Fouling Of Microfiltration Membranes Research Articles

Development of underwater superoleophobic polyamide-imide (PAI) microfiltration membranes for oil/water emulsion separation

Fouling of microfiltration membranes by the adhesion of oil onto the membrane surface and/or penetration into its pores is a major challenge for effective treatment of oily wastewater. In this study, polyamide-imide (PAI) was used to make hydrophilic and underwater superoleophobic microfiltration membranes via non-solvent induced phase separation technique. Membranes were modified with hydrophilic additives, including polyethylene glycol (PEG, 0.4 and 6 kDa) and polyvinylpyrrolidone (PVP, 10 and 360 kDa) to improve their hydrophilicity further. Oil rejection experiments were conducted for three consecutive cycles at a very low transmembrane pressure (0.5 bar) to evaluate the reusability of the synthesized membranes. The use of additives resulted in a wide range of membrane morphology, porosity, pore size, and surface chemical property, which affected the permeation rate and flux recovery. However, all synthesized membranes showed > 98% oil rejection with permeation rate as high as 210 Lm−2 h−1. Membranes modified with PEG 0.4 kDa, PEG 6 kDa, and PVP 10 kDa had underwater oil contact angle (OCA) above 150° and showed almost 98% flux recovery ratio. In the case of PVP 360 kDa, a lower flux recovery was observed due to a reduced oleophobic property (OCA = 124°). This study proposes a facile approach for the production of high-performance oil-rejecting membranes without employing complex surface modification methods.

Comparison of NLDH and g-C3N4 nanoplates and formative Ag3PO4 nanoparticles in PES microfiltration membrane fouling: Applications in MBR

Development of antifouling membranes for wastewater treatment technology can serve as an economic and efficient approach urgently demanded. Attempts have been made to develop cost-effective blended microfiltration membranes containing ZnAlCu nanolayered double hydroxide (NLDH) or g-C3N4 nanosheets, and Ag3PO4 and NH2-Ag3PO4 nanoparticles with the view of finding the effect of their chemical and structural properties on the membranes performance. The obtained ZnAlCu-NLDH/polyethersulfone (PES) and g-C3N4/PES nanocomposite membranes exhibited the significant flux recovery ratio (FRR), as an antifouling index, of 75.8 and 70.7%, respectively, as compared with the pristine PES membrane having 50.9% of FRR. Inclusion of Ag3PO4 and NH2–Ag3PO4 nanoparticles remarkably increased the permeate flux of the membranes, so that the pure water flux of nanoparticles blended membranes at the pressure of 0.5bar was found to be 292.6 and 319.5Lm−2h-1, respectively, as compared with 229.2Lm−2h-1 for the pristine PES microfiltration membrane. Moreover, the fabricated membrane containing Ag3PO4/NLDH and NH2–Ag3PO4/g–C3N4 nanofillers showed a high flux, wettability and antifouling properties, with regard to the prevention of the interaction of the organic foulant and the hydrophilic membranes. Consequently, the self-cleaning property of nanocomposite blended membranes and the low leaching of nanocomposites could lead to the fabrication of a promising mixed matrix membrane for practical wastewater treatment in membrane bioreactors (MBRs). The increase in the critical flux (CF) also showed the desirable application of the nanocomposite microfiltration (MF) in MBR.

Investigation of the PES microfiltration membrane fouling characteristics for five substances

This article proposes two new concepts, adsorption and rejection accumulation and the membrane fouling efficiency per unit accumulation to quantitatively characterize the membrane fouling capacity of different single substances. The membrane fouling caused by bovine serum albumin (BSA), sucrose, glycerol triacetate, l-glutathione and maltodextrin on a polyethersulfone (PES) microfiltration membrane was studied. The real-time variations in filtrate concentration and transmembrane pressure were measured with an ultraviolet (UV) detector and pressure sensor during constant-flux filtration. The results showed that the PES membrane had rejection effects for the five substances. However, adsorption phenomena on the PES membrane were observed only for BSA and l-glutathione filtration. The membrane fouling capacity depended on the accumulation and fouling coefficient of the fouling component. The adsorption and rejection accumulation over 40 min followed the order of BSA (1441.39 µg·cm−2) > sucrose (908.53 µg·cm−2) > glycerol triacetate (290.29 µg·cm−2) > l-glutathione (145.18 µg·cm−2), while the membrane fouling efficiency per unit accumulation followed the order of l-glutathione (6.06 × 108 m−1·µg−1·cm2)>BSA (2.44 × 108 m−1·µg−1·cm2) > glycerol triacetate (2.08 × 108 m−1·µg−1·cm2) > sucrose (8.41 × 107m−1·µg−1·cm2). Based on these two factors, the membrane fouling was the most severe with BSA, followed by sucrose, l-glutathione and glycerol triacetate. The membrane fouling caused by maltodextrin was severe in the early stage and weakened in the later period due to the periodic formation and collapse of the maltodextrin cake layer on the membrane surface.

Facile surface modification of ceramic membranes using binary TiO2/SiO2 for achieving fouling resistance and photocatalytic degradation

Inorganic surface modification was carried out using a TiO2/SiO2 sol–gel process to enhance photocatalytic activity and to mitigate fouling of alumina microfiltration membranes. Pristine alumina membranes were subjected to TiO2/SiO2 coating with varied TiO2 mole percentages. Upon the formation of the TiO2/SiO2 layer, small changes in the surface morphology, pore size, and specific surface area were detected. Particularly, as the pore size decreased with the decrease in TiO2 content, the pure water permeability also gradually diminished. By examining the binary TiO2/SiO2 compositions, the optimized conditions demonstrating both higher flux performance and greater photocatalytic activity were determined. Thus, the inorganic surface modification by TiO2/SiO2 coating could contribute significantly to the realization of self-cleaning ceramic membranes while extending the membrane cleaning cycle and accelerating productivity.

Study of the effect of morphological structure on microfiltration membrane fouling

Study of the effect of morphological structure on microfiltration membrane fouling

Effect of charged nano-particles on ceramic microfiltration membrane fouling

After the filtration experiment with the SiO2, TiO2, and ZnO nanoparticles (NPs) for 250min, the flux decreased by 68%, 47%, and 48% for the Al2O3 ceramic membrane while it was 61%, 37%, and 26% for TiO2 ceramic membrane. Compared to Al2O3, the presence of TiO2 in the ceramic membrane improved fouling resistance. The 25nm particle size was observed to create the most severe fouling. The results indicated that the filtration of neutral charged NPs exhibited the highest flux in the membranes of either neutral or positive charges when compared to NPs with other charges.

Removal characteristics of organic matter during pretreatment for membrane-based food processing wastewater reclamation

In this study, we investigated coagulants such as polyaluminum chloride (PACl) and ferric chloride (FeCl3) and the combination of a coagulant and powdered activated carbon (PAC) for the removal of dissolved organic matter (DOM) from fish processing effluent to reduce membrane fouling in microfiltration. The efficiency of each pretreatment was investigated through analyses of dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UVA254). Membrane flux and silt density index (SDI) analyses were performed to evaluate membrane fouling; molecular weight distributions (MWD) and fluorescence excitation-emission matrix (FEEM) spectroscopy were analyzed to assess DOM characteristics. The results demonstrated that FeCl3 exhibited higher DOC and UVA254 removals than PACl for food processing effluent and a combination of FeCl3 and PAC provided comparatively better results than simple FeCl3 coagulation for the removal of DOM from fish processing effluent. This study suggests that membrane fouling could be minimized by proper pretreatment of food processing effluent using a combination of coagulation (FeCl3) and adsorption (PAC). Analyses of MWD and FEEM revealed that the combination of FeCl3 and PAC was more efficient at removing hydrophobic and small-sized DOM.

Analysis of organic foulants in the coagulation-microfiltration process for the treatment of Taihu Lake

ABSTRACTThis paper analysed organic foulants in the coagulation-microfiltration process for Taihu Lake treatment. High-performance size-exclusion chromatography (HPSEC) and fluorescence excitation–emission matrices (EEM) were applied to elucidate the influence of characteristics of organics on microfiltration (MF) membrane fouling. Results showed that coagulation pretreatment could extend the operation duration of MF based on the fact that pretreatment could effectively remove macromolecular substances as well as a portion of small molecular weight (MW) organics. The analysis of foulants indicated that organics of strong hydrophobic acids (SHA) and neutral hydrophilic (Neut) fractions (based on hydrophobicity) and medium and small MW components (based on MW distribution) contributed greatly to irreversible fouling. EEM fluorescence analysis of chemical solutions exhibited that aromatic proteins and soluble microbial products were mainly a response to irreversible fouling.

Polyacrylamide in hydraulic fracturing fluid causes severe membrane fouling during flowback water treatment

Sustainable wastewater management strategies are required to further minimize impacts of high-volume hydraulic fracturing (HVHF) as current practices such as reuse or direct disposal have long term limitations. Membranes can provide superior effluent quality in HVHF wastewater treatment, but the application of these systems is severely limited by membrane fouling. However, the key fouling components in HVHF wastewater have not yet been clearly identified and characterized. Here we demonstrate that fouling of microfiltration membranes by synthetic flowback water is mostly due to polyacrylamide (PAM), a major additive in slickwater fracturing fluids. A synthetic fracturing fluid was incubated with Marcellus Shale under HVHF conditions (80 ℃, 83 bar, 24 h) to generate synthetic flowback water. Different HVHF conditions and fracturing fluid compositions generated a fouling index for flowback water ranging from 0.1 to 2000 m−1, with these values well correlated with the peak molecular weight (MW) (ranging from 10 to 1.5 × 104 kDa) and the concentration of high MW components in the water. The lowest fouling index was observed when PAM was further degraded by ammonium persulfate under HVHF conditions, although this is infrequently used with PAM in current fracturing operations. These results highlight the importance of PAM and its degradation products in fouling of subsequent membrane systems, providing insights that can help in the development of effective treatment processes for HVHF wastewater.

Algal fouling of microfiltration and ultrafiltration membranes and control strategies: A review

Abstract Microalgae are ubiquitous in aquatic systems and are a highly diversified group of uni- and multicellular microorganisms. In low pressure-driven membrane systems, these cells and their secretions have a strong tendency to foul membranes and lead to a very low filtration efficiency. A significant amount of investigation on algal fouling of microfiltration (MF) and ultrafiltration (UF) membranes has been conducted in recent years. In this paper, recent knowledge of both MF and UF membrane fouling by microalgal suspensions, including the mechanisms and factors influencing algal fouling control strategies, is reviewed. The main components and properties of microalgae suspension are summarized. As algal cells and algogenic organic matter (AOM) are major foulants in microalgae suspension, their roles in algal fouling are compared and critically assessed. Based on the fouling mechanisms of these cells and AOM, strategies for mitigation of algal fouling are provided in detail, including pretreating feedwater, changing membrane properties, and enhancing hydrodynamic conditions. The breakup and growth of cells and their consequential influences on fouling receive special attention. Finally, useful directions for further work on MF and UF algal fouling are indicated.

Surface water biopolymer fractionation for fouling mitigation in low-pressure membranes

With the widespread application of liquid chromatography with organic carbon detection (LC-OCD) to investigate membrane fouling in low-pressure membranes such as microfiltration (MF) and ultrafiltration (UF), membrane fouling by macromolecular hydrophilic biopolymer fraction has been recognized. In this study, a drinking water source was intensively investigated over 16 months. Membrane filtration using hollow-fiber MF membranes was carried out in constant flux mode with periodic backwashing, and two pretreatments (aluminum coagulation and anion exchange) were examined in terms of biopolymer removal and fouling mitigation. Higher biopolymer removal rates achieved by anion exchange than coagulation did not cause better control of membrane fouling in MF. Coagulation and anion exchange removed different types of biopolymers, which implied diversity in the biopolymer fraction. A modified set-up of LC-OCD analysis in which two different columns were sequentially connected was examined. It was demonstrated that the biopolymer fraction detected as a single peak with molecular weight of > 10,000 Da with the conventional LC-OCD set-up comprised of molecules with a variety of molecular weights including > 1,000,000 Da. It was found that coagulation removed large-size biopolymers with higher fouling potentials; while anion exchange preferentially removed small-size biopolymers with lower fouling potential. Concentration of large-size biopolymers in the feed water collected on different dates correlated with the degree of membrane fouling. In an attempt to generalize the conclusion drawn from the experiments using the specific drinking water source, batch MF tests filtering biopolymers isolated from different drinking water sources were also carried out. Importance of the large-size biopolymer fraction in the evolution of membrane fouling was also suggested with different drinking water sources.

Fabrication of blend polyvinylidene fluoride/chitosan membranes for enhanced flux and fouling resistance

Abstract The fabrication of polyvinylidene fluoride (PVDF) membranes was studied using chitosan as a hydrophilic additive for flux enhancement and stability. Chitosan (CS) was blended with PVDF at 0.5, 1.0, 1.5, 2.0 and 2.5% (w/w) concentration, to prepare mixed matrix membrane using the phase inversion method. CS presence within the polymer matrix was confirmed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The fabricated membranes were also analyzed for their structural and surface characteristics, including pore size distribution, porosity, contact angle, wettability and surface roughness. The water contact angle of the membranes has decreased upon the addition of CS. However, the wettability of the membranes was affected more profoundly due to an increase in their pore size. Microfiltration tests showed that the addition of CS was helpful in the reduction of fouling by bovine serum albumin (BSA). However, membranes with CS content higher than 1.0% endured surface micro-ruptures during the filtration tests due to swelling resulting from high water uptake. This simple method of fabrication of PVDF/CS membranes is a potential solution for the low flux and fouling of common PVDF microfiltration membranes. Furthermore, understanding the impact of CS on the fabricated membranes can facilitate the fine tuning of the membrane properties to achieve higher efficiencies.

Efficient control of membrane fouling in MF by removal of biopolymers: Comparison of various pretreatments

In recent studies on membrane fouling in microfiltration (MF) and ultrafiltration (UF) for drinking water production, hydrophilic macromolecular organics referred to as biopolymers have been shown to be major players in the fouling. In this study, various pretreatments were compared to maximize removal of biopolymers and to control membrane fouling efficiently. Multiple water samples were collected from different drinking water sources and were used in this study. Coagulation using polyaluminum chloride (PACl) was carried out under conditions of different dosages and different pHs and was also carried out in combination with the use of powdered activated carbon (PAC) or magnetic ion exchange (MIEX®) resin. The efficiency of removal of biopolymers was highest by the combination of MIEX® and coagulation regardless of the type of sample. Efficient removal of biopolymers achieved by the combination of MIEX® and coagulation led to efficient control of membrane fouling in MF, which was confirmed by bench-scale filtration tests conducted under a constant flux of 62.5 LMH using commercially available hollow-fiber membranes. Enhanced coagulation with increased coagulant dosage or acidic coagulation (pH = 6) also exhibited good removal of biopolymers in some cases and led to control of fouling. In contrast, the combination of PAC and coagulation sometimes caused more rapid evolution of fouling by forming cake layers on the membrane surface. Results of bench-scale tests showed that the concentration of biopolymers in the feed water correlated well with the degree of physically irreversible fouling, which was dominant in this study. The strong correlation was shown with multiple water samples treated by various pretreatments, demonstrating that biopolymer concentration in feed water is a good index for fouling studies.

Mechanism analysis of powdered activated carbon controlling microfiltration membrane fouling in surface water treatment

The mechanism of powdered activated carbon (PAC) mitigating microfiltration (MF) membrane fouling for surface water treatment was investigated via blocking models, resin adsorption fractionation, high performance size exclusion chromatography (HPSEC) with peak-fitting, and interaction free energy theory. The results identified cake formation as the major mechanism of membrane fouling. Also, PAC pre-treated water showed a relatively lower fouling rate than untreated raw water and PAC had a positive effect on improving membrane flux on account of the enhanced removal of neutral hydrophilic compounds (NEU) and strongly hydrophobic acids (SHA) (based on fractionation), and building blocks and low molecular weight acids (BB&LMW-A) (based on HPSEC). Analysis of the interfacial energy between membrane and foulants via the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory found that AB interaction energy played a dominating role in the components of interaction free energies during MF process. PAC, by decreasing AB interaction energy, could thus control membrane fouling.

Fouling and Cake Behavior of Algal Organic Foulants on Microfiltration Membranes in Various Growth Phases

This study investigated the fouling behavior of algal organic foulants in various growth phases during microfiltration. The characteristics of the algogenic organic matter (AOM) in various growth phases were also determined to identify the membrane foulants on fouled membranes. The results indicated the stationary phase of the Aphanizomenon flos‐aquae and Anabaena flos‐aquae AOMs resulted in the most serious filtration flux, followed by their late exponential and primary exponential phases. The amounts of protein/protein‐like substances, the neutral hydrophilic fraction, and the macromolecular organics (including molecular weight) increased with cultivation time, potentially attributed to increasing membrane fouling. Analysis of organic hydrophobicity, molecular weight distribution and fluorescence excitation–emission matrix indicated that algal organic accumulation is a dynamic process of algal activity, biopolymers such as protein‐like and polysaccharides‐like substances were the major components of membrane foulants for the three algal growth phases. Moreover, pore plugging and cake layer formation were the dominant fouling mechanisms in membrane filtration. Timely monitoring of algal growth in water can be important for effectively predicting membrane fouling in microfiltration.

Impact of algal organic matter released from Microcystis aeruginosa and Chlorella sp. on the fouling of a ceramic microfiltration membrane

Algal blooms lead to the secretion of algal organic matter (AOM) from different algal species into water treatment systems, and there is very limited information regarding the impact of AOM from different species on the fouling of ceramic microfiltration (MF) membranes. The impact of soluble AOM released from Microcystis aeruginosa and Chlorella sp. separately and together in feedwater on the fouling of a tubular ceramic microfiltration membrane (alumina, 0.1 μm) was studied at lab scale. Multi-cycle MF tests operated in constant pressure mode showed that the AOM (3 mg DOC L−1) extracted from the cultures of the two algae in early log phase of growth (12 days) resulted in less flux decline compared with the AOM from stationary phase (35 days), due to the latter containing significantly greater amounts of high fouling potential components (protein and humic-like substances). The AOM released from Chlorella sp. at stationary phase led to considerably greater flux decline and irreversible fouling resistance compared with that from M. aeruginosa. The mixture of the AOM (1:1, 3 mg DOC L−1) from the two algal species showed more similar flux decline and irreversible fouling resistance to the AOM from M. aeruginosa than Chlorella sp. This was due to the characteristics of the AOM mixture being more similar to those for M. aeruginosa than Chlorella sp. The extent of the flux decline for the AOM mixture after conventional coagulation with aluminium chlorohydrate or alum was reduced by 70%.

Fouling of microfiltration membranes by biopolymers

ABSTRACTSuppression of fouling due to biopolymers of relevance to the brewing industry has been investigated. The effects of three model biopolymers: casein (protein), catechin (polyphenol), and dextran (polysaccharide) on fouling of asymmetric 0.65 μm polyethersulfone membranes during direct-flow filtration have been studied. While dextran is successful in disrupting interactions between casein and catechin, the associated reduction in aggregate size does not always result in reduced fouling. Solution conditions such as pH and ionic strength modulate the tendency of the aggregates to adsorb onto the membrane surface. Thus, optimizing solution conditions to suppress adsorption of aggregates is essential for increasing the membrane filtration capacity.

Fouling of microfiltration membranes by flowback and produced waters from the Marcellus shale gas play

There is growing interest in possible options for treatment or reuse of flowback and produced waters from natural gas processing. Here we investigated the fouling characteristics during microfiltration of different flowback and produced waters from hydraulic fracturing sites in the Marcellus shale. All samples caused severe and highly variable fouling, although there was no direct correlation between the fouling rate and total suspended solids, turbidity, or total organic carbon. Furthermore, the fouling of water after prefiltration through a 0.2 μm membrane was also highly variable. Low fouling seen with prefiltered water was mainly due to removal of submicron particles 0.4–0.8 μm during prefiltration. High fouling seen with prefiltered water was mainly caused by a combination of hydrophobic organics and colloidal particles <100 nm in size (quantified by transmission electron microscopy) that passed through the prefiltration membranes. The small colloidal particles were highly stable, likely due to the surfactants and other organics present in the fracking fluids. The colloid concentration was as high as 1011 colloids/ml, which is more than 100 times greater than that in typical seawater. Furthermore, these colloids were only partially removed by MF, causing substantial fouling during a subsequent ultrafiltration. These results clearly show the importance of organics and colloidal material in membrane fouling caused by flowback and produced waters, which is of critical importance in the development of more sustainable treatment strategies in natural gas processing.

Reducing fouling of polyethersulfone microfiltration membranes by corona air plasma

In this study, the surface of polyethersulfone (PES) microfiltration membranes was modified by corona discharge plasma in order to improve the antifouling properties and separation performance of the membranes. For this purpose, the PES microfiltration membranes were fabricated by the vapor-induced phase inversion coupled with the nonsolvent-induced phase inversion technique. The effect of the corona power and exposure time on the surface properties and separation performance of the membranes for microfiltration of skim milk was studied. The analysis of the filtration transport resistances was also performed to evaluate the antifouling performance of the corona-modified membranes. The results indicated that the exposure time and applied power of the corona treatment had effects on the membrane surface modification as the surface hydrophilicity, wettability, and morphology of the membranes were significantly changed depending on the corona modification conditions. Moreover, the analysis of the transport resistances revealed that the cake resistance was the main resistance to transport and the fouling, cake and total filtration resistances for the corona-modified PES membranes were low in comparison to the neat PES membranes, which implies that the fouling tendency of the PES membranes modified by the corona air plasma was considerably reduced.

Influence of microbial floatation on membrane fouling due to particles and organic matters in submerged microfiltration

AbstractThis study investigated the effect of microbubble floatation on the fouling of microfiltration membranes. Synthetic feed solutions containing either kaolin or alginic acid were used for the membrane filtration tests. A dissolve air flotation system using a pump-type microbubble generator was adopted as a pretreatment for microfiltration system. A multi-array submerged membrane filtration system was used to monitor the changes in transmembrane pressure with time under various operating conditions. Turbidity removal efficiency, particle counts, and fouling rate for the microfiltration membrane were measured after the microfiltration floatation. The effect of coagulant dose on the treated water quality and membrane performance was also investigated. Results showed that microbubble floatation without coagulant was effective to reduce membrane fouling by kaolin but it was not very effective to control fouling by alginate. With the aid of coagulant, microbubble flotation could control fouling by alginat...