on sludging amelioration than on suppressing fouling. Compared with the stationary membrane, sludging was reduced by an average of 45% compared with only 13% for fouling suppression at the reference flux of 15 L·m−2·h−1 applied. The specific energy demand of the mechanical shear application was calculated as being around 0.0081 kWh·m−3, significantly lower than values reported from a recent pilot scale study on a reciprocated immersed hollow fibre MBR. Whilst results appear promising in terms of energy efficiency, it is likely that the mechanical complexity of applying membrane movement would limit the practical application to low flows, and a correspondingly small number of membrane modules.

Study on Operational Conditions to Minimize Membrane Fouling in Membrane Bioreactor (MBR) System for Wastewater Treatment-Preliminary Pilot Tests

In this study, effect of antiscalant usage on minimizing of membrane fouling due to high water hardness during wastewater treatment tests run by a pilot-scale membrane bioreactor (MBR) system. The membranes used in these studies were Kubota flat sheet MBR membranes made from polyethylene with a pore size of 0.4 micrometer. Preliminary tests were carried out with tap water for sixty days of operation. To investigate the applicability and the effect of antiscalant usage, four experiments (two experiments with tap water and two experiments with wastewater) were carried out and each experiment lasted for 29 days. The tests were carried out in the presence and in the absence of antiscalant. Fouling on MBR membranes was investigated by monitoring flux decline versus time. In tap water tests, unstable flux was observed initially then a flux decline due inorganic scaling. On the other hand, the flux was almost constant up to end of the experiment in the presence of antiscalant. During wastewater tests (in the absence of antiscalant), the flux decline was observed within ten days of operation while during wastewater tests in presence of antiscalant, the flux did not decline until twenty days of operation. The use of antiscalant did not influencethe efuent quality. According to the quality analyses results for MBR efuent, removal efciencies for COD, PO4-P, and total N were 95%, 98% and 40%, respectively. In addition,99% of total suspended solid rejection and 98% of color rejection were obtained in the presence or absence of antiscalant.

CFD modelling of uneven flows behaviour in flat-sheet membrane bioreactors: From bubble generation to shear stress distribution

The efficiency of slug flow for fouling control of flat sheet (FS) membrane bioreactors (MBRs) is hindered by uneven bubble distribution leading to inhomogeneous shear stress profile on the membrane. In this work, a 3D CFD model was developed enabling prediction of the hydraulic performance of a novel aeration system designed to reduce the uneven bubble distribution in a full-scale FS MBR. Bubbles generated with aeration channel submerged in 8.0 g/L activated sludge were found to be unevenly distributed with up to 12 folds difference in gas mass flow per single nozzle. More than 41% higher gas mass flow was obtained at nozzles located at higher heights compared to lower nozzles at aeration intensities ranging from 12 m3/h to 20 m3/h. The subsequent uneven bubble distribution in membrane modules contributed to uneven shear stress distribution resulting in uneven fouling performance of the membrane module. Locating the aerator at a mediate distance of 20 cm to the membrane module (in the range of 15 cm to 25 cm) resulted in higher shear stress at locations closer to the permeate collector where higher flux occurred with a maximum 2.4 times increase in average shear stress. The CFD model was validated by comparison of the simulated height of the air column and bubble frequency with experimentally measured data obtained using a high-speed camera.

Impact of reactor configuration on treatment performance and microbial diversity in treating high-strength dyeing wastewater: Anaerobic flat-sheet ceramic membrane bioreactor versus upflow anaerobic sludge blanket reactor

In this study, an anaerobic flat-sheet ceramic membrane bioreactor (AnCMBR) was used to treat high-strength dyeing wastewater, and compared with an upflow anaerobic sludge blanket (UASB) reactor. The start-up phases of the AnCMBR and UASB reactor were accomplished within 60 d by using cultivated seed sludge. The results showed that the AnCMBR had better COD, TN, and TP removal rates than the UASB reactor. The CH4 production of the AnCMBR was higher than that of the UASB reactor. The AnCMBR was operated with low energy consumption due to good water permeability of the flat-sheet ceramic membrane. The AnCMBR and UASB reactor had similar CH4-producing Archaea; Methanosaeta, Methanosarcina, and Methanomassiliicoccus were the most abundant. The AnCMBR had a higher proportion of Desulfovibrio sp. and Desulfomicrobium sp., which are reported to have the potential to degrade reactive dyes. A large number of sulfate-reducing enzymes were deduced to contribute to the sulfate-reducing pathway.

Performance of a submerged membrane bioreactor for wastewater mimicking fish meal processing effluent

The objective of this work was to analyze organic matter removal, nitrification, biomass growth and membrane fouling in a submerged flat-sheet membrane bioreactor, fed with synthetic wastewater, of similar composition to the effluents generated in a fish meal industry. After biomass acclimatization with saline conditions of 12 gNaCl/L and COD/N ratio of 15 in the bioreactor, results showed that the organic matter removal was higher than 90%, for all organic loading rates (0.8, 1, 1.33 and 2 gCOD/L∙d) and nitrogen loading rates (0.053, 0.067, 0.089 and 0.133 gN/L∙d) tested during the study. However, nitrification was only carried out with the lowest OLR (0.8 gCOD/L∙d) and NLR (0.053 gN/L∙d). An excessive concentration of organic matter in the wastewater appears as a limiting factor to this process\'operating conditions, where nitrification values of 65% were reached, including nitrogen assimilation to produce biomass. The analysis of membrane fouling showed that the bio-cake formation at the membrane surface is the most impacting mechanism responsible of this phenomenon and it was demonstrated that organic and nitrogen loading rates variations affected membrane fouling rate.

CFD and experimental studies the effect of micro-channel turbulence promoter installation on the hydrodynamic performance of submerged flat-sheet membrane bioreactor

The aim of the present work is to investigate the effect of a micro-channel turbulence promoter(MCTP) installation on the hydrodynamic performance of a submerged membrane bioreactor(SMBR). The hydrodynamic and filtration performance of the micro-channel turbulence promoter installation in the submerged flat-sheet membrane bioreactor carried out by computational fluid dynamics (CFD) simulations and filtration performance experimental. The CFD simulation results and the experimental results showed that the average fluid velocity, average gas velocity, turbulent kinetic energy, wall shear stress and gas holdup of SMBR equipped with MCTP in the vertical orientation compared with MCTP in the horizontal orientation are above 8.7%, 11.26%, 37.76%, 15.79% and 9.8%, respectively. That is to say, the enhancement effect of SMBR equipped with MCTP in the vertical orientation was better than that of SMBR equipped with MCTP in the horizontal orientation.

A new hybrid sewage treatment system combining a rolled pipe system and membrane bioreactor to improve the biological nitrogen removal efficiency: A pilot study

Abstract A new hybrid pilot plant configuration based on a modularized rolled pipe system (RPS) combined with a submerged flat sheet membrane bioreactor (MBR) was investigated to enhance the sewage treatment and membrane performance. The system was operated under actual conditions for more than four months, that is, at a constant flow rate of 30 m³/d and with two internal recycling ratios. The results indicate that the hybrid system produces an excellent effluent quality and considerably mitigated membrane fouling. The average concentrations of SS, COD, TN, NH4+-N, NO3−-N, and PO43--P remained below 2.81, 8.29, 8.77, 0.15, 8.17, and 1.49 mg/L, respectively. It was estimated that the periodic chemical cleaning of the membrane could be extended to approximately six months. The MBR and RPS can virtually complete nitrification and denitrification, respectively. The highest average denitrification rate of the RPS is 116.95 mg NO3-N/(g MLVSS d), with a hydraulic retention time of 1.05 h. Therefore, the RPS–MBR hybrid system has potential to improve the sewage treatability. The emerging RPS technique can obtain high rates of denitrification coupled with a compact design, ease of installation, and small footprint.