Submerged Membrane Bioreactor Research Articles

Impacts of micron-sized aeration bubble on sludge properties and hydraulic dynamics in relation to membrane fouling alleviation

This investigation elucidates the influence of micron-scale aeration bubbles on the improvement of anti-fouling characteristics within submerged membrane bioreactors (sMBRs). A systematic examination of sludge properties, hydraulic dynamics, and fouling tendencies revealed that the application of microbubble aeration, specifically at dimensions of 100 μm, 80 μm, and 30 μm, significantly reduced sludge electrostatic repulsion and augmented particle size distribution, as opposed to the utilization of coarse bubble aeration of 1 mm. Notably, the employment of 100 μm bubbles achieved a significant reduction in the proportion of smaller particles (<10 μm) and sludge viscosity, thereby facilitating a more homogenous and vigorous turbulence at the membrane interface. These optimized conditions were instrumental in the substantial reduction of membrane fouling, which was corroborated by the diminished rate of fouling, reduced resistance accumulation, and lesser foulant deposition. The investigation identified sludge particle size, turbulent kinetic energy, and shear stress as the predominant factors influencing the development of membrane fouling. The findings underscore the pronounced advantages of employing 100 μm-sized bubbles in aeration strategies, providing enhanced understanding for the optimization of aeration parameters to improve sMBR efficiency and maintenance.

Optimizing neural network algorithms for submerged membrane bioreactor: A comparative study of OVAT and RSM hyperparameter optimization techniques.

Hyperparameter tuning is an important process to maximize the performance of any neural network model. This present study proposed the factorial design of experiment for screening and response surface methodology to optimize the hyperparameter of two artificial neural network algorithms. Feed-forward neural network (FFNN) and radial basis function neural network (RBFNN) are applied to predict the permeate flux of palm oil mill effluent. Permeate pump and transmembrane pressure of the submerge membrane bioreactor system are the input variables. Six hyperparameters of the FFNN model including four numerical factors (neuron numbers, learning rate, momentum, and epoch numbers) and two categorical factors (training and activation function) are used in hyperparameter optimization. RBFNN includes two numerical factors such as a number of neurons and spreads. The conventional method (one-variable-at-a-time) is compared in terms of optimization processing time and the accuracy of the model. The result indicates that the optimal hyperparameters obtained by the proposed approach produce good accuracy with a smaller generalization error. The simulation results show an improvement of more than 65% of training performance, with less repetition and processing time. This proposed methodology can be utilized for any type of neural network application to find the optimum levels of different parameters.

MIL-101(Cr) incorporated hollow fiber membrane for rubber wastewater treatment using membrane bioreactor

The hollow fiber (HF) membrane in this study was modified using polyethersulfone (PES) and MIL-101(Cr) metal–organic framework (MOF) for the treatment of synthetic rubber effluent using an aerobic submerged membrane bioreactor (MBR). The phase inversion and wet spinning techniques were used for membrane preparation and to manufacture the MOF-incorporated HF membranes, respectively. The manufactured HF membranes were characterized using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR-KBR), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Tensile Strength (TS), and Water Contact Angle (WCA) studies. The MIL-101(Cr)/PES HF membrane has increased porosity by 14%, surface roughness increased by 38%, and surface hydrophilicity increased by 15% compared to the pure PES HF membrane. The results demonstrated that the higher hydrophilicity of the metal–organic framework (MOF) MIL-101(Cr) positively affected the HF membrane surface properties and performance in the bioreactor. Additionally, it was shown that the removal efficiency for total suspended solids (TSS), total dissolved solids (TDS), biological oxygen demand (BOD5), and chemical oxygen demand (COD) were 45.5%, 65.6%, 90%, and 94% respectively.

Evaluating the performance and membrane fouling of a submerged membrane bioreactor (MBR) treating plywood industry wastewater.

This study evaluates the performance of a membrane bioreactor (MBR) for treating wastewater from the laminated plywood industry. To this end, a pilot-scale MBR was operated for 60 days with a hydraulic retention time of 20 h and a solid retention time of 20 days. The reactor's performance was assessed based on the removal of chemical oxygen demand (COD), phenol, turbidity, and apparent color. Furthermore, we monitored the solids content, dissolved oxygen concentration, and pH of the mixed liquor, as well as the progression of the transmembrane pressure (TMP). The wastewater exhibited a COD/biochemical oxygen demand (BOD) ratio of 5.5, suggesting low biodegradability, usually when this ratio is higher than 4.0. Nevertheless, it was observed that the MBR's performance was stable and satisfactory, with average removal efficiencies of 98% for COD, 70% for phenol, 99% for turbidity, and 93% for true color. The evolution of TMP indicated gradual membrane fouling; however, the operational limit of 0.6 bar was not reached during the study period. In conclusion, the utilization of MBR presents a promising approach to mitigate the environmental impacts associated with wastewater from the laminated plywood industry.

Performance evaluation of submerged membrane bioreactor for the removal of microalgae from the source water of a water treatment plant

Freshwater algal blooms negatively impact the operations of water treatment plants when they are present in the source water. In the present study, an application of a low-cost submerged microfiltration membrane bioreactor for the removal of microalgae from a source water reservoir of a water treatment plant was evaluated. The experiments were conducted in different phases to systematically evaluate how different fouling control methods such as air scouring and water backwashing in combination with vibration technique can enhance the flux and removal efficiency of microalgae in a submerged flat sheet microfiltration membrane bioreactor. Combining backwashing with air scouring (Phase 3) positively enhanced the flux by reducing the TMP, but it did not improve the permeate quality in terms of microalgae and turbidity removal. The results of Phase 4 studies confirmed that vibration had a profound effect on microalgae removal compared to backwashing technique while reducing the TMP from 105 to 103 kPa. The average turbidity removal was increased from 76.75% to 82% when vibration is applied. Combining all fouling control methods such as air scouring, backwashing and vibration methods did not appear to be effective for the removal of microalgae and turbidity (Phase 5). In order to signify the energy input on membrane fouling control, flux in each phase was assessed with respect to total power input. In overall, air scouring at a rate of 7 L/min with 50 Hz of vibration appeared to be an optimum condition in controlling fouling without any frequent backwashing.

Effect of organic loading rates on the performance of membrane bioreactor for wastewater treatment behaviours, fouling, and economic cost

Although submerged membrane bioreactor (MBR) are widely used in treating municipal wastewater and recovery of potential resources, membrane operational parameters and membrane fouling control remain debated issues. In this study, the treatment of municipal wastewater by MBR at high-biomass sludge (MLSS (g/L) ranging from 5.4 g/L to 16.1 g/L) was assessed at an organic loading rates (OLRs) ranging from 0.86 to 3.7 kg COD/m3d. The correlation between trans-membrane pressure and total fouling resistance was thoroughly investigated in this study. According to the findings, greater OLRs of 0.86 to 3.7 kg COD/m3d caused a decrease in COD, BOD, and NH4–N removal efficiency, and higher OLRs of 3.7 kg COD/m3d resulted in a higher increase in total fouling resistance (Rt). The economic study of using the MBR system proved that for a designed flow rate of 20 m3/d, the payback period from using the treated wastewater will be 7.98 years, which confirms the economic benefits of using this MBR for treating municipal wastewater. In general, understanding the challenges facing the efficiency of MBR would improve its performance and, consequently, the sustainability of wastewater reclamation.

Simultaneous removal of ciprofloxacin and disinfection from wastewater by combined photocatalytic reactor (PCR) and membrane bioreactor (MBR) system

Integrated photocatalytic-biological wastewater treatments are being explored as an effective alternative for removing emerging contaminants and pathogens. This study investigates ciprofloxacin (CPX) antibiotic removal and inactivation of Escherichia coli in simulated wastewater by using two systems (i) photocatalytic reactor (PCR) with 0.5 g/L of Ag-doped TiO2 nanoparticles (Ag:Ti in 1:1.7 molar ratio) with 180 min of blue LED light exposure and continuous mixing, and (ii) submerged membrane bioreactor (MBR) operated in continuous mode at 2.75 days hydraulic retention time (HRT) and 30 days of solid retention time (SRT) with 0.68 bar transmembrane pressure (TMP). TEM, XRD, and UV-Vis DRS characterization suggested that Ag doping in the lattice of 25 nm-sized nanoparticles lowered the bandgap from 3.10 to 2.41 eV, improving its photocatalytic performance. Studies on individual PCR, MBR, and combined systems were performed for optimum CPX removal and disinfection. MBR followed by PCR (MBR-PCR) was observed to be the best treatment among all four strategies achieving 99% removal of chemical oxygen demand (COD) and nitrogen from the system, and ensuring ∼99% CPX removal with complete disinfection of 106 CFU/mL E. coli. The study also suggested CPX biodegradation with marginal adsorption on bio-sludge in MBR, and predominant role of h+ over •OH radicals in CPX photocatalysis and bacterial cell disruption. The absence of E. coli zone of inhibition indicated the elimination of CPX toxicity in the treated effluent. Thus, integrated MBR-PCR may find application in the removal of such pharmaceutical compounds and disinfection from wastewater.

Improving the Antibiofouling and Operational Properties of PVDF Membranes Using Synthesized Cu‐SiO2 Nanoparticles in a Submerged Membrane Bioreactor

AbstractThe effects of synthesized hydrophilic Cu‐SiO2 nanoparticles on the morphology and antibiofouling performance of polyvinylidene fluoride (PVDF) membranes in a membrane bioreactor system were examined. As a result, the pure water flux of the PVDF membrane increased from 47.61 to 71.93 L m−2h−1 in the presence of 1.0 wt % Cu‐SiO2 nanoparticles. Also, the better‐developed finger‐like bulk pores and thicker sponge‐like surface pores for the nanocomposite membranes confirmed the lower phase inversion rate. The total fouling ratio of the membranes was reduced from 53.79 % to 24.13 % in the presence of 1.0 wt % Cu‐SiO2 nanoparticles, while the flux recovery ratio increased from 54.61 % to 88.73 %. In addition, extracellular polymeric substances analysis showed lower protein and carbohydrate formed on the membrane surface for the nanocomposite membranes.

Integrating of electrocoagulation process with submerged membrane bioreactor for wastewater treatment under low voltage gradients

Treating and reusing wastewater has become an essential aspect of water management worldwide. However, the increase in emerging pollutants such as polycyclic aromatic hydrocarbons (PAHs), which are presented in wastewater from various sources like industry, roads, and household waste, makes their removal difficult due to their low concentration, stability, and ability to combine with other organic substances. Therefore, treating a low load of wastewater is an attractive option. The study aimed to address membrane fouling in the submerged membrane bioreactor (SMBR) used for wastewater treatment. An aluminum electrocoagulation (EC) device was combined with SMBR as a pre-treatment to reduce fouling. The EC-SMBR process was compared with a conventional SMBR without EC, fed with real grey water. To prevent impeding biological growth, low voltage gradients were utilized in the EC deviceThe comparison was conducted over 60 days with constant transmembrane pressure and infinite solid retention time (SRT). In phase I, when the EC device was operated at a low voltage gradient (0.64 V/cm), no significant improvement in the pollutants removal was observed in terms of color, turbidity, and chemical oxygen demand (COD). Nevertheless, during phase II, a voltage gradient of 1.26 V/cm achieved up to 100%, 99.7%, 92%, 94.1%, and 96.5% removals in the EC-SMBR process in comparison with 95.1%, 95.4%, 85%, 91.7% and 74.2% removals in the SMBR process for turbidity, color, COD, ammonia nitrogen (NH3–N), total phosphorus (TP), respectively. SMBR showed better anionic surfactant (AS) removal than EC-SMBR. A voltage gradient of 0.64 V/cm in the EC unit significantly reduced fouling by 23.7%, while 1.26 V/cm showed inconsistent results. Accumulation of Al ions negatively affected membrane performance. Low voltage gradients in EC can control SMBR fouling if Al concentration is controlled. Future research should investigate EC-SMBR with constant membrane flux for large-scale applications, considering energy consumption and operating costs.

Anoxic Treatment of Agricultural Drainage Water in a Venturi-Integrated Membrane Bioreactor.

Due to low sludge production and being a clean source without residuals, hydrogen-based autotrophic denitrification appears to be a promising choice for nitrate removal from agricultural drainage waters or water/wastewater with a similar composition. Although the incorporation of hydrogen-based autotrophic denitrification with membrane bioreactors (MBRs) enabled almost 100% utilization of hydrogen, the technology still needs to be improved to better utilize its advantages. This study investigated the anoxic treatment of both synthetic and real drainage waters using hydrogen gas in a recently developed membrane bioreactor configuration, a venturi-integrated submerged membrane bioreactor, for the first time. The study examined the effects of the inflow nitrate concentration, and the use of a venturi device on the removal efficiency, as well as the effects of the presence of headspace gas circulation and circulation rate on membrane fouling. The study found that using the headspace gas circulation through a venturi device did not significantly affect the treatment efficiency, and in both cases, a removal efficiency of over 90% was achieved. When the inlet NO3--N concentration was increased from 50 mg/L to 100 mg/L, the maximum removal efficiency decreased from 98% to 92%. It was observed that the most significant effect of the headspace gas circulation was on the membrane fouling. When the headspace gas was not circulated, the average membrane chemical washing period was 5 days. However, with headspace gas circulation, the membrane washing period increased to an average of 12 days. The study found that the headspace gas circulation method significantly affected membrane fouling. When the upper phase was circulated with a peristaltic pump instead of a venturi device, the membrane washing period decreased to one day. The study calculated the maximum hydrogen utilization efficiency to be approximately 96%.

Comparative analysis of membrane fouling mechanisms induced by operation modes of membrane bioreactors with aerobic granular sludge

This experimental work investigated fouling characteristics induced by two different configurations of membrane bioreactor (MBR), which are submerged MBR and sidestream MBR with aerobic granular sludge. Submerged membrane bioreactor with granular sludge (Sub-MGSBR) ran the longest operation time 61 days with a steady overall TMP increase rate; Sidestream membrane bioreactor with granular sludge (SS-MGSBR) performed only 39 days, which exhibited Sub-MGSBR had more efficiently retarding membrane fouling. In both membrane bioreactors with flocculent sludge (MFSBRs) as a control, membrane foulants were compact, and cake resistance was the dominant fouling factor. In MGSBRs, however, pore blocking resistance turned out the key fouling factor. Especially in Sub-MGSBR, it went beyond 75%, and there was the most conglomeration of microorganisms of foulants with the highest porosity. Extracellular polymeric substances (EPS) content of foulants proved membrane fouling was hardly just for granules accumulation into cake but microorganisms’ growth in MGSBRs.

Treatment Performance of Municipal Sewage in a Submerged Membrane Bioreactor (SMBR) and Mechanism of Biochar to Reduce Membrane Fouling

Submerged membrane bioreactors (SMBRs) are a promising technology for municipal sewage treatment, but membrane fouling has limited their development. In this study, biochar (BC), which has a certain adsorption capacity, was added to an SMBR to investigate its potential in treating municipal sewage and alleviating membrane fouling. The results showed that the average removal rates of ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) were 94.38%, 59.01%, 44.15% and 83.70%, respectively. After BC was added and operation was stable, the ratio of mixed liquor volatile suspended solids to mixed liquor suspended solids (MLVSS/MLSS) was maintained between 0.78 and 0.81. The concentrations of soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) were stabilized between 63.05 ± 8.49 mg/L and 67.12 ± 1.54 mg/L. Trans-membrane pressure (TMP) and scanning electron microscopy (SEM) analyses showed that BC reduced the TMP by reducing the thickness and compactness of the cake layer on the membrane surface. The high-throughput sequencing results showed that the microorganisms associated with biofilm formation (proteobacteria, γ-proteobacteria and α-proteobacteria) were significantly reduced in the BC-enhanced SMBR system. BC promoted the enrichment of functional microorganisms such as Chloroflexi, Acidobacteriota, Anaerolineae and Planctomycetes. Compared with traditional anti-fouling methods, the results of this study may provide a low-cost membrane fouling mitigation method for industrial applications of SMBRs.

Membrane fouling mechanism of submerged membrane bioreactor during erythromycin removal

Background: Based on the previous studies, antibiotics can have affected biological properties of biomass and fouling properties of mixed liquor in aeration tank. The present study was conducted to explore the fouling mechanisms of membrane bioreactor (MBR) system during the treatment of wastewater containing erythromycin (ERY) antibiotic under several mixed liquor suspended solids (MLSS) concentrations. Methods: A lab-scale two-chamber MBR system equipped with a polypropylene hollow fiber submerged membrane was fed with synthetic wastewater containing different initial concentrations of ERY. MBR system was operated under the constant flux mode and different MLSS concentrations (5.0-13.0 g/L) and the obtained results were evaluated using different individual and combined fouling models. Results: The variation of MLSS concentrations had not significantly affected the kind of best-fitted model. From the individual models, the standard model indicated the best performance for permeate prediction under different MLSS concentrations (R2 adj&gt;0.997). For all studied MLSS concentrations, the R2 adj values of combined fouling models were higher than 0.986 and demonstrated good fitness performance of combined models compared to individual models. Overall, the cake-intermediate model showed the lowest fitness, and cake-complete and complete-standard models were the most successful models in filtrated volume prediction in comparison with other combined fouling models. Conclusion: This study indicated that mechanistic models are suitable for fouling prediction of MBR systems in ERY removal and under a wide range of MLSS concentrations and provide valuable information on fouling mechanisms of full-scale MBR systems.

Biodegradation of Natural Rubber Wastewater in the Submerged Membrane Bioreactor by Pichia Guilliermondii and Yarrowia Lipolytica

Abstracts: Despite the many services that natural rubber provides to humanity, its production generates significant quantities of polluted effluents which have a negative impact on health and the environment. In order to reduce this pollution and allow water to be reused after treatment, a synthetic effluent treatment trial was carried out in a submerged membrane bioreactor in the presence of two strains of yeast (Yarrowia lipolytica, Pichia guilliermondii) and biodegradation parameters (COD, NH4+, NO2-, NO3-) were followed. The Mohlman Index (MI), the particle size distribution, the Lowry method for proteins and the Dubois method for sugars have made it possible to characterize the sludge generated during biodegradation. It appears from these experiments that the reduction rate of COD was 98% and that of nitrification and denitrification 90%. There is a decreasing linear relationship between the MI and SS (Suspended Solids) with an R2 of 95%. The distribution of the particle size of the sludge is tri-modal with a maximum of sludge having an average size of 1000 µm. The sludge formed resists filtration with a polysaccharide/protein ratio of 0.45.

Biodegradation of Natural Rubber Wastewater in the Submerged Membrane Bioreactor by Pichia Guilliermondii and Yarrowia Lipolytica

Abstracts: Despite the many services that natural rubber provides to humanity, its production generates significant quantities of polluted effluents which have a negative impact on health and the environment. In order to reduce this pollution and allow water to be reused after treatment, a synthetic effluent treatment trial was carried out in a submerged membrane bioreactor in the presence of two strains of yeast (Yarrowia lipolytica, Pichia guilliermondii) and biodegradation parameters (COD, NH4+, NO2-, NO3-) were followed. The Mohlman Index (MI), the particle size distribution, the Lowry method for proteins and the Dubois method for sugars have made it possible to characterize the sludge generated during biodegradation. It appears from these experiments that the reduction rate of COD was 98% and that of nitrification and denitrification 90%. There is a decreasing linear relationship between the MI and SS (Suspended Solids) with an R2 of 95%. The distribution of the particle size of the sludge is tri-modal with a maximum of sludge having an average size of 1000 µm. The sludge formed resists filtration with a polysaccharide/protein ratio of 0.45.

Granular activated carbon stimulates biogas production in pilot-scale anaerobic digester treating agro-industrial wastewater

This work examines the continuous addition (5 g/L) of conductive granular activated carbon (GAC) in an integrated pilot-scale unit containing an anaerobic digester (180 L) and an aerobic submerged membrane bioreactor (1600 L) connected in series for the treatment of agro-industrial wastewater. Biogas production increased by 32 % after the addition of GAC. Methanosaeta was the dominant methanogen in the digester, and its relative abundance increased after the addition of GAC. The final effluent after post-treatment with the aerobic membrane bioreactor had a total solids content <0.01 g/L and a chemical oxygen demand between 120 and 150 mg/L. A simple cost analysis showed that GAC addition is potentially profitable, but alternatives ways of retaining the GAC in the system need to be found. Overall, this study provides useful scientific data for the possible application of GAC in full-scale biogas projects.

Making waves: Why do we need ultra-permeable nanofiltration membranes for water treatment?

Over the last few decades, developing ultra-permeable nanofiltration (UPNF) membranes has been a focus research area to support NF-based water treatment. Nevertheless, there have been ongoing debates and doubts on the need for UPNF membranes. In this work, we share our perspectives on why UPNF membranes are desired for water treatment. We analyze the specific energy consumption (SEC) of NF processes under various application scenarios, which reveals the potential of UPNF membranes for reducing SEC by 1/3 to 2/3 depending on the prevailing transmembrane osmotic pressure difference. Furthermore, UPNF membranes could potentially enable new process opportunities. Vacuum-driven submerged NF-modules could be retrofitted to existing water/wastewater treatment plants, offering lower SEC and lower cost compared to conventional NF systems. Their use in submerged membrane bioreactors (NF-MBR) can recycle wastewater into high-quality permeate water, which enables energy-efficient water reuse in a single treatment step. The ability for retaining soluble organics may further extend the application of NF-MBR for anaerobic treatment of dilute municipal wastewater. Critical analysis of membrane development reveals huge rooms for UPNF membranes to attain improved selectivity and antifouling performance. Our perspective paper offers important insights for the future development of NF-based water treatment technology, which could potentially lead to a paradigm shift in this burgeoning field.

Performance evaluation of submerged membrane bioreactor for municipal wastewater treatment: Experimental study and model validation with GPS‐X software simulator

AbstractIn this study, flat sheet submerged MBR (FS‐SMBR) was investigated under 6 and 4 h hydraulic retention times (HRT) and 40 days solid retention time with real municipal wastewater. The implementation of the treatment system was evaluated in terms of physico‐chemical and microbial analysis as well as sludge characterization. The permeate of FS‐SMBR complied with the standards for reuse and non‐detectable levels of faecal coliform was achieved at 6 and 4 h HRTs, with pore‐blocking resistances (Rt) of 28 × 1011 and 40 × 1011/m, respectively. Examining another dominant factor, that is, sludge viscosity, the best results were acquired using HRT 4 h for domestic wastewater. Furthermore, the results obtained were validated and calibrated using the GPS‐X software simulator, and the results of modelled data were completely matched with the experimental data under the same conditions.

Municipal wastewater treatment and recycle by an electrocoagulation process and a submerged membrane bioreactor system

To remove phosphates and nitrates from municipal wastewater, an electrocoagulation process with membrane bioreactor process (EC-MBR) was used. Experiments were carried out incrementally to evaluate the new design. In a lab-scale (EC-MBR) treatment of municipal wastewater, the structure and distribution of the organic matter removal utilizing the membrane are being examined. The study's objectives were to evaluate the efficiency of the Al-Hawraa wastewater's organic matter removal process for nitrate (NO-3) and phosphate (PO4-3) as well as how it related to machine learning indicators. It was chosen to use an EC-MBR with operational parameters of 25 Co, pH 7 and DO (4-6 mg/L), initial and final concentrations of NO-3 (4.4-0.6 mg/L), and (PO4-3) (6.0-0.1 mg/L) to collect and analyze effluent from municipal wastewater treated using biological and chemical methods. According to the results, it may be possible to measure the effectiveness of organic matter removal using a neural network method. The results also showed that an overall reactor had agreeablemaximum NO-3 and (PO4-3) removal efficiencies of (87.6% and 98.1%), respectively. The accuracy model by its (98.1 and 85.7) for both NO-3 and (PO4-3) was effective, according to the models' accuracy results.

Modeling and Simulation of ASM1-SMP Model to Better Control Fouling in a Submerged Membrane Bioreactor for Wastewater Treatment Under Different COD: N Ratios Using Matlab and Aquasim

Modeling and Simulation of ASM1-SMP Model to Better Control Fouling in a Submerged Membrane Bioreactor for Wastewater Treatment Under Different COD: N Ratios Using Matlab and Aquasim