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Electrochemical filtration systems hold significant promise for advanced water purification, but the influence of different conductive interface structures on performance and electrocatalytic mechanisms remains unclear. This study explores how varying Carbon Nanotubes (CNT) integration strategies, surface modification versus internal fabrication, affect the electrocatalytic activity and contaminant degradation pathways of CNT-based membranes. By comparing surface-modified membranes with CNT layers to those with uniformly embedded CNT networks, we reveal that interface-induced structural variations critically modulate reactive oxygen species (ROS) generation, electrochemical performance, and fouling resistance. The membrane with an internal CNT network exhibited superior long-term stability and resistance to organic fouling due to its ability to sustain uniform ROS generation and maintain consistent electrochemical activity across multiple filtration cycles. In contrast, the surface-modified CNT membrane showed rapid pollutant degradation but was more prone to surface fouling due to localized ROS production at the interface. Our findings highlight the crucial role of interface design in optimizing electrocatalytic processes within electrochemical filtration systems, offering valuable guidance for the development of next-generation filtration technologies for sustainable water treatment. [Display omitted] • CNT distribution modulates ROS generation and degradation pathways. • Internal CNT network enhances long-term stability and fouling resistance. • Interface structure insights aid in designing efficient filtration systems. [ABSTRACT FROM AUTHOR]

Fe(II)/PMS pretreatment demonstrates substantial potential to improve ultrafiltration performance by controlling membrane fouling, though its underlying mechanisms remain incompletely understood. This study provides a detailed investigation of these mechanisms from thermodynamic and molecular perspectives, uncovering the dual roles of oxidation and coagulation in membrane fouling mitigation. Fouling tests revealed that Fe(II)/PMS pretreatment significantly reduced sodium alginate (SA) membrane fouling, achieving a 95.2 % decrease in specific filtration resistance (SFR) and a 27.8 % increase in flux recovery ratio (FRR). Quantum chemical simulations, coupled with experimental characterizations, indicated that oxidation predominated over coagulation, disrupting the SA crosslinked network and leading to an 87.3 % reduction in SFR. Flory-Huggins lattice theory analysis clarified that changes in chemical potential are linked to SA crosslinked structure disruption, highlighting its important role in reducing SFR. Additionally, limited floc formation through coagulation lowered SA viscosity by 65.5 %, thereby improving fouling resistance. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling and SEM analysis demonstrated that the combined effects of oxidation and coagulation reduced the SA-membrane contact area by 53.6 % and decreased interfacial interaction energy by 38.8 %, significantly weakening SA adhesion. These findings provide critical insights into the dual mechanisms of Fe(II)/PMS pretreatment, offering a foundation for optimizing fouling control in ultrafiltration applications. [Display omitted] • Dual function of oxidation and coagulation significantly mitigates membrane fouling. • Oxidation dominates over coagulation, disrupting fouling layer and reducing filtration resistance by 87 %. • Flory-Huggins theory links fouling layer structure disruption to drastic reductions in filtration resistance. • SA-membrane contact area and adhesion energy decrease by 53 % and 39 % after Fe(II)/PMS pretreatment. • Mechanistic insights offer new perspectives for optimizing Fe(II)/PMS pretreatment process. [ABSTRACT FROM AUTHOR]

The enzymatic membrane reactor (EMR) offers a sustainable approach to biomanufacturing, yet maintaining stable performance over prolonged periods remains a significant challenge due to membrane fouling and enzyme activity decline. To tackle these issues, we innovatively utilized a loose ultrafiltration membrane in a cross-flow EMR that completely retains enzymes while lacking the capability to separate intermediate and target products, thereby preventing the excessive retention of target products by the fouled membrane. By optimizing the dextran/dextranase ratio and substrate residence time, we achieved flexible control over the molecular weight (Mw) of products in the permeate. Our findings indicate that decreased enzyme activity exacerbates concentration polarization, leading to reduced permeate flux and prolonged residence time. This dynamic facilitates a re-matching of the substrate/enzyme ratio with residence time, effectively addressing the instability of the EMR caused by declining enzyme activity. Notably, this study reveals the intrinsic relationships between enzyme activity, permeate flux, and membrane fouling dynamics, alongside their self-regulation mechanisms for product Mw. Leveraging the ability of dextranase to preferentially degrade higher Mw dextran, a continuous feeding mode was employed under optimal conditions, allowing the EMR to sustain steady-state operation for 28 h while consistently producing oligodextran within the target Mw range of 3–6 kDa. Furthermore, the successful application of industrial-grade dextran substrate highlights the scalability and industrial relevance of EMRs for continuous oligodextran production. [Display omitted] • A loose UF membrane is used in EMR to avoid excessive retention of target products caused by fouling. • Product molecular weight is well controlled by optimizing dextran/dextranase ratio and residence time. • Self-regulation effect among enzyme activity, permeate flux, and residence time in the EMR is clarified. • It exhibits unique fouling behavior in a mixed molecular weight dextran and enzymatic reaction system. • Industrial-grade dextran is used in the EMR for the first time and shows similar results as pure dextran. [ABSTRACT FROM AUTHOR]

The combined crystallization and diffusion (CCD) method has been introduced in recent years to produce polyvinylidene fluoride (PVDF) and other polymeric ultrafiltration (UF) membranes with high permeation/separation performance. However, the CCD PVDF membranes can easily be fouled by protein adsorption, which deteriorates their permeance over time. This study addresses this issue by incorporating polyacrylonitrile (PAN) into PVDF in the separation layer at different percentages via a dual-casting technique in the CCD method to prevent irreversible fouling. The anisotropic CCD membrane morphology with interconnected microchannels was preserved after PAN was blended in the separation layer without phase separation or delamination, as determined by scanning electron microscopy (SEM). Antifouling studies revealed that even after two fouling cycles, the 10 % PAN-doped dual-cast PVDF membrane presented very high pure water permeance (PWP) at 640 L per square meter membrane area per hour (LMH) under 1 bar pressure difference across the membrane (LMH bar−1), that is over 4 times greater than the initial water permeance of well-known commercial PVDF membranes from industry leaders (∼150 LMH bar−1) at the same mean flow pore size range (30–35 nm). This research provides an efficient and facile route for fabricating high-performance ultrafiltration membranes with superior antifouling and flux recovery characteristics for long-term operation. [Display omitted] • PAN integration into the separation layer reduces pore size and improves flux recovery. • The WCA decreased from 85° to 44° after the separation layer was blended with 25 wt% PAN. • The pore size decreased from 34 nm to 17 nm with a 25 wt% PAN content in the separation layer. • The addition of 10 wt% PAN resulted in a 71 % increase in flux recovery at the same pore size. • The through-pore porosity doubled to 24 % with the addition of 25 wt% PAN to the separation layer. [ABSTRACT FROM AUTHOR]

Membrane fouling is a major issue in many membrane applications. There are numerous methods used in attempt to mitigate membrane fouling, with one method being membrane surface patterning. However, it is still unclear how the ratio of foulant size to pattern size affects membrane fouling. In this study, we investigated constant foulant size while varying the pattern size on the membrane surface to be smaller than (300-nm), equal to (10-μm), and larger than (50-μm) the foulant (10-μm) on polyamide nanofiltration membranes. These membranes were compared to a commercial nanofiltration membrane and a control flat synthesized membrane. The membranes were tested with water, 2000 ppm Na 2 SO 4 , and three cycles of a n -dodecane (as oil) brine solution in a dead-end cell to assess the fouling resistance and flux recovery ability of each polyamide membrane type. From the fouling experiments, it was determined that none of the pattern sizes significantly affect the flux recovery ratio, but smaller than and larger than patterns decreased the fouling rate on the polyamide membranes by a small margin. [Display omitted] • Describes a method to synthesize semi-aromatic nanofiltration (NF) polyamide layers on patterned polysulfone supports. • Patterned NF membranes of three sizes were compared to flat NF membranes for oil fouling reduction and flux recovery. • NF membranes with patterns smaller and larger than the 10-μm foulant size showed less flux reduction. • All synthesized NF membranes (flat and patterned) showed similar flux recovery ratios. [ABSTRACT FROM AUTHOR]

Nanoemulsions with droplet diameters from 20 to 200 nm have emerged as attractive adjuvants in the development of novel vaccines and as an advanced method of drug delivery for hydrophobic drugs. However, the large size of the nanoemulsion droplets leads to very low capacities during the final sterile filtration step used to ensure sterility of parenteral drug products. The objective of this study was to examine the sterile filtration of a model nanoemulsion made using squalene as the oil and Tween 20 and Span 85 as stabilizing surfactants. Data were obtained with different commercial sterile filters with different morphology and chemistry during constant pressure filtration. In each case, there was essentially no filtration until the transmembrane pressure exceeded a critical value related to the force required to push the deformable nanoemulsion droplets through the membrane pores. The filter capacity increased with increasing pressure, going from 700 g/m2 at 140 kPa to 1300 g/m2 at 280 kPa for a dual layer polyethersulfone sterile filter, with the flux decline well described by the complete pore blockage model. The dual layer asymmetric membranes showed much higher capacities than corresponding single layer filters due to the effectiveness of the upper layer in removing larger nanoemulsion droplets that would otherwise block the pores of the sterile filter. The capacity of the different sterile filters was also well-correlated with the initial filtrate flux, with both of these parameters governed by the pore size distribution and surface chemistry of the filters. These results provide important insights into factors controlling the sterile filtration of highly concentrated nanoemulsions used in the formulation of vaccines and drug products. [Display omitted] • Sterile filtration of nanoemulsions used in drug delivery limited by membrane fouling. • No flow below a critical intrusion pressure needed to push nanodroplets through pores. • Fouling during constant pressure filtration due to complete pore blockage. • Rate of pore blockage decreases with increasing pressure due to droplet deformation. • Filter capacity well-correlated with initial flux due to effects of pore size distribution. [ABSTRACT FROM AUTHOR]

Despite the widespread adoption of membrane technologies for efficient water treatment, membrane fouling remains a significant challenge, reducing separation efficiency, shortening lifespan, and increasing operational costs. Various studies have explored chemical membrane modifications to mitigate fouling, often resulting in adverse effects on flux and selectivity. Based on numerical modeling and experimental investigation, this work introduces real-time induced magnetic vibration as a sustainable approach for membrane antifouling without compromising permeability and selectivity. By preventing or delaying particle deposition on the membrane surface, magnetic vibration reduces fouling intensity. Experimental results demonstrated that different frequencies of magnetic vibration influenced the deposition of foulants (Humic Acid and Sodium Alginate) on the membrane surface. Notably, vibrating the membrane at 10 Hz with centrally attached iron particles led to a 22.4 % reduction in flux when treated with Humic Acid, compared to a 33.9 % reduction without vibration. Exposure to vibrations at the resonance frequency (5 Hz) for 6 h resulted in only a 10 % reduction in flux, effectively preventing the formation of a dense cake layer. Similarly, in the case of Sodium Alginate, a 10 Hz vibration for 2 h decreased the flux reduction from 21.4 % without vibration to 7.3 %, suggesting the preventive effect of vibration on aggregated SA deposition or facilitating continuous displacement for flux retention. Moreover, the study examined the influence of the configuration of iron particles attached to the membranes on the effectiveness of vibration. The study revealed that a striped configuration was more effective than a centralized configuration, owing to the distributed vibration effect across each part of the membrane. Furthermore, the fouling mechanism and rejection percentage were further investigated to enhance understanding of the fouling processes. [Display omitted] • Real-time induced vibration prevents the cake layer formation. • Vibration at the resonance frequency of the membrane provides the maximum antifouling. • The position of magnetic particles in/on the membrane affects the vibration effectiveness. [ABSTRACT FROM AUTHOR]

Membranes for water-in-oil (W/O) emulsion separation require high emulsion permeance, oil purity selectivity, high water-fouling resistance, and reusability. Therefore, a functional membrane structure that satisfies these needs is required. Herein, we describe the effective modification of a membrane surface by forming functional silica particles on a porous polyketone (PK) membrane to form a hierarchical membrane structure with enhanced roughness and superhydrophobicity. We also demonstrate the potential application of the membrane for W/O emulsion separation based on enhanced performance and fouling resistance. Membranes were fabricated by forming silica particles on a porous PK membrane by a sol–gel method using tetraethoxysilane (TEOS). By modifying these silica particles with fluoroalkyl silane (FAS), a superhydrophobic membrane with a high contact angle of up to 162° was fabricated. The resulting FAS-modified membrane had higher permeance with regard to a toluene W/O emulsion than an unmodified PK membrane or a commercially available polyvinylidene fluoride (PVDF) membrane. It was possible to recycle the FAS-modified membrane by simply washing it in toluene to remove external fouling. This effective membrane surface modification helps to enhance both emulsion permeance and fouling resistance during W/O emulsion separation. [Display omitted] • Superhydrophobic PK membrane was prepared for W/O emulsion separation. • Effective surface modification for enhancement of emulsion permeance and fouling resistance. • Superhydrophobic membrane was fabricated by forming silica particles and bonding fluoroalkyl silane. • Membrane had superior W/O emulsion permeance than unmodified membrane. • Membrane was easily recycled by simple solvent washing because external fouling occurred. [ABSTRACT FROM AUTHOR]

The use of forward osmosis (FO) membranes for simultaneous thickening and digestion of waste activated sludge (WAS) (FO-MSTD) has recently garnered significant interest. However, a major challenge hindering the widespread adoption of the FO-MSTD process is severe membrane fouling, which results from increasing sludge concentrations and deteriorating sludge properties. In response, this study proposes a novel FO membrane fouling control strategy based on the critical flux concept, involving a variable draw solution (DS) operating mode. Two operating modes were examined based on the critical flux behavior of the FO membrane: a constant DS concentration mode (with a fixed DS concentration of 1.5 M, referred to as Constant DS1.5) and a variable DS concentration mode (with varying DS concentrations at different operational stages, referred to as Variable DS1.5-1.0 and Variable DS1.5-0.75). Over 21 days of operation, the MLSS concentrations of WAS in the Constant DS1.5, Variable DS1.5-1.0, and Variable DS1.5-0.75 reactors increased from initial values of 3.46, 3.88, and 4.20 g/L to 35.2, 31.5, and 29.2 g/L, respectively. Concurrently, the cumulative digestion rates of MLVSS in the three FO-MSTD processes reached 29.3 %, 29.0 %, and 36.3 %, respectively. After adjusting the DS concentration, the FO membrane flux decay rates for Constant DS1.5, Variable DS1.5-1.0, and Variable DS1.5-0.75 were 57.7 %, 49.4 %, and 13.8 %, respectively. In addition to experiencing a lower flux decline, the Variable DS1.5–0.75 mode achieved a significantly higher flux recovery rate of 98.5 % compared to the other two modes. Moreover, the biovolume of proteins and microorganisms in the membrane fouling layer decreased by 85.2 % and 72.7 %, respectively, in the Variable DS1.5–0.75 mode compared to the Constant DS1.5 mode. These findings indicate that operating with a DS below the critical concentration can significantly improve the reversibility of membrane fouling and reduce the presence of organic and biological foulants in the fouling layer, thereby mitigating membrane fouling in the FO-MSTD reactor. [Display omitted] • Critical flux-based fouling control method was proposed for FO membrane. • Critical flux of FO membrane varied under different sludge concentrations. • Variable DS operation mode alleviated FO membrane fouling during sludge treatment. • Below critical flux contributed to minimizing biofoulants deposition. • Below critical flux was beneficial for the recovery of FO membrane flux. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) is an exciting new therapeutic approach, using small interfering RNA (siRNA) to silence specific genes for treating various diseases. Ultrafiltration has been widely used for the concentration and purification of monoclonal antibodies and other biotherapeutics; however, its application in the downstream processing of double-stranded oligonucleotides remains underexplored. This study investigates the use of ultrafiltration in the final formulation for concentrating a siRNA drug substance. Initial experiments were conducted with Ultracel™ composite regenerated cellulose membranes over a range of molecular weight cutoffs (MWCO) at different siRNA feed concentrations. Results demonstrated significant effects of both fouling and concentration polarization, with the maximum achievable concentration falling well below the target required for subcutaneous injection. Novel surface-modified ultrafiltration membranes were made by reaction of the cellulose with bromopropanesulfonic acid. These negatively charged membranes showed improved siRNA retention, reduced fouling, and a large increase in the maximum achievable siRNA concentration (from 52 to >180 mg/mL). These findings offer critical insights into novel approaches for developing high performance ultrafiltration processes for siRNA concentration. [Display omitted] • First analysis of ultrafiltration of small interfering RNA (siRNA) presented. • Data demonstrate that flux determined by both fouling and concentration polarization. • Novel charged membranes provide much better performance due to repulsive interactions. • Maximum achievable siRNA concentration increased >3-fold due to membrane charge. • Charge-modified membranes provide better siRNA yield due to greater siRNA retention. [ABSTRACT FROM AUTHOR]

Sacrificial membranes have emerged as a promising solution to mitigate membrane fouling through their ability to be removed and regenerated while preserving membrane integrity and performance. In this study, we synthesized sacrificial trilayers on a commercial polyamide nanofiltration membrane using layer-by-layer (LbL) assembly of two-dimensional molybdenum disulfide (MoS 2) nanosheets and polyelectrolytes. Quartz crystal microbalance with dissipation (QCM-D) studies showed the trilayers to be MoS 2 -dominant by mass and have a total areal density of 2.37 μg/cm2 after the deposition of two trilayers. The trilayer membrane showed a slight decrease in water permeability and an increase in calcium chloride rejection compared to the pristine nanofiltration membrane. The trilayer membrane demonstrated improved organic fouling resistance over the pristine nanofiltration membrane, maintaining permeability throughout six consecutive cycles. Interestingly, the trilayer membrane after gypsum scaling exhibited sacrificial layer removal and permeability recovery with simple hydraulic cleaning. This suggests the potential for membrane regeneration and sustained fouling resistance that may be achieved by utilizing disruptive interactions with the trilayer materials. In conclusion, sacrificial membranes made of MoS 2 nanosheets and polyelectrolytes exhibited excellent organic and inorganic fouling resistance and promising potential for layer removal and regeneration. [Display omitted] • Sacrificial membranes made by layer-by-layer assembly of MoS 2 and polyelectrolytes. • The sacrificial trilayer membrane contains 96 % MoS 2 by mass. • Sacrificial layers enhanced the membrane resistance to long-term organic fouling. • Gypsum scaling enabled removal of sacrificial trilayers by simple salt cleaning. [ABSTRACT FROM AUTHOR]

We synthesized copolymers of carboxymethyl betaine and methyl methacrylate (P(CMB-co-MMA)) by radical polymerization, and blended them with polyvinylidene fluoride (PVDF) to produce a low-fouling microfiltration membrane by non-solvent induced phase separation. The P(CMB-co-MMA) blends improved the pure water permeability of the membrane and prevented fouling. In particular, a membrane prepared from a dope solution comprising 15 wt% PVDF and 3.0 wt% P(CMB-co-MMA) in 82 wt% dimethyl sulfoxide had the highest pure water permeability and the most excellent low-fouling property against bovine serum albumin and lysozymes. The optimized membrane recovered its performance after immersion for 24 h in an aqueous solution of sodium hydroxide (pH 11). Moreover, it retained its excellent performance, even after immersion in pure water for 6 months, suggesting that the blend copolymer did not detach from the membrane. Based on these results, we conclude that P(CMB-co-MMA) is potentially useful for blending with PVDF to develop low-fouling microfiltration membranes. [Display omitted] • Carboxymethyl betaine and methyl methacrylate copolymers were blended with PVDF. • The blend was used to produce a membrane with high pure water permeability. • The membrane resisted fouling by BSA and lysozymes. • The membrane performance was recovered by immersion in aqueous NaOH (pH 11). • The membrane retained its performance after immersion in pure water for 6 months. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) is a crucial process for treating waters across various salinity levels, but membrane fouling persists as an inherent challenge. While surface modification with hydrophilic polymers such as polyethylene glycol (PEG) and its derivatives is a prevailing strategy to alleviate fouling, its effectiveness has primarily been explored in low-salinity conditions, leaving a critical knowledge gap regarding the performance of such membranes in high-salinity environments and their susceptibility to feed salinity variations. We here investigated the antifouling characteristics of PEG-modified RO membranes for high-salinity wastewater and seawater treatment. Remarkably, our findings indicated a substantial decrease in fouling resistance under high-salinity conditions compared to low-salinity wastewaters used as control. The reduction in Lewis acid-base interactions, induced by decreased water structuring, was found to be a critical factor for the diminished fouling resistance based on the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis. Complementary experimental and theoretical studies unveiled the disruptive role of high-concentration NaCl on PEG-water hydrogen bonds, causing PEG dehydration and configurational compression, which thus compromised the enthalpic barrier and entropic repulsion against fouling. Our study emphasizes the pivotal role of feed salinity in determining the fouling resistance of membranes modified with hydrophilic polymers, a factor often neglected in prior research. [Display omitted] • PEG-modified membranes show reduced antifouling property under high salinity. • High-concentration NaCl disrupts the hydrogen bonds between PEG and water. • Polymer shifts from a thick, soft state to a thin, rigid one as salinity increases. • High salinity induces a "salting out" effect that impacts antifouling performance. [ABSTRACT FROM AUTHOR]

The rare earth metal neodymium (Nd) is widely used in advanced industries such as hybrid cars and aerospace. Therefore, recovering neodymium from wastewater presents valuable opportunities for secondary recycling. The recovery of Nd3+ from wastewater using ion imprinting technology (IIT) for efficient selective separation holds significant importance. In this study, hydrophilic Nd(III) ion-imprinted membranes, termed Nd(III)–P/P/TIIM, were synthesized using the IIT technique. Nd(III)–P/P/TIIM exhibited efficient and selective separation capabilities for Nd3+ with a remarkable retention rate of 95.68 % and a high water flux reaching up to 636.94 L·m−2·h−1. Additionally, its relative selectivity coefficients for interfering ions (K La , K Eu , K Cu) were 3.9, 29.5, and 37.9, respectively. Various analyses, including DFT calculations, HOMO and LUMO calculations, MEP images, and XPS spectroscopy, confirm that the mechanism of selective retention of Nd3+ by Nd(III)–P/P/TIIM in solution is due to Coulombic adsorption between the –COO− anion and Nd3+ as well as an imprint memory effect. Even after undergoing three water-BSA cycles, the membrane maintained a water flux of 357.96 L·m−2·h−1. The antifouling principle of Nd(III)–P/P/TIIM was investigated by XDLVO theory, attributed to the increase of electron donor tension (γ−) and Lewis acid-base interactions ( Δ G AB) at the membrane surface. This work provides an insightful guidance for engineering high-performance membranes and has the potential to provide an alternative method for recycling neodymium. [Display omitted] • A composite membrane with high neodymium selectivity is prepared. • The membrane exhibited high water flux of 636.94 L·m−2·h−1. • DFT, HOMO and LUMO calculations elucidate the mechanism of separating Nd3+. • The antifouling mechanism is deduced through XDLVO theory. [ABSTRACT FROM AUTHOR]

This study developed a new protocol to prepare feed spacers in the membrane module, by combining the optimization of spacers' geometrical parameters with subsequent chemical modification of the spacers' surface, to enhance filtration performance comprehensively. Geometrical parameters of columnar spacers were optimized using an object-oriented and automatic optimization method based on computational fluid dynamics (CFD) simulation coupled with response surface optimization. In chemical modification, polydopamine was firstly used to provide anti-adhesive properties, followed by the even integration of silver nanoparticles (AgNPs) to exhibit antimicrobial activity. Anti-biofouling experiments involving Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria demonstrated that the combined structurally optimized and chemically modified spacers resulted in over 10 % improvement in permeate flux and a 27 % reduction in feed channel pressure (FCP) drop. Chemical modification enhanced the structural optimization resistance to flux attenuation and FCP drop increase by over 220 % and 200 %, respectively. Analysis of the anti-biofouling behavior indicated that the primary mechanism of the integrated, optimized spacers lies in the increased wall shear, bactericidal activity of AgNPs, and improved interfacial interaction energy between the spacers and foulants. This study not only developed a novel modification method for anti-biofouling spacers, but also provides in-depth understanding of the roles of modified spacers, all of which are important for their practical applications in improving membrane filtration performance. [Display omitted] • Membrane spacers were structurally optimized and chemically modified simultaneously. • Dual-functional anti-adhesive and antibacterial spacers were successfully prepared. • The spacers exhibit high antimicrobial efficacy against Gram-negative and Gram-positive bacteria. • The modified spacers synergistically control biofouling and improve membrane permeability. [ABSTRACT FROM AUTHOR]

Membrane filtration processes with flux reversal for backwashing are employed to manage fouling during colloidal fluid treatment. This flux reversal accompanies filtration cycles where the total resistance increases over time. However, little is known about the initial phase of filtration. We focus on early filtration phase and present a microfluidic filtration system that allows precise observation of filtration resistances under constant flux or constant pressure operation for soft matter dead-end filtration with subsequent percolation of pure solvent. We identified temporal hydraulic resistance fluctuations during the start-up phase, which significantly differed from the steady-state condition. We focus on the experimental filtration of soft core–shell poly(N-isopropylacrylamide)-co-acrylic-acid microgels and observed a distinct peak in filter cake resistance with a subsequent reduction down to 50% of the initial peak resistance. To comprehend the phenomenon, we complement the experiments with temporal and spatial confocal microscopy studies linking cake compression and cake density gradients to its resistance. By comparing filtration, dialysis, and centrifugation as different microgel purification methods, we discover microgel shell degradation leading to detached polymer chains permeating in the downstream which causes the observed resistance reduction. This result demonstrates the permeation-induced degradation of macromolecular colloids during membrane filtration. [Display omitted] • Core–shell microgels as model foulants in ultrafiltration. • Visualizing inter-cake particle distances and correlation to hydraulic resistance. • Shear stress in microgel purification methods induces shell degradation. • Resistance decrease during start-up phase of soft matter filtration. [ABSTRACT FROM AUTHOR]

Membrane fouling has been a major factor hindering the development of ultrafiltration membranes. Herein, a novel in situ oxidation system was constructed via introducing MnFe 2 O 4 /MWCNTs into polyvinylidene fluoride (PVDF) membranes, utilizing sunlight to synergistically activate persulfate (PMS) to mitigate ultrafiltration membrane fouling. The mechanism of mitigating membrane fouling in MnFe 2 O 4 /MWCNTs-PVDF ultrafiltration membranes was systematically explored under four system (single filtration, single sunlight irradiation, single PMS oxidation and sunlight co-activated PMS). The MnFe 2 O 4 /MWCNTs-PVDF membranes exhibited different fouling characteristics under the four systems, with the sunlight and MnFe 2 O 4 /MWCNTs membrane co-activated PMS filtration system showing the highest humic acid (HA) removal efficiency of 90.2 %, as well as the lowest Rr (0.2108 × 1012m−1) and Rir (0.4525 × 1012m−1). To further evaluate the practicality and effectiveness of the sunlight-MnFe 2 O 4 /MWCNTs-PMS system, the secondary effluent was selected to verify the treatment effect on natural organic matter (NOM) of actual water. By observing the microscopic morphology of the fouled membrane surface, it was evident that, compared with the other three filtration systems, the filter cake layer on the MnFe 2 O 4 /MWCNTs membrane surface of the sunlight co-activated PMS system was obviously reduced, and the structure of the cake layer was more loose. It can be concluded that the principle behind the synergistically activated system to alleviate the membrane fouling was to accelerate the mineralization rate of HA molecules, oxidize the HA into a smaller particle size that can pass through the membrane pores. The main reactive oxygen species and HA degradation mechanism in the synergistic activation system were further elucidated by electron paramagnetic resonance (EPR) analysis and density functional theory calculations (DFT). The results indicated that the degradation of HA by the synergistically activated PMS system involved a combination of free radicals (·O 2 −、SO 4 ·− and ·OH) and non-free radicals (1O 2). Overall, the in-situ oxidation system provided an alternative way to alleviate ultrafiltration membrane fouling. [Display omitted] • Preparation of a tailored catalyst MnFe 2 O 4 /MWCNTs-PVDF ultrafiltration membrane. • Systematic investigating the membrane fouling performance of different filtration system. • The co-activation filtration system of sunlight and MnFe 2 O 4 /MWCNTs-PVDF membranes showed lowest fouling resistance. • Exploring the performance of the different filtration system in secondary effluent. • XDLVO theory and the membrane fouling model was used to explain the mitigating membrane fouling mechanisms. [ABSTRACT FROM AUTHOR]

The management of hypersaline brine is a critical challenge to achieving a circular water economy. Traditional brine treatment technologies mainly rely on thermal evaporation, which requires intensive energy, cost, and/or areal footprint. Electrodialytic crystallization (EDC) has been recently developed as a novel process that enables brine crystallization without evaporation. However, the potential effects of mineral scaling and organic fouling on the performance of EDC have not been revealed. In this study, we systematically investigated mineral scaling and organic fouling in EDC. We demonstrate that the ion transport and crystallization efficiencies of EDC are generally unaffected by a variety of mineral scalants and organic foulants, despite an increase of energy consumption in the presence of humic acid. Further, EDC is shown to be less susceptible to gypsum scaling than RO, mainly due to the difference in concentration polarization between these two membrane processes. To mitigate gypsum scaling in an assumptive EDC-RO treatment train towards zero liquid discharge (ZLD), polyacrylic acid (PAA) is employed as an antiscalant that prevents gypsum scaling in RO while not adversely affecting EDC performance at relatively low concentration. Our study unravels the behaviors of EDC when treating feedwater with high scaling and fouling potentials, providing valuable insights for understanding mineral scaling and organic fouling when applying an ED-based technology for hypersaline brine treatment towards ZLD. [Display omitted] • The effects of membrane scaling and fouling on EDC performance are explored. • EDC performance is generally unaffected by a variety of mineral scalants and organic foulants. • The presence of humic acid increases energy consumption of EDC. • EDC is less susceptible to gypsum scaling than RO within an integrated treatment train. • Antiscalant PAA can mitigate gypsum scaling in RO without adversely affecting EDC performance. [ABSTRACT FROM AUTHOR]

The presence of microplastics (MPs) in aquatic environments is a direct consequence of human activities and social development. Consequently, the removal of MPs is essential in water treatment processes, including the membrane filtration of roofing rainwater. Additionally, MPs carried by roofing rainwater pose potential risks to both the ecosystem and human health. However, the fouling behavior of MPs and their impact on the performance of gravity-driven ceramic membranes (GDCMs) remains largely unexplored. In this study, we investigated the effects of the coexisted MPs in rainwater, specifically granulate and fiber MPs, on the formation of fouling layers. We examined their physical and biological characteristics, such as components and microbial community structure. The results demonstrated a positive correlation between the formation of the biological functional layer and the diverse morphology of MPs, which led to a significant decrease in membrane permeability and exacerbated membrane fouling, while having no remarkable influence on permeate quality. Furthermore, different shapes of MPs exhibited varying characteristics: the cake layer of the granulate-MPs group exhibited superior compressibility, while the fiber-MPs group formed and matured more rapidly. MPs not only directly combined with organic matter but also induced metabolic products of microorganisms. Therefore, understanding the primary mechanisms of membrane fouling by MPs in GDCMs for roofing rainwater reuse is of utmost importance. Our study presents novel insights into the mechanisms of membrane fouling in the presence of coexisting MPs in roofing rainwater reuse and provides guidance for improving the performance of GDCMs in the presence of MPs. [Display omitted] • The shape of MPs in rainwater exhibits significant effect on membrane fouling. • Granulate-MPs cake layer was easily compacted and fiber-MPs benefit for the cake layer growth. • The complexation of MPs and organic was confirmed as the dominant fouling mechanism. • MPs in rainwater only affect membrane fouling behavior but not permeate quality. [ABSTRACT FROM AUTHOR]

Sterile filtration is one of the critical steps in the production of lipid nanoparticle (LNP)-based biotherapeutics. However, LNP fouling can limit the overall capacity of the sterilizing-grade filter. Effective design and control of this unit operation enables a robust manufacturing process. The objective of this study was to examine the sterile filtration of mRNA-LNP through the dual-layer Sartopore 2 XLG membrane during both constant flux and constant transmembrane pressure (TMP) filtration experiments. The complete pore blockage model effectively described the fouling behavior at constant TMP, with the rate of pore blockage decreasing with increasing TMP. However, a novel modification of the complete pore blockage model was needed to describe the fouling behavior during constant flux operation, with the rate of pore blockage found to be a function of both the instantaneous TMP and the TMP gradient. This new model successfully describes the TMP profiles during constant flux operation at multiple fluxes and the flux profiles during constant TMP operation at multiple TMPs, all using the same model parameters. These findings establish a foundational framework that mathematically describes the fouling behavior of mRNA-LNP and can be used to design and optimize sterile filtration processes for this class of biotherapeutic. [Display omitted] • Sterile filtration of mRNA lipid nanoparticles limited by membrane fouling. • Fouling during constant pressure filtration due to complete pore blockage. • Rate of pore blockage decreases with increasing pressure. • Fouling at constant flux determined by both pressure and pressure gradient. • New fouling model successfully describes TMP and flux profiles. [ABSTRACT FROM AUTHOR]

Nanofiltraion (NF) membranes are promising candidates for overcoming critical global issues of access to clean water. However, current NF membranes are hampered by the trade-off between the water permeability and selectivity as well as the fouling propensity. In this work, a facile surface decoration simultaneously combined with solvent activation strategy was adopted for the NF membrane modification via simply immersing membrane into the polyoxometalates (POMs) ethanol solution. The introduction of POMs by coordination assembly increases the membrane hydrophilic and electronegativity, and the ethanol loosens the membrane selective layer, leading to the enhanced membrane perm-selectivity and anti-organic fouling property. The permeance and Na 2 SO 4 rejection of the optimized modified NF membrane are 14.90 ± 0.21 LMH/bar and 99.20 ± 0.38 %, which are ∼20 % and more than 3 % increments compared with those of the control membrane, respectively. The modified NF also reveals a lower permeance decline as well as a higher flux recovery toward both positive and negative charged foulants. In addition, benefiting from the biocidal activity of the POMs, the membrane anti-biofouling property is also significantly improved under an extremely low loading of POMs. More importantly, the chemical stability of the modified NF membrane is reinforced due to the protection from the introduced POMs. Our work contributes to revitalizing the prospect of developing NF membranes with excellent filtration performance and antifouling property. [Display omitted] • Nanofiltration membranes were fabricated by a surface decoration combined with solvent activation strategy. • The modified membrane presents simultaneously improved permeability and selectivity. • The modified membrane shows enhanced anti-organic fouling property toward both electronegative and electropositive foulants. • The modified membrane possesses stronger biocidal activity against E. coli and S. aureus. [ABSTRACT FROM AUTHOR]

This study evaluates the performance of forward osmosis (FO) to concentrate and dewater apple pomace extract for subsequent pectin recovery. After pretreatment by sieve filtration and centrifugation, the FO water flux during real apple pomace extract concentration was 7.8 L m−2·h−1 and was comparable to the FO process for a one-component model pectin solution. However, due to fouling, at 75% water recovery, up to 70% flux decline was observed. Osmotic backwashing using a spent draw solution as the osmotic agent was effective and could completely restore the water flux (ca. 100% flux recovery) after multiple filtration cycles. A comprehensive techno-economic assessment was also conducted to demonstrate significant reduction in capital investment and operating cost when applying FO for concentrating apple pomace extract prior to pectin recovery. The investment payback period was shortened from over 5 to 2 years, at 80% water recovery. Results in this study highlight the utility of FO to replace the traditional evaporation method for enhance the economic viability and environmental friendliness of pectin recovery. [Display omitted] • Sieve filtration and centrifugation improve apple pomace extract pretreatment prior to FO dewatering. • Membrane fouling during FO dewatering of pomace extract is caused by particulate matter. • Osmotic backwashing results in complete water flux recovery (ca. 100 %). • FO application reduces capital investment & operating cost of pectin recovery. [ABSTRACT FROM AUTHOR]

Forward osmosis membrane has shown great potential in the fields of seawater desalination and sewage treatment. However, the concentration polarization phenomenon and membrane fouling in the water treatment process greatly reduce the water treatment performance and restrict its application. To address these challenges, we employed a pre-buried seed-in-situ growth method to facilitate the Zn–Al layered double hydroxide (Zn–Al LDH) growth on the thin nanofiber membrane, and use it as the support layer for the preparation of a Zn–Al LDH modified forward osmosis membrane. Studies have shown that the introduction of Zn–Al LDH significantly improves the water treatment efficiency of the forward osmosis membrane (In Al-DS mode, the water flux increased by 87.5 %, up to 50.50 LMH, with a low specific salt flux of 0.13 g L−1). It also exhibits exceptional antibacterial, anti-membrane fouling, and photocatalytic degradation properties. This research presents a novel approach for the development of advanced high-efficiency forward osmosis membranes. [Display omitted] • The in-situ growth of Zn–Al LDH on the nanofiber membrane was realized. • FOMs have ultra-high water flux and low reverse salt flux. • FOMs has excellent antibacterial, Anti-membrane fouling and photocatalytic ability. [ABSTRACT FROM AUTHOR]

This study investigated the membrane fouling behaviors triggered by different characteristics of anaerobic digestion (AD) effluents in the operation of 851-h membrane distillation (MD). The AD effluents with different concentration factors (CF) were used as the feed separately. Results illustrated a stable normalized water flux in the treatment of raw AD effluent (CF = 1) over the 851-h MD experiment, showing negligible membrane fouling. While the sharp decreases in normalized water flux occurred when treating the concentrated AD effluents. The membrane fouling mechanism tended to change from inorganic scaling to organic fouling when the CF value increased from 1 to 3, while the combination of organic and inorganic fouling dominated the membrane fouling when CF was 5. Inorganic fouling was further intensified when the CF value increased to 10. The regression analysis demonstrated that the complete blocking model was the dominant development mechanism for CF = 3 treatment. The membrane fouling mechanism of CF = 5 treatment switched from the cake filtration model in the intermediate phase to the standard blocking model in the final phase. Additionally, there was a transition from the complete blocking model to the standard blocking model for CF = 10 treatment. The study may provide an in-depth knowledge of membrane fouling control during the actual AD effluent concentrating process. [Display omitted] • Membrane fouling caused by intrinsic characteristics of AD effluent was explored. • Slight membrane fouling occurred in 851-h MD treatment of raw AD effluent (CF = 1). • Flux first stabilized and then declined when treating concentrated AD effluents. • Foulants consisted of inorganics, polysaccharide, protein, and humic substance. • Membrane fouling mechanisms were elucidated based on classical blocking filtration. [ABSTRACT FROM AUTHOR]

Membrane scientists and engineers routinely compare the performance of membranes for different applications. Such comparisons are required to optimize surface chemistries and to evaluate and select the best membrane to scale-up industrial applications. In most cases, the potential of the feed to foul membrane surfaces is also critical. When different membranes under consideration have different resistances R m , such comparisons must be done with care. Here we elucidate the impact of R m on fouling kinetics for a range of fouling mechanisms and experimental protocols. We show that traditional plots of flux versus time for constant pressure operation, or pressure versus volume in constant flux operation, obscure two important performance criteria: accumulated volume over a defined time period (i.e., productivity) and energy consumption; practical implications include the risk that higher performance may be attributed to membranes that actually have lower productivity and/or that consume more energy, and that lower performing membranes may be inadvertently chosen from screening studies as offering superior performance. To facilitate membrane comparison with different R m , we have developed a graphical approach using normalized coordinates. This approach yields linear plots having slopes that are a function of fouling parameters only, and are independent of membrane resistance R m. Therefore, such normalization coordinates, presented for each fouling mechanism and each operation mode, can be employed to isolate fouling potential. In addition, we developed a new graphical approach employing contour plots of iso-volume or iso-energy lines to visualize the potential trade-offs between antifouling performance, membrane permeability, and either productivity in the case of constant pressure operation, or specific energy in the case of constant flux operation. This study provides a framework for judging the performance of different membranes under fouling conditions, considering fouling, energy consumption and productivity as metrics, independent of membrane resistance. This framework will help guide process design and the design and preparation of antifouling membranes. [Display omitted] • Plots of flux decline (constant pressure) or pressure increase (constant flux) can be biased by membrane resistance. • Productivity and specific energy consumption are better criteria to assess membrane performance. • A new graphical approach using normalized coordinates isolates fouling potential independent of membrane resistance. • A new graphical approach employing contour plots of iso-volume or iso-energy evaluates performance trade-offs visually. • This framework will help guide membrane selection, membrane modification, and process design. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) holds promise for cost-effectively concentrating wastewater toward zero liquid discharge (ZLD), while membrane fouling problems still hinder its practical application, especially for high-strength wastewater containing complex constituents. This study investigated the effects of different foulant components in actual landfill leachate (LFL) on MD deep concentration performances. The fouling behaviors of LFL components were revealed by comprehensively characterizing and analyzing the physicochemical properties of the fouling layers and membrane-foulant interactions. Results illustrated that suspended solids (SS) and macromolecular organics (MO) played significant yet distinct roles in fouling layer formation. SS (>0.45 μm, ∼24 % TOC) possessed strong adhesion energies with membrane surfaces and constructed the main skeleton of the fouling layer at the preliminary concentration stage; while MO (>20 kDa, 0.36 % TOC) deposition resulted in a densely packed fouling layer, influencing the salt crystallization potential and interfering with water and ammonia transport. In contrast, the low-molecular organics with the highest content (<20 kDa, ∼75 % TOC) were mainly electron-donor monopolar substances weakly adsorbed on the nonpolar membrane surface. Removing SS and MO from LFL notably prevented fouling layer formation and maintained high membrane efficacies (water flux decline mitigated from ∼50 % to ∼15 % and ammonia rejection increased from 71 % to 88 %), even as water recovery increased to 95 %. The findings of this work imply conventional anti-fouling strategies (e.g., complete removal or degradation of organic components) may have gone beyond what is necessary, and will inspire the development of simpler and greener methods to maintain membrane efficacy during high-strength wastewater treatment toward ZLD. [Display omitted] • Effects of foulant components on MD deep concentration of LFL were investigated. • Crucial yet distinct roles of SS and MO on fouling layer formation were revealed. • Influence mechanisms of membrane fouling on mass transport were analyzed. • LO are electrodonor monopolar substances and weakly adsorbed on membrane surface. [ABSTRACT FROM AUTHOR]

Microbial quorum quenching (QQ), which addresses biofouling resistant to physical and chemical methods, presents a compelling solution. Enhancements in sustainability are imperative to ensure its long-term stability. This study explores QQ media preservation for extended use. Three media types were tested over 150 days: fresh BH4 cells, preserved/reactivated BH4 cells, and BH4 cell extracts. Initial QQ activities ranged in the appropriate levels from 1.08 to 1.24 h−1. Preservation in 50 mM Tris-HCl at 4 °C showed that media with whole cells retained approximately 60 % activity after 60 days, unlike cell extract media, which lost all activity. However, the dehydration and reactivation of BH4 cell media fully recovered the initial QQ activity while maintaining it for 150 days. In MBR tests, reactivated QQ media performed as effectively as those prepared with freshly cultured BH4 cells, delaying membrane fouling by 2-fold. Revitalizing QQ media in combination with chlorine-based chemically enhanced backwashing (CEB) further delayed fouling by 2.5 times compared to CEB alone. Reactivated QQ media retained robust activity even after prolonged MBR use. This study showcases the effectiveness of dehydration and reactivation techniques for preserving QQ media, ensuring its reliable long-term storage and utilization. However, further enhancements are necessary to optimize cell viability. [Display omitted] • The extended preservation of diverse quorum quenching (QQ) media was investigated. • Whole BH4 cell QQ media were preserved better than cell extract QQ media. • The reactivation of QQ media preserved after dehydration restored their initial activity. • The reactivated QQ media exhibited the same fouling mitigation efficacy as fresh media. • The combination of QQ and chlorine-based backwash substantially reduced fouling. [ABSTRACT FROM AUTHOR]

During the application of extracorporeal membrane oxygenation (ECMO), protein adsorption on the membrane not only leads to a decline in the efficiency of gas exchange but also triggers a series of adverse effects and even blood coagulation. Herein, we provide the hydrophilic and low-surface-energy strategy to prepare a fouling-resistance and fouling-release membrane for ECMO. Polyvinylimide (PEI) was grafted with tannic acid (TA) on the PES membrane to form a hydrophilic coating, on which fluorinated small molecules with low surface energy were subsequently grafted by ring-opening reaction to form low-surface-energy domains. The hydrophilic coating resists fouling adhesion by forming hydration layers, while the low surface energy of the hydrophobic domains facilitates the release of pollutants. Moreover, the introduction of the hydrophobic domains facilitates gas-liquid exchange in the ECMO-simulated environment. After PBS rinsing, BSA and BFG removal improved by 97.81 % and 227.83 %, respectively. Finally, in our ECMO-simulated gas-liquid circulation detection device, the modified membrane exhibits excellent gas exchange properties (The O 2 and CO 2 exchange rates reach 123.37 and 168.52 mL min−1·m−2, respectively) and is resistant to plasma leakage. This study provides a new surface modification anti-fouling strategy with simultaneous enhancement of hemocompatibility and gas exchange efficiency. [Display omitted] • A novel anti-fouling modification strategy fitting ECMO membranes is provided. • Simultaneously improves anti-fouling, gas exchange and leakage resistance properties. • The surface modification method is easily scalable for industrial production. [ABSTRACT FROM AUTHOR]

Microfiltration membranes are increasingly used to retain the cells inside bioreactors while continuous harvest of the desired biopharmaceutical occurs in perfusion processes. One method of microfiltration is Alternating Tangential Flow (ATF) filtration, which involves moving the cultivation broth tangentially back and forth across the membrane, which results in a backwash effect that reduces fouling. In this study, fouling was investigated with asymmetric polysulfone hollow fibers operated in ATF mode attached to a bioreactor producing a recombinant protein in Chinese Hamster Ovary (CHO) cells. Fouling was assessed through different approaches, including determination of critical flux using an improved flux-step method. Fouling was studied through measurements of Transmembrane Pressure (TMP), protein transmission, membrane pore size and staining of the membrane after operation to visualize the distribution of biological fouling inside the membrane. For critical flux determination, fluxes of up to 69 LMH were used without exceeding the critical flux. No sign of fouling was observed for the short-term (<3.5 h) critical flux experiment. However, during prolonged operation at 8.3 LMH the TMP jumped to 0.9–0.95 bar, indicating fouling. At this state, the protein transmission remains at the same high level (>88 %). [Display omitted] • Mammalian cell culturing for production of recombinant protein. • Reverse asymmetric membrane hollow fiber filtration in perfusion process. • Critical flux determination in Alternating Tangential Flow Filtration. • Distribution of biological fouling in membrane by staining techniques. • Constantly high protein transmission even though significant fouling is present. [ABSTRACT FROM AUTHOR]

Membrane fouling is considered a persistent challenge in membrane technology for water and wastewater treatment. Membrane surface patterning is a chemical-free means of controlling membrane fouling. Previous studies mainly focused on nano- and micro-scale patterns, with little attention paid on millimeter-scale patterns on the membrane surface. In this study, the millimeter-scale patterned microfiltration membranes with different pattern heights (PM50, PM55 and PM60) were fabricated, the performances in resisting particle deposition and membrane fouling with synthetic wastewater were examined compared with flat-sheet membrane (FM), and the underlying hydrodynamic mechanism was unveiled using computational fluid dynamics (CFD). CFD simulation results reveal that compared to micro- and nano-scale patterns, millimeter-scale patterns exert a notable increase in maximum velocity, average shear stress and maximum shear stress. All the three millimeter-scale patterned membranes exhibit superior resistance to both particle deposition and membrane fouling than FM, owing to the improvement of hydrodynamic properties instead of enlarged membrane area. PM55 shows the lowest flux decline ratios and least particle/foulant deposition among the three millimeter-scale patterned membranes in both particle deposition and membrane fouling experiments. Pattern height plays a crucial role, as small pattern height cannot generate significant vortices, while high pattern height leads to flow separation. For PM55, the vortices form in the valley regions and locate close to bulk flow, which help transport the deposited particles or foulants back to the bulk flow. The design of pattern configuration is suggested to be tailored based on particle size. Future research can focus on the pilot testing of millimeter-scale patterned membranes, as well as the long-term stability with actual influent. [Display omitted] • Millimeter-scale patterns exert a significant impact on overall hydrodynamic properties. • Patterned membranes show enhanced resistance to both particle deposition and fouling. • An optimal pattern height is needed to transfer deposited particles back to bulk flow. • Implications for application of patterned membranes and fouling control are proposed. [ABSTRACT FROM AUTHOR]

Achieving accurate dosing of scale inhibitors in full reverse osmosis (RO) membrane systems for industrial applications is a critical challenge due to a lack of understanding of membrane fouling characteristics. To address this, this study investigated membrane performance at different inhibitor concentrations and proposed a method using ultrasonic phased arrays (UPA) to evaluate the fouling layer's spatial and density characteristics. The study also examined the relationship between fouling reversibility and compaction, and the results showed a clear conversion process from inhibition to exacerbation of membrane fouling by scale inhibitors. Additionally, the fouling layer distribution characteristics were opposite at different concentrations. At insufficient concentrations, the scaling layer forms near the outlet and spreads to the far-end with a continuously decreasing thickness. Conversely, at surplus concentrations, the opposite effect was observed. At sufficient concentrations, the fouling layer thickness and range exhibited a discontinuous distribution. The high-density layer was dominant on the membrane surface and showed low fouling reversibility. However, scale inhibitors were found to minimize fouling density by interfering with ion deposition, reducing the ion content and significantly increasing its reversibility. These findings have significant implications for scale inhibitor efficiency evaluation and scientific application, which can improve industrial membrane system performance. [Display omitted] • The relationship between scale inhibitor concentration and membrane fouling layer characteristics was investigated. • Ultrasonic phased array was introduced to monitor fouling layer spatial and density characteristics. • The membrane fouling layer spatial distribution was significantly affected by the scale inhibitor dosage. • Over dose scale inhibitor increases fouling layer thickness and reduces its reversibility. [ABSTRACT FROM AUTHOR]

Zero liquid discharge (ZLD) strategy provides significant potential for industrial brine treatment. Still, the application has been constrained by the inadequate water recovery and membrane fouling of its membrane-based brine concentration system. Herein, a pilot-scale system was established that integrated pretreatment, reverse osmosis (RO), nanofiltration (NF), and disk tube reverse osmosis (DTRO), and demonstrated over a 6-month operation for the first application in treating steel industry brine. Meanwhile, novel insights were offered into the spatial evolution of DTRO membrane fouling. The overall ZLD system reached ultra-efficient water recovery at 91% with relatively low energy consumption (7.27 kWh/m3). The RO and NF units concentrated the brine and selectively separated ions of different valences, simultaneously eliminating various contaminants. The DTRO unit enriched the highly saline NF permeate with a remarkable 7.5-fold concentration effect, producing an extremely hypersaline brine salinity (138,472 ± 34,804 mg/L, Cl−/SO 4 2− mass ratio of 56) that ultimately yielded ultra-pure NaCl salt. Additionally, DTRO special fouling patterns revealed a distinctive "W"-shaped fluctuation in humic acid along the device water flow, with concurrent reduction in iron/aluminum oxides leading to their deposition at the outlet. This synergistic fouling, coupled with silicon, coincides with the transformation of silica colloids into silicate compounds. The multistage membrane-based strategy and the spatial membrane fouling evolution pattern proposed and investigated in this work provide a highly efficient and cost-effective solution for industrial brine treatment with ZLD. [Display omitted] • A pilot-scale "pretreatment-RO-NF-DTRO" system was established for steel cold-rolling brine treatment. • High concentration and purity NaCl salt solution was obtained while achieving 91% water recovery. • Effects of the RO-NF-DTRO system on resource recovery were studied. • Spatial evolution mechanisms of DTRO membrane fouling for industrial brine treatment were first revealed. [ABSTRACT FROM AUTHOR]

Spiral wound membrane elements for reverse osmosis (RO) seawater desalination are increasingly important to produce clean water to cope with the rising global freshwater scarcity. Spiral wound elements are prone to biofouling development which can be monitored in-situ using optical coherence tomography (OCT). Although OCT has emerged as a dominant technology for nondestructive monitoring of membrane fouling, the application of OCT to study fouling on feed spacers has been limited because image processing of spacers is complex. In this study, an automated image processing algorithm was developed for visualization and quantification of fouling in spacer filled channels. The spacer shadow was used to estimate the location of the spacer in the OCT image. Subsequently, a computed tomography (CT) scan of the same spacer type was overlaid, providing a clear indicator of the spacer position. The spacer position was used to i) correct the distortion below the spacer, ii) visualize fouling in 3D with reference to the membrane and spacer, and iii) reproducibly and precisely locate images to make time series and compare parallel experiments. The results showed that the addition of a spacer geometry as a solid object in a 3D representation of an OCT-scan greatly improves visualization, because fouling and the spacer can be distinguished and the position of fouling relative to the spacer and membrane can be clearly seen. Moreover, the ability to select a dataset relative to the orientation of the spacer will enable objective and automated quantitative analysis in future work. [Display omitted] • Automated combination of spacer geometry (CT) and fouling image (OCT). • Spacer-related coordinates allow reproducible imaging on same location. • Spacer as solid object improves visualization of biofouling. • Image distortion below the spacer is corrected. • Improved image allows more precise numerical analysis. [ABSTRACT FROM AUTHOR]

Atomic scale modeling is crucial for characterizing the interactions responsible for fouling, which is a major limitation in the use of membrane filtration technologies for the recovery of polyphenols. In this work, a methodology to model a porous ultrafiltration polyethersulfone (PES) membrane is presented. Subsequently, various systems containing tannic acid (TA) molecules at different concentrations (9 or 30 g/L) were studied, with two additional systems incorporating a PES membrane, through 100 ns all-atom molecular dynamics simulations. The results show that up to 90% of the TAs are self-aggregated, associated with the formation of intermolecular H-bond and π-stacking interactions. Furthermore, adsorption of 48–67% of the TAs onto PES was observed. TA-PES H-bond and π-stacking interactions are also formed. The number of adsorbed TAs molecules over time and the evolution of the mean size of TA aggregates exhibits similar temporal trends, suggesting a parallel progression in both phenomena. Moreover, the same atoms were involved in both aggregation and adsorption, leading to the conclusion that the two phenomena compete. These results shed light on the fouling mechanism, which appears to occur through the formation of a cake layer combined with adsorptive fouling, and could support the design of new antifouling agents adapted for polyphenol filtration. [Display omitted] • All-atom modeling of a PES membrane with pore size ranging from 3 to 13 nm. • Molecular dynamics simulations on PES membrane and tannic acid were conducted. • Identification of interactions governing the adsorption of tannic acid onto PES. • The competition between tannic acid adsorption and self-aggregation was revealed. [ABSTRACT FROM AUTHOR]

Flux decay is the core factor that affects membrane performance and the long-term operation for emulsion separation. Herein, a double-barrier and multi-functional membrane for emulsion separation was fabricated via in-situ growth of MIL-88A on the Fe-phenolic network. This membrane performs enhanced anti-pollution ability of hydration layer and the self-cleaning ability of photo-Fenton catalysis to ensure high separation performance. Wettability and organic matter degradation performance of the membranes were experimentally determined. It could well implement emulsion separation (flux ∼ 2602.55 LMH; separation efficiency ∼ 99 %) solely by gravity-driven. After a brief photo-Fenton catalysis, the water flux recovery ratios (FRR) of the membrane after 8 cycles (320 min) reach 94.87 % (CTAB-stabilized emulsion) and 89.27 % (SDS-stabilized emulsion), respectively. Interestingly, the flux and FRR of the membrane exhibit a negative relationship when it circularly filters different types of emulsion. Based on the Hermia models analysis, this difference mainly originates from that electrostatic repulsion assists in mitigating irreversible pollution while disfavors rapid demulsification and improving flux. The reverse was true when there was the opposite potential between the membrane surface and emulsions. Meanwhile, a novel optical transmission system is applied to transmit light in cloudy emulsion to achieve long-term operation (90 min). [Display omitted] • M4 was prepared by in-situ growth of MIL-88A on the Fe-phenolic network. • M4 performed an enhanced wettability and self-cleaning ability of photo-Fenton. • M4 could prevent contamination from the process and terminal simultaneously. • The membrane fouling behaviors were analyzed in detail by Hermia models. • A novel optical transmission system could support long-term operation of M4. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) has become an established process for advanced treatment of drinking water, while membrane fouling remains as the main issue slowing the widespread application of the process. In this study, the key foulants were identified, and their spatial distribution and potential interactions were investigated based on a two-stage NF engineering project for municipal drinking water treatment. Over half a year of operation showed that the membrane fouling was mostly chemically reversible. Characterizations of the cleaning waste revealed that inorganic fouling dominated at both stages, which was mainly caused by the deposition of Al, Ca, and Si. While the overall fouling was much more severe at Stage 2, the organic fouling was the reverse. Autopsy of one full-size membrane element from each stage indicated that in addition to Al, P and humic acid-like compounds were abundant in the fouling layer for both stages despite the spatial differences. The spatial distribution of foulants was influenced by both concentration effects and presence of feed channel spacers. For the free membrane area, inorganic foulants and humic acid-like compounds had higher contents at Stage 2 than Stage 1. While for the membrane area contacting with spacers, Al and P at Stage 1 were 0.74 and 1.51 times higher than those at Stage 2, respectively. Moreover, statistical analysis, complexation experiments and engineering operation strongly supported that the residual Al and natural organic matter (NOM) were key foulants for the NF process, mainly by forming Al-NOM complexes. Besides the Al-NOM complexes, condensed phosphate, primarily sourced from the dosed phosphate-containing antiscalants, might also co-precipitate with Al or Al-NOM complexes. [Display omitted] • Membrane fouling was dominated by the reversible inorganic fouling in NF system. • The residual Al and natural organic matter (NOM) were key foulants for the NF process, mainly by forming Al-NOM complexes. • The spatial distribution of inorganic and organic fouling were the reverse. • Feed channel spacers caused local non-uniform distribution of membrane foulants. [ABSTRACT FROM AUTHOR]

The contribution of granules to membrane fouling alleviation in aerobic granular sludge-membrane bioreactor (AGMBR) has been increasingly investigated, yet the inoculated granules in MBR are more unstable than those in conventional AGS system and thus in-depth insight into the effects of the mutual transformation between granules and flocs on membrane fouling as well as corresponding bio-cake formation is necessary. Herein, we found that the disintegration of granules was accompanied by the release of soluble microbial products (SMP) and the increase of microbial diversity. The re-granulation phase occurred when granules gradually re-dominated the sludge system with the growth of biomass and the massive secretion of extracellular polymeric substances (EPS), corresponding to the declined microbial diversity and stable pollutants removal (COD: 93.45–98 %, TN: 21.06–36.86 %). Compared with the granule disintegration phase, less flocs deposition and fewer contents of SMP containing high molecular weight (>100 kDa) compounds in bio-cakes in the re-granulation phase resulted in the longer filtration period, as evidenced by lower attractive interaction energies between sludge foulants and membranes according to extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Microbial community analysis demonstrated higher relative abundance of filamentous bacteria (Thiothrix) and lower relative abundance of denitrifiers (e.g, Hydrogenophag , Trichococcus , Arenimonas , Acinetobacter) in bio-cakes in the re-granulation phase. Besides, the genera Thiothrix , norank_f__env.OPS_17 and Aeromonas may be responsible for the organic foulants accumulation on membrane surface. More importantly, stronger positive correlations among microbial populations between bio-cake and suspended sludge in the re-granulation phase indicated the lower propensity of membrane fouling. The systematic insights into the effects of granules disintegration and sludge re-aggregation on fouling layer may have important implications for the future development of membrane fouling control in AGMBR system. [Display omitted] • AGS disintegration exhibited higher fouling propensity than sludge re-aggregation. • Organic foulants in granule disintegration phase was dominated by high MW SMPs. • Bio-cake in re-granulation phase contained more Thiothrix and less DNBs. • Thiothrix , norank_f_env.OPS_17 and Aeromonas favored organic foulants accumulation. • Positive interactions among microbiota were more intensive in re-granulation phase. [ABSTRACT FROM AUTHOR]

In this study, a novel piezoelectric RO membrane with vibrating mechanism when exposed to an electric field was developed. The vibration due to the piezoelectric effect can disturb the concentration polarization layer on the membrane surface and minimize membrane fouling. Polyvinylidene fluoride (PVDF) which has piezoelectric properties was selected as the porous substrate for a thin film composite (TFC) polyamide RO membrane in this study. Electrical poling was performed to enhance the piezoelectric properties of the PVDF substrate. RO membranes fabricated via interfacial polymerization using different PVDF substrates (i.e., with and without pre-wetting the PVDF substrate, with and without polyethylene terephthalate (PET) non-woven fabric support (denoted as NWF and no-NWF, respectively), with and without electrical poling) were systematically investigated. The results indicated that RO membrane fabricated on poled PVDF-NWF substrate shows reasonable pure water permeability of ∼2 LMH/bar and sodium chloride (NaCl, 2000 ppm) rejection of ∼98.9 % when tested at 15 bar. In the accelerated fouling study using colloidal silica particles (∼20 nm in diameter, 200 ppm with background of 2000 mg/L NaCl), when the RO membrane fabricated using both unpoled and poled PVDF-NWF substrates were excited with AC signal, membrane fouling was significantly reduced. These findings suggested that electrical poling may not be necessary for such piezoelectric RO membrane. [Display omitted] • Novel piezoelectric RO membrane with vibrating mechanism was developed. • Piezoelectric RO membranes fabricated on porous PVDF membrane. • Performance of piezoelectric RO membranes affected by properties of PVDF. • Flux enhancement was observed for piezoelectric RO with non-woven support. • Antifouling behaviors of RO membranes observed when AC signal applied. [ABSTRACT FROM AUTHOR]

This study reveals the importance of the module geometry on the flow field and pressure distribution during membrane permeation for multibore membranes. The pathways of permeation are unraveled within a custom-made multibore single membrane module. For this, we combine flow velocimetry of magnetic resonance imaging (flow-MRI) with computational fluid dynamic (CFD) simulations and permeation experiments. First, a systematic simulation study identifies flow patterns based on simplified geometrical features that are supported experimentally through flow-MRI measurements. This comprehensive study shows how small geometric deviations from the idealistic assumptions result in unexpected fluid flow on the shell and lumen side in the module. Second, the influence of those non-ideal flow patterns during the filtration of silica particles are revealed by MRI. The results indicate heterogeneous silica deposition due to geometry induced flow fields. Contrary to the idealized assumption, the subsequent backwashing is also influenced by those deposition patterns. Hence, unavoidable non-idealities of membrane positioning during the construction of the module influence the performance of the membrane filtration. With this study, we stimulate to analyze and pioneer new strategies to optimize module design and fully recover the membrane's performance after filtration cycles during backwashing. Even more, extensive future studies on multiple multibore membranes can reveal their mutual interaction closing the gap between the single multibore membrane behavior and multibore membrane module properties. Image 1 • Combining capabilities of MRI, flow-MRI, CFD simulations and fouling experiments. • Membrane positioning inside membrane module influence pressure and flow field. • CFD and Flow-MRI unravel pathways of flux and backwashing flow in membrane modules. • Non-ideal membrane positioning in the module causes heterogeneous fouling. • Local effective backwashing flux is reduced due to non-ideal membrane position. [ABSTRACT FROM AUTHOR]

In this study, the application of photoacoustic spectroscopy (FT-IR/PAS) is proposed to investigate membrane fouling phenomena. Ultrafiltration membranes made of polyether sulfone (PES) in modules operated at different flow regimes (dead-end and cross-flow) were used in this paper. Solutions of water-soluble poly(acrylic acid) and suspensions of a natural red clay were used as model media during the filtration tests. The research performed involved the possibility of tracking the in-situ rate of membrane fouling during filtration of these two types of media. Moreover, the influence of the molecular weight of the separated particles on the intensity of the membrane blocking was studied. The results of the experiments showed that fouling phenomena progress for various types of media filtrated is characterized by different particle sizes and can be simply detected using photoacoustic spectroscopy. It was also noted that an increase in the molecular weight of the filtrated medium, e.g., poly(acrylic acid) from 30 to 250 kDa, increased the intensity of membrane blocking of 57 and 87% for membrane installation with dead-end and cross-flow regime, respectively. The performed studies demonstrated that FT-IR/PAS can be also used to assess the efficiency of the methods used for membrane cleaning. The obtained results were confirmed by two other methods: a radiotracer technique and scanning electron microscopy. Image 1 • Photoacoustic spectroscopy was applied to study the rate of membrane fouling. • The impact of molecular weight of PAA on the intensity of membrane fouling was analysed. • Changes in the quantity of deposits formed on the membrane were measured using the PAS method. • Results were confirmed by the radiometric method and SEM analysis. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs), as a group of micropollutants with high toxicity, are commonly detected in the environment and difficult to remove. In this work, five commercial polyamide (PA) nanofiltration (NF) membranes were used to treat three PAHs in the synthetic solution or coking wastewater and their removal mechanisms were discussed. By comparing water permeability and PAHs rejections of the NF membranes before and after PAHs adsorption, we found that the PAHs adsorption into the membrane was the dominant rejection mechanism at the initial filtration stage. Due to the limited adsorption capacity and increasing diffusion of PAHs in the membrane, the PAHs rejections would drop rapidly and then reach steady. Size exclusion mechanism was also important to PAHs removal by NF, especially for PAHs with weaker polarity and higher molecular weight. Although the polysulfone intermediate layer could adsorb substantial PAHs resulting in an increase of filtration resistance, the pore blocking and narrowing effects on the PA separation layer were still the main reasons for the permeability loss of NF membranes. However, the glucose rejection did not change obviously after the PAHs adsorption in the membrane. Through analyzing porosity and pore size distribution of the NF membranes before and after PAHs adsorption, we found that for the NF membrane with small pore size and narrow pore size distribution (e.g. NF270), PAHs adsorption produced indiscriminate pore blocking effect, and thus the average pore size and its distribution as well as glucose rejection did not change obviously after fouling formation; while for the NF membrane with large pore size and wide pore size distribution (e.g. NF10), PAHs adsorption occurred more seriously in the larger pores leading to a pore narrowing effect, but the reduced pore size was still too large to affect glucose rejections. The outcomes of this work suggested that the PAHs adsorption in both separation and intermediate layers of NF membranes should be avoided, and the NF membrane with narrow pore size distribution was preferred for PAHs removal. Image 1 • PAHs adsorption and size exclusion are the main mechanisms of PAHs removal by NF. • PAHs adsorb in both polyamide separation layer and polysulfone intermediate layer. • Membrane permeability loss is mainly attributed to the porosity decrease by PAHs adsorption. • PAHs adsorption produces pore blocking and narrowing effects on NF270 and NF10, respectively. • PAHs adsorbed in the membrane are eluted by chemical cleaning and release to the environment. [ABSTRACT FROM AUTHOR]

Vanadium is an important rare element and has been widely used in metallurgical industry, aerospace industry and chemical industry due to its special physical and chemical properties. In this work we explored the feasibility of using forward osmosis (FO) to concentrate the vanadium leaching solution (VLS) using saturated sodium chloride as the draw solution. The effluent draw solution can be directly reused as a raw material in the vanadium production process without the need for regeneration. The VLS concentration performance was evaluated using commercial thin film composite (TFC) and cellulose triacetate (CTA) FO membranes. It was found that the FO water flux decline was due to the coupled effects of VLS concentration and fouling. TFC membrane exhibited higher initial water flux but also experienced more severe fouling and faster flux decline. Importantly, this study observed an existence of a critical concentration factor (CF) during VLS concentration. Below the critical CF, membrane fouling was mainly caused by surface crystallization and flux decline was relatively milder; above the critical CF, severe bulk crystallization occurred in the feed VLS, which caused significant membrane scaling and dramatical flux decline. The critical CF concept was further used to guide the FO operation for VLS concentration in this study. While severe membrane fouling at a CF above the critical value could be removed by a brief water rinse, operating the FO below the critical CF is preferred for which cyclic VLS concentration process was demonstrated to be feasible without the need for periodic membrane cleaning. Overall, the results suggest that the FO can be a promising solution for highly efficient and low-energy VLS concentration. Image 1 • FO was used for energy-efficient concentration of vanadium leaching solution (VLS). • The existence of a critical concentration factor (CF) was observed for VLS concentration by FO. • Below the critical CF membrane fouling was caused by surface crystallization and flux decline was mild. • Above the critical CF membrane was severely fouled due to bulk crystallization and flux decline was dramatic. • Operating the FO concentration processes below the critical CF is preferred. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate membrane fouling performance of anaerobic side-stream reactor (ASSR) coupled membrane reactors (MBR), and effects of representative enhancement strategy, namely packing carriers and low-strength ultrasonication, on sludge properties and membrane fouling by four pilot-scale MBRs. Compared to anoxic/oxic MBR (AO-MBR) for control, ASSR coupled AO-MBR (ASSR-MBR), ASSR-MBR with ASSR packed with carriers (AP-MBR) and AP-MBR with part of sludge ultrasonicated before fed into ASSR (AUP-MBR) reduced sludge production by 8.4%, 17.5% and 32.9% with efficient pollutants removal. ASSR-MBR showed more severe membrane fouling because inserting ASSR disintegrated sludge floc structure, increased the secretion of extracellular polymeric substances (EPS) and deteriorated viscoelastic property of sludge. Packing carriers in ASSR alleviated membrane fouling of ASSR-MBR by inhibiting EPS-secreting bacteria (Flavobacteriia, γ-Proteobacteria, δ-Proteobacteria and norank_Saccharibacteria), enlarging particle size and improving dewaterability. AUP-MBR showed the most severe membrane fouling and obvious cake layer fouling because ultrasonication disintegrated sludge to small particles, increased adherence property of EPS, and deteriorated dewaterability and viscoelastic property of sludge. MiSeq sequencing revealed Proteobacteria and Bacteroidetes were responsible for membrane fouling at the phylum level, and norank_Neisseriaceae , Arcobacter , norank_Parcubacteria and Mycobacterium were dominant genera easily attached on membrane surface. Image 1 • Membrane fouling (MF) of anaerobic side-stream reactor (ASSR) - MBR was studied. • ASSR-MBR deteriorated MF, dewaterability and flowability due to sludge reduction. • Carriers in ASSR alleviated MF by inhibiting EPS secretion and enlarging particles. • Ultrasonication caused severe MF due to flocs disintegration and high EPS adhesivity. • MiSeq sequencing revealed dominant bacteria easily attached on membrane surface. [ABSTRACT FROM AUTHOR]

Abstract D-amino acid (DAA) an environmentally friendly biofilm inhibitor, has low efficiency for membrane biofouling control due to its instability. To address this challenge, a novel nanocomposite was prepared with DAA adhering to polydopamine (PDA)-coated halloysite nanotube (HNTs) through the interactions of H-bonding and π-π stacking between PDA and DAA. Membrane modified with such nanocomposite was fabricated via blending phase inversion, and the nanocomposite was uniformly distributed in the modified membrane matrix. In comparison with the pristine membrane, the addition of nanocomposites resulted in robust mechanical property for modified membrane with the ultimate stress and strain increased by 23.97% and 35.62%, respectively. Moreover, an excellent tradeoff between water flux (2.5 folds of pristine membrane) and selectivity was achieved, probably due to the improved membrane hydrophilicity. Meanwhile, bovine serum protein (BSA) static adsorption as well as dynamic filtration experiments exhibited excellent antifouling ability of the modified membrane. Most importantly, a superior anti-biofouling stability over a 10-day period was obtained for the membrane modified with nanocomposite, indicating that the activity of DAA to mitigate biofouling was effectively maintained. This study developed a novel and promising strategy for membrane biofouling mitigation. Graphical abstract Image 1 Highlights • A new D-amino acid/polydopamine/halloysite nanotube nanocomposite was synthesized. • A novel nanocomposite-modified membrane was fabricated. • D-amino acid supported on PDA and HNTs effectively mitigated membrane biofouling. • The improved filtration and anti-fouling performances of the modified membrane were obtained. [ABSTRACT FROM AUTHOR]

Abstract In ultrafiltration (UF) applications, the antifouling modification of semi-crystalline poly (vinylidene fluoride) (PVDF) membrane aroused extensive attention. However, efforts have paid less attention to the roles of PVDF polymorphs in fouling alleviation. In this study, we report a new strategy to tailor the polymorphs and pore structure of the PVDF membranes, simultaneously, via incorporating the in-situ blending of Pluronic F127 (F127) with a sodium chloride (NaCl) coagulation bath (CB). The NaCl CBs were utilized to create ion-dipole interactions between Na+ and PVDF molecule chains, and to promote the formation of polar β-PVDF phase during phase inversion process. When cooperated with the NaCl CBs, due to the intensified copolymer-polymer interactions, blending amphipathic F127 was demonstrated more effective in manipulating the membrane morphology compared with blending hydrophilic additives. The prepared membrane possessed a highly porous surface with narrowed size distribution, resulting in a great enhancement for both the permeability and selectivity. Furthermore, isopropanol (IPA) post-treatment was purposely performed to wash out the F127 embedded in the membrane matrix. The dominating β-PVDF phase almost doubled the surface energy of the pure PVDF membrane compared with the α-PVDF phase, especially in electron donor functionality, which endowed the membrane enhanced fouling resistance for natural organic matter. As the fouling resistance introduced by polymer itself is more attractive than by exotic additives due to the better stability, we anticipate this new strategy will have numerous potential applications in the future. Graphical abstract Image 1 Highlights • Ion-dipole interactions induced the formation of polar β-PVDF phase. • Copolymer-polymer interactions played important role in tailoring pore structure. • Dominant β-PVDF phase enhanced membrane electron donor ability and wettability. • Membrane's permeability, selectivity and fouling resistance were simultaneously improved. [ABSTRACT FROM AUTHOR]

Abstract Activated Sludge Membrane Bioreactors (AS-MBR) are recognized as a commercially competitive alternative to conventional wastewater treatments. However, membrane fouling remains one of the main challenges and disadvantages of the process. This study evaluates the suitability of Optical Coherence Tomography (OCT) in monitoring the cake layer development in-situ in AS-MBR under continuous operation. Real-time direct imaging of the cake layer was feasible when limiting the continuous movement of the AS flocs in the reactor by turning aeration off for few minutes prior to scanning a given membrane area. The cake layer morphology was evaluated using both 2D and 3D image analysis. The 3D analysis respect to 2D analysis provided a more representative characterization of the fouling formed in the system. The non-invasive nature of OCT imaging enabled monitoring fouling development over time, where an increase in thickness and a decrease in roughness was observed in the first 200 h of operation. The 3D OCT image analyses were also compared with the 3D confocal laser scanning microscopy (CLSM) image analyses performed at the end of the study. Results demonstrate that OCT imaging can be applied for online, real-time monitoring and analysis of fouling behavior in AS-MBR systems. Graphical abstract Image 1 Highlights • OCT enabled monitoring the fouling in-situ non destructively in real-time in MBR. • The imaging was performed when the reactor aeration was turned off for few minutes. • Fouling deposited on the membrane in the first 120 h was heterogenous. • Over the time the cake layer become thicker and more homogeneous. • 3D analysis respect to 2D analysis was more accurate and more representative. [ABSTRACT FROM AUTHOR]

Abstract Highly enriched grapefruit juice is expected to be obtained through forward osmosis (FO) without degradation of its nutrients. However, this technology is facing several key issues that must be explored to validate the suitability of FO as a dewatering process, namely, membrane performance testing, fouling control, and product quality assessment. In this work, grapefruit juice was dewatered using a commercial thin-film composite FO membrane that exhibited stable performance. The simulation results also suggested that the dewatering could be further enhanced by improving the S value of the current TFC FO membrane. Severe membrane fouling was observed, and it was predominantly due to suspended particles larger than 0.45 μm, such as pectin. However, sustainable osmotic dewatering operation could be attained by implementing appropriate fouling control strategies, such as separating large-sized particles by sedimentation or centrifugation prior to osmosis and recovering the declined water flux by physical cleaning. The dehydrated feed exhibited no significant loss of nutritional value, suggesting that the FO membrane dewatered the juice effectively while retaining its constituents. In addition, the FO process could be further improved to obtain enhanced-quality grapefruit juice by applying pressure to the feed stream or employing a sugar-based draw solution such as glucose. Graphical abstract Image 1 Highlights • This work probed the challenging issues in osmotic dewatering of grapefruit juice. • Stable flux induced by TFC FO membrane can be improved further by reducing S value. • The severe fouling by particulate substances was alleviated by their separation. • Hydraulic flushing well restored the declined flux caused by dissolved matters. • Applying pressure or adopting glucose further reduced the reversely diffused salts. [ABSTRACT FROM AUTHOR]

Abstract This study investigates the performance of a new electrically tuneable polyaniline (PANI) membrane, and shows that this synthesis method has the potential to address key challenges of small-acid doped PANI membranes, including: acid dopants leaching out during filtration and low mechanical strength. The novel in-situ polymerisation used poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), as polymer acid template leads to the formation of inter-polymer complexes of PANI and polymer acid. The developed membranes were comprehensibly evaluated through visual, chemical, mechanical and filtration studies and compared to small-acid doped membranes (PANI-HCl membranes). The PANI-PAMPSA membranes were smooth, acid leach resistant, had higher tensile strength and showed conductivity three magnitudes higher compared to PANI membrane with post cast doping. The developed membrane showed in-filtration performance stability, electrical tuneability (in-situ control of flux and rejection) and fouling removal characteristics under applied electrical potential. Data obtained by SEM, IR spectroscopy, electrical analysis and cross-flow filtration confirm these results. The overall results showed that the proposed membrane fabrication procedure resulted in a significant improvement in performance across a range of critical parameters, including conductivity, stability, flexibility, permeance and fouling removal with additional advantage of being electrically tuneable. Highlights • Defect free PANI-PAMPSA membrane formed from in-situ synthesised PANI-PAMPSA powder. • PANI-PAMPSA membranes overcame acid dopant leaching and membrane brittleness. • The membranes showed significant improvement in permeance under electrical potential. • Application of electrical potential led to removal of fouling from the membranes. [ABSTRACT FROM AUTHOR]