Fouling Of Microfiltration Membranes Research Articles

Effects of Pore Size and Surface Modification on the Alumina Microfiltration Membrane Fouling in MBR with Backwashing

Effects of Pore Size and Surface Modification on the Alumina Microfiltration Membrane Fouling in MBR with Backwashing

Application of coagulation-microfiltration for membrane fouling mitigation in highly saline dyeing wastewater: Anti-fouling modification of membrane and novel insight of salt into regulation of cake layer formation

Cake layer formation is the dominant microfiltration (MF) membrane fouling mechanism after long-term operation. The regulation of cake layer characteristics is less clarified in the coagulation-microfiltration (CMF) technique due to an incomplete understanding of flocculation mechanism; however, gaining such insight will contribute to improving MF efficiency for water purification. Herein, an antifouling MF membrane for high saline textile wastewater was constructed using polydopamine (pDA) co-deposition with sodium p-styrenesulfonate (SS), and methoxypolyethylene glycols (mPEG). Thereafter, the cake layer formation in the CMF technique could be precisely regulated by adjusting salt concentration (NaCl or Na2SO4). Results indicated that the inorganic salt-induced transformation of flocculation mechanism endows a desired regulation of cake layer characteristics, consequently leading an increase in membrane flux. Various properties and formation of flocs were caused via different flocculation mechanisms (from predominant charge neutralization to integrated interaction) in response to a salt variation, giving rise to a directed transition behavior of cake layer formation from compact to porous structure. Particularly, the coagulation mechanism was validated by the experimental analysis and molecular dynamics simulations. Furthermore, the high salt permeation (>90%) and acceptable dye rejection (>98%) of two commercial reactive dyes could be obtained by the proposed CMF technique, exhibiting a satisfactory fractionation behavior of dyes/inorganic salt. A beneficial contribution is the direct reuse dyeing of NaCl from the spent dyeing bath in new dyeing operations. These results could provide a further understanding of the underlying mechanisms of coagulation-enhancing MF behavior and inspire the precise regulation of cake layer characteristics to achieve efficient MF.

Effect of granular activated carbon adsorption on mitigating microfiltration membrane fouling by algal organic matter

Abstract Algal blooms can seriously affect the operation of water treatment processes including low-pressure (micro- and ultrafiltration) and high-pressure (nanofiltration and reverse osmosis) membranes mainly due to the accumulation of algae-derived organic matter (AOM). This study investigated the effect of granular activated carbon (GAC) pretreatment on PVDF microfiltration performance for the removal of AOM. Dissolved organic matter (DOM) solution of commercial humic acid, extra- and intracellular organic matter from two species of algae, and Cyanobacteria were used for the investigation of the fouling potential of the membrane. A comparison study of different DOM removal and fouling behaviors of microfiltration (MF) after GAC adsorption as pretreatment was evaluated under variable GAC dosage and solution pH. Almost 15–20% improvement in flux and decline in irreversible fouling occurred due to the pretreatment using 1.0 g/L of GAC for an hour. The intracellular material caused higher membrane fouling than humic acid due to the hydrophilic nature of the AOM. Membrane fouling and decline in flux increased with increasing pH in the range of 5.0–8.0. The comparison results might help to provide insights into the real challenge of dealing with the treatment of algal-laden water.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks.

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Rejection and fouling of track-etched microfiltration membranes by Acholeplasma laidlawii: Clues to mycoplasma behavior during “sterile” dead-end filtration

Mycoplasma contamination is commonplace during processing of biopharmaceuticals necessitating its sterile filtration. Consequently, we measured the passage of Acholeplasma laidlawii (a small bacterium lacking cell wall like mycoplasma) across track-etched membranes rated at 100 nm and 220 nm that are designated as “sterile filters” and analyzed the entire progression of fouling beginning with pore occlusion before transitioning to a cake. Initial biofouling was quantified to be intermediate blocking before bacteria formed highly compressible cakes. Under identical experimental conditions, phase inversion membranes of the same nominal pore rating rejected A. laidlawii to a significantly greater extent suggesting depth filtration and capture within the polymer matrix in contrast to surface capture by their track-etched counterparts. A facile fluorescence microscopy method to rapidly detect slow-growing A. laidlawii cells was demonstrated under conditions of low retention. Evidence of cake relaxation by depressurizing the filter and subsequent mobilization of individual cells upon re-pressurization is given. Multiple lines of evidence demonstrated the pressure-induced deformation of individual cells resulting in their incomplete rejection by membranes with pore ratings smaller than the bacterium's unstressed diameter: (i) complete retention of rigid silica colloids of similar size, shape, and zeta potential regardless of pressure in contrast to incomplete A. laidlawii removals, (ii) reduced bacterial removal by both membranes with increasing filtration pressure, (iii) 150–600 fold less permeable bacterial cakes at any given pressure compared with silica cakes, and (iv) presence of flattened and irregularly shaped A. laidlawii cells in electron micrographs whereas they were near perfect cocci at atmospheric pressure.

Modeling and mitigating fouling of microfiltration membranes for microalgae dewatering

Dewatering is energy-intensive for microalgae production, and microfiltration (MF) membranes are attractive because of their high energy efficiency. However, the membranes suffer from fouling by organic matter in the algae solutions, and there needs fundamental understanding of membrane fouling with actual algae solutions. Herein we thoroughly evaluate the dewatering performance of commercial polyethersulfone (PES) MF membranes using an integrated experiment and modeling approach. The effect of algae concentration, testing time, feed flow rate, and chemical cleaning on the dewatering performance and fouling-layer morphology are investigated. The fouling behavior can be successfully described using the Hermia and gel layer models with a gel concentration of 48 g/L for algae solutions. Furthermore, the PES membrane surface was grafted with hydrophilic zwitterions, which mitigated the fouling. For example, when challenged with 10 g/L algae solution in dead-end cells, the pristine and modified membrane exhibit water permeance of 80 and 170 L m−2 h−1 bar−1, respectively. Three cycles of dewatering and NaOH cleaning were performed to demonstrate the promise of the MF membranes for practical dewatering application.

Improvement of permeation flux by evaluating the effects of coagulated-humic acids flocs and pH during coagulation-microfiltration hybrid process for water treatment: Performance, fouling modeling, specific energy consumption, and processes comparison

The objective of this study is to analyze the relation between flocs shape and the permeation flux stability in a pilot-scale Coagulation/Flocculation-Microfiltration hybrid process for humic acids removal from water under different coagulant dose and pH values. Besides, the treatment performance was examined. The results showed that at pH 7.1 and polychloride of aluminum coagulant of 10−1 mmol Al.L−1, coagulation/flocculation was effective in maintaining membrane permeability flux. Also, UV254, TOC, and turbidity removal efficiencies were almost ≥ 90%. In addition, this condition proved a potent effect on residual aluminum control and specific energy consumption, where they were, respectively, 0.0852 kWh.m−3 and 20 µg.L−1. Furthermore, humic acids fouling using four Hermia mechanisms (individual and combined) was modeled. Complete pores blocking and cake filtration appeared to be the major mechanisms of microfiltration membrane fouling. Finally, this hybrid process was compared with the most used technologies for the humic acids removal from water. It was concluded that the former process is more reliable, efficient, and cost-effective.

Microfiltration pretreatment of polymer-flooding produced wastewater before desalination: Role of Ca2+ and Mg2+ in membrane fouling

To better control membrane fouling during microfiltration pretreatment of polymer-flooding produced wastewater (PFPW) before desalination, an accurate elaboration of the fouling mechanisms of anionic polyacrylamide (APAM) in high-salinity environments is vital. Herein, the effects of divalent cations (Ca2+ and Mg2+) on APAM-induced membrane fouling were comprehensively investigated. Both Ca2+ and Mg2+ aggravated membrane fouling. The pseudo-stable flux decreased from 0.38/0.38 to 0.35/0.32, 0.28/0.25, 0.23/0.20, and 0.19/0.15 as the ionic strength of Ca2+/Mg2+ increased from 0 to 1000, 2000, 5000, and 10,000 mg/L. Results of fouling resistances, morphology images of fouled membranes, and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory supported this. In comparison with hydrated Mg2+, the charge density of hydrated Ca2+ is larger, which provides more efficient electrostatic screening. Moreover, Ca2+ can coordinate with APAM carboxylate to form APAM-Ca2+ complexes with a regular porous structure. Consequently, under identical ionic concentration, APAM-Ca2+ could provide weaker osmotic pressure. Accordingly, lower fouling resistances, rejection rates, and higher flux recovery rates were achieved in the case of Ca2+. This study distinguishes the roles of Ca2+ and Mg2+ in microfiltration membrane fouling by polymeric organics, which will be targeted to guide the efficient microfiltration process of PFPW before advanced desalination.

Application of the radiotracer method to study the fouling of tubular microfiltration membranes

This paper presents a study on the fouling of ceramic microfiltration (MF) membrane. Such membranes are often used in the treatment of liquid radioactive waste. In the investigation of the phenomenon of fouling, a radiotracer method with a short-lived lanthanum isotope (140La) is applied. The effect of the molecular weight (MW) of the complexing agent, used to bind the radionuclides in the MF-enhanced process, was studied in radiotracer experiments. Poly(acrylic acid) with a MW of 30 kDa, 100 kDa and 250 kDa is used as the complexing agent. The distribution of particles with different MWs at various positions along the membrane module is examined. The test results show that the particles with the lowest MW (i.e. 30 kDa) blocks the membranes the quickest, causing the greatest decrease in the permeate flux. However, the amount of deposit formed on the membrane, which is reflected by the level of radioactivity measured, is the lowest in this case. This indicates the existence of different membrane blocking mechanisms, which depend on the size of the particles contained in the filtered medium.

Influence of foulant particle shape on membrane fouling in dead-end microfiltration

In view of the proliferating applications involving membrane-based separation, the inevitable membrane fouling phenomenon is well-studied. However, the influence of foulant shape on membrane fouling remained incompletely understood. Therefore, the goal of this study was to investigate the fouling behaviors by three different shapes of latex particles (namely, peanut, pear and sphere) with similar mean diameters in the range of 3.5–3.8 μm. External and internal fouling were studied using polycarbonate track-etched (PCTE) membranes with nominal pore sizes of 2 and 8 μm, respectively. Flux data were taken, and fouling models, optical coherence tomography (OCT) and field-emission scanning electron microscope were employed. Regarding external membrane fouling, the sphere-shaped particles displayed the worst flux decline, which is tied to the greatest tendency to deposit on the membrane pores, as revealed by the network fouling model. As for internal fouling, the flux decline curves were more similar among the particle types. The fouling model shows the sphere-shaped particles gave the densest internal cake, which caused slightly steeper flux decline in the latter part of the filtration. Furthermore, OCT indicates that the highest fouling fractions at 7.5 μm below the membrane were exhibited for the peanut-shaped particles, which is due to the preferential vertical orientation resulting in deeper penetration. Results here highlight the non-negligible influence of foulant particle shape, which warrants further understanding and accounting for membrane fouling studies. • Used OCT to reveal influence of foulant particle shape on membrane fouling. • Spheres were more prone to pore-blockage and thus gave worst flux decline. • Non-spherical particles gave less dense internal cakes due to rotational effects. • Peanut-shaped particles penetrated deeper due to preferential vertical orientation. • Particle shape affected flux decline more when external fouling was dominant.

Pre-depositing versus mixing powdered activated carbons for gravity-driven membrane systems during treated domestic wastewater filtration: Permeability stabilization and removal performance

Pre-deposition of powdered activated carbons (PACs) is an effective method to improve the permeate quality of gravity-driven membrane (GDM) system but always with a limited or even negative effect on its fouling behavior. PAC dosing strategies play dominant roles on the fouling of microfiltration and ultrafiltration membranes under constant flux mode, owing to the alteration of PAC-membrane interactions. Hence, how to further increase the membrane flux in the PAC-GDM system needs more investigation. In this study, the effects of PACs on the fouling by treated domestic wastewater were evaluated during GDM filtration using three different PAC dosing strategies: pre-depositing PACs onto membrane surfaces, and mixing PACs with bulk feeds in reactors totally before filtration and mixing PACs with bulk feeds in reactors periodically during filtration. PACs in three dosing modes all improved the removal of organics, but showed conflict effects on the fouling. Unlike mixed PACs increasing the final flux by more than two times than that obtained in the control system, pre-deposited PACs showed a dramatically negative effect on the flux development with a final value decreased by 75.0%. As demonstrated by the scanning electron microscopy images of biofilm structures and the contents of dissolved organic carbon and adenosine triphosphate in reactors, pre-deposited PAC layer aggravated the accumulation of organics and microorganisms with the formation of a stratified and compact structure, which hindered their back-transport to the bulk water. However, mixed PACs induced the formation of a uniform and porous biofilm, which favored the retained organics and microorganisms migrating back into concentrated waters, especially for pre-mixed PACs. This study links PAC dosing strategies, physical structures of biofilms and spatial distributions of organics and microorganisms, with practical relevance for the hydraulic performance of GDM systems, hopefully leading to a wider application of PAC-GDM systems in wastewater treatment.

Effect of Processing Conditions on Membrane Fouling in Microfiltration by a Miniaturized Modular Device

Effect of Processing Conditions on Membrane Fouling in Microfiltration by a Miniaturized Modular Device

Fouling of microfiltration membranes by bidisperse particle solutions

Fouling of filtration membranes is a key process that degrades performance and reduces membrane lifetime. Nevertheless, obtaining direct information about fouling mechanisms is still a significant challenge, especially fouling that occurs within the internal pore spaces. Here, we combined highly multiplexed single-particle tracking methods with alternating laser excitation, which allowed the direct visualization of the transport of nanoparticles within microfiltration membranes, where the advective motion and retention of 200 nm and 40 nm diameter particles was simultaneously imaged within filtration membranes with 650 nm nominal pore size, as membranes became increasingly fouled as a function of total particle throughput. We found that internal membrane fouling consisted of three stages, fouling site formation, fouling site growth, and fouling site coalescence. Larger particles had a greater chance to be retained initially, nucleating the fouling sites. These sites tended to capture other particles passing through the membrane, causing the fouling sites to grow in size. Eventually, isolated fouling sites grew large enough to coalescence with neighboring sites, blocking a large region of membrane pores, leading to significant fouling. Importantly, the presence of small numbers of large particles significantly increased the retention of small particles and also accelerated the rate of particle retention. This mechanistic information about internal membrane fouling will assist in the design and optimization of filtration processes to reduce membrane fouling and expand the fundamental understanding of complex mass transport of polydisperse particle distributions.

Effect of seasonal succession of algal communities on fouling of MF membrane

An emerging threat to membrane application is the seasonal proliferation of algae in water sources such as rivers, reservoirs and lakes. This study investigated the link between feed parameters and the membrane performance of a pilot-scale microfiltration (MF) plant for 7 months. The seasonal succession of algae in relation to temperature dynamics was monitored. Temperature-dependent seasonal patterns for algae species were observed. The water temperatures during the dominance of cyanobacteria, especially Microcystis, were relatively higher (over 25 °C) than those during the dominance of diatoms. Diatoms did not much affect membrane performance (less than 0.2 kgf/cm2), however, under the cyanobacterial dominance condition, especially Microcystis sp., transmembrane pressure (TMP) reached up to the limited level (0.4 kgf/cm2) within one month. Concurrently UV absorbance at 254 nm wavelength and dissolved organic carbon values increased significantly during the Microcystis bloom and the build-up rate of TMP increased up to 0.005 kgf/cm2/day. Membrane autopsy also showed that during the dominance of diatom, application of cleaning agents can fully remove foulants on the membrane surface. However, during the dominance of cyanobacteria, there is a lot of Al, Si and organic complex on the fouled membrane, indicating the formation of Al-organic complexes that contributed to the residual membrane fouling. It is suggested that the irrecoverable fouling layer still contained some Al, mostly in complex with organics. Thus, organic matter originated from cyanobacteria may cause a serious impact on membrane fouling by forming the complex with metal ions originated from coagulant.

Fouling and Chemical Cleaning of Microfiltration Membranes: A Mini-Review.

Membrane fouling is one of the main drawbacks encountered during the practical application of membrane separation processes. Cleaning of a membrane is important to reduce fouling and improve membrane performance. Accordingly, an effective cleaning method is currently of crucial importance for membrane separation processes in water treatment. To clean the fouling and improve the overall efficiency of membranes, deep research on the cleaning procedures is needed. So far, physical, chemical, or combination techniques have been used for membrane cleaning. In the current work, we critically reviewed the fouling mechanisms affecting factors of fouling such as the size of particle or solute; membrane microstructure; the interactions between membrane, solute, and solvent; and porosity of the membrane and also examined cleaning methods of microfiltration (MF) membranes such as physical cleaning and chemical cleaning. Herein, we mainly focused on the chemical cleaning process. Factors affecting the chemical cleaning performance, including cleaning time, the concentration of chemical cleaning, and temperature of the cleaning process, were discussed in detail. This review is carried out to enable a better understanding of the membrane cleaning process for an effective membrane separation process.

Fouling Characteristics of MF membrane operated for separation of nitrocellulose from wastewater.

Membrane processes for wastewater treatment have become one of the emerging technologies, which affords a fast development through the past few decades. This study investigated the occurrence of fouling membrane and its composition factors and its effect on membrane performance. In this study, a project pilot scale forward the opposition to cluster transport from one side to the other side of membrane is eventual of the membrane and due to the coat of material on the membrane surface and into the membrane. Effect of severalparameters including trans-membrane compressing (pressure), crossflow velocity, and organic matteron microfiltration (MF) membrane fouling are investigated. The results show that theorganic material existing in the actual wastewater NC30 does not induce foulingin 0.14µm MF membrane with NC fines.

A comprehensive analysis of membrane fouling in microfiltration of complex linear macromolecules based on theoretical modeling and FESEM images

AbstractBACKGROUNDMembrane technology is an attractive alternative to conventional water/wastewater treatment technologies as it is sustainable and can be used as an independent process as well as being a part of integrated systems with other treatment technologies. Notwithstanding the abundant benefits that membrane‐based systems offer, their commercial application is overshadowed by the ubiquitous fouling. However, accurate prediction and identification of membrane fouling mechanisms can help to open new doors in recognition of appropriate arrangements for developing more effective membrane synthesis methods and fundamental strategies to achieve better performance, especially in large‐scale production.RESULTSIn this study, three fouling models, namely resistance‐in‐series (RIS), Hermia's and combined cake filtration–pore blockage models, were applied to precisely analyze fouling behavior in dead‐end microfiltration (MF) of collagen solution, as model foulant, using pure high‐density polyethylene and modified high‐density polyethylene membranes. The RIS model was shown to be not representative of the real fouling mechanism in MF membrane units. Similarly, none of the classical models were able to accurately predict fouling in the entire MF process. However, the combined cake–intermediate blockage model provided excellent fits for the membranes.CONCLUSIONSObtained results also demonstrated that physical cleaning was not enough for organic fouling elimination in MF processes. Finally, computational results were validated with experimental observations of collagen rejection and field emission scanning electron microscopy analyses as well. © 2020 Society of Chemical Industry

New insights into the structure of membrane fouling by biomolecules using comparison with isotherms and ATR-FTIR local quantification

ABSTRACT The objective of this paper was to propose a deepened analyze of a microfiltration membrane fouling by two biomolecules: a protein (Bovine Serum Albumin) and a peptide (Glutathione). In addition to an analysis of flux decline, the mass of biomolecules accumulated on the membrane during filtration was quantified and compared to adsorption experiments, using Fourier Transform Infra Red spectroscopy in Attenuated Total Reflection mode (ATR-FTIR). It was demonstrated that the same quantity of accumulated biomolecules on the apparent membrane area can generate totally different flux declines because of different fouling mechanisms. On the one hand, Glutathione can adsorb in the whole porous media of the membrane, penetrating through the pores, modifying the hydrophilicity at low concentrations and generating pore constriction at high concentrations. On the other hand, BSA organize a dense irreversible fouling in the first minutes of filtration containing a quantity equivalent to more than 45 monolayers, leading to pore blocking and pore constriction. This structure is resistant to rinsing and NaOH cleaning. Then a reversible fouling, containing a quantity equivalent to more than 90 monolayers is settled. The above structure can be removed with an intensive water rinsing and corresponds to a rather porous cake leading to a low resistance to water permeation, whereas the intermediate structure can only be removed with chemical cleaning and has a higher impact on water permeation. The original approach detailed in this paper allowed to go deeper in the understanding of the membrane fouling by soft matter, not detailed in previous papers.

Impact of removal of natural organic matter from surface water by ion exchange: A case study of pilots in Belgium, United Kingdom and the Netherlands

Natural organic matter (NOM) fractions cause problems in drinking water treatment and supply. In the North Sea region, anionic ion exchange (IEX) in non-fixed bed configurations has been considered for NOM removal in drinking water treatment plants. This paper discusses several experiences of the impact of anion IEX on NOM removal and on NOM-related problems in water treatment locations of the North Sea region, considering the specific situation of the sites. The investigated parameters include the effect of anionic IEX on the removal of total NOM and specific NOM fractions, the amount of chemicals used for coagulation, the development of trans membrane pressure in microfiltration, the formation of assimilable organic carbon and the energy consumption during advanced oxidation, the removal of organics by activated carbon, and the formation of disinfection by-products. The pilot experiences at three treatment locations in Belgium, United Kingdom and the Netherlands show that anionic IEX (1) removed typically 40 to 60 percent of total NOM; (2) targeted mostly humic NOM fractions, and was not effective to remove biopolymers (3) contributed to lower coagulant doses and energy consumption in UV/advanced oxidation; (4) had limited influence on limiting the fouling of microfiltration membranes; (5) lowered the formation of disinfection by-products; and (6) it can improve biological stability.

Membrane fouling in microfiltration of alkali/surfactant/polymer flooding oilfield wastewater: Effect of interactions of key foulants

HypothesisMembrane filtration is a promising technology for the treatment of alkali/surfactant/polymer (ASP) flooding oilfield wastewater, which contains high concentration of salt, surfactant, polymer and crude oil. The interactions of key foulants may influence the degree of membrane fouling. By comparing flux decline and interfacial free energies, it should be possible to derive the foulants governing the interactions with the membrane. ExperimentsPolytetrafluoroethylene microfiltration membrane was employed to treat eleven types of model solutions to understand the effect of the interactions of key foulants on membrane fouling. The extended Derjaguin–Landau–Verwey–Overbeek theory was used to quantify the foulant-membrane and foulant-foulant interaction energies. The cake models were implemented to analyze the fouling form. Fourier transform infrared spectroscopy, atomic force microscopy, and contact angle were used to study the surface properties of various membranes. FindingsMicrofiltration experiments and thermodynamic analysis revealed that both ions and sodium dodecylbenzenesulfonate could mitigate membrane fouling caused by anionic polyacrylamide (APAM) and crude oil. Moreover, APAM would produce a “shielding effect” on crude oil fouling. In addition, complete pore blocking, which primarily occurred on the membrane surface and formed a fouling layer, was the dominant form of membrane fouling.