Control In Membrane Bioreactors Research Articles

Benefits of fungal-to-bacterial quorum quenching as anti-biofouling strategy in membrane bioreactors for wastewater treatment and water reuse

This study addresses membrane biofouling in membrane bioreactors (MBRs) by exploring fungal-to-bacterial quorum quenching (QQ) strategies. While most research has been focused on bacterial-to-bacterial QQ tactics, this study identified fungal strain Vanrija sp. MS1, which is capable of degrading N-acyl-homoserine lactones (signaling molecules of Gram-negative bacteria). To determine the benefits of fungal over bacterial strains, after immobilization on fluidizing spherical beads in an MBR, MS1 significantly reduced the fouling rate by 1.8-fold compared to control MBR, decreased extracellular polymeric substance levels in the biofilm during MBR operation, and favorably changed microbial community and bacterial network, resulting in biofouling mitigation. It is noteworthy that, unlike Rhodococcus sp. BH4, MS1 enhanced QQ activity when switching from neutral to acidic conditions. These results suggest that MS1 has the potential for the effective treatment of acidic industrial wastewater sources such as semiconductor and secondary battery wastewater using MBRs.

Development of a novel membrane-based quorum-quenching microbial isolator for biofouling control: Process performance and microbial mechanism

Quorum quenching (QQ) can mitigate biofouling in membrane bioreactors (MBRs) by inhibiting cell-to-cell communication. However, it is difficult to maintain long-term QQ activity. Here, a novel microbial isolator composed of tubular microfiltration membranes was developed to separate QQ bacteria (Rhodococcus sp. BH4) from sludge. The time to reach a transmembrane pressure of 50 kPa was delayed by 69.55 % (p = 0.002, Student’s t test) in MBR with QQ microbial isolator (MBR-Q), compared to that in the control MBR (MBR-C) during stable operation. The concentration of proteins in the extracellular polymeric substances of sludge was reduced by 20.61 % in MBR-Q relative to MBR-C. The results of the bacterial community analyses indicated less enrichment of fouling-associated bacteria (e.g., Acinetobacter) but a higher abundance of QQ enzymes in MBR-Q than in MBR-C. This environmentally friendly technique can decrease the cleaning frequency and increase the membrane lifespan, thus improving the sustainability of MBR technology.

Combination of membrane bioreactor with chemical coagulation for the treatment of real pharmaceutical wastewater: Comparison of simultaneous and consecutive pre-treatment of coagulation on MBR performance

In this work, the combination of the coagulation process with the MBR system to reclaim effluent in pharmaceutical industries was investigated. In this research, comparison/concentration optimization of two modes of integrations, including simultaneous; one-step one pot, and consecutive coagulation MBR were investigated. Results showed that COD removal in simultaneous and consecutive modes at optimum values were 85 % and 95.8 %, respectively, which were considerably higher than that of control MBR; 53.89 %. The total fouling ratio for control MBR, simultaneous, and consecutive modes at optimum conditions were 70.69 %, 37.3 %, and 42.5 %, respectively, confirming that the integrated coagulation process and MBR system were considerably effective. Analyzing the secreted metabolite, e.g. protein, carbohydrate, and LB/TB-EPS ratio in the MBR tank as well as on the membrane surface showed that the charge-neutralization and entrapment of bio-foulants by aggregated clots during the coagulation hinder the adhesion of the biofouling agents on the membrane surface, therefore in-line with the flux attenuation trend, lower metabolite concentration results in less membrane fouling. It was found that simultaneous coagulative MBR with 100 mg/L FeCl3 concentration demonstrates better fouling mitigation in comparison with consecutive (even with poly aluminum chloride; PACl as coagulant aid) MBR, while the latter mode shows better performance in terms of wastewater treatment. These findings open avenues for future techno-economic assessments of a coagulation-assisted MBR, providing a cost-effective solution for treating high-strength wastewater on a larger scale.

Semi-interpenetrating network hydrogels-based microcapsule for quorum quenching bacteria biocontainment to enhance biofouling control in membrane bioreactor

Microbial quorum quenching (QQ) has been proven to be a sustainable anti-biological fouling strategy for membrane bioreactors (MBR), but the long-term stability and practical application in MBR were uncertain. We reported a novel semi-interpenetrating network (SIPN) hydrogels-based design of QQ bacteria (Rhodococcus sp. BH4) encapsulation for both biofouling control and enhancement of organic pollutants removal in MBR. The microcapsule included the alginate core, chitosan thin intermediate compartment and SIPN (sodium alginate / polyacrylamide) shell, which exhibited near-perfect biocontainment, including preventing detectable QQ bacteria escape and improving mechanical strength. The QQ-microcapsules in the MBR demonstrated its significant anti-biofouling effect for treating synthetic wastewater (i.e., membrane fouling was delayed by 233%-280% compared to the control MBR membrane). Meanwhile, the efficiency of phosphorus removal was developed in QQ-microcapsule MBR because of the enhanced phosphorus removal triggered by the flocculation of polyacrylamide (PAM) fraction in SIPN. This promising QQ media brings the broad potential for biofouling control and long-term efficient operation in actual MBR wastewater treatment.

Optimum quorum quenching bacteria concentration in the better-quality cell entrapping beads to control biofouling in membrane bioreactor

Quorum quenching (QQ) by cell entrapping beads (CEBs) is known to inhibit biofouling by its biological and physical cleaning effect. Although there are better QQ media reported, due to the ease of fabrication of QQ-CEBs, this study focused on improving the quality of CEBs by comparing two distinct bead-making methods – polyvinyl alcohol-alginate (PVA-alginate) and phase inversion – and on finding the optimum concentration of QQ bacteria in the CEBs. The evaluation of PVA-alginate bead showed better uniformity, and higher mechanical and chemical strength in comparison with the phase inversion bead. Through the operations of two control membrane bioreactors (MBRs) (no bead, vacant bead) and four QQ-MBRs with different Rhodococcus sp. BH4 concentrations (2.5–15 mg cell ml−1) in PVA-alginate CEBs, the maximum QQ effect was observed by 5 mg ml−1 BH4 concentration beads. This implies that an optimum cell concentration of QQ-CEBs is crucial to economically improve MBR performance using QQ.

Isolation and application of Bacillus thuringiensis LZX01: Efficient membrane biofouling mitigation function and anti-toxicity potential

Significant progress has been made in mitigating membrane biofouling by microbial quorum quenching (QQ). More efficient and survivable QQ strains need to be discovered. A new strain named Bacillus thuringiensis LZX01 was isolated in this study using a low carbon source concentration “starving” method from a membrane bioreactor (MBR). LZX01 secreted intracellular lactonase to enable QQ behavior and was capable of degrading 90 % of C8-HSL (200 ng/mL) within 30 min, which effectively delayed biofouling by inhibiting the growth of bacteria associated with biofouling and improving the hydrophilicity of bound extracellular polymeric substances. As a result, the membrane biofouling rate of MBR adding LZX01 was four times slower than that of the control MBR. Importantly, LZX01 maintains its QQ activity even in environments contaminated with typical toxic pollutants. Therefore, with high efficiency, toxicity resistance, and easy culture, LZX01 holds great potential and significant promise for biofouling control applications.

A novel membrane bioreactor inoculated with algal-bacterial granular sludge for sewage reuse and membrane fouling mitigation: Performance and mechanism

In this study, a novel membrane bioreactor (MBR) inoculated with algal-bacterial granular sludge (ABGMBR) was established to improve pollutant removal and alleviate membrane fouling. The ABGMBR system showed higher pollutant removal rate and longer operation time (152 day) compared to the control MBR (AGMBR). Moreover, the contents of the pollutants such as granular sludges, extracellular polymeric substances (EPS), and soluble microbial products on the membrane were remarkably reduced, leading to the formation of a porous and loose cake layer on the membrane and a slow increase in transmembrane pressure. Standard blocking was the main mechanism of membrane fouling; however, the membrane pore blockage was significantly reduced in ABGMBR. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the aggregation and adhesion of foulants on the membrane were greatly inhibited in ABGMBR. Furthermore, correlation analysis showed significant differences in membrane fouling characteristics between AGMBR and ABGMBR. The ABGMBR system effectively retarded sludge disintegration and increased the repulsion between the sludge and membrane owing to the favorable mixed liquor characteristics. This study showcases the superior operational efficiency and anti-fouling performance of ABGMBR, offering a novel perspective on sewage reuse and membrane fouling mitigation.

Effects of High Pharmaceutical Concentrations in Domestic Wastewater on Membrane Bioreactor Treatment Systems: Performance and Microbial Community.

Despite pharmaceuticals being widely detected in water-bodies worldwide, what remain unclear are the effects of high pharmaceutical concentrations on the treatment efficiency of biological wastewater treatment processes, such as membrane bioreactor (MBR) systems. This study investigated the efficiency of MBR technology in the treatment of synthetic wastewater containing a mixture of five typical pharmaceuticals (ofloxacin, sulfamethoxazole, sulfamethylthiadiazole, carbamazepine and naproxen) with a total concentration of 500 µg/L. Both the control MBR (MBRc) without pharmaceutical dosing and the MBR operated with high influent pharmaceutical concentrations (MBRe) were operated under room temperature with the same hydraulic retention time of 11 h and the same sludge retention time of 30 d. The removal efficiency rates of total nitrogen and total phosphorus were 83.2% vs. 90.1% and 72.6% vs. 57.8% in the MBRc vs. MBRe systems, and both MBRs achieved >98% removal of organics for a 180-day period. The floc size decreased, and membrane fouling became more severe in the MBRe system. Microbial diversity increased in the MBRe system and the relative abundances of functional microbe differed between the two MBRs. Furthermore, the total relative abundances of genes involved in glycolysis, assimilating nitrate reduction and nitrification processes increased in the MBRe system, which could account for the higher organics and nitrogen removal performance. This work provides insights for MBR operation in wastewater treatment with high pharmaceutical concentrations.

Mediation of Bacterial Interactions via a Novel Membrane-Based Segregator to Enhance Biological Nitrogen Removal.

The regulation of microbial subpopulations in wastewater treatment plants (WWTPs) with desired functions can guarantee nutrient removal. In nature, "good fences make good neighbors," which can be applied to engineering microbial consortia. Herein, a membrane-based segregator (MBSR) was proposed, where porous membranes not only promote the diffusion of metabolic products but also isolate incompatible microbes. The MBSR was integrated with an anoxic/aerobic membrane bioreactor (i.e., an experimental MBR). The long-term operation showed that the experimental MBR exhibited higher nitrogen removal (10.45 ± 2.73 mg/L total nitrogen) than the control MBR (21.68 ± 4.23 mg/L) in the effluent. The MBSR resulted in much lower oxygen reduction potential in the anoxic tank of the experimental MBR (-82.00 mV) compared to that of the control MBR (83.25 mV). The lower oxygen reduction potential can inevitably aid in the occurrence of denitrification. The 16S rRNA sequencing showed that the MBSR significantly enriched acidogenic consortia, which yielded considerable volatile fatty acids by fermenting the added carbon sources and allowed efficient transfer of these small molecules to the denitrifying community. Moreover, the sludge communities of the experimental MBR harbored a higher abundance of denitrifying bacteria than those of the control MBR. Metagenomic analysis further corroborated these sequencing results. The spatially structured microbial communities in the experimental MBR system demonstrate the practicability of the MBSR, achieving nitrogen removal efficiency superior to that of mixed populations. Our study provides an engineering method for modulating the assembly and metabolic division of labor of subpopulations in WWTPs. IMPORTANCE This study provides an innovative and applicable method for regulating subpopulations (activated sludge and acidogenic consortia), which contributes to the precise control of the metabolic division of labor in biological wastewater treatment processes.

Comparison of NaOH and NaOCl on-line chemical enhanced backwash on membrane fouling of high flux membrane bioreactor treating sewage

Different physio-chemical and biological methods have been applied to reduce membrane fouling and to maintain the flux of membrane bioreactor (MBR). Periodic chemically enhanced backwash (CEB) has been recently developed and displayed good performance to recover the membrane permeability. However, the comparative effect of on-line CEB (using NaOCl and NaOH) on fouling mitigation and the effluent quality of MBR was poorly known. This study aimed to evaluate the changes in membrane resistance, membrane fouling and the effluent quality with and without CEB in MBR to reveal the effect of different NaOCl and NaOH concentrations. Lab-scale MBR treating sewage at high flux were operated for 8 min continuously at a flux of 20 L/(m2.h) followed by a backwash duration of 30 s. In reference MBR permeate (without chemical) was used as a backwash solution. The study found that MBR with CEB has higher operational time and lower fouling rates than reference MBR. Overall, backwash with NaOH increased the run-time by 29% – 45% compared to the control MBR, and backwash with NaOCl increased run-time from 34% to 61% compared to the control MBR. NaOCl was significantly more effective by 7% – 28% compared to NaOH in fouling reduction at different concentrations. CEB has no significant (p > 0.05) effect on the removal efficiencies of different pollutants. The chemical oxygen demand removal efficiencies varied between 82 and 84%. The removals of total kjeldahl nitrogen (50 – 54%) and total phosphorus (45 – 52%) were lower due to the short solids and hydraulic retention time. This study highlights the potential of periodic CEB and concentrations of chemicals on MBR fouling and provides insights into potential approaches for mitigating this issue in MBR systems.

Membrane surface coated with zwitterions for fouling mitigation in membrane bioreactor: Performance and mechanism

Zwitterionic surface engineering is an effective strategy to improve membrane antifouling ability. In this present study, zwitterions were introduced onto hollow-fiber (HF) membrane via a simple flow-through coating method using zwitterionic organosilica material, and then the membrane was incorporated into a membrane bioreactor (MBR) to demonstrate improvement in fouling control. Zwitterions endowed the membrane with superior fouling resistance in the MBR; the critical flux of the membrane was improved from 25 LMH to 35 LMH, which signified higher allowable operation flux; the transmembrane pressure (TMP) development was greatly retarded, which resulted in fouling cycle extended by approximately 2 times (from 32 d to 66 d) and less cleaning frequency. Batch fouling experiments with key foulants found that zwitterion-coated membrane had superior resistance to extracellular polymeric substances (EPS) and soluble microbial polymer (SMP) adsorption. In particular, it presented exceptionally high resistance against protein adsorption. Interfacial free energy analysis revealed that zwitterions substantially altered interfacial interaction between the membrane and the EPS/SMP; the Lifshitz-van der Waals and Lewis acid-base attractive forces were obviously attenuated. As a result, the energy barrier for foulants attaching on membrane surface was greatly elevated. Our study provided a deeper insight into the antifouling mechanism of zwitterion-coated membrane and demonstrated its good potential for improving fouling control in MBR.

Evaluating the effect of aeration rate on quorum quenching membrane bioreactors: Performance of activated sludge, membrane fouling behavior, and the energy consumption analysis

Microbial quorum quenching (QQ) has recently been proven to be an efficient approach to mitigate biofouling in membrane bioreactors (MBRs). It can reduce biopolymers production and improve sludge conditions. Also, aeration intensity is considered to be directly interconnected with membrane fouling. In this study, the impact of aeration rate on the performance, membrane fouling, and the energy consumption of quorum quenching membrane bioreactor (QQ-MBR) and conventional membrane bioreactor (C-MBR) were exposed. We investigated the synergistic effects of aeration intensity and QQ on membrane fouling control in MBRs and analyzed the energy consumption of reactors under different conditions. QQ was found to mitigate biofouling significantly, but the membrane fouling mitigation efficiency was lowest (only 17.9 %) at high aeration intensity. Moreover, QQ reduced the content of SMP and EPS in sludge (over 20 % decreasing), and a better QQ performance was observed at middle aeration intensity. As for energy consumption, the most energy was consumed at high aeration intensity. QQ can minimize the aeration intensity required for the regular operation of MBR, thereby optimizing the energy consumption.

Antibiofouling Characteristics and Mechanisms in an Anammox Membrane Bioreactor Based on an Optimized Photocatalytic Technology─Photocatalytic Optical Fibers.

As an ecofriendly photocatalytic antifouling technology for membrane bioreactors (MBRs), photocatalytic optical fibers (POFs) can decrease the replacement cost of modified membranes and prevent the proliferation of photosynthetic bacteria caused by direct light illumination. Here, POFs were applied in situ in an anaerobic ammonium oxidation (anammox) MBR for membrane biofouling control. Compared with the control MBR without POFs treatment, the average fouling cycle of the POFs-loaded MBR was extended by 137%, and the energy consumption caused by membrane fouling was saved by 18%. In the antibiofouling process, •OH was the key photocatalytic reactive species. On the fouled POFs-loaded membranes, the membrane-adhered foulant was significantly decreased by photocatalytic degradation of the proteins, polysaccharides and humic substances in the microbial metabolites. The membrane-attached bacteria were inactivated by the POFs by the mechanisms of cell-membrane destruction and cell-membrane permeabilization, which caused bacterial necrosis and apoptosis, respectively. Moreover, the total nitrogen-removal efficiencies of the two MBRs were maintained at 85.3-90.4%, and the abundance of anammox bacteria increased from 21.3% to 46.2% during the 202 days of operation, indicating an efficient anammox process with excellent nitrogen-removal performance, biomass retention, and anammox bacteria enrichment. The systematic insights into the antibiofouling performance and mechanisms of POFs in anammox MBRs will promote application and development of membrane-filtration technology in wastewater treatment using environmentally friendly and energy-efficient antifouling strategies.

New insights into biofilm control and inhibitory mechanism analysis based on the novel quorum quenching bacterium Acinetobacter pittii HITSZ001

Quorum quenching (QQ) has proven its potential as an innovative approach for biofouling control in membrane bioreactor (MBR) for wastewater treatment. In this study, a novel quorum-quenching bacterium, Acinetobacter pittii HITSZ001, was isolated from activated sludge. In contrast to previous studies, in which QQ bacteria were directly applied in the MBR system, in this investigation, this strain was co-cultured with Pseudomonas aeruginosa to illustrate the inhibitory effect of the QQ strain on the key genes involved in biofilm formation. The types of QQ enzymes secreted by A. pittii HITSZ001 and its functional ahlm gene was also identified. To better apply this strain, it was encapsulated in the QQ beads with great activities, which could well adapt to a complex real activated sludge environment and effectively controlled biofilm formation on the membrane. The results of this study suggest that A. pittii HITSZ001 represents a novel and promising strain for biofilm mitigation to promote MBR performance and that it would be economically and technically feasible to expand biofouling control with this strain to plant-scale MBRs and similar environmental engineering systems.

Dynamic scouring of multifunctional granular material enhances filtration performance in membrane bioreactor: Mechanism and modeling

The granular material (GM) is able to effectively improve the membrane fouling control in membrane bioreactor (MBR) by dynamic scouring, adsorption behavior and enzymatic degradation. However, their roles and effects on the filtration performance of MBR remain unclear. The present work investigated the GM dynamic scouring mechanism, revealed the multifunctional quantitative evaluation, and clarified the filtration performance at various GM operating conditions in MBR. First, the aerobic granular sludge (AGS)-filtration process was still limited by the presence of irreversible membrane fouling, which decreased the filtration performance in MBR (threshold flux [169.5 L m−2 h−1] and (turning point of membrane fouling resistance [1.1 × 1012 m−1]). To solve this problem, the GMs (activated carbon [AC] and laccase immobilized activated carbon [LAC]) was added into the AGS-filtration process to enhance the filtration performance. Above all, based on momentum conservation, the dynamic scouring mathematical model was put forward to elucidate the dynamic scouring mechanism of GM towards the membrane surface. The scouring stress on the membrane surface was proportional to the total mass of GM and offered an additional shear effect for clearly promoting the collision between GM and foulant, and decreasing their deposition on the membrane surface via friction with the membrane. Then, both AC and LAC exhibited a highly desirable adsorption efficiency for foulant removal, whereas the enzymatic degradation of LAC also furtherly straightened this effect. Furthermore, a new contribution quantification model was proposed for evaluating the contribution rates of dynamic scouring (59.1%), adsorption behavior (36.4%) and enzymatic degradation (4.6%) to boost the filtration performance, implying that the dynamic scouring and adsorption behavior brought about the dominated promotion. At the GM of 8 g/L and size of 300–600 μm, AGS-filtration exhibited an optimized performance in term of threshold flux, turning point of membrane fouling resistance and membrane cleaning. The present study offers insights into the mechanism that GM multifunctional scouring enhanced filtration performance in MBR.

Isolation of Bacteria Capable of Degrading Various AHLs for Biofouling Control in Membrane Bioreactors

Membrane bioreactors (MBRs) are widely used to treat wastewater, mainly due to the production of high-quality effluent. However, biofilm forming on the surface of membranes can cause many problems, which remains one of the major limitations of this technique. Bacterial quorum quenching (QQ) has been proven to be a successful strategy to control biofouling in MBRs. However, for many QQ bacterial isolates, the detailed degradation rates of acyl homoserine lactones (AHLs) have rarely been reported. Therefore, this study aimed to isolate potential QQ bacteria and investigate their degradation rates against eight different AHLs. Results showed that four isolates (A9, A12, B11, and D3) exhibited consistent C8-HSL–(N-octanoyl-L-homoserine lactone) removal capabilities. These four isolates removed at least 70% of all AHLs tested within 180 min. They might have different QQ enzymes, based on our observation that the locations of enzyme activities differed. The bacteria most closely related to A9, A12, and B11 were Brucella anthropic, Bacillus cereus, and Bacillus toyonensis, respectively. Bacillus species have shown QQ activity in many studies, but AHL-reducing Brucella species have not been previously reported. Overall, this study extends our current knowledge of QQ bacteria that could be used to mitigate biofilm formation on MBR membranes.

Modification of nitrifying microbial community via DC electrical field application

The performance and operational stability of nitrifying-based treatment processes are closely associated with microbial community structures and species-to-species interactions. In this work, we investigated the effect of intermittent direct current (DC) on the change of nitrifying community structure and process performance in a membrane electro-bioreactor (MEBR). Microbial populations and dynamics were characterized using a fluorescent in situ hybridization (FISH) technique. The outcomes demonstrated that the MEBR system achieved substantial nitrification rates compared to a conventional membrane bioreactor (MBR). The MEBR enhanced the removal of NH3+−N to almost 99%. FISH analysis indicated a dominance of different nitrifying bacteria species in both reactors, leading to differences in nitrification and NH3+−N removal performance. In robust MEBR system, rapid nitrifiers, such as AOB (Nitrosomonas spp.) and NOB (Nitrobacter spp.) were dominat. In contrast, slower nitrifier consortiums like AOB (Nitrosospira spp.) and NOB (Nitrospira spp.) occupied the control MBR. Taken together, the development of fast and robust nitrifying community can lead to extra savings in capital and operational costs of the WWTPs, suggesting the adoption of MEBR oxic/anoxic process. Moreover, a better understanding of biological processes taking place in the new MEBR system and microbial environmental preferences would be valuable for process control and optimization, as well as beneficial for designing bioaugmentation processes, in order to avoid potential washout of target bacteria not adapted to real conditions in bioreactors. Such bio-electrically enhanced processes presented in this work can be used in a new WWTP design or retrofitting existing treatment plants.

Simultaneously enhanced treatment efficiency of simulated hypersaline azo dye wastewater and membrane antifouling by a novel static magnetic field membrane bioreactor (SMFMBR)

Operation performance and membrane fouling of a novel static magnetic field membrane bioreactor (SMFMBR) for treatment of hypersaline azo dye wastewater was investigated. The results showed that SMFMBRs possessed higher efficiency of dye decolorization, COD removal and detoxification than the control MBR without SMF. The (3#) SMFMBR equipped with 305.0 mT (the highest intensity) SMF displayed the best treatment performance among all the four reactors (named as 0#–3#, equipped with SMFs of 0 mT, 95.0 mT, 206.3 mT and 305.0 mT, respectively). Potentially effective microbes belonging to Rhodanobacter, Saccharibacteria genera incertae sedis, Defluviimonas, Cellulomonas, Cutaneotrichosporon, Candida and Pichia were enriched in three SMFMBRs, in both of suspended sludge and bio-cakes. The relative abundance of Candida and Pichia in suspended sludge of 3# SMFMBR was the highest among all the four reactors, suggesting their successful colonization and potentially persistent effect of bioaugmentation. On the other hand, SMF of higher intensity effectively mitigated membrane fouling. Less production of soluble microbial products (SMP) and extracellular polymeric substances (EPS), lower protein/polysaccharide (PN/PS) ratio in SMP and EPS, looser structure of bio-cakes on membrane surface, as well as lower relative abundance of potential fouling causing microbes (mainly bacteria) in microbial communities were determined in 3# SMFMBR than the other three groups.

Insights on fouling development and characteristics during different fouling stages between a novel vibrating MBR and an air-sparging MBR for domestic wastewater treatment

Membrane fouling remains a major hindrance to a prevalent application of membrane bioreactor (MBR) for wastewater treatment. Vibrating membrane technology has recently attracted increasing attention in energy-efficient fouling control in MBR compared to air sparging. However, little is known about its fundamental fouling control mechanism and whether the vibrating MBR (VMBR) is a highly effective strategy to control fouling constitutions and fouling sources compared to the conventional air-sparging MBR (ASMBR). This study operated two parallel MBRs with vibrating or air-sparging membrane modules for long-term (215 d) real domestic wastewater treatment. Effects of air sparging and vibration rates on fouling control, fouling development and fouling sources across three fouling stages were comprehensively evaluated. Results showed that the VMBR achieved 70% lower fouling rates compared to the ASMBR due to a remarkable retardation in each fouling stage by membrane vibration. The VMBR significantly reduced over 62.7% of colloidCL and SMPCL within the cake layer (CL) to simultaneously alleviate the reversible and irreversible fouling compared to the ASMBR. The comparatively lower dissolved organic matter (DOM) and biopolymer contents in the cake layer of the VMBR resulted in a slower TMP rise. The main DOMs in the foulants of both MBRs were found in the following order: aromatic protein > soluble microbial by-products > other organics. EPSML from mixed liquor (ML) contributed more DOMs to form membrane foulant than the SMPML in both MBRs. Aromatic proteins and soluble microbial products in the EPSML were markedly reduced in the VMBR but increased in the ASMBR in high-shear phase, demonstrating higher effectiveness in fouling control by membrane vibration. This study provided insights into understanding fouling control, fouling development characteristics and fouling mechanisms between the VMBR and ASMBR, which might guide the researchers and engineers to apply novel vibrating MBRs to better control membrane fouling for holistic wastewater treatment in full scale.

Novel strategy for membrane biofouling control in MBR with nano-MnO2 modified PVDF membrane by in-situ ozonation

In this study, ozonation catalyst nano-MnO2 blended polyvinylidene fluoride (PVDF) membrane was fabricated via phase inversion method and applied to membrane bioreactors (MBR), and then coupled with in-situ ozonation to study the anti-biofouling performance and reveal its mechanism. Results showed that, compared with pristine PVDF membrane (MBR_M0), 0.75 wt% and 1.00 wt% nano-MnO2 modified PVDF membrane (MBR_M0.75 and MBR_M1.00) could mitigate the membrane biofouling rate. Meanwhile MBR_M1.00 coupled with in-situ ozonation could increase the membrane cleaning cycle to 1.5 and 2.7 times, compared with MBR_M0 and MBR_M0.75 without in-situ ozonation. The possible mechanisms included that the nano-MnO2 modification coupled with in-situ ozonation directly removed the biofouling on the membrane surface, improved the hydrophilicity of the membrane surface and enhanced the chemical oxidation and biodegradation of membrane biofouling contaminants in the sludge mixture. The results of this work provide a new strategy for the control of membrane biofouling in MBR to treat industrial wastewater.