Initial Fouling Research Articles

Enhanced anti-fouling and selective performance of GO-modified nanofiltration membranes for lithium extraction from salt lake brine

Nanofiltration (NF) is a promising method in lithium extraction from salt lake brine with a high Mg2+/Li+ mass ratio. However, membrane fouling challenges its applicability and productivity. This study incorporated graphene oxide (GO) into the polyamide (PA) selective layer of NF membranes to enhance anti-fouling properties and improve lithium extraction from brine. Membrane structure analyses revealed that 0.002 wt% and 0.01 wt% GO facilitated the interfacial polymerization reaction. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results indicated that the PA selective layers in the GO-0.002 % and GO-0.01 % membranes were denser, smoother, and thinner. In contrast, the addition of 0.05 wt% GO resulted in the Turing structures on the membrane surface. Adsorption kinetics indicated pollutant adhesion in the following order: GO-0.05 % > GO-0 % > GO-0.002 % > GO-0.01 %, which was attributed to calcium-carboxyl complexation, as directly measured by AFM and consistent with carboxyl density. The GO-0.002 % and GO-0.01 % NF membranes demonstrated excellent anti-fouling properties in brines, with lower initial fouling rates and higher flux recovery after cleaning, underscoring the significant role of calcium-carboxyl complexation in membrane fouling. The retention of Mg2+ increased to 95 %, while that of Li+ decreased to below −28 % for GO-0.002 % and GO-0.01 % membranes, indicating promising potential for Mg and Li separation. This study provides valuable insights into developing NF membranes with high Mg/Li selectivity and anti-fouling capabilities for lithium extraction from salt lake brine.

Catechol-Fe(III) complexes modified PVDF membrane for hazardous pollutants separation and antifouling properties

Organic pollutants, such as toluene and xylene, in industrial wastewater negatively impact the environment. Membrane treatment is one of the best methods to reduce impurities in wastewater. Existing membranes that coat the water surface with hydrophilic material only effectively resist the initial fouling, resulting in poor oil and water selectivity. Here we report a simple and efficient method to enhance the water flux and antifouling properties of polyvinylidene fluoride (PVDF) membranes. This method involves developing and applying Catechol-Fe(III) complexes with a rough surface to the PVDF surface. Forming Catechol-Fe(III) complexes on the surface better anchors them to the membrane than the dip-coating method. The PVDF membranes with rough Catechol-Fe(III) complexes are superoleophobic, with an oil contact angle of 152 ° and high permeability, with pure water flux of 10487 Lm‐2h‐1bar‐1 and 1 wt% toluene in water emulsion flux of 4697 Lm‐2h‐1bar‐1. Overall, the straightforward manufacturing process, increased permeability, and outstanding antifouling capabilities of the PVDF membrane incorporating rough nanoparticles offer promising prospects for designing and implementing suitable membranes for oil in water emulsion separation applications.

Flow-through electrode system (FES): An effective approach for biofouling control of reverse osmosis membranes for municipal wastewater reclamation

Emerging electrochemical disinfection techniques provide a promising pathway to the biofouling control of reverse osmosis (RO) process. However, the comparative effectiveness and mechanism of it under flow-through conditions with low voltage remains unclear. This study investigated the effect of a flow-through electrode system (FES) with both direct current (DC) and alternating pulse current (AC) on RO biofouling control compared with chlorine disinfection. At the initial stage of biofouling development, the normalized flux of AC-FES (67% on Day 5) was saliently higher than the control group (56% on Day 5). Subsequently, the normalized fluxes of each group tended similarity in their differences until the 20th day. After mild chemical cleaning, the RO membrane in the AC-FES group reached the highest chemical cleaning efficiency of 58%, implying its foulant was more readily removable and the biofouling was more reversible. The biofouling layer in the DC-FES group was also found to be easily cleanable. Morphological analysis suggested that the thickness and compactness of the fouling layers were the major reasons for the fouling behavior difference. The abundance of 4 fouling-related abundant genera (>1%), which were Pseudomonas, Thiobacillus, Sphingopyxis, and Mycobacterium exhibited a salient correlation with the biofouling degree. The operating cost of FES was also lower than that of chlorine disinfection. In summary, AC-FES is a promising alternative to chlorine disinfection in RO biofouling control, as it caused less and easy-cleaning biofouling layer mainly due to two advantages: a) reducing the regrowth potential after disinfection of the bacteria, leading to alleviated initial fouling, (b) reshaping the microbial community to those with weaker biofilm formation capacity.

Very simple method to produce superhydrophobic stainless steel surfaces at room temperature

The development of superhydrophobic (SHP) and self-cleaning surfaces has gained significant attention due to their potential applications in various fields. This study presents a rapid, simple, and environmentally friendly method for producing superhydrophobic and self-cleaning surfaces on AISI 347 stainless steel. The process involves mild chemical etching followed followed by Plasma Enhanced Chemical Vapor Deposition (PECVD) deposition of a fluorocarbon film using 1,1,1,2-tetrafluorethane (C2H2F4) as a precursor. The resulting surfaces exhibited contact angles (CA) of up to 164° and sliding angles (SA) as low as 3°. Characterization of the surfaces revealed favorable mechanical properties, including a maximum hardness of 1.1 GPa and an elastic modulus of 9.7 GPa. The method offers potential for large-scale applications and anti-fouling purposes, as demonstrated by initial fouling tests. The findings contribute to the development of cost-effective and durable superhydrophobic surfaces with enhanced mechanical strength and corrosion resistance.

Numerical Analysis of the Deposition Characteristics in the Initial Deposition Stage in RSC

The coal gasification syngas cooler is important for recovering the sensible heat generated during coal gasification. The ash layer formed on the heat transfer surface can seriously decrease the heat exchange efficiency. Establishing the initial layer is a prerequisite for massive ash deposition and will accelerate the accumulation of the ash and slag particles. In this study, numerical simulations are conducted to analyze the behavior of ash particles in large-scale industrial equipment. The deposition characteristics during the initial fouling and slagging stage in RSC are explored. The results show that in this stage, ash or slag particles mainly stick on the side wall, and only small particles deposit on the upper cone. The surface energy is the dominant factor influencing the composition of the initial layer. The adhesion ratio of FeS2 and ZnS particles is over ten times higher than that of SiO2 particles. With the decrease of the inlet flow rate and the increase of the inlet swirl velocity, the location corresponding to the maximum deposition proportion moves upward, and the local maximum deposition proportion increases.

The Construction of Alkaline Phosphatase-Responsive Biomaterial and Its Application for In Vivo Urinary Tract Infection Therapy.

Urinary tract infections caused by urinary catheter implantations are becoming more serious. Therefore, the construction of a responsive antibacterial biomaterial that can not only provide biocompatible conditions, but also effectively prevent the growth and metabolism of bacteria, is urgently needed. In this work, a benzophenone-derived phosphatase light-triggered antibacterial agent is designed and synthesized, which is tethered to the biological materials using a one-step method for in vivo antibacterial therapy. This surface could kill gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). More importantly, because this material exhibited a zwitterion structure, it does not damage blood cells and tissue cells. When the bacteria interact with this surface, the initial fouling of the bacteria is reduced by zwitterion hydration. When the bacteria actively accumulate and metabolize to produce a certain amount of alkaline phosphatase, the surface immediately started the sterilization performance, and the bactericidal effect is achieved by destroying the bacterial cell membrane. In summary, an antibacterial biomaterial that shows biocompatibility with mammalian cells is successfully constructed, providing new ideas for the development of intelligent urinary catheters.

New insight in algal cell adhesion and cake layer evolution in algal-related membrane processes: Size-fractioned particles, initial foulant seeds and EDEM simulation

A clear understanding of algal cell adhesion and cake layer evolution in algal-related membrane processes (ARMPs) is urgently required to mitigate the membrane fouling. In this study, the effect of microparticles (10 μm–30 μm), subvisible particles (0.45 μm–10 μm), and ultrafine particles (50 kDa-0.45 μm) on the membrane fouling were explored based on the filtration performance through Hermia models, thermodynamic analysis, and simulation of extended discrete element method (EDEM). The results illustrated that microparticles played an important role in algal cell aggregation and the formation of initial clusters. Intermediate blocking fouling occurred when filtrating the subvisible particle, which facilitated internal adhesion and enhanced biofilm formation. In addition, the interfacial attractive force for the initial algal adhesion was obviously increased when the membrane surfaces were in high concentration of protein and polysaccharide. Moreover, the EDEM simulation demonstrated that subsequent particles, particularly the particles with small sizes, preferred to occupy the spaces among the previously deposited particles. This study provided new insights into the contributions of size-fractioned particles to initial fouling and their influence on the successive adhesion of other contaminants.

Comparison of membrane fouling induced by protein, polysaccharide and humic acid under sodium and calcium ionic conditions

To further compare the effect of sodium and calcium on the membrane fouling mechanism of typical organic matters, the adsorption behavior of sodium alginate, humic acid and bovine serum albumin on PVDF membranes were explored by quartz crystal microbalance and dissipation (QCM-D), while the adhesion force between foulants and between the foulants and membrane were examined by using atomic force microscopy (AFM) detection with foulant-coated probes. Results demonstrated that the adhesion force between organic and membrane had significant impact on the adsorption rate at the initial fouling stage, whereas the interaction force among the organic was connected with the degree of irreversible fouling and the structure of the fouling layer. Ca2+ made organic fouling more severe and irreversible due to the complexation effect under the same ionic strength conditions, which is consistent with the XDLVO theory. Compared to the other two organics, BSA demonstrated deposition more in mass, higher in adsorption rate and irreversibility under both Ca2+ and Na+ conditions, which attributed to stronger interaction forces among BSA molecules and the thus formed denser fouling layer. During the adsorption process the pseudo-second-order agreed well with fouling behavior of SA and BSA, while HA conformed to the pseudo-first order kinetic model.

Impact of polysaccharide and protein interactions on membrane fouling: Particle deposition and layer formation

Membrane fouling, which limits the application of membrane bioreactors, has received considerable research attention in recent years. In this work, filtration modeling was performed in combination with surface plasmon resonance (SPR) analysis to investigate the membrane fouling mechanism. Sodium alginate (SA) and bovine serum albumin (BSA) were used to perform dead-end filtration on hydrophilic and hydrophobic poly (vinylidene fluoride) (PVDF) membranes. The initial foulant deposition and layer formation on membranes as well as the interaction between the BSA and SA were comprehensively analyzed. Results indicated that during SA filtration, initial fouling on hydrophilic membranes were primarily attributed to the particle–membrane interactions, while the fouling on the hydrophobic membrane were dominantly caused by the interactions among SA particles. The interaction between BSA and SA led to more severe membrane fouling and hydrophobic membrane was more sensitive to it, especially in the initial filtration process. The SPR results helped clarify the in-situ deposition behavior of BSA and SA particles on the PVDF surface. Compared to SA, BSA adsorbed faster on the PVDF membrane, and specific interactions played an essential role in BSA adsorption, whereas the deposition of SA on PVDF could be easily removed by shear force. Interactions between BSA and SA could alleviate the bonding between BSA and the PVDF membrane.

Influence of Solute Size on Membrane Fouling during Polysaccharide Enrichment Using Dense Polymeric UF Membrane: Measurements and Mechanisms.

Fouling mechanisms associated with membrane-based polysaccharide enrichment were determined using a dense ultrafiltration (UF) membrane. Dextran with different molecular weights (MWs) was used as a surrogate for polysaccharides. The influence of dextran MW on fouling mechanisms was quantified using the Hermia model. Flux data obtained with different dextran MWs and filtration cycles were plotted to quantify the more appropriate fouling mechanisms among complete pore blocking, standard pore blocking, intermediate pore blocking, and cake filtration. For 100,000 Da dextran, all four mechanisms contributed to the initial fouling. As the filtration progressed, the dominant fouling mechanism appeared to be cake filtration with a regression coefficient (R2) of approximately 0.9519. For 10,000 Da, the R2 value for cake filtration was about 0.8767 in the initial filtration. Then, the R2 value gradually decreased as the filtration progressed. For 6000 Da, the R2 values of the four mechanisms were very low in the initial filtration. However, as the filtration progressed, the R2 value for cake filtration reached 0.9057. These results clearly show that the fouling mechanism of dense UF membranes during polysaccharide enrichment can be quantified. In addition, it was confirmed that the dominant fouling mechanism can change with the size of the polysaccharide and the duration of filtration.

Improving membrane filtration performance through time series analysis

For ultrafiltration, and membrane filtration more generally, the quantitative determination of the modes of fouling remains a subject of great interest. Herein an integral method for determining the modes from a time series of volumetric flux Jleft(tright) is given and illustrated with previously published filtration data of bergamot juice (Ruby-Figueroa et al (J Membr Sci 524:108-116, 2017)). The integral method of fouling analysis has the potential to become the cornerstone of a robust empirical process. In addition to determining, in a clear-cut manner, the point at which there is a switch from one mode to another, the robust methodology yields characteristic Jleft(tright) equation for each mode that are an excellent fit to the data. The emphasis is upon the creation of a robust methodology which is best viewed as being a semi-empirical method that is indicative of the modes of fouling. For the example chosen, the initial 4 L/m2 generates some pore blocking after which the main mode of fouling is cake build-up. The variation of overall resistance with time is also informative and analysis of this series was used to check the result for the initial phase of fouling as determined from the time series of volumetric flux. A comparison against the ARIMA (Autoregressive integrated moving average) method, which has never been previously undertaken, is given herein. The integral method of fouling analysis was found to be superior, in part because of the quality of fit to the data and in part because it enables one to establish whether the initial fouling is different in character from the subsequent fouling. Having this information can improve membrane selection and overall membrane filtration performance.

Interfacial Chemistry Investigation of Initial Fouling Conditions in Isocyanate Production: The Antifouling Performance of AISI 316L Stainless Steel.

The fouling of AISI 316L stainless steel during themanufacture of polymeric methylene diphenyl diisocyanate (pMDI) has been investigated. Studies have been carried out using a laboratory-based rig that simulates the process chemistry of the production plant. A variety of solution concentrations and treatment times have been employed to represent different stages in the production process. Following exposure, steel coupons have been removed and studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The thickness of the fouling layer, determined by XPS, is found to vary inversely with exposure time and solution concentration. This is a result of the solubility of the different pMDI derivatives that have been formed at different stages, and a reaction scheme is developed to explain these inverse relationships. ToF-SIMS indicates the formation of metal chlorides as a result of the initial treatment of the steel in the reaction vessel with hydrogen chloride. Fragment ions characteristic of reacted and unreacted pMDI (at m/z = 106 and 132 au, respectively) were used as an indicator of the degree of reacted isocyanate groups within the fouling layer and show a decrease with increasing exposure time, as a result of the formation of intermediates such as amines, ureas, carbodiimides, and uretonimines. The ToF-SIMS data was also processed by principal component analysis (PCA). This generally reinforced the conclusions reached by XPS and ToF-SIMS but, in addition, gave confidence in the repeatability of the analyses with the repeat data (of four analyses) clustering very tightly in the PCA score plots.

Development of a new method to evaluate critical flux and system reliability based on particle properties in a membrane bioreactor

Membrane fouling occurs when the operating flux exceeds a certain point (i.e., critical flux). Critical flux has therefore been widely adopted to determine the initial operating flux in membrane bioreactor (MBR) processes. The flux steeping method currently used to measure the critical flux is time-consuming and uneconomical. This study was conducted to develop a novel approach for the evaluation of critical flux. Given that particle fouling is dominant during the initial fouling stage, we hypothesized that particle properties may be closely related to critical flux. A critical flux prediction model with an R2 of 0.9 was therefore derived, which indicates that particle properties regulate critical flux. The results imply that most of the fouling potential during the early stages of operation is caused by SS, and that the formation of cakes that comprise large particles is the dominant fouling mechanism. The new method proposed in this study reduced the measurement cost and time to evaluate critical flux by 3.5-and 8 times, respectively, compared to the flux-stepping method. In terms of practical application, the applicability of the model equation was identified by system reliability analysis, which indicates that the system failure increases significantly as the standard deviation of the variables increases. This study demonstrated that the prediction of critical flux and system reliability can be achieved through particle characteristic measurement. A similar approach is expected to be employed in real MBR plants as an economical and convenient fouling control strategy to solve problems involving resource shortages.

Development of a fluid dynamic gauging method for the characterization of fouling behavior during cross-flow filtration of a wood extraction liquor

A method based on fluid dynamic gauging (FDG) was developed to investigate the membrane fouling behavior of streams containing dissolved wood components and small particles extracted using a mild steam explosion pretreatment. Industrially chipped softwood was subjected to saturated steam at 7bar for 20min, followed by cross-flow filtration of steam explosion liquors using 10kDa polysulfone membranes at 2bar transmembrane pressure. The results showed a severe decline in permeate flux during the initial stages of the cross-flow filtration. The FDG profiles from five filtration experiments revealed that thicker fouling layers were formed during initial fouling on pristine membranes compared to subsequent fouling on non-pristine membranes. The difference in fouling behavior suggests that cake layer formation was dominant during initial fouling, whereas pore blocking was more pronounced during refouling. This study highlights how FDG can be used to gain a better mechanistic understanding of the fouling behavior of extracted wood components.

Natural organic matter separation by forward osmosis: Performance and mechanisms

The purification performance of a forward osmosis (FO) membrane on natural organic matter (NOM) contained in real surface water by was investigated systematically. FO could reject the natural dissolved organic matter (DOM) effectively with removal efficiencies of approximately 99.0%. When the natural water samples (e.g., raw surface water) had lower fouling tendencies, the active layer facing the draw solution (AL-facing-DS mode) provided a higher water flux than that in the alternative membrane orientation because the isoflux point occurred later in the process. It was found that the concentration of calcium ions had a more severe effect on decreasing the fouling flux of the FO membrane than that of the organic foulant. Furthermore, the concentrated feed solution had a more significant effect on the fouling flux decline of the natural DOM containing more small molecules than natural DOM containing more macromolecules. Additionally, the fouling that occurred in the AL-facing-DS orientation was compensated by the reduced internal concentration polarization (ICP) level based on the occurrence of the critical compensation point. It was also revealed that the permeation drag caused by the water flux and the chemical interactions induced by the feed solution pH and the calcium ion concentration played a significant role in the adsorption of small natural DOM molecules in the porous structure of the FO membrane. Based on the analysis of the interfacial free energies, the interactions between the natural DOM and the surface of the support layer dominated the initial fouling of the FO membrane, while subsequent fouling was controlled by the interaction between the approaching DOM molecules and the already adsorbed DOM.

Pre-chlorination effects on fouling during microfiltration of secondary municipal wastewater effluent

Chlorination-induced changes in the physicochemical characteristics of effluent organic matter (EfOM) and their role in fouling of hollow fiber polyvinylidene fluoride (PVDF) microfiltration membranes during wastewater reclamation was mechanistically investigated. Pre-chlorination strongly influenced pressure rise during constant flux forward filtration as well as hydraulically irreversible fouling by backwashing with low doses exacerbating it and high doses alleviating it. Dose-dependent fouling trends originated from alterations in EfOM size and polarity and consequently its interactions with the membrane based on whether applied chlorine concentrations were above or below a threshold value. Variations in macroscopic phenomena such as sorption tendency, streaming potential, and initial fouling upon exposure to pre-chlorinated EfOM were consistent with favorable adhesion energies calculated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Progressive fouling even though XDLVO theory predicted unfavorable EfOM-EfOM cohesive energies under all chlorination conditions demonstrated that hydrodynamics (permeation drag) dominated later stages of fouling. EfOM in the raw wastewater was largely deposited on the membrane surface resulting in compressible cake filtration. In contrast, pre-chlorination fragmented EfOM leading to intrapore fouling (standard blocking) at the beginning stages of filtration later transitioning to surface fouling (intermediate blocking).

Insights into the roles of membrane pore size and feed foulant concentration in ultrafiltration membrane fouling based on collision-attachment theory.

Membrane property and feed characteristics play critical roles in membrane fouling. This paper aims to clarify the roles of membrane pore size (φ) and feed foulant concentration (Cb ) in ultrafiltration fouling induced by polysaccharides. The fouling behaviors were expounded by collision-attachment theory, where the rate of membrane fouling is mainly determined by collision frequency (JCb ) and attachment efficiency (γ). At the initial fouling stage, rapid flux decline was observed at large φ or high Cb due to the great JCb and/or γ. At the later fouling stage, there existed a nearly identical maximum stable flux attributing to the same JCb and γ, which was independent of φ and Cb . Moreover, the smaller φ can lead to less foulants passed through the membrane and thus more foulants attaching on the membrane, while the higher Cb can give rise to more foulants on both the membrane surface and in the permeate. The results presented in current study provide fundamental basis in understanding membrane fouling. PRACTITIONER POINTS: Collision-attachment theory was employed to expound the UF fouling behavior. Rapid flux decline occurred at large membrane pore size or high feed foulant concentration in the initial fouling stage. Membranes with different pore size or feed foulant concentration had an identical flux at the latter fouling stage. Lowering membrane pore size or increasing feed foulant concentration can lead to more foulants attaching on the membrane surface.

Quantifying the dynamic evolution of organic, inorganic and biological synergistic fouling during nanofiltration using statistical approaches

The dynamic process of membrane fouling was characterized during relatively long-term (30 d) continuous nanofiltration (NF) of a real wastewater secondary effluent, with the roles of organic, inorganic and biological foulants quantified via statistical analyses. The analyses were based on time-series data of physical properties (morphology, roughness, hydrophilicity and charge), chemical compositions (X-ray and infrared responses) and biomass (adenosine triphosphate, ATP) on the membrane surface during fouling evolution. The individual and interactive contributions of organic factor (typical functional groups), inorganic factor (Ca as a representative) and biological factor (ATP amount) to fouling were quantified via multiple linear regression coupled with variance partitioning analysis. About 78% of the variance of filtration resistance can be explained by these factors, among which 16% was contributed by individual effect of organics (via e.g. physical adsorption), 21% by organic-inorganic binary effect (in the form of e.g. Ca-complex), 13% by organic-biological binary effect (organics as the nutrient/product of microorganisms), and 24% by organic-inorganic-biological ternary interaction. Organic matter was universally involved in these effects. The interrelations among fouling factors, foulant layer properties and filtration time were comprehensively explored via redundancy analysis, which clearly delineated the fouling evolution into three major stages: Stage I (0–1 d) for initial fouling mainly due to rapid organic adsorption; Stage II (1–10 d) mainly for the gradual growth of Ca-organic combined fouling; and Stage III (10–30 d) for the eventual maturation of biofouling. These may provide foundations for a targeted fouling control based on foulant type or fouling stage.

Characterization of the Initial Fouling Layer on the Membrane Surface in a Membrane Bioreactor: Effects of Permeation Drag.

In this study, the properties of the initial fouling layer on the membrane surface of a bioreactor were investigated under different operating modes (with or without permeate flux) to improve the understanding of the effect of permeation drag on the formation of the initial fouling layer. It was found that protein was the major component in the two types of initial fouling layers, and that the permeation drag enhanced the tryptophan protein-like substances. The attraction of the initial foulants to the polyvinylidene fluoride (PVDF) membrane was ascribed to the high zeta potential and electron donor component (γ−) of the membrane. Thermodynamic analyses showed that the permeation drag-induced fouling layer possessed high hydrophobicity and low γ−. Due to permeation drag, a portion of the foulants overcame an energy barrier before they contacted the membrane surface, which itself possessed a higher fouling propensity. A declining trend of the cohesive strength among the foulants was found with the increasing development of both fouling layers.

Fouling behavior of isolated dissolved organic fractions from seawater in reverse osmosis (RO) desalination process

Organic fouling is still elusive in seawater reverse osmosis (SWRO) desalination process. Classifying organics in seawater will provide an in-depth understanding of the important fraction on RO fouling. In this study, dissolved organic matter (DOM) in seawater was fractionated and concentrated by membrane technique into three major fractions (i.e., biopolymer fraction, humic substance with building block fraction, and low molecular weight fraction) by their molecular weight (MW) according to the definitions in liquid chromatography with organic carbon detection (LC-OCD) method. Overall recovery of >80% was attained. The isolated organic fractions were compared with common model foulants such as sodium alginate (SA), bovine serum albumin (BSA), and humic acid (HA), in terms of chemical analyses using fluorescence-excitation emission matrix (FEEM) and LC-OCD, as well as their fouling potentials. SWRO fouling experiments were carried out and fouling mechanism was investigated by atomic force microscopy (AFM) method and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Results showed that initial fouling (i.e., foulant-membrane interaction) was the main driver in SWRO organic fouling with biopolymer fraction as the major contributor followed by low molecular weight fraction. In addition, divalent ions was found to enhance the RO fouling by increasing the adhesion and cohesion forces between foulant-membrane and foulant-foulant.