Permeate Flow Rate Research Articles

Use of nanofiltration membrane technology for ceramic industry wastewater treatment

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+, Mg2+, Cl-, and SO42-. In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater quality.

Potential of Membrane Separation Processes in Cheese Whey Fractionation and Separation

Recently, membrane separation techniques are extensively used in a dairy industry, which contains many valuable substances (proteins, lactose, minerals) which can be further used, e.g. in food industry or biotechnologies. This paper summarises a potential of membrane separation process, namely ultrafiltration and nanofiltration, in fractionation of whey components, such as proteins and lactose. It also brings data from desalination of lactose from natural salty whey (from various Czech dairies). Whey was treated by pilot-plant ultrafiltration (Bollene, France) on tubular ceramic membranes (Membralox, Pall) and obtained permeates were purified by nanofiltration spiral wound membranes. We compared two different commercial nanofiltration membranes NTR-7450-S2F (Nitto Denko) and FILMTEC NF270-2540 (Dow) under various conditions. Permeate flow rates on the 500 nm ultrafiltration membrane achieved 6.9 – 44.5 L/h.m2.bar and mass concentration factors were 1.2 – 16.5. This value suggests potential industrial application. Lactose apparent rejections on NTR-7450-S2F were in a range of 82 – 98% and slightly lower (82 – 90%) on the FILMTEC NF270-2540 membrane. Rejections of ions were comparable for both membranes. All experiments confirmed severe membrane fouling on both membranes.

멤브레인 케이크 레이어 형성 과정 모사를 위한 수치 모델의 개발

Membrane filtration has become firmly established as a primary process for ensuring the purity, safety and efficiency of treatment of water or effluents. Several researches have been performed to develop and design membrane systems in order to increase the accuracy and performance of the processes. In this study, a lattice Boltzmann method for the cake layer has been developed using particle dynamics based on an immersed boundary method and the cake layer formation process on membrane has been numerically simulated. Case studies including various particle sizes were also performed for a microfiltration process. The growth rate of the cake layer thickness and the permeation flow rate along the membranes were predicted. The results of this study agreed well with that of previous experiments. Effects of various particle diameters on the membrane performance were studied. The cake layer of a large particle tended to be growing fast and the permeation flow going down rapidly at the beginning. The layer thickness of a small particle increased constantly and the flow rate was smaller than that of the large particle at the end of simulation time.

The effects of feed water temperature and dissolved gases on permeate flow rate and permeate conductivity in a pilot scale reverse osmosis desalination unit

Feed water temperature is an important parameter in determining the optimum conditions for an efficient seawater reverse osmosis (SWRO) process. Increased feed water temperatures are known to increase the permeate flux rate in commercial SWRO systems. There are several factors which link feed water temperature to the operational efficiency of the fundamental membrane desalination process. In this study we have obtained precise data on these effects using two different types of RO membranes in a small scale pilot unit with feeds of seawater, brackish water and pure water. The mechanisms involved have been examined in this work. Pre-heating the feed water to enhance RO efficiency may lead to greater cavitation within the RO membrane. Vapour cavities formed by cavitation have the potential to hinder permeate flow by blocking sections of the polymer matrix in the skin layer of the membrane. In earlier work, it was identified that the presence of dissolved atmospheric gases in seawater leads to a potential for cavitation within the porous membranes used in high pressure RO processes. It was also established that the almost complete removal of these dissolved gases prevented this cavitation. The effects of de-gassing on the permeate rate in a small scale pilot SWRO system was reported recently. This work has been extended here to include more hydrophobic membranes, which are more likely to produce cavitation. In addition, there is new evidence to support the view that de-gassing the feed water can remove/reduce vapour cavities in the membrane for improved flow, which is maintained even when the feed water is re-gassed.

Simulation of vacuum membrane distillation coupled with solar energy: Optimization of the geometric configuration of a helically coiled fiber

This work focuses on solar energy coupled with vacuum membrane distillation (VMD) for brackish water desalination. VMD is an evaporative process, using porous and hydrophobic membranes, permit to obtain the gaseous permeate, under vacuum, from the aqueous liquid feed. The aim of this work was to simulate the influence of operating conditions (feed flow, feed temperature) and hollow fibers membrane characteristics (pitch and curvature radius) on the permeate flow rate. The model formulation takes into consideration the variation of the physical characteristics of brackish solution and the water permeability of membrane. We used in this case a membrane module, composed of hollow fiber wound in helically coiled shape and placed in the absorber of the parabolic trough concentrator. Two dimensional Navier–Stokes equations were written and were solved with the finite element method. For the pitch of 32.2 mm and the coil radius of 95.7 mm, the simulation results of the permeate product are 0.2685 kg/h and 7.688 ...

Understanding dextran retention data for hollow fiber ultrafiltration membranes

Dextran retention tests have become a standard method for characterizing ultrafiltration (UF) membranes. However, most quantitative analyses of dextran transport have been performed with flat sheet membranes using simple stirred cells in which the transmembrane pressure is nearly uniform across the membrane. The objective of this work was to develop a more fundamental understanding of the factors governing dextran retention tests for large pore size hollow fiber ultrafiltration membranes suitable for use in bioprocessing applications, e.g., the purification of vaccines. Experiments were performed using experimental hollow fiber membranes provided by GE Healthcare. Data were analyzed using a theoretical model that accounts for: (1) the axial variation in transmembrane pressure, and in turn the filtrate flux, due to the pressure drop associated with flow through the fiber lumens, (2) the axial variation in the bulk mass transfer coefficient due to the growth in the concentration polarization boundary layer, and (3) the effects of dextran polarization on the local filtrate flux. The intrinsic sieving coefficients were evaluated using available hydrodynamic models assuming a log-normal pore size distribution. The measured dextran retention coefficients were a strong function of the permeate and feed flow rates. For example, the retention coefficient of a 1000 kDa dextran fraction decreased from R = 0.41 to less than 0.02 as the permeate flow rate was increased from 3 to 18 mL/min at a feed flow rate of 120 mL/min due to concentration polarization in the hollow fiber module. The experimental data were in excellent agreement with model calculations over the entire range of dextran molecular weights and flow conditions. The results provide important insights into the proper design and interpretation of dextran retention tests for hollow fiber ultrafiltration membranes.

Application of air flow for mitigation of particle deposition in submerged membrane microfiltration

This study investigates the effect of microfiltration operating conditions on membrane fouling of colloidal particles of kaolin clay. Experiments were conducted with a flat sheet membrane submerged in a suspension prepared from kaolin clay powder of size varying from 0.1 to 4 &mgr;m (Sigma) with a mean particle size 2.10 &mgr;m. The particle size distribution of clay was unimodal and the concentration of kaolin clay was similar to the biomass concentration in a membrane bioreactor (10 g/L). The effects of scouring and permeate flux rates were studied in terms of the membrane fouling rate. A linear relationship between the transmembrane pressure (TMP) and particle deposition was established for different air flow rates and permeate flow rates. Air scouring was more effective at a low permeate flux. There was only a minor change in the mean particle size of deposited colloidal particles on the membrane at a given flux under varying air flows and at the beginning all had a similar rise in TMP. However, at the later stages as particles accumulated on the membrane surface there was a significant rise in TMP. 15 LMH flux was observed as critical flux beyond which a rise in the permeate flux showed a sharp rise in the TMP which varied with air flow rates and particle deposition. The sharp TMP rise that occurred during the initial few hours of operation indicated that air flow for fouling mitigation strategies should target this period to optimise the membrane process. The study showed that air flow and flux rates are the two major governing factors for particle deposition on the membrane surface.

As(V) removal from drinking water by coagulation and filtration through immersed membrane

In this work we investigated As(V) removal by coagulation with FeCl 3 as coagulant combined with microfiltration through immersed membrane. The adsorption capacity of the coagulant was determined and the continuous removal of arsenic was performed with special emphasis on the membrane fouling rate. During a continuous experiment in a reactor with an immersed membrane, tap water was spiked with 100 μg/L of As(V) and treated with 5.16 mg Fe(III)/L. During the experiment, the concentration of As(V) in treated water was always under 10 μg/L. The configuration of the membrane allowed the maintaining of a high permeate flow rate at 60 L/m 2 h. Membrane fouling was mostly caused by the precipitation of scale on the membrane surface and into the membrane pores which contributed 50% to the total resistance while the cake resistance contribution to total resistance was low and reached 15% at the end of the experiment when suspended matter in the reactor reached 8.85 g/L. The initial permeability of the membrane could be restored by chemical cleaning with oxalic acid. The investigated process showed good efficiency and stability in removing As(V) from drinking water.

Effect of the concentration polarization on the fouling driving force of UF membranes

The main objective of this work was to investigate the effect of foulant concentration prevailing at the membrane surface on the rate of flux decline. The significant role of foulant membrane concentration was highlighted by analysis of the well-known filtration blocking laws. All blocking mechanisms were found to predict that the initial fouling rate depends on the product of feed concentration and initial permeate flow rate. Humic acid fouling data were analyzed to provide values of the fouling rate dJv/dt vs. membrane surface concentration Cm. The data of all runs, covering a rather broad range of conditions, fell within a narrow band thus supporting the contention that foulant concentration on the membrane is one of the main parameters governing the fouling rate.

Desalination of Iraqi surface water using nanofiltration membranes

Nanofiltration (NF) has received increased attention as a possible treatment process providing high rejection of solutes and high water flux rate. Using NF as a desalination process for Iraqi surface water is considered in this research. A small system with one membrane of 4 inch diameter and 1 m long was used to evaluate the performance of NF membrane for the desalination of Tigris River water in Baghdad, and compare it with a reverse osmosis (RO) membrane. The results showed that one could get double the permeate flow rate and spend about 20% less electric power when using NF membranes instead of RO membranes. Permeated water TDS values for NF membrane are low enough to allow for further adjustment for drinking water quality. NF rejection capacity for monovalent ions is lower than that of the divalent ions, and in general the salt rejection capacity is above 95%.

Reduction of chlorination byproducts in surface water using ceramic nanofiltration membranes

In this study, two ceramic nanofiltration membranes with a molecular weight cutoff of 450 Da (NF450) and 1000 Da (NF1000) were used to reduce the concentration of organic matter (OM) in natural water, and the effect on the formation of disinfection by-products (DBPs) was evaluated. The effects of pressure, conductivity and pH were studied. The formation of trihalomethanes, haloacetic acids, haloacetonitriles and haloketones was evaluated. The results of the study indicated that the permeation flow rate of NF1000 was greater than that of NF450. An increase in the operating pressure improved the efficiency of OM removal and reduced the formation of DPBs. Over 75% of the formation potential of trihalomethanes was eliminated using NF450 membrane. The NF1000 membrane produces smaller decreases in trihalomethanes. As the conductivity increased from 900 μS/cm to 4000 μS/cm, the reduction of trihalomethanes decreased from 51% to 22% and from 80% to 39% for NF1000 and NF450 respectively. The flow through NF450 and NF1000 decreased when the pH of the solution decreased from pH 8.3 to pH 4.5. The values of trihalomethanes rejections at pH 8.3 were 79% and 58% for NF450 and NF1000 respectively, and these values decreased to 65% and 40% at pH 4.5.

H2 Separation from Gas Mixtures Through Palladium Membranes on Metallic Porous Supports

Thin-film palladium membranes are one of the most promising technologies for hydrogen separation from gas mixtures, involving advantages, such as a separation efficiency approaching 100%, high permeability, and operating conditions compatible with upstream fuel conversion processes. In this work, palladium films, with thickness between 10 μm and 40 μm, were deposited above stainless steel porous tubular supports using a modified electroless plating technique. The application of vacuum during palladium deposition, together with support abrasion and oxidation above 700°C, were demonstrated to be effective in limiting the presence of film defects. The prepared membranes were then tested in an experimental set-up using a wide range of operating conditions (transmembranal pressure 2-20 bar, temperature 300-550°C) in order to evaluate their performances. A hydrogen permeation flow rate of 0.25 mol/ms, with a selectivity with respect to CO2 as high as 5000, was obtained at 450°C and 10 bar of partial transmembranal pressure. A mathematical model was set in order to interpolate the experimental data and simulate the permeation of hydrogen through palladium. A good agreement between experimental and simulation results was obtained.

Non-equilibrium sorption modeling for boron removal from geothermal water using sorption–microfiltration hybrid method

In this study, the boron removal performance of a hybrid system composed of ground ion exchange resin particles coupled with a microfiltration separation unit was investigated. A non-equilibrium sorption modeling approach was introduced so as to understand the contributions of mass transfer resistances on the effluent stream concentration profiles, as well as on the resin loading scheme of this sorption–microfiltration hybrid system. This modeling approach allowed us to suggest new system operations and/or scale-up processes of sorption–microfiltration hybrid systems. In this study, the highly porous crosslinked boron selective chelating resins Diaion CRB02 and Dowex XUS 43594.00 containing N-methyl-glucamine group were used. Geothermal water that has high levels of boron was fed into the stirred cell element of the microfiltration system. Kinetic behaviour of boron selective resins for boron removal from geothermal water by the microfiltration system was evaluated to investigate the effects of resin particle size, resin concentration, and permeate flow rate.

Performance of a cutinase membrane reactor for the production of biodiesel in organic media

The enzymatic transesterification of oils with an alcohol, using recombinant cutinase of Fusarium solani pisi microencapsulated in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reversed micelles, was performed in a membrane bioreactor (MBR). A tubular ceramic membrane with a nominal molecular weight cut off of 15,000 Da was used to retain the enzyme, and characterized in terms of rejection coefficients of the reaction components by transmission experiments. The performance of the MBR in a total recirculation-batch mode was compared with results obtained in a stirred batch tank reactor. The continuous operation of the MBR was also evaluated and the influence of the alcohol type and permeate flow rate on conversion degree and productivity (up to 500 g(product) /day/g(enzyme) was attained) were analyzed. Cutinase wild type and mutant T179C were tested for this process and the high long-term operational stability of the cutinase mutant demonstrated its potential as biocatalyst for the enzymatic continuous production of biodiesel.

The effects of feed water de-gassing on the permeate flux of a small scale SWRO pilot plant

The effects of pressure release on feed water cavitation have been studied using a small pilot scale SWRO system. The presence of dissolved atmospheric gases in seawater leads to a potential for cavitation within the porous membranes used in high pressure processes. The rapid application and release of applied pressures in the range of 10–60 atm was found to cause visible cavitation throughout the bulk solution phase. This phenomenon was not related to increased gas solubility under the applied pressure, since no additional gases were allowed into the system. It was found that almost complete removal of the initial dissolved atmospheric gases prevented this cavitation. Earlier laboratory scale studies had reported that removal of cavitation by feed water de-gassing enhanced permeate flow rates by 3–5% but this level of improvement was not observed in the pilot scale study operating at an applied pressure of 38 atm with seawater feed. It is possible that larger effects may be observed with the use of more ...

Cross-flow ultrafiltration of stable oil-in-water emulsion using polysulfone membranes

This paper focuses on the treatment of oily wastewater coming out from the post-treatment unit of petroleum industries using cross-flow mode of ultrafiltration. Four types of polysulfone (PSf) membranes which had been synthesized using different combinations of additives and solvents were used and their performances were evaluated by treating with laboratory made oil-in-water (o/w) emulsion and later the selected membranes were tested for their applicability to the industrial oily water also known as ‘produced water’. Experiments were carried out mainly to study the influence of cross-flow rate on membrane performance. The study showed that with increase in cross-flow rate, the flux increases significantly; but the oil rejection (%) shows a decreasing trend. Also change in morphological properties of membranes due to addition of different molecular weight PVP and PEG are found to have a significant impact on the permeate flow rate and hence subsequent oil removal. The oil retentions of all the four membranes were over 90% and oil concentration in the permeate was below 10 mg L −1 with the synthetic oily water, which met the requirement for discharge. However, the rejection was found to be below 80% for all the membranes with the ‘produced water’ although the flux was reasonably high. This suggests that the membranes need further modifications to improve their properties such as average pore size and pore size distribution in order to tackle the difficulty of lower oil separation due to penetration of the smaller oil droplets along with the permeate.

Methanol recovery during transesterification of palm oil in a TiO 2/Al 2O 3 membrane reactor: Experimental study and neural network modeling

High quality palm oil biodiesel can be produced by combination of alkali transesterification and separation processes in a TiO 2/Al 2O 3 membrane reactor. Due to the small molecular size, methanol molecules are able to pass through the membrane along with the products. Since methanol is one of the process reactants it is necessary to be recovered. Methanol recovery by means of continuous distillation was employed and the influences of different operational parameters including heating temperature permeate flow rate and reactants ratio were investigated. The results indicate that these parameters have significant effects on the rate of methanol recovery. To simulate the rate of methanol recovery an artificial neural network based approached was employed. The experimental data obtained in this work were used to train and validate the created neural network.

Simultaneous removal of nickel and zinc from aqueous solution by micellar-enhanced ultrafiltration and activated carbon fiber hybrid process

Simultaneous removal of nickel and zinc from aqueous solution by the micellar-enhanced ultrafiltration and activated carbon fiber (MEUF-ACF) hybrid process was performed at a constant permeate flow rate (40 mL/min) and operating retentate pressure (1 bar). The anionic surfactant, sodium dodecyl sulfate (SDS), was applied to enhance the removal efficiency of the ultrafiltration at molar ratios, SDS:Ni(II):Zn(II), ranging from 8.5:1:1 to 59.5:1:1. It was found that at the membrane molecular weight cut-off (MWCO) of 100 kDa and at the molar ratio of 25.5:1:1, the removal efficiencies of Ni(II), Zn(II) and SDS by MEUF alone were 96.3%, 96.7% and 61.0%, respectively. However, the MEUF-ACF hybrid process with the 100 kDa MWCO membrane and at the same molar ratio removed Ni(II), Zn(II) and SDS by 99.3%, 99.9% and 78.8%, respectively. It seemed that an SDS concentration higher than its critical micelle concentration (CMC) was a suitable dose for the MEUF system. It was clearly observed from the results that concentration polarization of micelles played a major role in removal of Ni(II), Zn(II), and SDS. In addition, under the constant permeate flow rate, the ACF component of the hybrid process was able to act as a good quality control unit for metal removal.

Effect of chlorine and acid injection on hollow fiber RO for SWRO

Bio-fouling results in deterioration of permeate quality and flux in reverse osmosis (RO) process. Cellulose triacetate hollow fiber membrane used for RO in SWRO has anti-chlorine property that makes technical sense compared to polyamide spiral-wound RO for overcoming bio-fouling. Mode of chlorine injection is the controlling factor of sterilization in SWRO system. This work evaluated the effects of five different modes of chlorine injecting system as well as HCl injection on the performance of HF RO system. In addition, effects of HCl and anti-scalants on anti-scale performance of HF RO system were also investigated, respectively. A brief list of chemical costs under different abovementioned operating conditions was covered in a cost analysis. The results indicated that the injecting mode that employed continuous chlorine with a relatively low concentration of 0.3–0.4 mg/L at pH 5.8–6.2 was preferable in the aspects of total bacterial count (TBC) removal, permeate flow rate, differential pressure, permeability ( P p ), performance factor (η) and chemical costs. HCl injection could improve the sterilization and prevent scaling on the membrane surface efficiently. The expense of anti-scalant (MDC220) was higher than HCl.

Factors affecting sludge cake formation in a submerged anaerobic membrane bioreactor

A laboratory-scale submerged anaerobic membrane bioreactor (SAnMBR) was operated for over 160 days to assess the potential to treat kraft pulp mill evaporator condensate. Cake formation was identified as a dominant feature contributing to the deterioration of membrane performance. The influence of various operational parameters and sludge properties on sludge cake formation rate (CFR) was investigated. These included biogas sparging and permeate flow rates, as well as mixed liquor suspended solids (MLSS), soluble chemical oxygen demand (COD s) in the mixed liquor, and particle size distribution (PSD) and fractal dimension ( D f) of particles. CFR was highly dependent on biogas sparging rate and permeate flow rate, and less dependent on MLSS. COD s, PSD and D f were found to significantly influence the CFR. Confocal laser scanning microscopic (CLSM) imaging and chemical analyses of extracellular polymeric substances (EPS) indicated that EPS was involved in sludge cake formation. Characterization of the sludge cake layers, when compared to the bulk sludge, indicated that smaller flocs and EPS preferentially accumulated in the sludge cake. The identification of factors including biogas sparging rate, permeate flow rate, COD s, EPS, PSD, and D f that impact the cake formation process provides a basis for selecting operating conditions to manage fouling in an SAnMBR.