Purification of Minute Virus of Mice using high performance tangential flow filtration

Membrane technology has proven to be a mainstay separation technology over the past two decades. Some major advantages of membrane technology are application without the addition of chemicals and a comparatively low energy use. With its current applications, membrane technology has been widely used in biotechnology processes. Cell harvesting and virus purification/removal are important processes in many downstream purifications of biopharmaceutical products. For this project, ultrafiltration (UF) for virus purification from cell culture broth was used. Recently, it has been demonstrated that UF is a powerful tool for purification of other viruses such as Aedes aegypti and virus-like particles. More precisely, high performance tangential flow filtration (HPTFF) will be used, which was first introduced by Robert van Reis in 1997. To date HPTFF has been used in other projects, as for protein concentration, purification, and buffer exchange as a single unit operation. The virus used in this study was the parvovirus Minute Virus of Mice (MVM); characterized by an average diameter of 22-26 nm and icosahedral symmetry. Experiments were conducted with 300, 100 and 50 kDa Sartorius membranes. Results obtained indicate that using the 50 or 100 kDa membrane, viral particles get excluded, whereas the 300 kDa membrane allows the passage of the virus particles into the permeate. In HPTFF mode the permeate flux decline of the 300 kDa ultrafiltration membrane is much greater than for the other membranes used. One possible explanation for this decay could have to do with the virus particles' access to the membrane pores (gradual pore narrowing). Additionally the permeate flux and level of protein rejection as well, are strongly affected by the cell culture medium.     

Tubular Membrane Filtration with A Side Stream and its Intermittent Backwash Operation

The tubular membrane filtration system is widely applied to solid-liquid separation processes. Any improvements to the filtration module would increase separation efficiency, thus reducing operating costs. In this experiment, PMMA powder with an average particle diameter of 0.8 µm was filtered by a ceramic tubular membrane with an average pore size of 0.2 µm, and the impacts of the operating variables, such as suspension concentration, the filtration pressure, and the crossflow velocity on the permeate flux were discussed. In order to understand the increased permeate flux, the proposed module is comparable to the tubular membrane filtration module, but with an additional side stream under the same filtration mass flow rate. In addition, variations of shear force on the membrane surface are analyzed by CFD simulation, and the influence of backwash operations on the permeate flux is discussed. The results show that the side stream membrane filtration increased the shear force on the membrane surface, reduced fouling on the membrane surface, and increased the permeate flux. Furthermore, a backwash operation with a side stream flow channel could effectively clean the particles deposited in the module, thus, increasing the permeate flux.     

Concentration of the baculovirus Autographa californica M nucleopolyhedrovirus (AcMNPV) by ultrafiltration

Concentration and retention of a rod-shaped virus during tangential flow ultrafiltration (UF) was assessed to evaluate the potential of membrane-based downstream methods with advantages such as easy scale-up for industrial processes. A recombinant baculovirus of the non-spherical Autographa californica M nucleopolyhedrovirus (AcMNPV), vHSGFP, expressing egfp was filtered using polyethersulfone membranes ranging from 30 to 1000 kDa molecular weight cut-off (MWCO). A 20-fold virus concentration was achieved when a membrane cut-off range of 100 to 1000 kDa was tested. Fouling was observed and cake formation and pore plugging were postulated as concurrent causes with different impact depending on the MWCO. A reduction of virus concentration in the range of 2 to 5 log units in the permeate was observed illustrating the potential of membrane-based virus filtration as a useful unit operation in downstream processing.     

Extraction and Separation of α-lactalbumin and β-Lactoglobulin from Skim Milk by Microfiltration and Ultrafiltration at High Shear Rates: A Feasibility Study

Abstract

This paper presents a two-stage membrane filtration process for extracting and separating α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg), from UHT skim milk, using dynamic filtration. The 1st stage separates casein micelles in retentate from whey proteins in the permeate with rotating 0.2 µm pores ceramic membrane disks. Casein micelles rejection was excellent, while α-La and β-Lg transmissions remained between 80 and 90%. The permeate flux at 40°C ranged from 105 to 40 Lh^?1m^?2 at a volume reduction ratio of VRR = 4. The 2nd stage consisted of ultrafiltration of the previous permeate with a metal disk rotating at 2000 rpm near a fixed 50 kDa PES membrane, in order to concentrate β-Lg in retentate, while collecting α-La in the permeate. The flux dropped from 270 Lh^?1m^?2 at VRR = 1, and remained nearly constant at 200 Lh^?1m^?2 until a VRR of 3.3. α-La transmission increased with VRR to reach 23% at VRR = 3.3, while β-Lg transmission decayed at increasing VRR to 3%, to give a maximum selectivity of 8.     

超滤膜直接过滤浑浊水的试验

采用聚丙烯腈中空纤维超滤膜,以自来水添加粘土配制成试验用水,进行了直接过滤试验。结果表明:超滤膜具有良好的除浊功能和除菌作用,对水中的有机物也有一定的去除作用。滤后水浊度小于0.1 NTU;菌落总数的去除率大于99.9%;TOC的去除率为10%～18%。原水浊度为300 NTU左右时,超滤的周期产水量比较稳定,归一化比渗透通量保持在55%以上。     

Treatment of Aqueous Ionic Surfactant Solutions by Dynamic Ultrafiltration

Abstract

This paper investigates the reduction of concentration of an ionic surfactant (sodium dodecyl benzene sulfonate) present in an aqueous solution by ultrafiltration. A dynamic filtration system consisting of a metal disk rotating near a flat circular organic membrane was used in this study. Membranes cut off tested were 10, 20, and 50 kDa. The maximum rejection rate was 92% at 10 kDa. Permeate fluxes kept increasing with transmembrane pressure until at least 1400 kPa, reaching 400 Lh^?1m^?2 at 10 kDa and 950 at 50 kDa for a rotation speed of 1000 rpm. However, raising the rotation speed above 500 rpm at 900 kPa had only a moderate effect on performance, indicating probably strong interactions between surfactant molecules and the membrane and that the permeate flux was mostly limited by pressure.     

Membrane choice for wastewater treatment using external cross flow tubular membrane filtration

Systematic investigations of activated sludge separation were conducted using membrane filtration. To accomplish this, different organic tubular membranes with different separation limits and diameters were examined. Furthermore, from the results obtained in the initial tests, an appropriate membrane was chosen for a long-term test. The investigations determined that for biomass separation by the tubular membranes in the tested system, neither the membrane material nor the separation limit within a range of 1 μm to 20,000 Da had a significant influence on the filtration characteristics. It was recognized that the application of a tubular membrane with a diameter of less than 8 mm is problematic, because high flow velocities were needed to prevent blockage of the membrane. When the flow velocity was in the range of 1 to 4 m/s, a linear relation between flux and velocity was found. This showed the potential for controlling the membrane filtration process and externally influencing the permeate rate. An average retention of TOC was about 75%. The retention of TOC was not significantly influenced by the nominal pore sizes of the membranes (except for the membrane WFNX 0505) which were tested here. The ultrafiltration membrane WFS 0120 (Stork) was prominent in the long-term test due to its very high flux, germfree permeate with a MWCO (molecular weight cut-off) of 100,000 Da, and was not blocked with a diameter of 14.4 mm, also at lower flow velocities. The results of the long-term test supported the hypothesis that a meaningful application of such a module concept is possible in a filtration plant for the preparation of samples or for the rejection of the biomass in small sewage treatment plants.     

FLUX ENHANCEMENT USING FLOW REVERSAL IN ULTRAFILTRATION

ABSTRACT

The effect of flow reversal on permeate flux in cross-flow ultrafiltration of bovine serum albumin (BSA) has been investigated experimentally. BSA is a well-studied model solute in membrane filtration known for its fouling and concentration polarization capabilities. Ultrafiltration experiments were performed with BSA feed solutions in a hollow-fiber membrane module. The BSA feed concentrations ranged from 0.01 to 5 wt% and were ultrafiltered at a transmembrane pressure of 20 psia. Permeate flux was determined both with and without the use of flow reversal for each concentration. The experimental results indicate that under flow reversal conditions, the permeate flux is enhanced significantly when compared with runs without flow reversal. The effect of flow reversal on flux enhancement is very pronounced for dilute BSA solutions.     

Optimization of backflushing conditions for ceramic ultrafiltration membrane of disperse dye solutions

In the ultrafiltration (UF) of disperse dye solutions using ceramic membrane, backflushing is necessary to minimize the formation of fouling by disperse dye, and to enhance the permeate flux. In this work, the effects of backflushing on the ultrafiltration performance and decolorization were investigated. In the optimum backflushing condition, the permeate flux increased slightly and the filtration performance was stable during filtration process.     

Comparative analysis of the processes of collagen concentration by ultrafiltration using different types of membranes

Tangential flow filtration of the collagen protein solutions with a molecular weight 12, 14, and 24 kDa is investigated using flat sheet membranes. The effects of tangential ultrafiltration (UF) on the permeate properties using two regenerated celluloses (RCs) and two polyethersulfone (PES) membranes with molecular weight cut-off (MWCO) of 5 and 10 kDa are reported. The permeate and concentrate obtained in the UF experiments are characterized from a physical–chemical point of view by determining the temperature, pH, electrical conductivity, nitrogen content, and protein concentration. In addition, the experimental data are modeled using Hermia's model. The UF experiments demonstrated that permeate flux declined with increasing molecular weight of collagen at constant concentration (1%). Regardless of the molecular weight of collagen, the rejections decrease in the following order: PES 5 kDa > RC5kDa > RC10kDa > PES10kDa. In case of membrane with higher MWCO, the clogging phenomenon is mainly due to the blockage of the internal pores of the membrane than the formation of a polarization layer. Morphologies and characteristics of the membranes are characterized using scanning electron microscopy.     

Recovery of Water from Sewage Effluents using Alumina Ceramic Microfiltration Membranes

Abstract

This work highlights the recovery of water from sewage effluents using alumina ceramic membranes with pore sizes of 0.2 and 0.45 µm respectively in dead‐end filtration mode. The work demonstrates the ability and advantages of alumina‐based microfiltration (MF) membranes in filtering microbes and other harmful pollutants normally present in sewage effluents in dead‐end filtration mode. The fouling behavior of the membranes in the filtration cycle is identified, which in turn helped to regenerate the fouled membranes for subsequent usage. Regeneration studies of fouled membranes also suggest that though chemical cleaning was effective in recovering membrane performance, the fouling had still been progressed slowly and the membranes showed the ability to perform at least five filtration cycles of highly‐contaminated sewage effluents. As expected, the filtration efficiency and flux characteristics at various transmembrane pressure (TMP) of the membranes varies with the pore size of the membrane and is explained in light of Darcy's and Poiseuille's laws of filtration. The results show that alumina ceramic membrane with disc geometry having a pore size of 0.2 µm is more effective in filtering the total suspended solids, turbidity and microbes of the sewage effluents as compare to that of 0.45 µm membrane to a level in which the permeate water appears to be benign for discharging into the surface thereby offering the possibility of recycling or reusing the recovered water from the sewage effluents for suitable purposes.     

高频振动膜处理含油污水实验研究

使用机械振动和超滤组件结合的高频振动剪切超滤膜过滤系统,来考察振动频率、进口压力、料液流量等因素对膜系统渗透通量和分离性能的影响。利用清水、含油污水和0．1％NaOH溶液来研究高频振动剪切超滤膜过滤系统的性能,对比了常规静态错流膜过滤与高频振动剪切膜过滤,验证振动剪切膜过滤方式的可行性和有效性。     

Chromate Removal from Water Using Surfactant-Enhanced Crossflow Filtration

Abstract

Removal of chromate from water was investigated using the surfactant enhanced crossflow filtration technique in which the cationic surfactant, cetyl trimethylammonium bromide (CTAB), was the carrier for the metal ions. The variation of chromate and surfactant rejections, and permeate flux with time were measured as a function of CTAB/chromate concentration ratio, while maintaining a constant transmembrane pressure drop, membrane pore size, and pH of the feed solution. The method was found to be effective in removing chromate from water. It was observed that the efficiency of chromate removal increased with increasing CTAB/ chromate ratio. It was also found that the chromate concentration had a significant effect on the CTAB concentration in the permeate and on the time taken to establish the secondary membrane which consists of a highly viscous surfactant phase in the hexagonal state in the absence of chromate. In the presence of chromate, permeate flux increased at the same CTAB concentration although the surfactant and chromate rejections decreased, indicating lowering of the secondary membrane resistance to permeate flow. These conclusions were confirmed by deadend filtration experiments which showed that the fouling index decreased by the addition of chromate while the opposite was valid when sodium chloride was present in the surfactant/water/electrolyte ternary system.     

Elimination of organic matter present in wastewaters from the cork industry by membrane filtration

BACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes. RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da). CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry     

A Novel Rig Design for Ultra- and Microfiltration Experiments

Abstract

The versatile rig for crossflow ultrafiltration and microfiltration experiments described in this paper can be operated at various concentrations of the feed stream by using a feed-and-bleed mode, either at controlled permeation flux or at controlled transmembrane pressure. Transmembrane pressure can be set as a static counterpressure through a bleed valve, or as a dynamic counterpressure achieved by circulating the permeate cocurrent to the retentate, to maintain an equal transmembrane pressure profile along the filtration path. The rig is equipped with extra independent controls (retentate and permeate temperature, retentate tangential flow velocity, retentate pressure) to enable to master filtration procedures by setting variables to the desired values through any operational pathway. It allows real time data monitoring and storing by a computer through a multichannel analyzer.     

Effect of Pore Size and Particle Size Distribution on Granular Bed Filtration and Microfiltration

Abstract

The paper reviews the effect of particle size distribution and pore size distribution on granular bed filter and crossflow microfiltration performance. The experimental results of the granular bed filter with pollen particles in suspension showed that the presence of large particles improved the filter efficiency of smaller particles in suspension. Microfiltration results with bi and tri‐modal latex suspensions showed that the permeate flux and the quality were significantly affected by the particle size and its distribution, especially when the particle size was smaller than the pore size of the membrane. The mathematical model simulation results of granular bed filtration show that media pore size distribution is an important parameter of filtration for the particle removal and pressure drop across the filter.     

Pilot plant study of an ultrafiltration membrane system fordrinking water treatment operated in the feed-and-bleed mode

A pilot plant study of a polysulfone ultrafiltration (MWCO of 30 kD) tubular membrane process was conducted for the treatment of reservoir water. The membrane separation system was operated in the cross-flow filtration mode at 4.7 m/s and the feed-and-bleed mode for a long term of 4000 h without chemical cleaning and backwashing. The results showed that the behavior of permeate flux of the membrane system operated in the feed-and-bleed mode was similar to that of membrane systems with a periodic backwashing. At the beginning of filtration, bleeding of highly concentrated retentate caused a significant increase in permeate flux by 20%. However, as filtration progressed over time, the permeate flux of the fouled membrane was almost independent of the change in concentration of retained materials by bleeding the retentate. Three distinct stages in permeate flux decline were observed as follows: (1) sharp decrease from 120 to 30 1/m²/h in 1250 h due to a rapid build-up of a fouling layer, (2) gradual decrease to 15 1/m²/h in 2800 h due to the role of tangential shear induced by cross-flow velocity, and (3) stable permeate flux until 4000 h due to the establishment of a pseudo-steady-state condition. Permeate quality was stable, regardless of concentrating and diluting retentate in each cycle and fouling for a long duration of filtration. Rejection efficiencies for ultraviolet absorbance at 260 nm (UV₂₆₀) and dissolved organic carbon (DOC) were around 58% and 49%, respectively. The measured turbidity and concentration of suspended solids in bleed water agreed with calculated values from a simple mass valance, while the measured DOC and UV₂₆₀ of bleed water were much lower than calculated values.     

Effect of Support Material Properties on Dynamic Membrane Filtration Performance

A dynamic membrane is defined as a cake layer which forms on a support material, for example, filter cloth or mesh when the liquid to be filtered includes suspended particles. Formation of an effective dynamic cake layer is highly related with the retention of particles on the support material surface. Therefore, support material properties are considered to be of prime importance in the performance of dynamic membrane treatment systems. This study investigates the effect of support material properties including pore size and structure of the material on dynamic membrane formation and performance. In this concept, a comparative evaluation was made between support materials which have different yarn types. The results showed that high total suspended solids removal efficiency (>98%) could be achieved by using dynamic membrane filtration technology. Mono-monofilament and staple filter cloths were determined as the most appropriate materials in terms of the critical fluxes which were 9.2 L/m² · h and 17–19 L/m² · h for mono-mono filament and staple materials, respectively. However, considering the results of more long-term experiments, mono-monofilament filter cloth was found more suitable for cake layer accumulation. Therefore, we postulate that mono-monofilament cloth can be used in dynamic membrane filtration systems as an alternative to traditional membranes in anaerobic membrane bioreactors.     

Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater

Abstract

Nanofiltration membranes (NF) are being employed in pretreatment unit operations in both thermal and membrane seawater desalination processes and as partial demineralization to seawater. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against seawater is presented in this paper. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in details to study their performance in filtering the salt mixture, synthetic and real seawater in a cross‐flow NF membrane process at a pressure range from 4 to 9 bars. The Spiegler‐Kedem model was used to fit the experimental data of rejection with the permeate flux in order to determine the fitting parameters of the reflection coefficient (σ) and the solute permeability (P_s). The results showed that the rejection increases with pressure for NF90 and slightly increases with pressure for NF270. Also, the NF90 membrane has shown to be able to reject both monovalent and divalent of all investigated mixtures and seawater with very reasonable values but at a relatively low flux. Moreover, it reduced the salinity of investigated seawater from 38 to 25.5 g/L using one stage of the NF membrane at 9 bars. This makes NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values. It has also reduced the seawater salinity to 33.6 g/L, but at a very high permeate flux. The SKM model fitted the experimental data of divalent ions in salt mixture and seawater.     

Filtration in hydrophobic media: 2. A triglyceride partition phenomenon as observed by tangential filtration of butter oil

Having demonstrated a partition of a hydrophobic medium (butter oil) under crossflow filtration and having tentatively explained the phenomenon on stereochemical and saturation basis, the molecular partition was studied by tangential filtration. Under specific hydrodynamic conditions, a filtration phenomenon was demonstrated. The solid fat content (SFC) at 20°C of the fractions obtained was investigated accordingly. When the molecular partition takes place, an SFC divergency between the permeate and the retentate is observed. The amplitude of the divergency depends on experimental conditions.