Early Stage Of Filtration Research Articles

Membrane technologies for the separation and purification of functional oligosaccharides: A review

Functional oligosaccharides have numerous health benefits. They hold considerable promise in the food processing and healthcare sectors. However, oligosaccharides derived from microbial fermentation, chemical decomposition, and enzymatic hydrolysis often contain impurities, necessitating further purification to enhance the quality and economic value of the final product. Among various purification techniques, membrane separation stands out owing to its operational simplicity, low energy requirements, and scalability, making it ideal for industrial applications. Recently, this method has increasingly been used to separate and purify functional oligosaccharides. Microfiltration and ultrafiltration membranes are typically used in the early stages of filtration to remove proteins, bacterial contaminants, and particulates. In contrast, nanofiltration membranes offer higher separation precision, making them preferable for the detailed purification, concentration, and classification of functional oligosaccharides. This review article mainly focuses on the applications of nanofiltration membrane technologies in the processing of typical functional oligosaccharides, such as fructooligosaccharides, galactooligosaccharides, and xylooligosaccharides. Recent advancements in nanofiltration are discussed, and the properties of the feed liquid, operational parameters, and challenges related to membrane fouling are analyzed. This review aims to serve as a comprehensive guide for the efficient separation and purification of functional oligosaccharide membranes, and advocates for the broader implementation of membrane technologies in the food and medical industries.

Biofouling metallic membranes in algae-laden water treatment: Performance, mechanism, and the role of the pre-coated layer

Biofouling is the primary factor limiting the performance of ultrafiltration membrane systems in drinking water treatment. This study systematically investigated the application effect and biofouling behavior of metallic membranes in the treatment of algae-laden water and evaluated the mitigation effect and mechanism of the pre-coated layer on biofouling. The findings demonstrate that the metallic membrane can almost completely remove algal cells (>99.99 %) and macromolecular organics in EOM (Extracellular Organic Matter) but has limited effects on micromolecules, such as humic acid and fulvic acid, in EOM (47.29 % and 17.72 % for TOC (Total Organic Carbon) and UV254, respectively). During direct filtration, algal cells can form a cake layer in front of the metallic membrane to reduce the membrane flux, whereas the presence of EOM makes the cake layer denser and hastens the decline in flux. In addition, irreversible membrane fouling is exasperated in acidic or Ca2+-rich solutions, whereas an increase in algal cell particles exacerbates reversible membrane fouling, causing a faster decline in flux. According to the membrane mechanism analysis, the fouling mechanism ranges from complete pore blocking to standard and intermediate blocking throughout the direct filtration process. In contrast, the application of a pre-coated kaolin layer significantly decreases membrane fouling compared with direct filtration. The pre-coated layer can prevent direct contact between the foulants and the membrane surface during the early stages of filtration, resulting in a delayed complete pore blockage stage. On the other hand, XDLVO (Derjaguin-Landau-Verwey-Overbeek) data reveals that the force between kaolinite and algae (−102.323 mJ/m2) is greater than that between kaolinite and metallic membranes (−61.424 mJ/m2), resulting in better backwashing efficacy. These findings support the use of metallic membranes in drinking water treatment.

Effects of Different TiO2/CNT Coatings of PVDF Membranes on the Filtration of Oil-Contaminated Wastewaters.

Six different TiO2/CNT nanocomposite-coated polyvinylidene-fluoride (PVDF) microfilter membranes (including -OH or/and -COOH functionalized CNTs) were evaluated in terms of their performance in filtering oil-in-water emulsions. In the early stages of filtration, until reaching a volume reduction ratio (VRR) of ~1.5, the membranes coated with functionalized CNT-containing composites provided significantly higher fluxes than the non-functionalized ones, proving the beneficial effect of the surface modifications of the CNTs. Additionally, until the end of the filtration experiments (VRR = 5), notable flux enhancements were achieved with both TiO2 (~50%) and TiO2/CNT-coated membranes (up to ~300%), compared to the uncoated membrane. The irreversible filtration resistances of the membranes indicated that both the hydrophilicity and surface charge (zeta potential) played a crucial role in membrane fouling. However, a sharp and significant flux decrease (~90% flux reduction ratio) was observed for all membranes until reaching a VRR of 1.1-1.8, which could be attributed to the chemical composition of the oil. Gas chromatography measurements revealed a lack of hydrocarbon derivatives with polar molecular fractions (which can act as natural emulsifiers), resulting in significant coalescent ability (and less stable emulsion). Therefore, this led to a more compact cake layer formation on the surface of the membranes (compared to a previous study). It was also demonstrated that all membranes had excellent purification efficiency (97-99.8%) regarding the turbidity, but the effectiveness of the chemical oxygen demand reduction was slightly lower, ranging from 93.7% to 98%.

Impact of biological activated carbon filtration and backwashing on the behaviour of PFASs in drinking water treatment plants

PFASs are present in surface water, tap water and even commercial drinking water and pose a risk to human health. In this study, the treatment efficiency of 14 PFASs was studied in a large drinking water treatment plant (DWTP) using Taihu Lake as the source, and it was found that the ozone/biological activated carbon (O3-BAC) process was the most effective process for the removal of PFASs in DWTPs. For the O3-BAC process, there were differences in the removal of PFASs by BACs (1,4,7,13 years) of different ages. The sterilization experiments revealed that for GAC, its physical adsorption capacity reached saturation after one year, while for BAC with mature biofilms, biosorption was the main mechanism for the removal of PFASs. The abundance of Alphaproteobacteria and Gammaproteobacteria in biofilms was positively correlated with the age of the BAC. The microbial community with higher abundance is beneficial to the biodegradation of organic matter and thus provides more active sites for the adsorption of PFASs. PFASs can leak in the early stage of filtration after backwashing, so it is necessary to pay close attention to the influent and effluent concentrations of PFASs during biofilm maturation after backwashing.

The impact of PET microplastic fibres on PVDF ultrafiltration performance – A short-term assessment of MP fouling in simple and complex matrices

Wastewater treatment plants (WWTPs) are key components for the capture of microplastics (MPs) before they are released into natural waterways. Removal efficiencies as high as 99% may be achieved but sub-micron MPs as well as nanoplastics have been overlooked because of analytical limitations. Furthermore, short MP fibres are of concern because of their low capture rate as well as the lack of understanding of their influence on purification system efficiency. This study has investigated the impact of poly(ethylene terephthalate) (PET) short nanofibres on the performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes during cross-flow operation. Model MP fibres with an average length of 10 ± 7 μm and a diameter of 142 ± 40 nm were prepared via a combination of electrospinning and fine cutting using a cryomicrotome. The manufactured MPs were added to both pure and synthetic domestic wastewater at a concentration of 1 mg.L−1 to determine their impact on the performance of PVDF ultrafiltration membranes. The results show that PET fibres attach to the membrane in a disorganised manner with low pore coverage. The water flux was decreased by 8% for MPs in pure water and no noticeable effect in wastewater after 3 days of filtration. Additionally, the nutrient removal efficiency of the membrane was not altered by the presence of PET MPs. These findings show that MP fibres do not significantly influence the early stages of filtration for a standard concentration of MPs in wastewater treatment plant studies.

Effects of Viscosity on Submerged Membrane Microfiltration Systems.

Submerged microfiltration has a wide range of applications in water and wastewater treatment. Membrane fouling is a major problem, resulting in a severe decline in flux, high energy consumption and frequent membrane cleaning and replacement. The effect of viscosity was not previously studied under controlled conditions to relate it to the air scour. Hence, this study investigated the effect of viscosity on membrane fouling during the operation of submerged membrane microfiltration by adding predetermined amounts of glycerol to a kaolin clay suspension. The addition of glycerol increased the viscosity (from 0.001 to 0.003 Pa·s), resulting in a 3-fold higher transmembrane pressure (TMP) development. An increased airflow (air scour) rate by 3 fold (from 0.6 m3/m2/h to 1.8 m3/m2/h), reduced TMP development by 65%. Membrane fouling quickly developed during the initial stage of microfiltration operation. Therefore, special precautions to control fouling during the early stages of filtration could significantly enhance the operation of the microfilter. Higher airflow caused a reduction in average specific cake resistance, whereas higher viscosity increased this value.

Dual-objective for the mechanism of membrane fouling in the early stage of filtration and determination of cleaning frequency: A novel combined model

It is great importance to clarify the mechanism of the membrane fouling in the early stage of filtration. In this study, a novel model based on the loss of effective filtration area was established to predict the variation of the transmembrane pressure (TMP) at the constant flux mode. The coefficient of available membrane filtration area (ω) was adopted to describe the inflection point varying from combined pore blocking and cake filtration mode to individual cake filtration mode. Model simulations could predict reasonably the rise of transmembrane pressure (TMP) with correlation coefficient of R2 > 0.99. The reliability of the model was evaluated under different operating conditions (flux and stirring speeds) and feed concentrations, wherein the flux presented higher contribution to TMP, resistance of cake filtration (Rc) and resistance of intermediate pore blocking (Ri) than others. The accuracy of predictions of the proposed model was higher than other previous models. Moreover, the wide adaptability of the model was validated by using various real wastewater as feed suspensions. Furthermore, the calculation of the timing of the cake layer formation from the proposed model provided an instructional suggestion for the determination of the cleaning frequency. In summary, the proposed model sheds light on the fouling mechanism in the early stage of filtration and provides guidance to the strategy of cleaning protocols in MBR operations.

Studying Fluid Characteristics Atop Surface Patterned Membranes via Particle Image Velocimetry

AbstractSurface patterning is a recent promising approach to promote performance of pressure‐driven membranes in water treatment and desalination. Nevertheless, knowledge about foulant deposition mechanisms, especially at early stage of filtration, is still lacking. The applicability of particle imaging velocimetry to study fluid characteristics atop surface patterned thin‐film composite membranes was investigated at different operating conditions. This work is an important first step toward reliable understanding of the impacts of topographical membrane surface modification on hydrodynamic conditions and foulant deposition mechanisms.

Ultrafiltration of up-flow biological activated carbon effluent: Extracellular polymer biofouling mechanism and mitigation using pre-ozonation with H2O2 backwashing

Biofouling is a key problem in membrane filtration, and extracellular polymer substances (EPS) play a key role in biofouling. Biofouling contributes to membrane fouling during ultrafiltration of up-flow biological activated carbon filter (UBACF) effluent. EPS are released when pollutants get attached with membrane surface and when pollutants are in solution phase from cell lysis and by cell secretions. In our study of EPS + humic acid (HA) prepared as the effluent pollutants for ultrafiltration, we found that EPS increased the interfacial forces between the pollutants and the membrane, resulting in membrane fouling. In the early stages of filtration, the main contribution of EPS to membrane fouling was to bond with organic colloids, which led to an increase in the pollutant particle size and zeta potential. This increased the short-range Lewis acid-base (AB) forces from −4.89 nN to −12.59 nN and accelerated the formation of a cake layer. In the late stage of filtration, the EPS increased both the AB and London–van der Waals (LW) forces, thus accelerating membrane fouling. In order to mitigate biofouling, we developed a method of pretreating the effluent with 0.4 mg/L ozone prior to ultrafiltration and backwashing with 8 mg/L H2O2 to sterilize bacteria attached to the membrane surface. This method not only changed the characteristics of the EPS, but also inactivated bacteria by disinfection with H2O2, thereby reducing the amount of EPS. The proposed method provided a long-term stable operation guarantee for ultrafiltration of UBACF effluent.

Low-pressure submerged membrane filtration for potential reuse of detergent and water from laundry wastewater

Membrane filtration is an attractive for laundry wastewater treatment especially when aiming for detergent and water reuse. However, its performance is largely restricted by membrane fouling, especially when it is run under high and trans-membrane pressure (△P) and in the sidestream configuration. The conventional treatment systems typically consist of multi-processes for removal of pollutants -including detergent- to meet the water discharge or reuse specification. This study assesses performance of a submerged membrane filtration under low △P for treatment of real laundry wastewater, obtained from local laundry shop, aiming for detergent and water reuse. Results show that low △P of as low as 0.05 bar offers the highest permeability of 297 ± 15.3 Lm−2 h−1 bar−1 without significant membrane fouling. Increasing the △P leads to decreasing trend in the permeability especially in the early stages of filtration. Aeration was found to be effective in enhancing hydraulic performance by 60 % at rates >1 Lmin−1, below which offers ineffective foulant scouring impact. The membrane effectively removes chemical oxygen demand, total nitrogen, total phosphorus and turbidity of 52 %, 13 %, 65 % and 97 % respectively, and the system offers recovery of detergent from the spent laundry wastewater by 78 %. Implementation of the concept in a laundry set-up can be done by treating wastewater from the washing cycle and reusing back the permeate for the following cycle. Our overall results suggest that the system is suitable to be applied for detergent and water reuse from wash cycle of industrial laundry.

Fundamental fouling mechanisms of dissolved organic matter fractions and their implications on the surface modifications of ceramic nanofiltration membranes: insights from a laboratory scale application

This work reports on the fundamental factors influencing inter-foulant and foulant-membrane interactions during simulated dissolved organic matter removal using ceramic nanofiltration. Fouling tests were performed using sodium alginate (SAL), humic acid (HA) and bovine serum albumin (BSA) as model foulants. Fouling potentials of each foulant and their mixtures were investigated using feed solutions containing fixed concentrations of K+, Na+, Mg2+ and Ca2+ with a total ionic strength of 10 mM. The impact of modification by atomic layer deposition on fouling mitigation was also assessed. The flux decline in the first 100 min for single foulants was 4.16 × 10-2, 2.69 × 10-2 and 1.60 × 10-2 Lm-2 for SAL, HA and BSA, respectively. These results demonstrated that for the single foulants, deposition on the membrane surface in the early stages of filtration was primarily governed by membrane-foulant interactions. Interestingly, cake filtration was the least fouling mechanism in feed solutions composed of BSA and SAL (R2 = 0.519, 0.374 for BSA + SAL and BSA + SAL + HA, respectively) and the most favorable fouling mechanism of feed solution which included HA and SAL (R2 = 0.972). The water contact angle dropped from 58o to 35° after coating, thus improving its anti-fouling properties.

A new approach for modeling flux variation in membrane filtration and experimental verification

It is important to model flux variation during the membrane filtration process, particularly in the early stage of filtration where severe fouling causes rapid flux decay in a short period of time. The objective of this study was to develop a combined fouling mathematical model based on energy head loss principle for prediction of flux variation in the membrane filtration. The complete-cake model was employed in the model in order to describe the loss of membrane available area due to pore clogging, while, the classical cake model was used for cake filtration. A new dimensionless parameter, namely the filter number (FN) was proposed in this study to account for the unmeasurable properties of the membrane in the model. The application of the proposed model was tested and compared with the existing models using experimental data for the filtration of wastewater sludge, microalgae suspension and sodium alginate solution with different membranes and pressures. The results showed that the flux calculated values of the new model had good agreements with the experimental data under different conditions. According to statistical analyses, the model improved the representing accuracy of flux variation in the early stage of filtration. In addition, the model provides better performance and efficiency in comparison to the existing models for high flux operations which is more conventionally applied in the industry and is expected to be more in the future.

Micropollutant rejection of annealed polyelectrolyte multilayer based nanofiltration membranes for treatment of conventionally-treated municipal wastewater

The ever-increasing concentrations of micropollutants (MPs) found at the outlet of conventional wastewater treatments plants, is a serious environmental concern. Polyelectrolyte multilayer (PEM)-based nanofiltration (NF) membranes are seen as an attractive approach for MPs removal from wastewater effluents. In this work, PEMs of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were coated in a layer by layer (LbL) fashion on the surface of a polyacrylonitrile ultrafiltration support to obtain PEM-based NF membranes. The impact of PEM post-treatment, by applying salt and thermal annealing, was then investigated in terms of swelling, hydrophilicity, permeability, and ion rejection. While thermal annealing produced a more compact structure of PEM, it did not improve the ion rejection. Among the different salt concentrations examined for the salt-annealing process, the highest ion rejection was observed for (PAH/PAA)15 membranes annealed in 100 mM NaNO3, interestingly without any decrease in the water permeability. This membrane was studied for the rejection of four MPs including Diclofenac, Naproxen, 4n-Nonylphenol and Ibuprofen from synthetic secondary-treated wastewater, over a filtration time of 54 h. At an early stage of filtration, the membrane became more hydrophobic and a good correlation was found between the compounds hydrophobicity and their rejection. As the filtration continued until the membrane saturation, an increase in membranes hydrophilicity was observed. Hence, in the latter stage of filtration, the role of hydrophobic interactions faded-off and the role of molecular and spatial dimensions emerged instead in MPs rejection. To test the suitability of the membranes for the ease of cleaning and repeated use, the sacrificial PEMs and foulants were completely removed, followed by re-coating of PEMs on the cleaned membrane. The higher MPs rejection observed in salt-annealed membranes compared to the non-annealed counterparts (52–82% against 43–69%), accompanied with still low ion rejection, confirm the high potential of PEM post-treatment to achieve better performing PEM-based NF membranes.

The cake layer formation in the early stage of filtration in MBR: Mechanism and model

It is important to clarify the mechanism of the cake layer formation in the early stage of filtration (initial stage and pseudo-steady stage). In this paper, a series of short-term dead-end microfiltration of sludge suspensions domesticated at three different ratios of carbon to nitrogen (C/Ns) (63:10, 100:5, 200:5) were conducted in constant pressure mode. Flux decline behaviors were analyzed and the structure of cake layer was characterized by 3D optical digital microscope (3D-ODM) to explore the mechanism of the cake layer formation. Results showed that the sludge floc was the key substance in the initial stage of the cake layer formation while colloid matters dominated later. Based on the inhomogeneous structure of the formed cake, a dynamic traversing mechanism was proposed to show the fact that colloid matters traveled through the hole formed by sludge flocs and accumulated on the membrane surface. Meanwhile, a piecewise function about the relationship of accumulated filtrated volume (v) and filtration time (t) was established to reveal this mechanism. Moreover, the model predictions showed good agreement with experimental data and its applications were also approved by other activated sludge suspensions, kaolin suspensions and real wastewater.

A mathematical model for the evolution of solute concentrations in a hemodialysis filter

We consider the process of hemodialysis performed by means of a hollow fiber dialyzer with a special focus on the dynamics of the light solutes (including metabolic waste products) through the porous fibers membrane. The model we illustrate here completes the one formulated in a previous paper in which solutes concentrations in the dialyzate were neglected. Exploiting the large difference between the characteristic time of the processes in the machine and the relaxation time to equilibrium in the body, we confine our study to the case of constant input data in order to emphasize the role of the solute transport mechanisms. Numerical solutions show that diffusion is dominant at the early stage of filtration.

Searching for ultrafiltration membrane molecular weight cut-off for water treatment in recirculating aquaculture system

Ultrafiltration (UF) has been proposed as a promising technology in recirculating aquaculture systems (RAS) to remove both organic contaminants and other fine contaminants including viruses and pathogenic bacteria. However, fouling is still a severe problem during this application. This paper investigated the fouling behavior of three different UF membranes examined using five different aquaculture contaminants. The experiments were performed using UF membranes with molecular weight cut-off 10, 50, and 100 kDa. Humic acid, shrimp feed, Spirulina sp., Vibrio harveyi and IHHNV were used as contaminant models. Scanning electron microscope was used to visualize the presence of foulant on the membrane surface. The results showed that fouling behavior was affected by both membrane cut-off (pore size) and foulant type. Two fouling behaviors were observed: (i) rapid flux decline at the early stage of filtration followed by relatively constant permeate flux until experiments finished, and (ii) rapid flux decline at the early stage of filtration followed by a gradual decrease in permeate flux. Due to its reliable flux value and high rejection, 100 kDa UF membrane should be considered as the most suitable UF membrane for RAS application.

Relationship between particle charge and electrostatic enhancement of filter performance

As an important particle collection method, filtration is significantly affected by particle precharging. The filtration of differently charged fly ash particles using membrane and fibrous filters was experimentally studied. Particle charge was directly measured and quantitatively related to the enhancement of filter performance. Particle penetration, which was observed in the fibrous filter during the early stages of filtration, exponentially decreased with increasing particle charge when the filter was clean and rapidly decreased with increasing particle load. A penetration reduction factor ψ was defined to represent the effect of particle charge on penetration, and its correlation with particle charge was defined on the basis of the fitting experimental results. The average porosity of the dust cakes that were formed on both filters increased with particle charge, which in turn exponentially decreased the pressure drop. The electrostatic effect on pressure drop was less prominent than that on penetration. A pressure drop reduction factor θ was defined to quantify the effect of particle charge on pressure drop. Correlations for predicting the evolution of average cake porosity and pressure drop in consideration of particle charge were proposed on the basis of the fitting experimental results.

Evolution of organic gel fouling resistance in constant pressure and constant flux dead-end ultrafiltration: Differences and similarities

A common type of ultrafiltration (UF) membrane fouling is due to organic gel, encountered in the treatment of various effluents and feed waters to desalination plants; polysaccharides are a major component of such fouling layers. In standard methods, dead-end UF tests under constant pressure are used to determine membrane-fouling propensity, but the results are applied with questionable success to the case of constant flux filtration, favored in practice. Observed differences between fouling resistances from the two modes of UF filtration have not been adequately explained yet. The temporal evolution of specific resistance α (considered as the most representative fouling parameter) is investigated herein, aiming to elucidate differences and possible similarities in the different filtration modes. During alginate-solution ultrafiltration, typical gel-type membrane fouling layers are formed with time-varying deposited mass density m (g/cm2) depending on permeate flux; thus, the temporal variation of specific resistance α, of pressure difference across the fouling layer/cake ΔPc, and of pressure drop per unit depth of cake (the latter proportional to ΔPc/m) are studied for both constant pressure P and constant flux J operation, within P and J ranges of practical interest. These detailed data suggest that permeation flux is the process variable controlling the development of resistance α. Specifically, for constant-flux filtration, the resistance α data are well correlated with flux J (as also shown recently), whereas in the constant-pressure mode the commonly observed constant resistance α, over a rather broad range of declining flux, is due to the high flux level prevailing in the early stage of filtration. A successful approach is demonstrated to compare and correlate the specific resistance α data obtained from the two different filtration modes. The usefulness of the new results in practice is also discussed.

Temporal changes in extracellular polymeric substances on hydrophobic and hydrophilic membrane surfaces in a submerged membrane bioreactor

Membrane surface hydrophilic modification has always been considered to mitigating biofouling in membrane bioreactors (MBRs). Four hollow-fiber ultrafiltration membranes (pore sizes ∼0.1 μm) differing only in hydrophobic or hydrophilic surface characteristics were operated at a permeate flux of 10 L/m2 h in the same lab-scale MBR fed with synthetic wastewater. In addition, identical membrane modules without permeate production (0 L/m2 h) were operated in the same lab-scale MBR. Membrane modules were autopsied after 1, 10, 20 and 30 days of MBR operation, and total extracellular polymeric substances (EPS) accumulated on the membranes were extracted and characterized in detail using several analytical tools, including conventional colorimetric tests (Lowry and Dubois), liquid chromatography with organic carbon detection (LC-OCD), fluorescence excitation - emission matrices (FEEM), fourier transform infrared (FTIR) and confocal laser scanning microscope (CLSM). The transmembrane pressure (TMP) quickly stabilized with higher values for the hydrophobic membranes than hydrophilic ones. The sulfonated polysulfone (SPSU) membrane had the highest negatively charged membrane surface, accumulated the least amount of foulants and displayed the lowest TMP. The same type of organic foulants developed with time on the four membranes and the composition of biopolymers shifted from protein dominance at early stages of filtration (day 1) towards polysaccharides dominance during later stages of MBR filtration. Nonmetric multidimensional scaling of LC-OCD data showed that biofilm samples clustered according to the sampling event (time) regardless of the membrane surface chemistry (hydrophobic or hydrophilic) or operating mode (with or without permeate flux). These results suggest that EPS composition may not be the dominant parameter for evaluating membrane performance and possibly other parameters such as biofilm thickness, porosity, compactness and structure should be considered in future studies for evaluating the development and impact of biofouling on membrane performance.

Effect of virus influent concentration on its removal by microfiltration: The case of human adenovirus 2

For safe water reuse, pathogenic viruses need to be efficiently controlled. Membrane filtration is considered to be an effective technology for virus removal. The present work explores mechanisms of human adenovirus 2 (HAdV-2) removal by a hollow fiber microfiltration membrane (dpore=0.2µm) as a function of influent virus concentration ranging from 1.3×107 to 3.4×108copies/mL. A gradual decrease of HAdV-2 removal over time was observed at the beginning of filtration and was attributed to the accumulation of rejected HAdV-2 at the membrane surface or within membrane pores. Flux decline analysis revealed that complete pore blocking and standard pore blocking dominated the early stages of filtration and then transited to cake filtration at longer filtration time as the primary reason for flux decline. Deposition of HAdV-2 onto the membrane during the later stages of filtration led to the formation of a partly irreversible fouling layer and an increase of HAdV-2 removal. The understanding of HAdV-2 behavior at the membrane surface revealed in this study can help with the development of antifouling membranes with high virus removal efficiency.