Membrane Fouling Resistance Research Articles

Prediction of fouling resistance and permeate flux in cross-flow micellar-enhanced ultrafiltration (MEUF)

Cross-flow micellar-enhanced ultrafiltration had been used to separate pollutants from waste water effectively, while permeate flux decline with time because of the increase of fouling resistance. According to resistances in series theory, total transport resistance is the sum of two parts: membrane hydrodynamic resistance and fouling resistance. By observing material balance and hydrodynamic type of filtration, we proposed an analysis method of fouling resistance that was based on cross-flow filtration and took into account the presence of micelles instead of traditional cake resistance theory that was built from dead-end filtration. We found permeate flux decline not only by the relationship of time t1/2 that traditional cake resistance theory said, but also by concentration of fouling layer ϕ (or φ). Retentate non-recycled and retentate recycled cross-flow experiments were carried out under different operate conditions (i.e., transmembrane pressure (TMP) and initial concentration) by using artificial cadmium (Cd) contaminated water and sodium dodecyl sulfate (SDS) and models showed excellent accuracy to predict permeate flux through correlation r2 from 0.935 to 0.990.

Energy consumption and recovery in reverse osmosis

Energy consumption is a key factor which influences the freshwater production cost in reverse osmosis (RO) process. Energy recovery and reuse options have already been very well explored in the current desalination industry. Achieving minimum theoretical specific energy consumption for water recovery is not feasible due to effects of concentration polarization, membrane fouling and hydraulic resistance to permeate flow. Due to these limitations, energy recovery along with water recovery can be a better alternative to improve energy consumption and economics of the RO process both in small and large scale applications. This paper reviews currently available process configurations, operating strategies, and discusses potential pathways to recover and recycle energy and water to improve the performance of the RO process.

Dynamic in-series resistance modeling and analysis of a submerged membrane bioreactor using a novel filtration mode

This study is focused on the physical filtration characteristics of a flatsheet membrane bioreactor (MBR) operated under a novel filtration mode. The objective of this research was to demonstrate the possibility of running an MBR with high MLSS concentration for prolonged periods without frequent blocking of the membranes. Current MBR designs, mostly dictated by the manufacturers, have restrictions on the level of MLSS due to fouling. It has been observed that this restraint can be eliminated by applying high shear rates for better removal of cake layer from membrane surface. A pilot scale MBR was setup at the inlet works of a domestic sewage treatment plant. The system was dynamically modeled and calibrated for flux, hydraulic permeability, transmembrane pressure using the in-series resistance model. Resistance components were experimentally determined and compared against the results of dynamic simulations. Intrinsic membrane resistance (R m) and fouling resistance (R f) were the major components contributing to total resistance with fractions of 69% (R m/R t) and 30% (R f/R t) respectively. It was found that cake resistance did not have major impact on the total resistance which was linked to the high aeration intensity. Proposed model was validated by experiments which indicated its potential use on other MBR systems.

Modeling of PVA Modified Non-Woven for Submerged Membrane Bioreactor Treating Synthetic Wastewater

In this study, a mathematical model has been developed for the submerged membrane bioreactor (SMBR). Polyvinyl alcohol (PVA) Modified Non-woven model is immerged in MBR to be used for synthetic wastewater treatment. The results show that membrane fouling resistance is mostly cake resistance occurring during filtration. Based on the concept of specific fouling resistance and Darcy law that describes the relationship between flux and resistance during filtration driven by pressure, a module is established to explain the relationship between specific fouling resistance and time during filtration controlled by cake resistance in SMBR. The decline trend of flux can be predicted by the model. The model is used to predict the decline trend of flux during pharmaceutical wastewater treatment. Compared with experimental data, the relative error is less than 10% at t>b, the relative error is less than 5% at t>2b. It shows that the model can predict the decline trend of flux during stable operation of SMBR. But the relative error is bigger during unstable operation at initial stage (t<b). The model developed in this study would provide a useful tool in optimizing operation conditions as well as design parameters for a SMBR system.

Analysis of an ultrafiltration model: Influence of operational conditions

Ultrafiltration is a widely used technique to remove hazardous pollutants from wastewaters. As ultrafiltration is a dynamic process, non steady-state UF models have been widely investigated and described in the literature. The main equations of most dynamic models found in the literature can be rearranged and simplified into a linear equation. In this work, experimental results from UF tests were expressed in terms of TMP 2 /J P 2 as a function of time to check linearity. Transmembrane pressure (TMP), feed concentration (FC), temperature and crossflow velocity (CFV) were varied during the experiments. The feed consisted in an aqueous solution of polyethylene glycol of 35 kg/mol molecular weight. The experimental results confirmed a linear relationship when TMP 2 /J P 2 was plotted vs. time. For severe fouling conditions, the linearity found when plotting experimental values of initial membrane fouling resistance vs. TMP was very high. A linear correlation between the initial membrane fouling resistance and the temperature was also found for the experimental conditions tested. However, it was found that, above 25 °C, increasing temperature did not result in a noticeable reduction of the gel layer resistance. The quotient r c /c g as a function of TMP and CFV was also evaluated to check if it followed any pattern.

Physical–chemical properties, separation performance, and fouling resistance of mixed-matrix ultrafiltration membranes

Herein we report on the formation and characterization of mixed-matrix ultrafiltration (UF) membranes hand-cast by nonsolvent induced phase inversion. We evaluated nanometer-to-micrometer sized inorganic fillers (silver, copper, silica, zeolite, and silver-zeolite) materials with polysulfone (PSf) as the polymeric dispersing matrix. In general, mixed-matrix membranes were rougher, more hydrophilic, and more mechanically robust. Only sub-micron zeolite-PSf mixed-matrix membranes exhibited simultaneous improvements in water permeability and solute selectivity; all other mixed-matrix membranes were more permeable, but less selective due to defects associated with poor polymer-filler binding. Protein and bacterial fouling resistance of mixed-matrix membranes containing silver, zeolite, and silver-zeolite nanoparticles were compared to a low-fouling, poly(acrylonitrile) (PAN) UF membrane. Zeolite and silver containing membranes exhibited better protein fouling resistance (due to higher hydrophilicity), whereas silver and silver-zeolite based membranes produce better bacterial fouling resistance due to antimicrobial properties. Overall, zeolite-PSf and silver exchanged zeolite-PSf membranes offered the best combination of improved permeability, selectivity, and fouling resistance — superior to the commercial PAN membrane.

Control and Cleaning of Membrane Biofouling by Energy Uncoupling and Cellular Communication

This study investigated possible biological control of membrane biofouling and membrane cleaning by disrupting energy metabolism of microorganisms. Results showed that 2,4-dinitrophenol (DNP), a typical uncoupler, could not only significantly inhibit membrane biofouling but also enhance biofilm detachment from nylon membrane. Inhibited ATP synthesis by a chemical uncoupler resulted in lowered production of autoinducer-2 (AI-2). The standard dead-end microfiltration tests further confirmed that the reduced AI-2 was positively correlated to the reduced fouling resistance of nylon membranes. It appears that inhibition of energy metabolism would be a promising alternative for control and cleaning of membrane biofouling.

Surface modification of commercial polyamide desalination membranes using poly(ethylene glycol) diglycidyl ether to enhance membrane fouling resistance

To improve fouling resistance, polyamide reverse osmosis (XLE) and nanofiltration (NF90) membranes were modified by grafting poly(ethylene glycol) (PEG) diglycidyl ether (PEGDE) to their top surfaces from aqueous solution. The effect of PEG molecular weight (200 vs. 1000) and treatment solution concentration (1% (w/w) vs. 15% (w/w)) on water flux and NaCl rejection was measured. PEGDE grafting density as well as surface properties of modified and unmodified membranes, including charge, hydrophilicity and roughness, were measured and compared. The fouling resistance of modified membranes to charged surfactants (i.e., sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB)) and emulsions of n-decane and these charged surfactants was compared to that of unmodified membranes. In general, modified membranes exhibited improved fouling resistance and an improved ability to be cleaned after fouling compared to unmodified membranes. Fouling resistance increased with increasing PEG molecular weight, but showed little dependence on treatment solution concentration, suggesting that further improvements in membrane fouling resistance might be obtained by using lower concentrations of higher molecular weight PEG for surface modification.

Antifouling performance of poly(acrylonitrile)-based membranes: From green synthesis to application

In order to develop clean ultrafiltration membranes able to prevent the fouling of biological compounds in filtration processes, poly(ethylene glycol) methyl ether acrylate (PEGA) was grafted to poly(acrylonitrile) (PAN) by free-radical polymerization in supercritical carbon dioxide (scCO2) and the grafted copolymer was blended with PAN to fabricate porous membranes using scCO2-induced phase inversion method. Fourier transform infrared (FT-IR) analysis, 1H nuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC) confirmed that the poly(acrylonitrile)-graft-poly(ethylene oxide) (PAN-g-PEO) was successfully synthesized, for the first time, in scCO2. The effect of increasing PEGA content on the initial monomer feed mixture on graft polymer morphology and average molecular weight was studied. Blended membranes with different PEGA contents were investigated by scanning electron microscopy (SEM), mercury porosimetry and dynamical mechanical analysis (DMA) to characterize their morphological, physico-chemical and mechanical properties. Moreover, water contact angle measurements, pure water permeability and filtration experiments were performed to evaluate membrane hydrophilicity and fouling resistance properties. Permeation experiments of model foulants, bovine serum albumin (BSA) and starch solutions were used to investigate antifouling character of blend membranes at different pHs. PAN:PAN-g-PEO (70:30) showed to be the ultrafiltration membrane with best performance. Furthermore, comparing with conventional technologies blended membranes of PAN:PAN-g-PEO prepared by a scCO2-assisted process showed enhanced hydrophilicity, larger protein and starch solution permeabilities and good resistance to irreversible fouling, indicating that the technology is an efficient process to prepare fouling resistant membranes for biomacromolecule separations.

Communications orales

The aim of this study was to examine the applicability of reverse osmosis (RO) for the concentration of blackcurrant juice by AFC-80 polyamide tubular membrane that has a salt rejection greater than 80%. The fresh juice had a total soluble solids content of about 16.5°Brix. The effect of centrifugation followed by depectinization with two commercially available pectinase enzyme preparations (Panzym Super E and Trenolin Rot DF) on the permeate flux has been evaluated. For the description of the concentration process, the resistance-in-series model has been used. It was concluded that the applied RO membrane is suitable for concentration of blackcurrant juice up to 28.6°Brix, which was achieved with the juice that had been treated with Panzym Super E. The total resistances were calculated and compared, taking into account membrane fouling and polarization layer resistance.

THE ROLE OF BLACK TEA FEED CONDITIONS UPON ULTRAFILTRATION PERFORMANCE DURING MEMBRANE FOULING AND CLEANING

ABSTRACT This article demonstrates the importance of feed condition upon filtration performance as a result of variations in fouling mechanism and cleaning efficiency during the clarification of black tea liquor by ultrafiltration. The filters studied were (1) FP and (2) RC ultrafiltration membranes. Specific fouling resistances, apparent membrane rejections and cleaning efficiencies were analyzed for variations in feed concentration, TMP, temperature, ionic strength and calcium content. Concentration polarization contributed predominantly to the increased total fouling resistance of both membranes as feed concentration was increased, although there was no extra effect upon deposit formation on the RC membrane, whereas rinsable fouling deposit did increase on the FP membrane because of slightly stronger interaction of the foulant with the membrane surface. Increasing the ionic strength increased the total fouling resistance, thus reducing performance while decreasing the severity of deposition fouling as a result of increased concentration polarization. Addition of calcium to the feed stream caused a significant increase in irreversible fouling deposition because of polar group–calcium complexation (bridging). This deposition could not be adequately removed by using standard sodium hydroxide cleaning protocols, or by the addition of surfactants and chelating agents. PRACTICAL APPLICATIONSThe nature of complex feeds and membrane filtration usually results in a progressive flux decline that has a marked effect upon the process economics and viability. The effect of black tea feed condition upon ultrafiltration as a clarification method is reported in this article. Membrane–foulant interactions and overall performance are discussed and are relevant to the optimization and clarification of black tea and other protein/polyphenol containing beverages during industrial processing in factory operation. Although cleaning of membranes is inevitably required during filtration of such a complex feed, an understanding of fouling can help reduce the frequency and environmental impact of cleaning in industrial practice.

An Improved Model for Cross-Flow Microfiltration Properties of Lactic Acid Fermentation Broth

An unsteady-state model for cross-flow microfiltration of lactic acid fermentation broth is presented in this manuscript. Compared with earlier models, the improved model can calculate specific cake resistance and membrane fouling resistance simultaneously. Filtration properties are obtained by solving the model with numerical integration and optimization. The model has been used for the analysis of experimental data and the results show good agreement with the experimental permeate flux. The model predicts smaller specific cake resistance by taking into account the membrane fouling resistance.

Effects of in-phase oscillation of retentate and filtrate in crossflow filtration at low Reynolds number

The effects of in-phase oscillation of the retentate and filtrate in crossflow filtration at low Reynolds number are investigated experimentally. Two flat membranes with mean pore size of 0.2 μm and a filter plate with pore size of 40 μm were used for the study. The experiments were performed with polymethylmethacrylate (PMMA) suspension and baker's yeast ( Saccharomyces cerevisiae) suspension. The solid volume fraction of the suspensions was φ s = 0.01. Reynolds number in the laminar range of 0 < Re < 300 was studied. The height of the non-oscillating crossflow velocity v is 0.02 m/s. The frequency f of the oscillation is in the range of 10 Hz < f < 50 Hz and the amplitude A = 0.43 mm. This yields oscillating velocity in the range of 0.06 m/s ≤ v o s c ≤ 0.10 m/s . The transmembrane pressure lies between 1.0 and 20 kPa was applied. The resulting flow was visualized using a CCD camera. The transmembrane flux due to the superimposed oscillations is significantly higher than the flux from conventional crossflow filtration. Manipulation of both the retentate and filtrate/permeate yields constant flux with time. Flux enhancement between 125% and 320% was obtained. The particle deposition on the surface of the filter materials is significantly reduced by the imposed oscillation. With the in-phase oscillation of both retentate and permeate, uniform transmembrane pressure is possible. In general, the flow reversal leads to reduction of membrane fouling and concentration polarization resistance. The calculated friction power input due to applied oscillation is comparatively low.

Modification of polysulfone membranes via surface-initiated atom transfer radical polymerization

Hydrophilic poly((poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) and poly(glycidylmethacrylate) (PGMA) brushes were grafted from chloromethylated polysulfone (CMPSF) membrane surfaces via surface-initiated atom transfer radical polymerization (ATRP). Prior to ATRP, chloromethylation of PSF was performed beforehand and the obtained CMPSF was prepared into porous membranes by phase inversion process. It was demonstrated that the benzyl chloride groups on the CMPSF membrane surface afforded effective macroinitiators to graft the well-defined polymer brushes. 1H NMR was employed to confirm the structure of CMPSF. The grafting yield of P(PEGMA) and PGMA was determined by weight gain measurement. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) and PGMA chains. Water contact angle measurements indicated that the introduction of P(PEGMA) and PGMA graft chains promoted remarkably the surface hydrophilicity of PSF membranes. The effects of P(PEGMA) and PGMA immobilization on membrane morphology, permeability and fouling resistance were investigated. It was found that P(PEGMA) and PGMA grafts brought higher pure water flux, improved hydrophilic surface and better anti-protein absorption ability to PSF membranes after modification. And evidently, macromonomer P(PEGMA) brought much better properties to the PSF membranes than PGMA macromonomer.

Advanced water treatment of high turbid source by hybrid module of ceramic microfiltration and activated carbon adsorption: Effect of organic/inorganic materials

We investigated the effect of organic or inorganic materials on membrane fouling in advanced drinking water treatment by hybrid module packed with granular activated carbon (GAC) outside a tubular ceramic microfiltra- tion membrane. Instead of natural organic matters (NOM) and fine inorganic particles in the natural water source, syn- thetic water was prepared with humic acid and kaolin. Concentrations of kaolin or humic acid were changed to see effects of inorganic or organic matter. And periodic water-back-flushing using permeate water was performed during 10 sec per filtration of 10 min. As a result, both the resistance of membrane fouling (Rf) and permeate flux (J) were influenced higher by concentration of humic acid rather than kaolin. It was proved that NOM like humic acid could be a more important factor on membrane fouling in drinking water treatment than fine inorganic particles. Treatment efficiencies of turbidity and UV254 absorbance were very high above 97.4% and 92.0%, respectively.

Concentration of blackcurrant juice by reverse osmosis

The aim of this study was to examine the applicability of reverse osmosis (RO) for the concentration of blackcurrant juice by AFC-80 polyamide tubular membrane that has a salt rejection greater than 80%. The fresh juice had a total soluble solids content of about 16.5°Brix. The effect of centrifugation followed by depectinization with two commercially available pectinase enzyme preparations (Panzym Super E and Trenolin Rot DF) on the permeate flux has been evaluated. For the description of the concentration process, the resistance-in-series model has been used. It was concluded that the applied RO membrane is suitable for concentration of blackcurrant juice up to 28.6°Brix, which was achieved with the juice that had been treated with Panzym Super E. The total resistances were calculated and compared, taking into account membrane fouling and polarization layer resistance.

Estimation of the gel layer concentration in ultrafiltration: Comparison of different methods

Fouling is one of the major limitations of membrane applications. Gel layer formation is a common fouling mechanism that increases the membrane fouling resistance. In this work the estimation of the gel layer concentration was performed from experimental values obtained in several ultrafiltration experiments using three methods: the gel-polarization model, the mechanistic model for gel layer formation proposed by Song and an expression of the concentration polarization modulus developed for tubular membranes and turbulent flow. The results were compared and analyzed. Two types of monotubular ceramic membranes with different MWCO (5 and 15 KDa) were used in the experiments. Polyethylene glycol (PEG) of 35,000 Da in distilled water was used as feed. The experiments were performed at different feed flow rates (1–3 m/s), transmembrane pressures (0.1–0.5 MPa), temperatures (15–40EC) and constant feed concentrations (5–15 g/L). Values of the gel layer concentration estimated with the gel-polarization model diff...

Modelling of submerged membrane bioreactor: Conceptual study about link between activated slugde biokinetics, aeration and fouling process

A mathematical model was developed to simulate filtration process and aeration influence on submerged membrane bioreactor (SMBR) in aerobic conditions. The biological kinetics and the dynamic effect of the sludge attachment and detachment from the membrane, in relation to the filtration and a strong intermittent aeration, were included in the model. The model was established considering soluble microbial products (SMP) formation-degradation. The fouling components responsible of pore clogging, sludge cake growth, and temporal sludge film coverage were considered during calculation of the total membrane fouling resistance. The influence of SMP, transmembrane pressure, and mixed liquor suspended solids on specific filtration resistance of the sludge cake was also included. With this model, the membrane fouling under different SMBR operational conditions can be simulated. The influence of a larger number of very important process variables on fouling development can be well quantified. The model was developed for evaluating the influence on fouling control of an intermittent aeration of bubbles synchronized or not with the filtration cycles, taking into account the effects of shear intensity on sludge cake removal.

Tethering hydrophilic polymer brushes onto PPESK membranes via surface-initiated atom transfer radical polymerization

Surface-initiated atom transfer radical polymerization (ATRP) was used to graft hydrophilic comb-like poly((poly(ethylene glycol) methyl ether methacrylate), or P(PEGMA), brushes from chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) membrane surfaces. Prior to ATRP, chloromethylation of PPESK was beforehand performed and the obtained CMPPESK was prepared into porous membranes by phase inversion process. It was demonstrated that the benzyl chloride groups on the CMPPESK membrane surface afforded effective macroinitiators to graft the well-defined polymer brushes. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) chains. Water contact angle measurements indicated that the introduction of P(PEGMA) graft chains promoted remarkably the surface hydrophilicity of PPESK membranes. The effects of P(PEGMA) immobilization on membrane morphology, permeability and fouling resistance were investigated. It was found that the comb-like P(PEGMA) grafts brought smaller pore diameters and higher solute rejections to PPESK membranes. The results of dynamic anti-fouling experiments showed the anti-fouling ability of the membranes was significantly improved after the grafting of P(PEGMA) brushes.

Impact of biological constituents and properties of activated sludge on membrane fouling in a novel submerged membrane bioreactor

A 12-l submerged membrane bioreactor was developed to remove carbon and nitrogen simultaneously using synthetic wastewater. In this study, the main objective was to investigate the impact of activated sludge properties on membrane fouling in the novel submerged MBR. The activated sludge properties were characterized by biological constituents (mixed liquor suspended solids (MLSS), extracellular polymeric substances (EPS) and soluble microbial products (SMPs)), morphological parameters (filament index (FI), volume equivalent diameter ( D (4,3)) and fractal dimension ( D f )) and rheological properties (apparent viscosity (η a )). The influences of activated sludge properties on membrane fouling were quantified using statistical methods. The results showed that D f and EPS have strong and moderate positive effects on the membrane fouling resistance respectively, while MLSS was inversely correlated to the membrane fouling resistance. This study indicated that D f , EPS and MLSS were the predominant factors affecting the membrane fouling resistance.