Ultrafiltration membrane

Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reclamation applications. In spite of more than a decade of significant advances in developing fouling mitigation methods, different physical and cleaning protocols are still necessary to be developed to limit the membrane fouling. The use of scouring agents in MBR applications has been paid attention as a new approach as an energy-efficient way to control membrane fouling. Recently, mechanical cleaning by scouring agents is becoming as intense research area considering high efficiency of fouling reduction while requiring low energy consumption. In this review, fundamental and comprehensive assessments of the mechanical cleaning concepts and their applications with porous and nonporous scouring agents for MBR system are critically reviewed. The existing challenges and future research prospects on the mechanical cleaning technology associated with scouring agents for the MBR applications are also discussed.

Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.

Summary: The goal of this project is to design a Polymer-Enhanced Ultrafiltration (PEUF) process for the removal of heavy metals from waste water which is a relatively new and commercially untested membrane technology. The process will be designed to accommodate wastewater from manufacturing facilities, with the output adhering to and surpassing wastewater regulations so that it can be reused in the facility or safely be returned back to the environment.
In PEUF, the metal ion-polymer complexes in the wastewater are retained by the membrane whereas solutes with relatively lower mass pass through. The heavy metal ions are adsorbed by the water-soluble polymer which is subsequently isolated in the retention stream. By manipulating the pH, PEUF technology enables an enhanced recycling rate of polymer while ensuring wastewater is treated efficiently.
The ultrafiltration membrane selected is polyethersulfone or PES-10 from Sepro Membranes Inc. [Mitsui Chemicals Inc, 2004].The water-soluble complexing polymer used will be poly(vinyl formamide-co-vinylamine) or Lupamin 9095. The monomers consist of a large number of vinyl formamide which which are good electron donors in coordination with metal ions [Rivas, 2003]. Vinyl formamide is polymerized and then hydrolyzed to form Lupamin 9095, a linear high molecular weight polyvinylamine [BASF Corporation, 2002].
The group has completed a working simulation model on SuperPro Designer. The results of the modelling and a comprehensive analysis of the theoretical and economic performance of the selected design are disclosed in the final report . The likelihood of this project’s success is high, as any setbacks in modelling can be overcome with technical aptitude and effort.

Recently, ultrafiltration membrane technology is challenged to maintain their sustainability and favourable economics by improving their flux, selectivity and durability.  Polysulfone membrane constitute the most extensively studied class of membrane materials due to its commercial availability, excellent chemical and thermal resistance, good mechanical properties and easy processing. However, polysulfone ultrafiltration membrane is susceptible to fouling and has low permeate flux due to hydrophobicity properties of the materials. Membrane modifications become unavoidable in order to reduce the fouling susceptibility. One simple and attractive method is blending polysulfone with additives. Previous studies show that the addition of additives in membrane solution could enhance membrane performances with higher porosity and flux. Meanwhile in surface water treatment application, humic substance has brought particular interest due to its nature which could produce some carcinogen substances that have negative effects on the human health in long term period. Therefore, the investigation to remove humic substances is considered as a sustainable solution in the field of surface water treatment. Many studies have been conducted with polysulfone based ultrafiltration membrane to remove humic substance from water, thus the factors that influenced humic substances fouling on polysulfone-based membrane and the effect of additive concentration on the improvement membrane performance for humic substance removal will be reviewed further in this paper.

In this study, ultrafiltration membrane for humic substance removal was prepared by blending polysulfone with high concentration of PEG400 as additives. The influences of the additive to the fouling resistance capability and humic substances rejection of the polysulfone membrane were investigated. The addition of 35%wt of PEG400 concentration improved pure water flux up to 200, but resulted in higher fouling resistance of humic substances. High concentration of PEG400 increased irreversible fouling and significantly reduced the flux recovery ratio of the membrane. More than 80% humic substances rejection is achieved when a high concentration of PEG400 was added into membrane solution.

Zirconia ultrafiltration membranes are widely developed and used for past several years. But the conventional sol-gel methods of zirconia membrane preparation involve many steps. In the present study an attempt was made to develop defect free zirconia ultrafiltration (UF) membrane in single step coating of zirconia nanopowder suspension by slip casting method over multichannel ceramic support. The porous support was made from a novel composition of clay and α-alumina having 19-channels circular configuration. Zirconia UF membrane was developed at the inner surface of the support up to 0.2 m length. Membrane had a mean pore diameter of 40 nm. Clean water permeability of 48 lm-2h-1bar-1 was obtained for the membrane under cross-flow filtration mode. Membrane was utilized for treatment of industrial and domestic wastewater. Membrane treated water was characterized to evaluate the reduction of organic and inorganic contaminants. About 82% and 92% removal of COD were obtained for tannery...

A theoretical model using the surface-renewal concept is developed for describing cross-flow ultrafiltration under dynamic and steady-state conditions. The model can predict the local permeate flux and concentration profile of dissolved solute in the filter. The rate of surface renewal (S) at the membrane surface and the diffusion coefficient (D) of the solute in the solvent are the two parameters of the model. The model is able to correlate literature data of transient permeate flux in the ultrafiltration of skim milk with an average root-mean-square error of 9.9%. The values of S and D, estimated from the model, are 0.84 - 1.74 * 10-3 s-1 and 0.55 - 2.07 * 10-9 m2/s, respectively.

Conductive membranes can offer innovative solutions for membrane-fouling control while maintaining enhanced filtration performance. Here, an emerging technique, vacuum filtration assisted layer-by-layer deposition of functionalized multi-walled carbon nanotubes (MWNTs), was used to prepare conductive surfaces on polysulfone (PSf) ultrafiltration membranes. PSf membranes were functionalized with oxygen-containing negatively charged functional groups, through oxygen plasma treatment. MWNT-PSf membranes were prepared
with 5, 10, 15, and 20 bilayers with amine- and carboxylic-functionalized MWNTs. The prepared membranes were characterized by the thickness, contact angle, and conductivity of membranes. SEM images of the membranes confirmed uniform MWNT distribution across the
membrane surface. MWNT-PSf membranes exhibited slightly reduced permeability, improved selectivity and greater conductivity with increasing number of MWNT bilayers and demonstrated almost complete inactivation of E. coli at low applied DC potential (1-3V).
Furthermore, significant (around 99%) degradation of methyl orange during electrofiltration was observed, supporting an expected reduction in organic fouling of the membrane.

In this work, the ultrafiltration of macromolecules was analysed using a response surface methodological approach. The behaviour of two different inorganic membranes was investigated. The membranes selected were a Carbosep M2 membrane (Orelis, France) with a molecular weight cut-off (MWCO) of 15 kDa and a Tami MSKT membrane (Tami Industries, France) with a MWCO of 5 kDa. The solute employed was polyethylene glycol of 35 kDa molecular weight. The influence of transmembrane pressure (0.1, 0.2, 0.3, 0.4 and 0.5 MPa), crossflow velocity (1, 2 and 3 m/s) and feed concentration (5, 10 and 15 g/L) on permeate flux and permeate flux decline was investigated. Analysis of variance was proved to be a useful tool to determine the effect of operating variables on both parameters. The method used demonstrated the presence of coupled effects between factors as well as squared effects that are relevant to the ultrafiltration process. The surface contours obtained from fitted models were used for the optimization of the operating conditions. The goal was to simultaneously maximize the average permeate flux and minimize the flux decline. The optimal operating conditions for the Carbosep M2 membrane were a transmembrane pressure of 0.38 MPa and a crossflow velocity of 3 m/s. The optimal operating conditions for the Tami MSKT membrane could not be determined by means of multiple response optimization due to the low accuracy of the regression model obtained for the cumulative permeate flux decline (SFD) response variable.

Gas sparging is used as a traditional way to control membrane fouling in submerged membrane bioreactors (MBRs) in wastewater treatment. However, the gas sparging accounts for the largest fraction in operational cost to run the MBR systems. In this study, membrane fouling was controlled by integrating scouring media with gas sparging to reduce fouling rate at relatively low operational energy. Comparative study was performed using a fluidized membrane reactor treating synthetic feed solutions between polyethylene terephthalate (PET) scouring media (SM) fluidized by gas sparging (GS), liquid recirculation (LR), and combination of them to control membrane fouling. Addition of PET scouring media reduced the gas flow rate by 67% more with 30% less in fouling rate than gas sparing only. Combined usage of gas sparging and liquid recirculation to fluidize the PET scouring media (LR + GS + SM) showed 37% lower in fouling rate than that obtained by the scouring media fluidized by liquid recirculation (LR + SM) only through the reactor. The LR + GS + SM configuration reduced energy consumption by 90% more than that required by gas sparging alone. Mechanical cleaning driven by fluidizing PET scouring media could reduce membrane fouling due to removing deposit of inorganic particles from membrane surface effectively. However, the PET scouring media was not very effective to reduce membrane fouling caused by organic colloids which are expected to contribute pore fouling significantly.

Four commercial tubular membranes (AFC80, AFC30, PU608, and ES404) have been investigated in this study for their performance of binary metal ions rejection under different feed conditions. A range of salts (tin chloride, tin sulphate, calcium chloride, calcium sulphate) with divalent cations were chosen to assess the effects of different anions (chloride and sulphate) on performance of the membranes. All membranes were tested by varying the feed concentration (2500, 5000, 10,000 mg L À1) at fixed cross flow velocity of 1.5 LPM and feed pressure 1400 kPa. Observed retention (R obs %) and permeate flux (J v) were key parameters to evaluate the performance of studied tubular membranes. It was found that increase in concentration adversely affected the both evaluation parameters i.e. permeate flux and rejection. Nevertheless, nanofiltration type tubular membranes (AFC80 and AFC30) showed higher rejection than their counterparts, i.e., ultrafiltration type tubular membranes (ES404, PU608) for all investigated salts. Maximum observed rejection for all salts was noted for AFC80 for all salts followed by AFC30, ES404 and PU608 tubular membranes. Furthermore, it is reveal that anion types (SO 4 2À , Cl À) of these salts played a vital role in retention of these tubular membranes when the salts with same cations were used as feed solution.

Zirconia nanopowder Ultrafi ltration membrane Slip casting Clay-alumina Wastewater • Clay-alumina based ceramic multichannel support was used for membrane preparation. • UF membrane was prepared in single step coating of zirconia nanopowder. • Stability of suspension of nanopowder was studied using CE64 with pH variation. • Defect free zirconia UF membrane was prepared over 19-channel support tube. • Developed membrane could reduce organic matters and MPN from various effl uents.

Zirconia nanopowder Ultrafi ltration membrane Slip casting Clay-alumina Wastewater • Clay-alumina based ceramic multichannel support was used for membrane preparation. • UF membrane was prepared in single step coating of zirconia nanopowder. • Stability of suspension of nanopowder was studied using CE64 with pH variation. • Defect free zirconia UF membrane was prepared over 19-channel support tube. • Developed membrane could reduce organic matters and MPN from various effl uents.

There has been upsurge of interests in anaerobic membrane bioreactor (AnMBR) for low-strength wastewater treatments. However, biofouling is still a long-standing problem in the AnMBR because it can increase a frequency of chemical cleaning while shortening membrane life-time. Foulants present in the AnMBR complicate analyses of the membrane fouling due to their wide-ranged particle size distributions present in microbial suspensions and various compressible colloidal materials produced by microbial activities. In general, gas sparging with a biogas produced in the bioreactor or applying very high hydraulic shear conditions along the membrane surfaces is being widely adopted to control biofouling in the AnMBR. However, each physical method requires much high energy consumptions, weakening many advantages of the AnMBR system to achieve energy-positive wastewater treatment. The anaerobic fluidized membrane bioreactor (AFMBR) is to combine anaerobic fluidized bed bioreactor (AFBR) with submerged membrane technology. Granular activated carbon (GAC) particles are used as fluidized media to control membrane fouling by their physical scouring actions and adsorptive capabilities on membrane surfaces. Since GAC particles are fluidized by a recirculation of bulk fluid alone through the reactor, the energy required to reduce membrane fouling can be about one-tenth of it obtained by existing method such as biogas sparing or cross-flow filtration. Nevertheless, both biofouling and energy requirements for fluidization in the AFMBR system can vary significantly depending upon the particle size distributions of the microbial suspensions and GAC sizes applied. This study focuses on combined effect of particle size distributions of the microbial suspensions from the AFBR system and GAC sizes as fluidized media on membrane fouling and energy consumptions using a laboratory-scale AFMBR. Effluents from a pilot-scale AFBR operated in a domestic sewage treatment plant were applied as test solutions to the AFMBR. Our results showed that larger GAC sizes resulted in less membrane fouling in the AFMBR combined with hollow-fiber membranes having 0.03 µm nominal pore size. However, smaller fouling components than 0.1 µm were not affected significantly by GAC fluidization, causing an irreversible membrane fouling. Most of these small colloidal materials consisted of polysaccharide and proteins which are main components in soluble microbial products and/or extracellular polymeric substances. The use of smaller GAC particles which are almost close to powdered activated carbon did not provide any beneficial effect on the reduction of the membrane fouling. As GAC sizes became smaller, the binding interactions between the GAC particles and membrane surface were very strong, accelerating additional external fouling on membrane surface. Energy consumption for fluidization increased exponentially with increasing GAC sizes in the AFMBR system, suggesting that a trade-off exist between fouling control and energy expenditure for GAC fluidization.

Conductive membranes can offer innovative solutions for membrane-fouling control while maintaining enhanced filtration performance. Here, an emerging technique, vacuum filtration assisted layer-by-layer deposition of functionalized multi-walled carbon nanotubes (MWNTs), was used to prepare conductive surfaces on polysulfone (PSf) ultrafiltration membranes. PSf membranes were functionalized with oxygen-containing negatively charged functional groups, through oxygen plasma treatment. MWNT-PSf membranes were prepared with 5, 10, 15, and 20 bilayers with amine- and carboxylic-functionalized MWNTs. The prepared membranes were characterized by the thickness, contact angle, and conductivity of membranes. SEM images of the membranes confirmed uniform MWNT distribution across the membrane surface. MWNT-PSf membranes exhibited slightly reduced permeability, improved selectivity and greater conductivity with increasing number of MWNT bilayers and demonstrated almost complete inactivation of E....

ABSTRACT Galactosyl-oligosaccharide (GOS) is a prebiotic carbohydrate, produced from lactose hydrolysis, that serves as a value-added functional food element for humans. Now GOS can be produced through enzymatic reaction with lactose either in batch mode or with immobilized enzyme on membrane. In the second case, the main concern is the fouling of the membrane that could reduce both the GOS yield and purity. The present study is thus an attempt to project the superiority of a membrane reactor called the rotating disk membrane bioreactor (RDMBR) over batch mode to obtain purified GOS with high yield. It was found that GOS yield and purity were 32.4% and 77% respectively in batch mode followed by diafiltration-assisted nanofiltration. However, in the immobilized state they were 67.4% and 80.2% at 105 rad s–1 membrane speed. Retention of monosaccharides that inhibit enzyme in the reaction volume of batch mode reduced the yield of GOS. On the contrary, simultaneous production and purification of GOS in RDMBR led to a high yield of GOS.

This study has applied the concept of hybrid PAC-UF process in the treatment of the final effluent of palm oil industry for reuse as feedwater for low-pressure boilers. In a bench-scale set-up, a low-cost empty fruit bunch – based powdered activated carbon (PAC) was employed for upstream adsorption of biotreated palm oil mill effluent (BPOME) with the process conditions: 60 g/L dose of PAC; 68 min of mixing time; and 200 rpm of mixing speed; to reduce the feedwater strength, alleviate probable fouling of the membranes and thus improve the process flux (productivity). Three polyethersulfone ultrafiltration membranes of molecular weight cut-off (MWCO) of 1, 5 and 10 kDa were investigated in a cross-flow filtration mode, and under constant transmembrane pressures of 40, 80, and 120 kPa. The permeate qualities of the hybrid processes were evaluated and it was found that the integrated process with the 1 kDa MWCO UF membrane yielded the best water quality that falls within the US EPA reuse standard for boiler-feed and cooling water. It was also observed that the permeate quality is fit for extended reuse as process water in cement, petroleum and coal industries. In addition, the hybrid system’s operation consumed 37.13Wh m-3 of energy at the highest applied pressure of 120 kPa, which is far lesser than the typical energy requirement range (0.8 – 1.0 kWh m-3) for such wastewater reclamation.