Membrane processes for water reuse from the effluent of industrial park wastewater treatment plant: a study on flux and fouling of membrane

Both the relationship between the flux and the fouling mechanism of ultrafiltration (UF) membrane and the effects of pretreatment before reverse osmosis (RO) process on the treatment of the effluent of industrial park wastewater treatment plant (IPWTP) were investigated to examine the application of membrane processes on the water reuse treatment. For the former, the flux data was first fitted to the Hermia model to give the implication of the fouling mechanism. Then, the fouling mechanism was further identified with the aid of the SEM morphology of membrane surfaces. For the latter, the changes of both water characteristics (turbidity, TOC, conductivity, particle size distribution, and organic solute molecular weight) and membrane properties (surface zeta potential and surface morphology) before and after the treatment of membrane processes were measured. It was found that the major blocking mechanisms of UF membrane process at initial and final stage were standard blocking of pore (causing from colloid materials) and cake blocking of pore (causing from suspended particles), respectively. On the other hand, it was concluded that the permeate from 1 μm/UF/RO process was suitable for the reuse of cooling water and low pressure boiler water.     

聚砜超滤膜的表面改性

本文用亲水性高分子，表面活性剂及丙烯酸化学反应对聚砜超滤膜进行表面改性，实验结果表明：丙烯酸化学改性效果最佳，可以同时提高膜通量，截留率及膜的抗污染性能。     

Natural organic matter (NOM) fouling in low pressure membrane filtration — effect of membranes and operation modes

The objective of this study was to evaluate the effects of operating modes, membrane materials and pore size on natural organic matter (NOM) fouling. A range of flat sheet microfiltration (MF) and ultrafiltration (UF) membranes were tested under conditions of various constant pressure and constant flux filtration modes. Based on experimental filtration profiles, molecular weight (MW) distributions of NOM obtained using high performance size exclusion chromatography (HPSEC) and autopsies of fouled membranes using force emission scanning electron microscopy (FESEM), it was concluded that medium to low MW component of NOM (300–1,000 Da) is responsible for the initiation of fouling, where bulk of the fouling observed is due to very high MW ‘colloidal’ NOM (>50,000 Da). This two stage fouling phenomenon was in good agreement with classical blocking laws. As a general observation hydrophilic membranes were less prone to NOM fouling. A comparison of constant pressure and constant flux tests confirmed that modest constant flux, as used in industry, provided the most beneficial conditions.     

Comparative Evaluation of Ultrafiltration Membranes for Purification of Synthetic Peptides

Abstract

Published information on the use of ultrafiltration to separate natural and synthetic peptides from each other, and from low-molecular-weight impurities, is reviewed. The suitability of commercial membranes of low nominal molecular weight cut-off (500-8000 daltons) for fractionation of synthetic peptides was evaluated with a model mixture of a hexapeptide (MW 844), insulin (MW 5730), and cytochrome c (MW 12,384) in 5% acetic acid. Diafiltration in a cross-flow thin-channel device allowed graphical determination of the retention coefficient for each solute on each membrane; fouling and cleanability were also assessed. Regenerated cellulose and cellulose acetate membranes did not foul, were chemically resistant, and fractionated efficiently. Other membrane types, including polysulfone and Teflon, fouled and were difficult to clean. Cellulosic membranes can be successfully integrated into the purification of synthetic peptides.     

混凝耦合多孔陶瓷膜净化河水简

Membrane filtration technology combined with coagulation is widely used to purify river water. In this study, micro filtration （MF） and ultrafiltration （UF） ceramic membranes were combined with coagulation to treat local river water located at Xinghua, Jiangsu province, China. The operation parameters, fouling mechanism and pilot-scale tests were investigated. The results show that the pore size of membrane has small effect on the pseudo-steady flux for dead-end filtration, and the increase of flux in MF process is more than that in UF process for cross-flow filtration with the same increase of cross-flow velocity. The membrane pore size has little influence on the water quality. The analysis on membrane fouling mechanism shows that the cake filtrationhas significant in fluence on the pseudo-steady flux and water quality for the membrane with pore size of 50, 200 and 500 nm. For the membrane with pore size of 200 nm and backwashing employed in our pilot study, a constant flux of 150 L-m^-2-h^-1 was reached during stable operation, with the removal efficiency of turbidity, total organic carbon （TOC） and UV254 higher than 99%, 45% and 48%, respectively. The study demonstrates that coagulation-porous ceramic membrane hybrid process is a reliable method for river water purification.     

Preparation,characterization and performance of cellulose acetate ultrafiltration membranes modified by charged surface modifying macromolecule

A charged surface modifying macromolecule (cSMM) was synthesized, characterized by FT-IR spectroscopy and blended into the casting solution of cellulose acetate (CA) to prepare surface modified UF membranes by phase inversion technique. With an increasing cSMM additive content from 1 to 4 wt%, pure water flux (PWF) and water content (WC) were increases whereas the hydraulic resistance decreases. Surface characteristic study reveals that the surface hydrophilicity increased in cSMM modified CA membranes. The pore size and surface porosity of the 4 wt% cSMM blend CA membranes increases to 41.26 Å and 0.015%, respectively. Similarly, the molecular weight cut-off (MWCO) of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. Lower flux decline rate (47.2%) and higher flux recovery ratio (FRR) (89.0%), exhibited by 4 wt% cSMM blend membranes demonstrated its fouling resistant characteristic compared to pristine CA membrane.     

Separation of Humic Substances by Porous Ion-Exchange Membranes from Sulfonated Polysulfone

Abstract

Ultrafiltration involving sulfonated polysulfone membranes provides high efficiency for humic matter removal from water. The increase in ion-exchange capacity of the polymer matrix from 0.24 to 0.96 mmol SO₃H groups per 1 g of dry membrane increases the membrane pore diameter and its hydrophilicity, and thus the permeate flux from 0.05 to 3.69 m³/m²·d. In order to decrease the manufacturing cost, membranes from polysulfone and sulfonated polysulfone blends were investigated. It was shown that a one-to-one blend resulted in a membrane having similar antifouling properties to pure sulfonated polysulfone. Both membranes reject humic matter in the 91–98% range and show a flux decline of 5–30% as a result of surface fouling.     

Nano SiO2 and TiO2 embedded polyacrylonitrile/polyvinylidene fluoride ultrafiltration membranes: Improvement in flux and antifouling properties

Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) ultrafiltration (UF) membranes are widely used in drinking water and wastewater applications. These membranes are prone to fouling and membrane efficiency decreases with time under constant operation. Significant improvements/modifications are necessary to apply these polymers as sustainable membrane materials. In this study, PVDF and PAN UF membranes were modified through incorporation of nanoparticles (NPs) namely SiO₂ and TiO₂. PVDF and PAN UF membranes were prepared by phase inversion method from polymer solutions having dispersed SiO₂ and TiO₂ NPs in it. Membrane surface hydrophilicity, charge, roughness, and morphology were studied. Equilibrium water content and molecular weight cut-off of the membranes were also measured. Addition of NPs increased membrane surface hydrophilicity, equilibrium water content, and surface potential. NPs modified membranes exhibited better membrane flux (35–79% higher) and antifouling properties (flux recovery ratio values 28–41% higher) than the virgin membranes.     

Influence of polydopamine deposition conditions on pure water flux and foulant adhesion resistance of reverse osmosis, ultrafiltration, and microfiltration membranes

The influence of polydopamine (PDOPA) deposition and poly(ethylene glycol) (PEG) grafting on pure water flux and bovine serum albumin (BSA) adhesion of two polysulfone ultrafiltration (UF) membranes, a poly(vinylidene fluoride) microfiltration (MF) membrane, and a polyamide reverse osmosis (RO) membrane is reported. When modified with PDOPA, all membranes exhibited a systematic reduction in protein adhesion. For example, 90 min of PDOPA deposition led to at least 96% reduction in BSA adhesion to these membranes at neutral pH. BSA adhesion was further reduced by subsequent PEG grafting to PDOPA (PDOPA-g-PEG). The membranes’ pure water flux values (i.e., with no foulants present) were influenced to different extents by PDOPA and PDOPA-g-PEG modifications. In the porous membranes (i.e., the UF and MF membranes), the pure water flux reduction due to these modifications correlated with membrane pore size, with the smallest flux reductions observed in the MF membrane (e.g., <1% flux reduction for all PDOPA modification times considered), which have the largest pores, and the largest flux reductions occurring in UF membranes (e.g., a 40% flux reduction after 90 min of PDOPA deposition), which have pore sizes on the order of the PDOPA deposition thickness. The RO membranes, which are essentially non-porous, exhibited a flux reduction of 25% after 90 min of PDOPA deposition.     

Analysis of deposition mechanism during ultrafiltration of glycerin-rich solutions

Clarification of glycerin-rich solution is one of the potential applications of membrane within the oleochemical industry. However, one of the barriers in successfully utilizing the use of membranes such as ultrafiltration (UF) has been due to the fouling. In this work, flux decline during ultrafiltration of the glycerin-rich solutions was studied by using commercialized polymeric polyethersulphone (PES) membrane. Influence of fatty acids as foulants model (palmitic acid, stearic acid and oleic acid), pH of feed solution (3-10) and molecular weight cut-off (5 kDa, 20 kDa and 25 kDa) were analyzed. All the experiments were performed at constant pressure (2 bar) and temperature (40 °C). The Hermia's model was used to analyze the fouling mechanism during the flux decline which involve cake layer model due to adsorption of solute as well as pore blocking model. All the different types of flux decline kinetics were found to occur during the permeation of glycerin-rich solutions. However, the contribution of resistance due to cake layer formation was small for all the conditions studied. The fouling mechanisms were found to depend on the hydrophobicity of the PES membrane itself as well as the nature of foulants used in the study.     

Thin-film nanofibrous composite membranes containing cellulose or chitin barrier layers fabricated by ionic liquids

The barrier layer of high-flux ultrafiltration (UF) thin-film nanofibrous composite (TFNC) membranes for purification of wastewater (e.g., bilge water) have been prepared by using cellulose, chitin, and a cellulose-chitin blend, regenerated from an ionic liquid. The structures and properties of regenerated cellulose, chitin, and a cellulose-chitin blend were analyzed with thermogravimetric analysis (TGA) and wide-angle X-ray diffraction (WAXD). The surface morphology, pore size and pore size distribution of TFNC membranes were determined by SEM images and molecular weight cut-off (MWCO) methods. An oil/water emulsion, a model of bilge water, was used as the feed solution, and the permeation flux and rejection ratio of the membranes were investigated. TFNC membranes based on the cellulose-chitin blend exhibited 10 times higher permeation flux when compared with a commercial UF membrane (PAN10, Sepro) with a similar rejection ratio after filtration over a time period of up to 100 h, implying the practical feasibility of such membranes for UF applications.     

Ultrafiltration of Coagulation-Pretreated Serratia marcescens Fermentation Broth: Flux Characteristics and Prodigiosin Recovery

The dead-end ultrafiltration (UF) of coagulation-pretreated fermentation broth of Serratia marcescens SMΔR for prodigiosin recovery was studied. Experiments were performed using different types (regenerated cellulose, YM; polyethersulfone, PES) and molecular weight cut-offs (MWCOs, 1–10 kDa) of the membranes, feed concentrations of prodigiosin (300–1000 mg/L), applied pressures (68.9–206.8 kPa), and stirring speeds (200–400 rpm). With the same MWCO, the YM membrane had a higher retention of prodigiosin and a lower flux than the PES membrane. A two-fold concentration of prodigiosin was observed in the retentate using a 1-kDa YM membrane compared to the concentration in the permeate using a 10-kDa YM membrane. In addition, the extent of membrane fouling was quantitatively analyzed in terms of the modified fouling index. Flux decline in the present batch UF process was mainly due to cake layer formation and partly due to pore blocking. A two-stage UF process was proposed for this purpose, with 81% recovery yield and four-fold concentration.     

Threshold flux measurement of an ultrafiltration membrane module in the treatment of two-phase olive mill wastewater

The critical and threshold flux theories represent an important advance in membrane knowledge. Comprehension of the flux behavior of ultrafiltration (UF) membranes is key to control the fouling issues during the steady operation of the plant. In this regard, differing between critical or threshold flux patterns in the treatment of wastewater effluents by UF is relevant to confirm the level of fouling expected and to verify if no fouling is predictable or if certain amount of fouling cannot be avoided. In the present study, the hydrodynamic behavior of a polymeric UF membrane was analyzed by means of both critical and threshold flux theories and diverse patterns were found depending on the feedstock pollutants concentration and particle size distribution. Results obtained from the pressure-cycling experiments point for a threshold flux pattern in the case of UF of the effluent derived from the extraction process (OMW) disregarding the applied pretreatment, whereas for 1:1 (v/v) mixture of the latter with the wastewater from the fruit washing (OWW) the membrane fits a critical flux trend, indistinctly of the performed pretreatment too, with negligible fouling below the critical conditions. These conclusions are supported by the experimental permeate flux profiles during batch-run operation experiments.     

Performance of RC and PES ultrafiltration membranes in filtration of pulp mill process waters

Issues of fouling and effective cleaning limit the adoption of UF in pulp and paper mill applications. The choice of an optimal membrane for a specific filtration application is a challenging task due to the fact that fouling is a complex phenomenon. This study compares regenerated cellulose (RC) and polyethersulphone (PES) membranes in UF of two chemithermomechanical pulp mill process waters. The process waters originated from hardwood and softwood pulping. Based on their flux recovery, PES membranes sustained greater fouling than RC membranes even though the hydrophobicity of RC membranes was increased remarkably by adsorptive fouling. The process water affected the performance of the membranes. The membrane characteristics were more important in determining fouling when softwood process water was used than when hardwood process water was used. Hydrophilicity and morphology of the membranes were seen to have a clear influence on fouling.     

RO membrane solute rejection behavior at the initial stage ofcolloidal fouling

This study investigated the rejection of salt and inert organic compounds by reverse osmosis membranes during the initial stage of colloidal fouling. Results of laboratory-scale experiments showed that colloidal fouling caused a marked decrease in flux, salt rejection and rejection of organics with molecular weight (MW) smaller than about 100 g/mol. Removal of neutrally charged organics was mainly by size or steric exclusion. Rejection of xylose, which has MW >100 g/mol, was not affected much by colloidal fouling. The decrease in salt and low MW organic rejections during the initial stage of colloidal fouling was attributed to cake-enhanced concentration polarization, whereby the colloidal cake layer hindered back diffusion of solutes from the membrane surface to the bulk solution, resulting in higher solute concentration gradient across the membrane. At higher channel wall shear rate, the rates of colloidal deposition, flux decline, decrease in salt rejection, and decrease in low MW organic rejection were lower.     

Synthesis and characterization of cellulose acetate-polysulfone blend microfiltration membrane for separation of microbial cells from lactic acid fermentation broth

This work is focused on synthesis and characterization of a polymer blend microfiltration membrane for separation of microbial cells from lactic acid fermentation broth in a continuous process. The membranes were prepared by blending hydrophilic cellulose diacetate (CA) polymer with hydrophobic polysulfone (PSF) polymer in wet phase inversion method. Polymers were blended in N-methyl-2-pyrrolidone (NMP) solvent (70 wt.%) where polyethylene glycol was added as a pore former. The membranes were characterized in terms of morphology, porosity, flux and microbial separation capability. The best prepared membrane with PSF/CA weight ratio of 25/75 yielded a pure water flux of 1830 LMH (liter/m² h) and a fermentation broth flux of 1430 LMH at around 1.5 bar TMP (trans-membrane pressure). The membrane was successful in complete retention of microbial cells from the broth in a continuous crossflow membrane module integrated with the fermentor.     

Pilot-scale spiral wound membrane assessment for THM precursor rejection from upland waters

The outcomes of a pilot-scale study of the rejection of trihalomethanes (THMs) precursors by commercial ultrafiltration/nanofiltration (UF/NF) spiral-wound membrane elements are presented based on a single surface water source in Scotland. The study revealed the expected trend of increased flux and permeability with increasing pore size for the UF membranes; the NF membranes provided similar fluxes despite the lower nominal pore size. The dissolved organic carbon (DOC) passage decreased with decreasing molecular weight cut-off, with a less than one-third the passage recorded for the NF membranes than for the UF ones.

The yield (weight % total THMs per DOC) varied between 2.5% and 8% across all membranes tested, in reasonable agreement with the literature, with the aromatic polyamide membrane providing both the lowest yield and lowest DOC passage. The proportion of the hydrophobic (HPO) fraction removed was found to increase with decreasing membrane selectivity (increasing pore size), and THM generation correlated closely (R² = 0.98) with the permeate HPO fractional concentration.     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, Polysulfone was functionalized by sulfonation and ultrafiltration membranes were prepared based on sulfonated polysulfone and cellulose acetate in various blend compositions. Polyethyleneglycol 600 was employed as a nonsolvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The total polymer concentration, cellulose acetate, and sulfonated polysulfone polymer blend composition, additive concentration, and its compatibility with polymer blends were optimized. The membranes prepared were characterized in terms of compaction, pure water flux, membrane resistance, and water content. The compaction takes place within 3–4 h for all the membranes. The pure water flux is determined largely by the composition of sulfonated polysulfone and concentration of additive. Membrane resistance is inversely proportional to pure water flux, and water content is proportional to pure water flux for all the membranes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1749–1761, 2002     

Hemicelluloses separation from caustic-containing process stream by ultrafiltration

The present work aimed to study the performance of ultrafiltration (UF) membranes for hemicelluloses separation, from a caustic-containing highly alkaline, cellulose purification solvent stream of viscose rayon production process, and to understand the membrane behaviour, effect of multiple use cycle, identify potential performance drawbacks and propose possible solutions. Screening experiments showed that an UF membrane with a nominal molecular weight cut-off value of 3 kDa can be used to separate hemicelluloses from alkaline process stream. UF membrane was found to be prone to performance deterioration with time due to fouling. Higher feed temperature helped in improving the membrane flux values while maintaining hemicelluloses retention.     

Preparation and characterization of asymmetric ultrafiltration membrane for effective recovery of proteases from surimi wash water

The wash water generated from the surimi processing industry contains a large amount of proteases which are widely used in the food and biotechnology industries. Asymmetric polysulfone and polyethersulfone ultrafiltration (PSf-UF and PES-UF) membranes with three different polymer concentrations were screened for their abilities to recover proteases from surimi wash water. In-house fabricated membranes were prepared via a simple dry/wet phase inversion technique and were characterized in terms of permeability coefficient, membrane morphology and molecular weight cut-off (MWCO). The ability of the UF membranes to remove commercial proteases was tested at various pressures (up to 10 bars). The membrane with the best performance, 15 wt-% PSf-UF, was further tested with actual surimi wash water. The effect of the pH of the feed solution (4 to 8) in the pre-treatment stage was also evaluated to recover the highest amount of proteases. The highest retention of protease was 96% with a flux of 25.6 L/(m²·h) which was achieved with the 15 wt-% PSf-UF membrane.