Membrane Fouling Tendency Research Articles

Functionalized graphene-based ultrafiltration and thin-film composite nanofiltration membranes for arsenic, chromium, and fluoride removal from simulated groundwater: Mechanism and effect of pH

Groundwater contaminant removal using ultrafiltration (UF) and nanofiltration (NF) membranes is complex due to limitations such as low selectivity-permeability and membrane fouling tendency. In this study, we fabricated a thin film composite (TFC) membrane over a highly permeable mixed matrix support UF membrane using sulfonic acid functionalized graphene oxide (SGO) and polyethersulfone (PES) for groundwater remediation application. The pure water permeability of the PES-SGO-TFC membrane was threefold (3.09 LMH bar−1) compared to the pristine PES-TFC membrane. The membrane showed excellent organic fouling resistance with more than 95% flux recovery. The salts and contaminant removal were checked in a cross-flow mode to understand a more practical approach to the applicability of the developed PES-SGO-TFC membrane. The membrane rejected Cr(VI), As(V), and fluoride to the extent of ∼89%, ⁓99%, and ∼77%, respectively, at pH ⁓7. The membrane separation performance varied as a function of pH, with more than 90% removal for monovalent fluoride at higher pH values. In a simulated groundwater matrix, the membrane demonstrated promising results for rejecting these ions. However, the simultaneous rejection of As(V) and fluoride may be impacted by interfering co-ions. This study offers a novel approach for developing highly permeable support UF-modified TFC membranes for better separation for groundwater remediation.

Highly Permeable Sulfonated Polydopamine Integrated MXene Membranes for Efficient Surfactant-Stabilized Oil-in-Water Separation.

MXene is an incredibly promising two-dimensional material with immense potential to serve as a high-performing separating or barrier layer to develop advanced membranes. Despite the significant progress made in MXene membranes, two major challenges still exist: (i) effectively stacking MXene nanosheets into defect-free membranes and (ii) the high fouling tendency of MXene-based membranes. To address these issues, we employed sulfonated polydopamine (SPD), which simultaneously serves as a binding agent to promote the compact assembling of Ti3C2Tx MXenes (MX) nanosheets and improves the antifouling properties of the resulting sulfonated polydopamine-functionalized MX (SPDMX) membranes. The SPDMX membrane was tested for challenging surfactant-stabilized oil-in-water separation with an impressive efficiency of 98%. Moreover, an ultrahigh permeability of 1620 LMH/bar was also achieved. The sulfonation of PD helps in improving the antifouling characteristics of SPDMX by developing a strong hydration layer and enhancing the oleophobicity of the membrane. The underwater SPDMX membrane appeared superoleophobic with an oil contact angle of 153°, whereas the ceramic membrane exhibited an oil contact angle of 137°. The SPDMX membranes showed an improved flux recovery (31%) compared to the nonsulfonated counterpart. This work highlights the appropriate functionalization of MXene as a promising approach to developing MXene membranes with high permeation flux and better antifouling characteristics for oily wastewater treatment.

Synthesis and performance of ultrafiltration membranes incorporated with different oxide nanomaterials: experiments and modeling

Abstract In membrane filtration technology, membrane fouling is the primary obstacle to optimizing efficiency and results in a short membrane lifetime and high operating costs. By incorporating nanomaterials into the membrane synthesis process, a mixed-matrix membrane with significantly enhanced characteristics and performance may be obtained. Graphene oxide (GO), aluminum oxide (Al2O3), tin oxide (SnO2), and titanium oxide (TiO2) were incorporated into a polyethersulfone (PESU) membrane. The water permeability of the modified membranes showed improvements when compared with the pure membrane. It increased from 65 L/m2 h bar for the pristine membrane (PES-1) to 143.6, 83.68, 92.12, 75.43 L/m2 h bar for Al2O3 (PES-2), TiO2 (PES-3), SnO2 (PES-4), and GO (PES-5) membranes, respectively. It was discovered that the membrane's surface hydrophilicity was significantly and directly affected by the incorporation of nanoparticles. Fouling parameters include Rr (Reversible fouling ratio), Rir (irreversible fouling ratio), Rt (total fouling ratio), and Frr (flux recovery ratio) and were measured to determine the membrane's fouling tendency. The results showed that the membrane's propensity for fouling could be reduced when nanoparticles were incorporated into it. The experimental results are best explained by the cake layer and both standard and intermediate blocking mechanism models, as determined by the traditional single fouling models.

A hybrid ZA@ZnO1−X nanocomposite-based tubular membrane process for enhanced degradation of organics: A bench scale study for Bismarck brown R effluent

Nanocomposite-based ceramic membrane with microbubble is an emerging hybrid technology for treating recalcitrant organics in wastewater. The current work is based on the synergistic effect of photocatalyst, microbubble, and membrane separation for enhanced degradation of Bismarck brown R, which is otherwise very low in the standalone process. In this study, we have fabricated a bench-scale membrane set up of submerged type, modified tubular membrane with the novel Zeolite A@ZnO1−X nanocomposite, and detailed analytical characteristics are investigated. The thin layer coating (average thickness 24.6 µm) of oxygen-deficient ZA@ZnO1−X photocatalyst gives a high photocatalytic efficiency under visible light without hampering the rejection rate. Here, we have treated Bismarck brown R contaminated wastewater in our prototype setup with simulated and natural wastewater collected from a local dying factory. The operational parameters such as Bismarck brown R concentration, solution pH, temperature, and flux are varied and analyzed optimized reaction conditions favorable for actual wastewater treatment. The hybrid ZA@ZnO1−X nanocomposite-based tubular membrane improved the degradation of natural wastewater to 95.4 % decolorization and 94 % COD removal in 90 mins at pH 8.15, solution flux 120 ml/min and temperature 30 °C. The scavenging experiment resolved responsible reactive species for organic dye degradation: holes and HO•. The tentative mechanistic degradation pathway involved homolytic cleavage of the azo bond followed by phenyl radical generation to a small intermediate of hydroxyquinol. This work represents an efficient alternative to conventional membrane technology with lesser membrane fouling tendency and enhanced catalytic efficiency in assistance with microbubbles simultaneously.

Enhanced Removal of Endocrine-Disrupting Compounds from Wastewater Using Reverse Osmosis Membrane with Titania Nanotube-Constructed Nanochannels.

This paper presents a comprehensive study of the performance of a newly developed titania nanotube incorporated RO membrane for endocrine-disrupting compound (EDC) removal at a low concentration. EDCs are known as an emerging contaminant, and if these pollutants are not properly removed, they can enter the water cycle and reach the water supply for residential use, causing harm to human health. Reverse osmosis (RO) has been known as a promising technology to remove EDCs. However, there is a lack of consensus on their performance, especially on the feed concentrations of EDC that vary from one source to another. In this study, polyamide thin-film composite (PA TFC) membrane was incorporated with one-dimensional titania nanotube (TNT) to mitigate trade-off between water permeability and solute rejection of EDC. The characterization indicated that the membrane surface hydrophilicity has been greatly increased with the presence of TNT. Using bisphenol A (BPA) and caffeine as model EDC, the removal efficiencies of the pristine TFC and thin-film nanocomposite (TFN) membranes were evaluated. Compared to TFC membrane, the membrane modified with 0.01% of TNT exhibited improved permeability of 50% and 49% for BPA and caffeine, respectively. A satisfactory BPA rejection of 89.05% and a caffeine rejection of 97.89% were achieved by the TNT incorporated TFN membranes. Furthermore, the greater hydrophilicity and smoother surface of 0.01 TFN membrane led to lower membrane fouling tendency under long-term filtration.

Desalination Performance and Membrane Fouling Tendency of Shale Gas Produced Water with Various Pretreatment Levels by Flow-Electrode Capacitive Deionization

Desalination Performance and Membrane Fouling Tendency of Shale Gas Produced Water with Various Pretreatment Levels by Flow-Electrode Capacitive Deionization

Dynamics of microbial community and their effects on membrane fouling in an anoxic-oxic gravity-driven membrane bioreactor under varying solid retention time: A pilot-scale study

Membrane fouling in a membrane bioreactor (MBR) is highly influenced by the characteristics of the influent, the mixed liquor microbial community and the operational parameters, all of which are environment specific. Therefore, we studied the dynamics of microbial community during the treatment of real municipal wastewater in a pilotscale anoxic-oxic (A/O) MBR equipped with a gravity-driven membrane filtration system. The MBR was operated at three different solid retention times (SRTs): 25, 40 and 10 days for a total period of 180 days in Nordic environmental conditions. Analysis of microbial community dynamics revealed a high diversity of microbial species at SRT of 40 days, whereas SRT of 25 days was superior with microbial richness. Production of soluble microbial products (SMP) and extracellular polymeric substances (EPS) was found to be intensely connected with the SRT and food to microorganism (F/M) ratio. Relatively longer operational period with the lowest rate of membrane fouling was observed at SRT of 25 days, which was resulted from the superior microbial community, lowest production of SMP and loosely bound EPS as well as the lower filtration resistance of larger sludge flocs. Abundance of quorum quenching (QQ) bacteria and granular floc forming bacterial genera at SRT of 25 days provided relatively lower membrane fouling tendency and larger floc formation, respectively. On the other hand, substantial amount of various surface colonizing and EPS producing bacteria was found at SRT of 10 days, which promoted more rapid membrane fouling compared with the fouling rate seen at other tested SRTs. To sum up, this research provides a realistic insight into the impact of SRT on microbial community dynamics and resulting characteristics of mixed liquor, floc size distribution and membrane fouling for improved MBR operation.

Ceramic membrane modified with rice husk ash for application in microbial fuel cells

Ceramic membranes have been widely used as an affordable cation exchange membrane in microbial fuel cells (MFCs). This study deals with the fabrication of low-cost ceramic membranes by blending rice husk ash (RHA) with soil for its application in MFCs. Ceramic membrane having 10% RHA exhibited higher proton mass transfer and lower oxygen diffusion. The presence of silica in RHA enhanced the hydration properties of the membrane and aided proton mobility form anode to cathode chamber. Performance of the MFCs using modified (with RHA, MFCT) and unmodified (without RHA, MFCC) membrane was evaluated for the treatment of rice mill wastewater under continuous mode operation. The maximum volumetric power densities were 2.14 W mˉ3 and 1.33 W mˉ3, and COD removal efficiencies were 70.7 ± 1.24% and 63.8 ± 1.08% for MFCT and MFCC, respectively. Form the electrochemical impedance spectroscopy (EIS) study, ohmic resistance (RΩ) of MFCC and MFCT was found to be 91.3 Ω and 47.1 Ω, respectively. The RHA composite membrane displayed less tendency of membrane fouling, making it more favorable for long-term operation. This study reveals that the RHA composite membrane could serve as a suitable alternative to expensive polymeric membranes in MFC with higher power performance and minimum oxygen diffusion.

Sulfate removal using colloid-enhanced ultrafiltration: performance evaluation and adsorption studies.

Colloid-enhanced ultrafiltration (CEUF), i.e., micellar-enhanced ultrafiltration (MEUF) and polymer-enhanced ultrafiltration (PEUF), was investigated to remove sulfate ions from aqueous solution in batch experiments, using cetyltrimethylammonium (CTAB) and poly(diallydimethylammonium chloride) (PDADMAC) as colloids, respectively. Ultrafiltration performance was evaluated under different initial concentrations of sulfate (0-20 mM) and CTAB/PDADMAC (0-100 mM). The highest retention rate (> 99%) was found in dilute sulfate solutions. At high sulfate concentrations (e.g., 10 mM), a dosage of 50 mM CTAB or PDADMAC can retain approximately 90% of sulfate ions. Though concentration polarization behavior was observed, membrane characterization indicated that the fouling was reversible and membranes can be reused. Furthermore, adsorption equilibrium and kinetics studies show that Freundlich isotherm and pseudo-second-order kinetics can describe the sulfate-colloid interaction, indicating that the surface of absorbents are heterogeneous and the rate-controlling step is chemisorption. Both MEUF and PEUF show potential as effective separation techniques in removing sulfate from aqueous solutions. Under the same conditions examined, PEUF shows advantages over MEUF in its higher retention at lower polymer-to-sulfate ratios, cleaner effluent, and higher adsorption capacity, but compromises on severer flux decline and a tendency of membrane fouling. To overcome this disadvantage, membranes with higher molecular weight cut-off can be used.

A Comprehensive Study of Custom-Made Ceramic Separators for Microbial Fuel Cells: Towards “Living” Bricks

Towards the commercialisation of microbial fuel cell (MFC) technology, well-performing, cost-effective, and sustainable separators are being developed. Ceramic is one of the promising materials for this purpose. In this study, ceramic separators made of three different clay types were tested to investigate the effect of ceramic material properties on their performance. The best-performing ceramic separators were white ceramic-based spotty membranes, which produced maximum power outputs of 717.7 ± 29.9 µW (white ceramic-based with brown spots, 71.8 W·m−3) and 715.3 ± 73.0 µW (white ceramic-based with red spots, 71.5 W·m−3). For single material ceramic types, red ceramic separator generated the highest power output of 670.5 ± 64. 8 µW (67.1 W·m−3). Porosity investigation revealed that white and red ceramics are more porous and have smaller pores compared to brown ceramic. Brown ceramic separators underperformed initially but seem more favourable for long-term operation due to bigger pores and thus less tendency of membrane fouling. This study presents ways to enhance the function of ceramic separators in MFCs such as the novel spotty design as well as fine-tuning of porosity and pore size.

Effect of a co-substrate supply in a MBR treating shipboard slop: Analysis of hydrocarbon removal, biomass activity and membrane fouling tendency

The paper reports the main results of an experiment carried out on a membrane bioreactor (MBR) plant designed for the treatment of shipboard slops. With a view of a co-treatment process of the slop with other wastewaters, sodium acetate, as external co-substrate, was supplied (high dosage – Period 1, low dosage – Period 2) to evaluate its effects on hydrocarbons removal. The MBR pilot plant enabled approximately 99% of total petroleum hydrocarbon (TPH) removal during the entire experiment, confirming the robustness of the MBR technology for the treatment of slops. The chromatography/mass spectrometry analysis showed that the removal efficiency for each alkane was close to the value observed for total mixture removal (>99%) and the hydrocarbons removal was mostly due to the microorganism-mediated biodegradation. The biological contribution to TPH removal increased from approximately 85% to 98% when the co-substrate was decreased. Biomass kinetics revealed that a lower co-substrate dosage enhanced the growth of bacterial groups able to use hydrocarbons as primary substrate. A clear predominance of Microthrix Parvicella under low co-substrate dosage was observed. However, the lower co-substrate addition caused a significant worsening in the physical properties of the activated sludge, which resulted enriched in soluble exopolymers (>70%), more hydrophobic (>90%) and with small and dispersed flocs (<30 μm). Consequently, the membrane permeability reduced because of the irreversible fouling increase.

Biological minimization of excess sludge in a membrane bioreactor: Effect of plant configuration on sludge production, nutrient removal efficiency and membrane fouling tendency

Excess sludge minimization was studied in a MBR with pre-denitrification scheme. Sludge minimization, nitrogen removal performance and membrane fouling tendency were investigated in two configurations, characterized by a different position of the sludge retention reactor (SRR). In particular, the SRR was placed: i) in the return activated sludge line (Anaerobic Side-Stream Reactor – ASSR configuration) and ii) in the mainstream between the anoxic and aerobic reactor (Anaerobic Main-Stream Reactor – AMSR configuration). The achieved results demonstrated that the ASSR enabled a higher excess sludge reduction (74% vs 32%), while achieving lower biological nitrogen removal (BNR) (TN = 63% vs 78%) and membrane fouling tendency (FR = 2.1 · 1012 m−1 d−1vs 4.0 · 1011 m−1 d−1) than the AMSR. It was found that metabolism uncoupling, destruction of EPS and endogenous decay simultaneously occurred in the ASSR. Conversely, selective enrichment of bacteria population with low biomass yield was found the main mechanism affecting sludge minimization in the AMSR.

The influence of solid retention time on IFAS-MBR systems: analysis of system behavior

ABSTRACTA University of Cape Town Integrated Fixed-Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant was operated at different values of the sludge retention time (SRT). Three SRTs were investigated at different durations: indefinitely, 30 and 15 days. The organic carbon, nitrogen and phosphorus removal, kinetic/stoichiometric parameters, membrane fouling tendency and sludge filtration properties were assessed. The findings showed that by decreasing the SRT, the pilot plant could maintain excellent carbon removal efficiencies throughout the experiments. In contrast, the biological carbon removal showed a slight nitrification and was slightly affected by the decrease of the SRT, showing high performance (approximately 91%, on average). Thus, the biofilm might have helped sustain the nitrification throughout the experiments. The average phosphorus removal performance increased slightly with a decrease in SRT, achieving the maximum efficiency (61.5%) at a SRT of 15 days. After a 30-day SRT, an increase in resistance due to pore blocking and a general worsening of the membrane filtration properties occurred.

Gold acid mine drainage treatment by membrane separation processes: An evaluation of the main operational conditions

Abstract Acid mine drainage (AMD) is an effluent characterized by low pH and high concentrations of sulfate, metals, and metalloids. AMD treatment by membrane separation processes (MSP), specifically nanofiltration (NF) and reverse osmosis (RO) is particularly interesting; as these processes can retain divalent ions efficiently to produce high quality permeate for industrial reuse. This study aimed to evaluate the main operational conditions of the gold AMD treatment by MSP, and conduct a preliminary capital and operational cost evaluation. The results showed that the NF had a higher potential to treat the AMD than the RO, as the NF had higher permeate flux and satisfactory solutes retention efficiency. The NF90 membrane had the highest retention efficiency among the NF membranes, while the NF270 membrane had the highest permeate flux. Effluent pH affected both the solutes retention efficiency and the membrane-fouling tendency. The best combination of membrane type and feed pH was the NF270 at pH 5.5. The maximum water recovery rate at this condition was 60%, when a sharper decrease in the retention efficiency and the permeate flux was observed. The estimated capital cost of the UF-NF unit considering an effluent volumetric flow rate of 15 m 3 /h was US$ 131,250.00, and the operational cost was 0.263 US$/m 3 of effluent.

Surface morphology of pvdf membrane and its fouling phenomenon by crude oil emulsion

In this study, polyvinylidene fluoride (PVDF) flat sheet membranes were fabricated via phase inversion process for crude oil emulsion separation. The PVDF solutions were formulated by varying polymer concentration from 16 to 19wt.% with one of the three different solvents: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP). The membranes morphologies as a result of different polymer concentration and solvents were characterized and their effects on the crude oil emulsion separation were evaluated. Results showed that 18wt.% PVDF-DMAc membrane was the optimum membrane for oil emulsion in term of flux recovery ratio (FRR) which showed better cleaning ability compared to other membranes. Under cake deposition fouling mode (with proven oil particle size bigger than the pore size), membrane fouling tendency is regardless of porosity or pore size. However, both of these properties do play important roles in the subsequent fouling cleaning process. Membrane with least porosity and smaller pore size has better cleaning properties.

Simultaneous nitrification and denitrification in a novel membrane bioelectrochemical reactor with low membrane fouling tendency.

Microbial fuel cells (MFCs) can use nitrate as a cathodic electron acceptor for electrochemical denitrification, yet there is little knowledge about how to apply them into current wastewater treatment process to achieve efficient nitrogen removal. In this study, two dual-chamber MFCs were integrated with an aerobic membrane bioreactor to construct a novel membrane bioelectrochemical reactor (MBER) for simultaneous nitrification and denitrification under specific aeration. The effects of chemical oxygen demand (COD) loading rate, COD/N ratio, hydraulic retention time (HRT), and external resistance on the system performance were investigated. High effluent quality was obtained in the MBER in terms of COD and ammonium. During the operation, denitrification simultaneously occurred with nitrification at the bio-cathode of the MBER, achieving a maximal nitrogen removal efficiency of 84.3%. A maximum power density of 1.8W/m3 and a current density of 8.5A/m3 were achieved with a coulombic efficiency of 12.1%. Furthermore, compared to the control system, the MBER exhibited lower membrane fouling tendency due to mixed liquor volatile suspended solids (MLVSSs) and extracellular polymeric substance (EPS) reductions, EPSp/EPSc ratio decrease, and particle size increase of the sludge. These results suggest that the MBER holds potential for efficient nitrogen removal, electricity production, and membrane fouling mitigation.

Inherent porous structure modified by titanium dioxide nanoparticle incorporation and effect on the fouling behavior of hybrid poly(vinylidene fluoride) membranes

ABSTRACTThe incorporation of nanoparticles (NPs) into a casting solution is a widely used practice for controlling the membrane fouling tendency, but the specific role of NPs in fouling control from an internal porous structure optimization has seldom been investigated. In this study, we evaluated the specific role of titanium dioxide (TiO2)–NPs (Degussa P25) in mitigating membrane organic fouling. We prepared the membranes by tailoring the concentrations of the NPs well; this resulted in an optimized membrane microstructure consisting of fingerlike voids (beneath the skin layer of the membrane) and spongy voids (adjacent to the fingerlike voids). The NP incorporation induced the formation of spongy voids beneath the skin layer, and the increase in the NP concentration increased the formation of spongy voids. Moreover, surface images obtained by scanning electron microscopy, X‐ray photoelectron spectroscopy results, and contact angles confirmed that TiO2–NPs were almost absent on the skin layer. Antifouling experiments were performed with a model organic foulant in two flow orientations [fingerlike voids facing the retentate (FVR) and spongy voids facing the retentate (SVR)]. The results show that the membrane fluxes in FVR decreased more than those in SVR. The membrane with 1.5 wt % TiO2 operated in SVR exhibited the lowest flux decline; this suggested that spongy voids with TiO2 exposure could mitigate fouling to a greater extent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43265.

Fabrication of Poly(acrylonitrile)/PAN Nanofiber Using a Drum Collector Electrospinning System for Water Purification Application

The development of filtration technique for water purification has been performed ranging from the conventional to the advanced technique such as coagulation, sedimentation, sand filtration, reverse osmosis and nanofiltration. However, the major challenge to be addressed in the filtration technique is the tendency of membrane fouling or clogging. This effect causes a decreasein the flux and effectiveness of membrane filtration. In this study, we reported the fabrication of poly (acrylonitrile)/PAN nanofiber membrane by electrospinning technique and their application for water purification. A drum collector electrospinning system was used to produce uniform nanofiber membrane. Nanofiber membrane was fabricated from precursor solution which was prepared by dissolving poly (acrylonitrile) that has molecular weight of 150.000 g/mol in n,n-dimethylformamide (DMF). PAN nanofiber membrane were fabricated via electrospinning technique with 8wt% in concentration. The morphology of the membrane was characterized by using Scanning Electron Microscopy (SEM). SEM analysis showed that uniform nanofiber was formed with average fiber diameter of 290-370 nm. Three different concentrations of antacid suspension were prepared as the sample in order to test the performance of PAN nanofiber as membrane filter. Flux test was carried out by applying various pressure against the membrane in order to obtain the flux values of each variation of waste water model. The purity of the filtrate was analyzed by using UV spectrophotometer and the result show a decreased absorbance by 93%.

Study on the Membrane Fouling of the Process of Using Two Layer Flat-Sheet Membrane for Sludge Thickening and Water Reuse

In this paper, the critical flux was applied to represent the tendency of membrane fouling. The response surface model was used to study different factors, such as sludge concentration, space between membranes and aeration rate, affecting membrane fouling of the upper and lower layer membrane module. It was found that the model is fitting and significant, moreover, the sludge concentration, space between membranes and aeration rate has a significant impact on the upper and lower membrane fouling. Meanwhile, it was also observed that the critical flux of both upper and lower layer membrane module sharply decreased with the increase of sludge concentration. However, the different variation tendency of membrane fouling between upper and lower layer membrane module was detected due to the change of space between membranes and aeration rate, when it was under different sludge concentrations. Finally, optimum operating parameters under different sludge concentration simulated by response surface model were successfully applied to the process of using flat-sheet membrane for four-stage sludge thickening.

Comparison between moving bed-membrane bioreactor and conventional membrane bioreactor systems. Part I: membrane fouling

The combination of moving bed biofilm reactor and traditional membrane bioreactor (MBR) shows great potential to be widely used in Liaohe River basin for wastewater treatment. The aim of this research is to compare the bioreactor performance and membrane fouling between integrated fixed-film activated sludge membrane bioreactor (IFAS–MBR) and MBR. Two lab-scale reactors were operated in parallel to treat synthetic municipal wastewater with continuous operation. The results indicated that both systems had the same high removal efficiency of ammonium, while the IFAS–MBR showed a higher ability to remove COD. The trans-membrane pressure in the MBR was higher than that in the IFAS–MBR during the entire operation, due to a higher total modified fouling index of the mixed liquor and the resultant higher membrane fouling potential. The concentrations of extracellular polymeric substances and soluble microbial products were higher in MBR, despite the functional groups were almost similar in two reactors. The conventional MBR had more small molecular weight components (<1 kDa) and soluble microbial metabolites. This seems to cause pore blocking, which directly results in membrane flux declining and membrane resistance rising in the MBR system. In addition, the MBR was characterized by a serious membrane fouling as more dense deposits were observed by scanning electron microscopy. On the contrary, the IFAS–MBR showed a lower membrane fouling tendency during the whole operation.