Ultrafiltration Membrane Fouling Research Articles

Effects of Fe(Ii)-Activated Persulfate/Sodium Percarbonate (Ps/Spc) Pretreatment on Ultrafiltration Membrane Fouling Control and Mechanisms

Effects of Fe(Ii)-Activated Persulfate/Sodium Percarbonate (Ps/Spc) Pretreatment on Ultrafiltration Membrane Fouling Control and Mechanisms

On-Line Monitoring of Ultrafiltration Membrane Fouling Based on EIT Sparse Imaging

On-Line Monitoring of Ultrafiltration Membrane Fouling Based on EIT Sparse Imaging

Renewable energy powered membrane technology: Energy consumption analysis of ultrafiltration backwash configurations

In the field of ultrafiltration (UF) membranes for water treatment, fouling is a severe problem that limits the potential of the technology UF membranes and results in increased energy consumption. In this study, a small-scale photovoltaic-powered membrane system was employed to investigate the energy consumption of two UF backwashing configurations – a bladder tank and a backwash (BW) pump powered by supercapacitors – under varied solar irradiance conditions. Fouling was induced via the addition of bentonite, and then examined at varied BW intervals using the bladder tank to optimize the total specific energy consumption (TSEC) – determined for both UF BW and reverse osmosis (RO) desalination processes. Simulated fouling – realized via a pressure drop across a ball valve – was proposed to induce inorganic fouling without requiring the addition of foulants. The TSEC of both bentonite and simulated fouling was compared. Under simulated fouling and constant solar irradiance operating conditions, the bladder tank exhibits a BW SEC of 0.3 Wh/L, while the BW pump exhibits SEC of 0.09Wh/L. The TSEC is maintained at ∼ 4 Wh/L under varied real “solar days” with the bladder tank, indicating that the energetic penalty for implementing one BW cycle every 90 min is small. A BW interval of 60 min exhibited a TSEC of 3.7 Wh/L and provided a good compromise between TSEC and the mitigation of membrane fouling. The concept of using a valve to simulate fouling in the system can assist with the UF membrane fouling studies without inducing irreversible fouling to the membrane. Despite its higher BW SEC, the bladder tank was a more robust setup and is recommended for adding BW functionality to renewable-energy powered membrane filtration systems.

Membrane fouling by nanofibres and organic contaminants – Mechanisms and mitigation via periodic cleaning strategies

The fouling of water filtration membranes by nano/microplastic fragments can result in the decline of the water flux across membranes, however, the impact of other types of nano/microplastics on filtration processes, such as nano/micro fibres, has not been well characterised. The flexibility and high aspect ratio of nano/micro fibres could favor their adsorption onto filtration membranes, hence the presence of such fibres in water streams constitutes a potential threat to membrane units. In this work, the fouling of ultrafiltration membranes by a mixed system of poly(ethylene terephthalate) nanofibres and organic contaminants commonly found in textile industry effluents was investigated before mitigation strategies based on periodic gas scouring were developed. The nanofibres were prepared by electrospinning and cryo-sectioning using a freezing agent containing the organic contaminants of interest, poly(ethylene glycol) and poly(vinyl alcohol). Results showed that the organic contaminants induced a water flux decline across the membranes of 50% in less than an hour due to internal pore blocking whereas the adsorption of pure fibres as loose entanglements contributed to less than 10% of the permeation loss observed due to low pore coverage. Although applying periodic gas scouring was not efficient to dislodge the organic contaminants from the pores, this cleaning procedure removed up to 75% of the nanofibres from the surface of the membranes due to the shear forces generated by the gas bubbles. Hence, this study suggests that ultrafiltration membranes and gas scouring procedures could be successfully applied to control and limit the presence of fibres present in complex water streams.

Improved anti-organic fouling and antibacterial properties of PVDF ultrafiltration membrane by one-step grafting imidazole-functionalized graphene oxide

At present, membrane fouling is a thorny issue that limits the development of polyvinylidene fluoride (PVDF) composite membrane, which seriously affects its separation performance and service lifespan. Herein, an imidazole-functionalized graphene oxide (Im-GO) with hydrophilicity and antibacterial performance was synthesized, and it was used as a modifier to improve the anti-organic fouling and antibacterial properties of PVDF membrane. The anti-organic fouling test showed that the maximum flux recovery ratios against bovine serum albumin and humic acid were 88.9% and 94.5%, respectively. Conspicuously, the grafted imidazole groups could effectively prevent the bacteria from growing on the membrane surface. It was gratifying that the antibacterial modifier Im-GO was almost not lost from the hybrid membranes even by the ultrasonic treatment, which was different from the conventional release-killing antibacterial agents. Owing to the long-term anti-organic fouling and antibacterial properties, Im-GO/PVDF hybrid membranes exhibit a great application potential in the fields of rough separation and concentration of biomedical products.

Synergistic mechanism of combined ferrate and ultrafiltration process for shale gas wastewater treatment

The operational issues of low-pressure ultrafiltration (UF) membrane are associated with its long-term membrane fouling caused by organic and inorganic matters, especially in treating shale gas wastewater (SGW) with complex water compositions. Herein, the effect of ferrate (Fe(VI)) pretreatment on UF membrane fouling and water quality in treating SGW was systematically investigated. Fe(VI) pretreatment significantly mitigated membrane fouling and slightly improved the effluent quality. The hydraulically irreversible fouling index and the total fouling index decreased by 69%–87% and 58%–84%, respectively. The mechanism of membrane fouling mitigation was comprehensively analyzed by the classical pore blocking model, correlation analysis between membrane fouling index and water quality, and the extended Derjaguin-Landau-Verwey-Overbeek theory. The synergistic mechanisms of membrane fouling mitigation were as follows: (i) Macromolecular organic matters (high molecular weight humics and biopolymers) which would block the membrane pores were oxidized into low fractions organics and removed by Fe(VI); (ii) Fe(VI) pretreatment improved interaction free energy of cohesion of foulants-foulants making foulants more hydrophilic and stable, and increased interaction free energy of adhesion of membrane-foulants making it more difficult for foulants to deposit on the membrane surface. Fe(VI) pretreatment had huge potential in alleviating membrane fouling in treating SGW and other complex wastewater.

Effects of micro-flocculation pretreatment on the ultrafiltration membrane fouling caused by different dissolved organic matters in treated wastewater

Abstract This study investigated the efficacy of using micro-flocculation as a pretreatment approach in alleviating ultrafiltration (UF) membrane fouling caused by organic matter in treated wastewater. Three typical model dissolved organic matters (DOM), humic acid, fulvic acid, and sodium alginate, were employed to simulate membrane fouling. The results showed that micro-flocculation using poly aluminum chloride (PAC) or polymerized ferric sulfate (PFS) as flocculant could effectively enhance the treatment performance of the UF process on DOM. With 6 mg/L PAC, the removal efficiency of humic acid, fulvic acid, and sodium alginate by micro-flocculation combined UF process reached 79.95%, 63.25%, and 51.14%, respectively. Specifically, after micro-flocculation, micromolecular hydrophilic organic matter (e.g., fulvic acid) tended to form a compact cake layer. The macromolecular hydrophobic organic matter (e.g., humic acid) and macromolecular hydrophilic organic matter (e.g., sodium alginate) generally led to a loose cake layer. At PAC dosage of 6 mg/L, the membrane specific flux (J/J0) at the end was improved by 11.71%, 10.27%, and 2.2% for humic acid, sodium alginate and fulvic acid solutions, respectively, compared with the UF process alone. It could be inferred that micro-flocculation pretreatment can effectively mitigate the membrane fouling when treating wastewater containing humic acid, sodium alginate, or fulvic acid.

Coagulation combined with ultraviolet irradiation activated sodium percarbonate as pretreatment prior to ultrafiltration: Analysis of free radical oxidation mechanism and membrane fouling control

Novel pre-coagulation–sedimentation integrated with ultraviolet activated sodium percarbonate (SPC) (Fe(III)-UV/SPC) processes are promising methods for ultrafiltration (UF) pretreatment to ensure the safety of rural drinking water and mitigate UF membrane fouling. The process of surface water purification using the integrated coagulation-advanced oxidation processes (AOPs)-UF system relies on the idea that pre-coagulation can remove hydrophobic macromolecular organic compounds, thus facilitating the oxidation of hydrophilic molecules or medium-sized macromolecules to improve the utilization efficiency of free radicals in AOPs. Compared with the UV/SPC process, the removal rates of UV254 and DOC in the Fe(III)-UV/SPC process (Fe(III) = 0.1 mM, SPC = 0.5 mM) were increased from 87.39 % to 41.45 %–93.56 % and 52.51 %, respectively. Furthermore, the dosage of SPC was reduced from 0.75 mM in UV/SPC process to 0.5 mM due to effects of pre-coagulation. The free radical quenching experiment showed that a significant radical sink of reactions with organic contaminants was formed by •OH and CO3•- in the UV/SPC process, rather than a single specific radical. The destruction of the cake layer structure, reduction in contaminant concentration, and appearance of many permeable holes on the membrane surface were the main reasons for the alleviation of UF membrane fouling. Finally, the trans-membrane pressure and reversible membrane resistance decreased from 22.33 kPa to 3.68 × 1011 m−1 to 18.28 kPa and 0.93 × 1011 m−1, respectively. These results provide new insights into the behavior of membrane fouling control and offer technical references for the long-term stable operation of the UF process.

Impacts on characteristics and effluent safety of PVDF ultrafiltration membranes aged by different chemical cleaning types

Chemical cleaning is an effective way to remove the irreversible fouling of ultrafiltration (UF) membranes. However, chemicals can also damage membranes. In order to investigate the effects of chemical cleaning on various properties of the membrane, three chemical agents, sodium hydroxide (NaOH, alkali), sodium hypochlorite (NaClO, disinfector), and citric acid (CA, acid), were used to clean polyvinylidene fluoride (PVDF) UF membranes. After two, six, and ten days of chemical cleaning, a series of changes in the physical and chemical properties proved that the structures of aged membranes were destroyed by the three agents. The aging of the membrane led to a decline in the retention performance, and the effluents were found to contain large amounts of PVDF microplastics (MPs). The concentration of PVDF MPs and the MP release rate increased rapidly with aging time. The proportion of each MP shape was fragment ˃ fiber ˃ sphere, and the proportion decreased with the increase of each MP size. The longer the aging time, the larger the proportion of small-sized MPs. Among the three agents, NaOH may be the most beneficial to the stability of ultrafiltration membrane effluent safety.

A polyethersulfone composite ultrafiltration membrane with the in-situ generation of CdS nanoparticles for the effective removal of organic pollutants and photocatalytic self-cleaning

Ultrafiltration membranes are usually used to remove organic pollutants. However, the organic contaminants trapped in the membrane pores and on the membrane surface would limit the reuse of membranes. In this study, polyacrylic acid grafted polyethersulfone membrane was prepared; CdS was then generated in-situ on the membrane surface by subsequently immersing the membrane in Cd2+ and S2− solutions to fabricate photocatalytic composite membranes. Scanning electron microscopy and X-ray photonic energy spectroscopy revealed that the generated CdS were uniformly deposited on the surface of the membrane. The obtained membrane could effectively chemisorb rhodamine B (RhB) dye in dark, and show good photocatalytic degradation performance for RhB under visible irradiation. Meanwhile, the received membranes exhibited enhanced photocatalytic degradation performance compared with the membrane prepared by blending doping method, and displayed better removal performance (77.8 %) in the pH = 7 and low concentration (10 mg/L) RhB solution. Moreover, the degradation and removal ratio could still be stable at over 70 % after 3 cycles. In addition to degrading RhB, the composite membrane also exhibited good photocatalytic degradation for antibiotic organic pollutants. Then, free radical capture experiments showed that the photocatalytic degradation of the membrane was mainly derived from the superoxide anion free radicals. Besides, the prepared membrane also exhibited excellent RhB rejection and fast photocatalytic self-cleaning performances under visible light. Thereby, the photocatalytic composite membrane effectively solved the problem of the easy fouling of ultrafiltration membrane, and showed high potential applications in wastewater remediation.

Presence of powdered activated carbon/zeolite layer on the performances of gravity-driven membrane (GDM) system for drinking water treatment: Ammonia removal and flux stabilization

Gravity-driven membrane (GDM) filtration is a promising alternative for decentralized water supply, while its widespread application was hindered by the poor removals of organics and ammonia during long-term operation. In this study, powered activated carbon (PAC) and granular zeolite were selected as typical adsorbents to investigate the impacts of pre-deposited adsorbent layers on contaminant removal and membrane fouling. Results showed that the pre-deposited PAC layers exhibited higher removal of organics than the control, while the zeolites deposited layers exhibited low removal of organics. The presence of PAC only enhanced the NH4+ removal at subsequent stable stage, while zeolites were effective in deal with sudden high NH4+ concentration due to ion exchange. The presence of mixed adsorbents layers had similar organic removal with PAC and NH4+ removal with zeolite. The pre-deposited PAC layers could effectively alleviate membrane fouling in short-term UF tests, while the stable fluxes (5.88–6.54 L/(m2·h)) in long-term GDM operation were slightly lower than the control (6.63 L/(m2·h)). The zeolites deposited layer aggravated membrane fouling in both short-term ultrafiltration and long-term GDM (5.03–3.84 L/(m2·h)), but a higher stable flux (6.10 L/(m2·h)) was observed for GDM using the mixed adsorbents. The pre-deposited adsorbent layers resulted in increased concentrations of biomass, tri-phosphate (ATP) and extracellular polymeric substances (EPS), forming cake layers with a denser structure than the control. Finally, the fouling mechanism for GDM using different adsorbent layers was proposed based on fouling analysis and characteristics of biological fouling layer. The results and conclusion in this study could provide helpful information for the application of GDM with pre-deposited adsorbent layer in treating raw water with organics and/or sudden high ammonia concentration to produce potable water.

Ultrafiltration fouling behavior of natural organic matter: a perspective of EEM and molecular weight distribution

Abstract As natural organic matter (NOM) can cause serious ultrafiltration (UF) membrane fouling, most previous studies on UF fouling caused by NOM focused on the contribution of NOM characteristics. In this study, the correlation of molecular weight and fluorescence characteristics was examined and the fouling behavior of NOM was examined in a comprehensive manner through a lot of analysis including redundancy analysis (RDA), parallel factor analysis (PARAFAC) and atomic force microscopy (AFM). The results showed that NOM from Tong Xin river was composed of humic acid (500 Da–8,000 Da), tryptophan-like substance, soluble microbial product (SMP) and aromatic protein (600,000 Da–2,000,000 Da). Notably, UF performance was significantly affected by the humic acid-like substance. Concurrently, the combined mechanism (CM) model was adopted to evaluate the fouling mechanism of NOM. The results indicated that the cake-intermediate model played an important part during membrane fouling and the cake layer fouling had a larger predominance over the intermediate blocking, which can be further proved in the membrane morphology detection.

Enhanced ultrafiltration membrane fouling alleviation by module rotation with Fe-based flocs

The modules of ultrafiltration (UF) membrane always occupy a fixed position during filtration. This results in a gradual aggravation of membrane fouling because of the continuous pollutants deposition. However, it is known that the cake layer is composed of loosely hydrolyzed flocs. Therefore, in this study, the rotation concept of membrane-module was investigated in conjunction with the integrated floc (Fe-based)-UF process. We found that the Fe-based flocs can be easily peeled off the membrane surface during rotation, and the UF membrane fouling was alleviated, particularly with spiral module rotation because of the strong shearing force induced. The fouling behavior after spiral module rotation was similar for different floc dosages because of the looseness cake layer formed. The applied computational fluid dynamics model showed that a greater spiral rotation height corresponded to a larger water velocity distribution and stronger shearing force in the membrane tank, and this resulted in a reduction in the fouling degree due to the thinner cake layer formed. Moreover, in comparison with alkaline conditions, a slightly more severe fouling degree was observed under acidic conditions because of the induced denser cake layer with smaller Fe-based floc sizes; however, a significantly higher humic-acid removal efficiency was observed. In addition, UF membrane performed well with river water samples taken from the South-to-North water diversion project in China (Beijing), thereby indicating the rotating module potential application in membrane-based drinking water treatment.

The stimulation of microbial activity by microplastic contributes to membrane fouling in ultrafiltration

Research has demonstrated that dissolved organic carbon leaching from plastics can stimulate microbial activity in the ocean. However, similar situation has not been reported in freshwater, like rivers and lakes. The interaction between microplastic and microorganism may probably change water quality, causing operational issues during membrane water treatment, such as increased biofouling, pore blockage or formation of filter cake. In this study, the influence of microplastics (polyethylene, PE) on membrane biofouling and the microbial community during continuous-flow ultrafiltration was investigated. Results demonstrate that PE microplastics stimulate microbial activity in natural surface water and increase the production of extracellular polymeric substances (EPS). The images of scanning electron microscope-energy dispersive spectrometer (SEM-EDS) mapping have confirmed the presence of biofilm covered on the surface of microplastic particles. Biofouling layer became more hydrophobic with a dense and compact surface due to the accumulation of EPS stimulated by microplastics. Specific components of EPS, especially tryptophan-like soluble microbial byproducts with molecular weight distribution from 4 kDa to 30 kDa, were increased with the addition of microplastic and more likely to be entrapped by membrane pores aggravating membrane fouling. The components of EPS stimulated with the presence of microplastic was the main factor that caused membrane fouling. The microbial diversity was also affected with the addition of microplastic. In conclusion, the mechanism of membrane biofouling causing by microplastics in surface water is clear.

Exploring the influence mechanism of ozonation on protein fouling of ultrafiltration membranes as a result of the interfacial interaction of foulants at the membrane surface

Ozonation was widely used before ultrafiltration processes, but its effect mechanism on protein fouling is still controversial. Ozonation of bovine serum albumin (BSA) solutions was performed in the present work. The interfacial forces of BSA at the membrane surface were measured before and after ozonation. The adsorption behaviour of BSA onto the membrane surface and the fouling layer structures under different ozone dosages were also investigated. These results were combined with the membrane fouling behaviour to identify the effect of ozonation on protein fouling. The results showed that ozonation could weaken the interaction forces between the membrane and BSA effectively, but this did not have any effect on membrane fouling. In contrast, in terms of membrane fouling behaviour after pre-ozonation, the contribution of the changes in the covalent disulfide bonds between BSA molecules outweighs those of the non-covalent bonds. The number of disulfide bonds gradually increased as the O3:DOC ratio increased from 0 to 0.3, and began to decline when the O3:DOC ratio was further increased to 0.45 and 0.6. This could have altered the deposition rate of foulants onto the membrane surface and the structure of the fouling layers, and may have caused the membrane fouling first to be enhanced and then to decline with increasing ozone dosages.

Importance of origin and characteristics of biopolymers in reversible and irreversible fouling of ultrafiltration membranes

The present work compares the chemical properties of isolated biopolymers of different origins and their fouling potential during ultrafiltration (UF). The biopolymers were extracted from secondary wastewater effluent as effluent organic matter (EfOM) and from surface water as natural organic matter (NOM). Multiple analytical techniques were used to characterize the isolates. The characterization results revealed that EfOM biopolymers were more enriched in protein-type structures compared to the NOM organics, and they presented significant differences in the reversibility of membrane fouling. Dissolved in pure water, EfOM biopolymers led to more irreversible fouling than that caused by NOM isolates. Dosing divalent cations (e.g., Ca2+) into the solutions increased the irreversibility of both types of fouling, while aggravating NOM fouling more significantly. Further investigation was conducted to understand the interaction between EfOM and NOM biopolymers during formation of the fouling layer. The results showed that the interaction between these two types of organics was negligible in the absence of salts. These findings highlight the importance of a comprehensive understanding of biopolymers from different origins, considering their chemical properties and water chemistry, which have valuable implications for selecting suitable membrane fouling control strategies for treating water from different origins.

A novel mixed matrix polysulfone membrane for enhanced ultrafiltration and photocatalytic self-cleaning performance

Photocatalytic materials can be used as self-cleaning functional materials to alleviate the irreversible fouling of ultrafiltration membranes. In this work, the small size g-C3N4/Bi2MoO6 (SCB) blended polysulfone (PSF) ultrafiltration membranes was fabricated by hydrothermal and phase inversion methods. As a functional filler of ultrafiltration membranes, the small size g-C3N4 nanosheet decorated on the surface of Bi2MoO6 can enhance the photocatalytic performance for bovine serum albumin (BSA) degradation, and remove irreversible fouling under visible light irradiation. In addition, the introduction of SCB microspheres into PSF matrix obviously increased the porosity of ultrafiltration membranes. Therefore, the SCB-PSF ultrafiltration membranes displayed excellent antifouling performance (flux recovery ratio is 82.53%) and BSA rejection rates (94.77%). SCB-PSF also had high photocatalytic self-cleaning activity, indicating excellent application prospects in organic wastewater treatment.

Role of different dimensional carbon nanoparticles in catalytic oxidation of organic pollutants and alleviating membrane fouling during ultrafiltration of surface water

• Different types of carbon nanoparticles (CNPs) were used for catalytic oxidation. • CNPs/peroxymonosulfate (PMS) were proposed for membrane fouling control. • The catalytic activity of PMS showed the order of CMK-3 > CNTs > CMK-8 > CNFs. • SO 4 − , OH, O 2 − and 1 O 2 were identified as the main reactive oxygen species. • The formation of cake layers on membrane surfaces was delayed. In this study, carbon nanoparticles (CNPs) in different structural dimensions, including carbon nanotubes (CNTs), carbon nanofibers (CNFs), hexagonally (CMK-3) and cubically (CMK-8) ordered mesoporous carbons were proposed for peroxymonosulfate (PMS) activation. The performance for catalytic oxidation of organic pollutants and alleviating ultrafiltration membrane fouling was systematically investigated and compared. The results showed that CMK-3 performed best for PMS activation in the reduction of typical micropollutants and natural organic matter, whereas the efficiency of CNFs was relatively limited. The CNPs/PMS processes were efficient alternatives for alleviating membrane fouling, whereas discrepancies existed in the performance for different CNPs. Both the decomposition of macromolecular biopolymers and the degradation of fluorescent components reduced the foulants directly contacting with membranes, thus contributing to the fouling mitigation. The characterization of fouled membranes (i.e., surface morphologies and functional groups) further verified the fouling alleviation. From a comparison view, the decomposition of PMS by CMK-3 was more effective compared to the other CNPs, with the catalytic capacity of CMK-3 > CNTs > CMK-8 > CNFs. The discrepancy was likely ascribed to the microstructure differences of carbonaceous materials. To be specific, CNTs exhibited a curled-like shape with smaller diameter and larger specific surface area than CNFs, while CMK-3 showed long straight and parallel channels with decreased internal resistances than CMK-8. The electron paramagnetic resonance analyses revealed that SO 4 − , OH, O 2 − and 1 O 2 were the main reactive oxygen species generated in the systems. The CNPs/PMS processes significantly changed the fouling mechanisms by delaying the formation of cake layers and prolonging the transition volumes. These findings possess a guiding significance for the application of carbon-based catalytic oxidation in membrane water treatment processes.

Mitigation mechanism of ozonation in the casein fouling of ultrafiltration membranes: Possible application in dairy wastewater treatment

Membrane fouling control is one topic of concern during the application of ultrafiltration in dairy wastewater treatment. Casein is abundant in dairy wastewater; thus, in this work, preozonation for the casein solutions were carried out, and the membrane fouling behavior was investigated before and after preozonation. To reveal the effect mechanism of preozonation in casein fouling of ultrafiltration membranes, we explored the changes in casein's interfacial forces at the membrane surface, fouling layer structures, and its properties after pre-ozonation. Results showed that the casein molecules without ozonation could hold together tightly to form larger micelles, which were retained on the membrane surface to form a gel scale with poor fluidity and permeability, and also caused the most serious membrane fouling. By contrast, once preozonation occurred, the hydrophobic forces and the hydrogen bonds between membrane and casein, and between casein molecules were disrupted, which not only mitigated the adsorption/deposition of ozone-treated casein onto the membrane surface, but also destroyed the micellar structures of stable casein and resulted in a more open-and-loose fouling layer. Eventually, the membrane showed less fouling. Therefore, preozonation could effectively mitigate casein fouling of ultrafiltration membranes.

Mechanism of pre-ozonation in control of protein fouling of ultrafiltration membranes: Synergistic effect between ozone oxidation and aeration

Pre-ozonation is often used before ultrafiltration (UF) to control membrane fouling, usually by supplying ozone into water or wastewater via aeration. However, the role of aeration in pre-ozonation for mitigation of membrane fouling has not been well elucidated. Hence, in this study, bovine serum albumin (BSA) was used as a protein-type foulant in experiments on the outcomes and underlying mechanisms of pre-ozonation. The change in the membrane fouling behavior, the transformation of BSA, and the fouling-layer properties were investigated after pre-ozonation with and without aeration. The results showed that the membrane fouling notably declined after pre-ozonation, which mainly attributed to the synergistic effect between ozone oxidation and aeration. Ozone oxidation unfolded the BSA molecules and exposed their hydrophobic groups, and these unfolded BSA aggregated and adhered to the surface of the microbubbles produced by aeration. This induced BSA foaming and aggregation in the ozonated suspension. With pre-ozonation for a short contact time of 5 min, small BSA aggregates in water were retained on the UF membrane surface to form a highly porous deposition layer with a low filtration resistance. With pre-ozonation for a contact time of 10 min or longer, BSA foaming led to the formation of large aggregates that were efficiently removed from water in the ozone reactor, which greatly reduced the foulant loading of the water and its subsequent membrane fouling rate. In contrast, when quantitative and quiescent ozonation was performed without aeration, ozone oxidation alone worsened the membrane fouling propensity of the BSA solution.