Effect Of Transmembrane Pressure Research Articles

Separation of ovalbumin from chicken egg white using two-stage ultrafiltration technique

With increasing demand of high quality proteins in different aspects of bio-pharmaceuticals, ultrafiltration (UF) techniques are emerging as an attractive route for separation of ovalbumin from chicken egg white (CEW). In this study, the feasibility of separation of ovalbumin from CEW was investigated using Amicon stirred cell fitted with polyether sulfone (PES) membrane. A two-stage ultrafiltration scheme employing 30 and 50 kDa flat disk PES membranes was used for accomplishing the desired separation. Prior to UF, centrifugation and dilution by 200 mM NaCl solution to required CEW concentration were carried out to prepare feed for ultrafiltration. The effects of trans-membrane pressure, stirrer speed, solution pH, feed dilution on permeate flux and rejection have been studied thoroughly. In this study, total protein concentration and individual protein concentrations were observed at each stage of separation along with the permeation rate. Results of the investigation showed that a high purity ovalbumin (98.7% dry basis) could be produced by the proposed separation train with operating trans membrane pressure (TMP) 4.5 kgf cm −2, stirring speed 200 rpm, pH 2.5 and CEW–solvent ratio 1:1.

Effect of transmembrane pressure on overall membrane resistance during cross-flow filtration of solutions with high-ionic content

The purpose of the study was to investigate the change in membrane resistance in relation to operating pressure for clean RO and NF membranes during filtration of a bioreactor effluent. Experiments were conducted using a SEPA CFII membrane element cell and effluent from a bioreactor with high-ionic content. Flux–pressure profiles of two RO and one NF membranes were analyzed and compared with those for filtration of deionized water. The flux–pressure profile increased linearly with increasing pressure for all three membranes during filtration of deionized water. However, during filtration of the bioreactor effluent, the rate of increase in flux decreased after the pressure reached a critical level with both RO membranes. The changes in flux and membrane resistance were analyzed in relation to the operating pressure which was correlated to transmembrane pressure using logarithmic and second order polynomial correlations. Experimental results showed that a second order polynomial function described the flux–pressure profile more adequately than the linear correlation. The use of the flux ratio (i.e., flux with bioreactor effluent to flux with deionized water) allowed a basis for comparison of change in membrane resistance with transmembrane pressure for different membranes. The critical pressure which resulted in the minimum membrane resistance was determined by the change in the membrane resistance expressed in dimensionless form as the ratio of the observed membrane resistance with bioreactor effluent and deionized water.

Analyses of hydrodynamic resistances and operating parameters in the ultrafiltration of grape must

Grape must destined to the production of white wine was clarified by cross-flow ultrafiltration (UF), on laboratory scale, by using polysulphone hollow fibre membranes with a molecular weight cut-off of 100 kDa. The effects of transmembrane pressure (Δ P), feed flow rate ( Q f) and temperature ( T) on permeation flux and resistances were studied. Results showed that permeate fluxes decreased with time until a steady-state was established. A maximum steady-state permeate flux was reached at a Δ P of about 100 kPa. Steady-state permeate fluxes increased with temperature in the range 15–39 °C. It was also observed that flux increased by increasing bulk flow rates according to the concentration polarization model. The permeate flux decay was analysed through the resistance-in-series model. Analyses of results showed that the membrane resistance ( R m) was constant, while both cake layer resistance ( R c) and fouling resistance ( R f) increased with Δ P and decreased with Q f. An increasing of temperature determined a significant decreasing of the cake layer resistance in the range 15–23 °C, while the fouling resistance showed a little increase in all the range of the investigated temperatures. Observed rejections of the UF membrane towards total soluble solids (TSS) and total phenolics increased by increasing Δ P in the range 20–130 kPa. A decreasing of the color intensity associated to an increasing of the clarity of the clarified must was observed when the pressure is raised. pH and acidity of the clarified must were not affected by the operating pressure.

Effect of transmembrane pressure on rejection of viruses by ultrafiltration membranes

Although partial penetration of ultrafiltration membranes by viruses and bacteria is well documented, there is no satisfactory explanation for the phenomenon. The current study seeks a possible explanation by studying the retention of viruses at different transmembrane pressures (TMPs). In contrast to previous predictions, higher TMPs lead to reduced virus retention levels. Based on indirect evidences it is proposed that the penetration occurs because of the formation during operation, rather than the initial presence, of abnormally large pores. It is therefore suggested that since pore enlargement is induced by high TMPs, high virus retention levels can be obtained only at low TMP values.

Response surface methodology to evaluation the recovery of amylases by hollow fiber membrane

This work aimed to study the pH and the transmembrane pressure effects during the recovery of alpha and beta amylases enzymes from corn malt (Zea mays) by hollow fiber membrane. The optimal condition was obtained for a statistical model, established by response surface methodology (RSM). The response surface analysis showed that the best operation condition for amylolitics enzymes recovery by hollow fiber membrane was 0.05 bar and pH 5.00, while the enzymes were purified about of 26 times.

Purification by membrane technology of an intracellular Ehrlichia ruminantium candidate vaccine against heartwater

This work describes the development of a downstream process based upon membrane technology for the purification of Ehrlichia ruminantium (ER) elementary bodies, which can be used as an inactivated vaccine against heartwater for wild and domestic ruminants. Currently, ER purification is performed by a time consuming multistep centrifugation leading to a high level of host endothelial cell protein contamination. Herein, a simple and scaleable process based on depth filtration for clarification, and tangential flow filtration for concentration to effectively recover ER from infected endothelial cell microcarrier cultures is described. Specifically, depth filtration using 20 and 3 μm pore size membranes was applied to remove microcarriers from the bulk culture while tangential flow filtration was used to simultaneously remove additional cell debris and concentrating the ER to an appropriate level of volume reduction. The effects of transmembrane pressure and tangential filtration mode on ER purification were evaluated; three purification processes were compared to the commonly used centrifugation technique. Results showed that an ER recovery yield of 58% and volume reduction of 87% was achievable in less than 1 h of processing time when using membrane-based processes. This process enables a rapid purification of ER elementary bodies with a minimum of unit operations, reducing the overall cost of the vaccine production; similar approaches may be applied for the purification of other obligate intracellular bacteria with emerging impact on human and animal health.

Ultrafiltration of kiwifruit juice using modified poly(ether ether ketone) hollow fibre membranes

Modified poly(ether ether ketone) (PEEKWC) hollow fibre (HF) membranes were prepared via the dry–wet spinning technique through the phase inversion process. The membranes were characterised by scanning electron microscopy (SEM), pure water permeability ( L p 0 ) and dextran rejection ( R%). On the basis of the obtained results, HF membranes were selected and tested for the clarification of kiwifruit juice. The effect of transmembrane pressure (Δ P), temperature ( T), feed flow rate ( Q f) and suspended solids concentration on the permeate flux was evaluated in experimental runs performed according to the total recycle configuration. Permeate fluxes decreased with time until they reached a steady-state value. Higher permeate fluxes were obtained by increasing temperature and feed flow rate. The steady-state permeate flux reached a maximum at Δ P of 75 kPa. For suspended solids content higher than 5% the permeate flux became independent of this parameter. The performance of the membrane modules in terms of productivity was evaluated in experimental runs performed according to the batch concentration mode. In optimal operating conditions the initial permeate flux of 50 l/m 2 h decreased until to reach a steady-state value of 25 l/m 2 h. These values were remarkably higher than those reported in literature concerning the ultrafiltration (UF) of the kiwifruit juice. The permeate flux decay was analysed through the resistance-in-series model. In particular, the influence of Δ P and Q f on cake layer, fouling and total resistance was evaluated. The membrane resistance ( R m) controlled the permeate flux at Δ P lower than 30 kPa, while at the higher Δ P the permeate flux was controlled by the fouling resistance ( R f). Over the whole range of investigated Q f the fouling resistance was the major resistance to the permeate flux. The resulting juice after filtration showed a clarity of about 99% and the complete removal of suspended solids without significant loss of other physico-chemical characteristics of the original juice.

Flux enhancement during ultrafiltration of produced water using turbulence promoter

Concentration polarization and membrane fouling remain one of the major hurdles for the implementation of ultrafiltration of produced water. Although many applications for ultrafiltration were already suggested, only few were implemented on an industrial scale. Among those techniques, turbulence promoter can be more simple and effective in overcoming membrane fouling and enhancing membrane flux. As for the result that turbulence promoter increase fluid velocity, wall shear rates and produce secondary flows or instabilities, the influence of turbulence promoter was investigated on permeate flux during produced water ultrafiltration and the potential application of this arrangement for an industrial development. Experimental investigations were performed on 100 KDa molecular weight cut-off PVDF single-channel tubular membrane module using four kinds of turbulence promoters. It is observed that the significant flux enhancement in the range of 83%–164% was achieved while the hydraulic dissipated power per unit volume of permeate decreased from 31%–42%, which indicated that the using of turbulence promoter is more efficient than operation without the turbulence promoter. The effects of transmembrane pressure and cross-flow velocity with and without turbulence promoter were studied as well. Among the four kinds of turbulence promoters, winding inserts with 20.0 mm pitch and 1.0 mm wire diameter showed better performances than the others did.

Evaluation of permeate flux in microfiltration of Tamarind ( Tamarindus indica L.) juice using polypropylene membrane

The fruit juice industry has presented a pro-duction increase. In this context, the membranetechnology has been successfully employed infruit juice clarification. A rising number of stud-ies evaluate the increase of yield and final prod-uct quality (color, flavor and taste) as well as theinfluence of the process operating conditions, inorder to obtain better fluxes. The major factorthat limits the use of this technology in largescale is the decrease of permeation flux withtime, due to fouling and polarized layer formation. The aim of this work is to study the effects oftransmembrane pressure and crossflow velocity inpermeates fluxes during the tamarind juice clari-fication, using or not using enzymatic treatment.

Momentum balance analysis of permeate flux for ultrafiltration in tubular membranes with gradually increasing incidental angles of a wired-rod insert

It was reported in previous works that the performance of ultrafiltration in tubular membranes could be improved by concentrically inserting a steel rod, and further improved by wrapping a wired spiral of uniform angles on the entire rod, to increase fluid velocity and thus, to decrease the concentration polarization resistance. Since the thickness of the concentration polarization layer increases along the cross-flow channel while transmembrane pressure decreases. Thus, the smaller inclined angle of wire spiral, as well as smaller increment in fluid velocity, around the inlet region, is sufficient to reduce the lower concentration polarization resistance, while still preserving the effective transmembrane pressure around the outlet region. Accordingly, it was found that membrane performance with inserts with a varying angle wire wrap on the rod was considerably higher then those with constant angle wrapping. The new theoretical analysis of present modified module was based on the momentum balance coupled with the application of resitance-in-series model. Correlation predictions are qualitatively agreement with the experimental results for ultrafiltration of dextran T500 aqueous solution in a tubular ceramic membrane with gradually increasing angles of a wired-rod insert.

Particle deposition in outside-in hollow fiber filters and its effect on their performance

Effect of transmembrane pressure (TMP), particle deposition and reentrainment coefficients, and specific cake resistance on the performance of a dead-end outside-in hollow fiber (DOIHF) filter and hollow fiber membrane (HFM) adsorber is studied using the adsorption–peptization model. It is shown that the increase in TMP causes a higher decline in the permeate velocity for both a DOIHF filter and HFM adsorber. The rise in the adsorption (particle deposition) coefficient can considerably increase the productivity (produced volume of clarified liquid) of these membrane devices. The increase in the peptization (particle reentrainment) coefficient can noticeably decrease their productivity. The volume of clarified liquid produced by the HFM adsorber is 1.6–2 times higher than that produced by the DOIHF filter for the same operation time and process parameters. The values of the particle deposition coefficient, particle reentrainment coefficient, and specific cake resistance are suggested to be adjusted by changing process parameters such as the ionic strength, TMP, and pH, as well as by choosing the material of hollow fibers that provides favorable (attractive) surface interactions between the membrane and particles.

Extractive ultrafiltration for the removal of carboxylic acids

The liquid–liquid extraction of three carboxylic acids (valeric acid, malic acid and lactic acid) from aqueous solutions using a tubular UF ceramic membrane as phase separator (extractive ultrafiltration) has been investigated. The extraction mechanisms for the more effective extracting systems among those tested for each organic acid are explained. Extraction results show the contribution of the physical extraction by the diluent and the reactive extraction by the extractant, with the formation of different acid–extractant complexes, whose stoichiometries can be related to the physico-chemical characteristics of each acid. Equilibrium constants were obtained for all the partition and complex formation reactions involved in the extraction mechanisms. The extractive ultrafiltration – a separation technique, which combines an extraction step with a membrane filtration step – of the aforementioned acids was carried out using three operating modes (total recycle, concentration and continuous modes). A different behavior depending on the nature of each acid (and the complexes they form during the extraction process) was found, showing that solute–membrane interactions play an important role. The effect of transmembrane pressure on permeate flux during the experiments carried out at total recycle show linear trends for all conditions tested. Concentration experiments allowed obtaining the maximum organic to aqueous phase ratio achievable for the three case studies (with the best extraction systems). From an initial 0.1 ratio, values of 0.88, 0.62 and 0.75 could be obtained for valeric, malic and lactic acids, respectively. Finally, a continuous operation showed the evolution of flux and acid concentration in both the aqueous permeate and the rejected emulsion as the organic phase becomes saturated.

Membrane Blocking In Ultrafiltration: A New Approach to Fouling

In this study a model was developed that describes membrane blocking during cross-flow ultrafiltration (UF). This fouling model is able to predict the relative importance of internal pore blocking, blocking of the pore entrance and filter cake formation related to permeation of model solutions of dextran T-70 and dextran 2000. The effects of transmembrane pressure, solute concentration and kind of solute on permeate volume were studied. When using a 0.1% dextran T-70 solution, membrane fouling was due to both internal pore blocking and cake formation. For the other operating conditions, membrane permeation was governed by just one blocking mechanism.

Membrane treatment for palm oil mill effluent: Effect of transmembrane pressure and crossflow velocity

A pilot-scale ultrafiltration (UF) membrane study was conducted to investigate the influence of transmembrane pressure and crossflow velocity on the performance of a palm oil mill effluent (POME) treatment. Two commercial UF membranes, ceramic and polyvinylidene difluoride (PVDF), were used in this study. The permeate flux of both membranes decreased with filtration time until it reached steady-state values. The significant reduction in flux was observed during the fouling layer built up while the steady-state values were obtained once the fouling layer was developed. The steady-state flux increased with increasing crosslow velocity and transmembrane pressure. The percentage rejection for suspended solids, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were also analyzed for both membranes. The crossflow velocity significantly affected the percentage rejection of COD and BOD of the ceramic membrane. Suspended solids in the permeate obtained from both membranes were almost completely absent.

Membrane Filtration with Reversible Adsorption: The Effect of Transmembrane Pressure, Feed Flow Rate, and the Geometry of Hollow Fiber Filters on Their Performance

The effect of transmembrane pressure, feed flow rate, and the geometry of hollow-fiber filters on their performance is studied for depth membrane filtration with reversible adsorption. Mathematical models for rectangular and radial filters are used to find the maximal operation times with a filter retention of not less than 0.9 at constant product (permeate plus filtrate) flow rates for the treatment of a latex suspension in continuous-flow and batch operations. It is shown that the maximal operation time and, hence, product volume is achieved when the feed flow rate approaches the initial permeate flow rate. It is also found that several filters with a lower initial permeate flow rate allow one to achieve a much longer operation time than one filter with the same total initial permeate flow rate.

Ultrafiltration behavior in the treatment of agro-industry effluent: Pilot scale studies

This pilot-scale study deals with highly polluting agro-industry's wastewater, palm oil mill effluent (POME). Ceramic ultrafiltration membrane was applied to treat this effluent. UF separation behavior of POME is reported. The effects of transmembrane pressure and crossflow velocity on permeate flux, limiting flux and percentage rejection for suspended solids and dissolved organic matters were investigated. The limiting flux obtained was further applied to determine critical flux and deposit resistance, R c , using the possible theoretical link of critical flux and limiting flux. The verified values of critical flux are useful in the operation of ultrafiltration to minimized membrane fouling; thus, longer lifespan of the membrane can be expected. Both transmembrane pressure and crossflow velocity show their significant effects to the permeate flux, whereas only the crossflow velocity influences the rejection of dissolved organic matters in terms of COD and BOD.

Removal of fluoride from electronic industrial effluentby RO membrane separation

The electronics industry generates large amounts of fluoride-containing effluents. The objective of this studyis to study the feasibility of applying reverse osmosis (RO) membrane separation to reduce fluoride load to less than 1 kg/d. The effect of transmembrane pressure on the removal of fluoride ion has been investigated in detail, and the design parameters of a small RO separation unit were estimated. The present study indicated that the rejection of fluoride ion is typically higher than 98%, considering that the RO membrane was fully regenerated after each set of experiments. The effect of upstream concentration on the required mechanical pressure was determined by estimating the theoretical osmotic pressure of the feed solution. For industrial effluents, the process developed in this work allows us to reduce the treated volume from 6 m 3/d to 0.36 m 3/d without any pretreatment or adding additional compounds. The cost of the designed RO separation plant (€76,000) is much less than that of the conventional treatment (€533/m 3) that deals mainly with volumes rather than specific

Microfiltration of Bovine and Ovine Milk for the Reduction of Microbial Content: Effect of Some Operating Conditions on Permeate Flux and Microbial Reduction

In the present work a study on bovine and ovine milk microfiltration in a tubular ceramic membrane is reported. The study was aimed at the reduction of milk microbial content through a cold technology, with the obvious advantages for the preservation of essential elements. Considering the low availability of ovine milk, which was daily provided by local farmers, most of the tests were performed with bovine milk, which was commercially available. Few tests were then performed also with ovine milk. Firstly, some tests were performed using bovine milk with different fat content. In the presence of fats, a gradual start‐up procedure (realized by treating a milk diluted with distilled water prior to microfiltration of pure milk) was demonstrated to be fundamental for the achievement of a permeate. Further tests with skim bovine milk evidenced the positive effect of temperature and the negative effect of transmembrane pressure on permeate flux: in fact, average permeate fluxes were 850 and 650 L h−1 m−2 when transmembrane pressure was 0.6 and 1.9 bar, respectively, at 40°C, and 650 and 400 L h−1 m−2, respectively, at 30°C. The subsequent tests with ovine skim milk, performed at 40°C and 0.6 transmembrane pressure, revealed a significant flux decline from 700 to 200 L h−1 m−2 in the first 60 min processing and a relatively stable permeate flux around 200 L h−1 m−2 for further 30 min. In any case, the microbial decimal reduction was about 2–3, in agreement with values found in the literature. Authors are grateful to Mr. Marcello Centofanti, Dr. Raffaella Marino, and Dr. Laura Patini for their helpful collaboration in the experimental work.

CFD modeling of permeate flux in cross-flow microfiltration membrane

This paper reports the results of a study on a three-dimensional computational fluid dynamics (CFD) simulation for predicting the water permeate flux through a microfiltration membrane. The pressure distribution upon the membrane surface was obtained using an in-house CFD package. The localized permeate flux was obtained by using local pressures in the well-known Darcy equation. The total flux was calculated by integrating the local permeate fluxes over the whole membrane surface. The permeate flux is predicted for various input–output pressures as well as various cells setup, including a cell equipped with three types of barrier and the same cell without any barrier. In order to validate the CFD predictions, laboratory experiments were carried out using a commercial GVWP microfiltration membrane, supplied by Millipore Company. The results show that the CFD flux prediction is more accurate in comparison with a simple calculation, in which the average input–output pressures substituted for feed side pressure in the Darcy equation. The effect of transmembrane pressure and fluid mass flow rate on simple and CFD predictions were investigated. The higher performance of CFD prediction was obtained in lower transmembrane pressures.

Effect of varying incidental angles of a wire-rod insert on the performance of tubular ultrafiltration membranes

Increasing the fluid velocity in cross-flow membrane ultrafilter has two conflicting effects: one, the decrease in concentration polarization resistance, which is good for ultrafiltration; while the other, the decrease in average transmembrane pressure is bad for performance. Along the flow channel of a cross-flow membrane ultrafiltration, concentration polarization increases while transmembrane pressure decreases. Therefore, proper adjustment of the convection strength along the flow channel might effectively suppress the undesirable concentration polarization resistance while still preserving effective transmembrane pressure, and thereby lead to improved permeate recoveries. The effect of hydraulic behavior on membrane ultrafiltration in a tubular module inserted concentrically with a steel rod wrapped by a wire spiral with a wire angle varied at a uniform rate along the flow channel was investigated, and the appropriate manner of wire-angle variation along the tube discussed. It was concluded that for the modules of fixed average wire-spiral angle, the best manner of wire-angle variation is such that the wire angle should increase gradually from 0° along the flow channel.