Recovery of microbial polysaccharides from fermentation broths by microfiltration on ceramic membranes

This paper investigates the extraction of microbial polymers (polysaccharides) from fermentation broths of Sinorhizobium meliloti M5N1CS using crossflow filtration through ceramic membranes of various pore sizes from 0.1 to 0.8 µm. The duration of fermentation was set at 70 h in order to maximize the production of high molecular weight polysaccharides (average 2 × 10⁵ Da). The 0.1 µm membrane underwent rapid fouling and was found inadequate for this application. For the other membranes, the sieving coefficients decreased from 95% to about 20% in 90 min, at a slower rate than the permeate flux. The largest permeate and mass fluxes were obtained with the 0.5 µm membrane (18.5 × 10⁻⁶ m s⁻¹ and 20 × 10⁻⁶ gm⁻²s⁻¹). Increasing the fluid velocity from 3 to 6 m s⁻¹ increased both the permeate flux and sieving coefficients, while raising the transmembrane pressure from 50 kPa to 100 kPa increased the flux slightly but decreased the sieving coefficient. Polysaccharide extraction will be maximized by operating at high velocities and low transmembrane pressure (TMP) which may require cocurrent recirculation of the permeate. Experiments with cell‐free solutions showed that the permeate flux is mostly limited by the bacterial layer deposited on the membrane while the presence of cells has a positive effect on the sieving coefficient. Irreversible fouling due to polymer adsorption on the membrane decreased with increasing pore size and velocity but increased strongly with TMP. © 1999 Society of Chemical Industry     

Experimental study on the enhancement of yeast microfiltration with gas sparging

Gas‐sparged microfiltration experiments with baker's yeast suspensions were performed using a 0.15 µm PCI multi‐tubular membrane module. The permeate flux and the enhancement from gas sparging were measured over the following operational parameter ranges: yeast suspension concentration 0.01–10% (wt), transmembrane pressure 0.5–4.0 bar, liquid crossflow velocity 0.36–1.8 ms^?1, gas superficial velocity 0.18–1.02 ms^?1. It was demonstrated that injecting air to create a gas–liquid two‐phase crossflow operation can significantly increase the permeate flux. The observed enhancement, resulting from injecting a relatively small amount of gas with a superficial velocity of 0.18 ms^?1, ranges from 10% when fouling is insignificant to 135% when fouling tendency is severe. Controlled pulse injection leads to further increase in permeate flux. Examining the dependence of permeate flux on transmembrane pressure, it is clearly demonstrated that the injection of gas will elevate the value of the limiting flux. There is also evidence to show that the value of critical flux is increased when gas injection is applied. Further quantitative analysis will be performed in our future work. © 2001 Society of Chemical Industry     

Chromate removal from wastewater using micellar enhanced crossflow filtration: Effect of transmembrane pressure and crossflow velocity

Removal of chromate from wastewater was investigated using Micellar Enhanced Crossflow Microfiltration Technique (MEMF) with cationic surfactant, cetyltrimetylammoniumbromide (CTAB). The variation of chromate, surfactant rejections and permeate flux with time were measured at two different CTAB concentrations as a function of transmembrane pressure drop (ΔP) and crossflow velocity, while CTAB/chromate, membrane pore size, temperature and pH of the feed solution was kept constant. For low CTAB concentration, it was observed that the efficiencies of chromate and surfactant removal increased with increasing ΔP, but decreased with increasing crossflow velocities. It was also observed that the effects of crossflow velocities and ΔPs on the rejections decreased for high CTAB concentration. It was found that fouling of the membrane by surfactant is very rapid at low crossflow velocity and high ΔPs at low CTAB concentration. As a result of this case, both transient permeate flux (J) and steady state permeate flux (J^?) decreased with decreasing crossflow velocity and increasing ΔP for both CTAB concentration. Unlike, modified fouling index (MFI) values increase with decreasing crossflow velocity and increasing ΔP. It was also observed that the effect of surfactant concentration in the 150, 200, and 250 kPa pressure and 3, 4, and 5 m/s crossflow velocity intervals dominates at high surfactant concentration.     

Crossflow Ultrafiltration of Binary Biomolecule Mixture: Analysis of Permeate Flux,Cake Resistance and Sieving Coefficient

The aim of this paper is to demonstrate the effects of hydrodynamic conditions on the permeate flux, cake resistance and sieving coefficient in a crossflow ultrafiltration process separating biomolecules of different molecular weights. A binary mixture of L‐phenylalanine (L‐phe) and lipase was ultrafiltered through a hydrophobic polyether sulphone (PES) membrane with 10 kDa molecular weight cut‐off. The changes in permeate flux, cake layer resistance and observed sieving coefficient with different transmembrane pressures (TMP) and crossflow velocities were evaluated. The effect of TMP was examined at two different velocities (0.114 m s^–1 and 0.176 m s^–1) and the effect of velocity was examined at two different TMP (20 kPa and 115 kPa) for the experimental system designed. In the initial stage of the crossflow filtration, it was determined that the TMP was more effective than the velocity. The cake layer resistance increased with increasing TMP and it decreased with increasing velocity for the high TMP value of 115 kPa. A maximum of the observed sieving coefficient was achieved with increasing velocity. An increase in TMP at low inlet velocity (0.114 m s^–1) affected the observed sieving coefficient positively.     

Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s^?1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s^?1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.     

气液两相流强化卷式纳滤膜分离硫酸镁水溶液

气液两相流强化卷式纳滤膜分离实验是针对DK2540卷式纳滤膜,采用气液两相流强化分离技术,对硫酸镁溶液进行研究,较系统地研究了温度、料液浓度、过膜压力、料液流速、气体流速等因素在分离硫酸镁溶液时,对膜通量、截留率和膜通量增加率的影响,并总结了气液两相流强化效果。结果表明,气液两相流强化卷式纳滤膜分离有明显的效果。温度宜在30~40℃。料液浓度越大、过膜压力越小、气液比越大,气液两相流强化效果越明显。     

Treatment of Oily Waste Water Using Low-Cost Ceramic Membrane: Flux Decline Mechanism and Economic Feasibility

Abstract

This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10^?6 m³/m²·s·kPa and 5.78 × 10¹¹ m²/m³, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ranging from 41.37 to 165.47 kPa. The membrane exhibited 96.97% oil rejection efficiency and 21.07 × 10^?6 m³/m²·s permeate flux after 30 min of experimental run at 165.47 kPa trans-membrane pressure for 50 mg/L oil concentration. Different pore blocking, models such as complete pore blocking, standard pore blocking, intermediate pore blocking and cake filtration were used to gain insights into the nature of membrane fouling during permeation. The observed trends for flux decline data convey that the decrease in permeate flux was initially due to intermediate pore blocking (during 1 to 10 minutes of experimental run) followed with cake filtration (during 10 to 30 minutes of experimental run). Based on retail prices of the inorganic precursors, the membrane cost was estimated to be 130 $/m². Finally, preliminary process economic studies for a single stage membrane plant were performed for the application of the prepared membrane in industrial scale treatment of o/w emulsions. A process economics study inferred that the annualized cost of the membrane plant would be 0.098 $/m³ feed for treating 100 m³/day feed with oil concentration of 50 mg/L.     

Poly(ether imide) membranes modified with charged surface‐modifying macromolecule—Its performance characteristics as ultrafiltration membranes

Modification of poly (ether imide) (PEI) ultrafiltration (UF) membranes was attempted by blending charged surface modifying macromolecule (cSMM). Compared to the pure PEI membrane, blending of PEI with cSMM resulted in blend membranes with enhanced UF characteristics such as lower hydraulic resistance (R_m) and higher pure water flux (PWF) coupled with higher water content (WC). Among the various modified membranes, blend membranes with 5 wt % cSMM concentration exhibited higher PWF (60.38 L m^?2 h^?1), WC (73.6%), protein permeate flux (27.12 L m^?2 h^?1) and lower flux decline rate (R_fd) (55.1%), R_m (5.21 kPa/L m^?2 h^?1), bovine serum albumin (BSA) rejection (87.1%). Meanwhile, the fouling resistant ability was studied by flux recovery ratio (FRR) after water and alkali cleaning, irreversible and reversible fouling rate. Higher FRR after water cleaning (95.07%), FRR after alkali cleaning (97.1%), reversible fouling rate (50.14%) and lower irreversible fouling rate (5%) exhibited by 5 wt % cSMM membranes showed its better antifouling ability compared to pure PEI and other blend membranes because of its higher hydrophilic nature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40320.     

PERFORMANCE CHARACTERISTICS OF A CERAMIC MEMBRANE SYSTEM FOR MICROFILTRATION OF CORN STARCH HYDROLYSATE

A ceramic microfiltration membrane was used for the clarification of corn starch hydrolysate, having a dextrose equivalence of 95, to study the effect of process variables (transmembrane pressure, cross-flow velocity, and feed concentration) on permeate flux. Flux increased with increased cross-flow velocity for all transmembrane pressures and feed concentrations up to a volume concentration ratio of 100. Flux became asymptotic at pressures of 200-375kPa, indicating that microfiltration performance was limited by concentration-polarization. The optimum transmembrane pressure was higher at higher cross-flow velocities. A process model based on the resistances-in-series concept adequately described the observed variation of permeate flux with process variables such as transmembrane pressure, cross-flow velocity and feed concentration. Resistance due to concentration polarization decreased linearly with increase in cross-flow velocities for all feed concentrations, while fouling resistance increased linearly with increase in feed concentration.     

Use of a Helical Baffle for Red Wine Clarification on a Mineral Membrane

Abstract

We present the use of a helical baffle inserted in a mineral membrane (Carbosep) for the clarification of a highly charged red wine. Baffles of different geometries were made of stainless steel by winding a steel wire on a rod. The baffles were centrally placed. The wine was analyzed before and after its clarification for its filtration index, turbidity, color, and microbiological control. Experiments made at different transmembrane pressures and feed flow rates show that the permeate flux increased from 13 L/h·m² (without baffle) to 30 L/h·m² (with baffle). Long-term experiments at the same hydraulic dissipated energy gave a mean permeate flux of about 20 L/h·m² from a baffled membrane compared to 10 L/h·m² for a membrane without a baffle. The volume of permeate collected during the same time was 145% more for a baffled membrane. It was found that membrane fouling due to polarization concentration was reduced by a factor of 3 with the use of baffles. Analysis of permeate at three optical densities (420, 520, and 620 nm) and turbidity measurements confirm that the quality of the permeate was good. It is concluded that the presence of a baffle in the membrane did not change the characteristics of the filtered wine and that its use is very simple for the enhancement of permeate flux.     

Factors influencing critical flux in membrane filtration of activated sludge

Membrane filtration of biomass is usually accompanied by significant flux decline due to cake‐layer formation and fouling. Crossflow filtration with flux controlled by pumping the permeate can produce stable fluxes if a ‘critical flux’ is not exceeded. Below critical flux the transmembrane pressure is typically very low and increases linearly with imposed flux. Above the critical flux the transmembrane pressure rises rapidly signifying cake‐layer formation which is usually accompanied by a continued rise in transmembrane pressure and/or a drop in delivered flux. A range of microfiltration and ultrafiltration membranes with pore sizes from 0.22 to 0.65 µm and molecular weight cut‐off of 100 kDa was used. The feed was an activated sludge mixed liquor with concentration in the range of 3–10 g dm⁻³. The results show that the critical flux depends on feed concentration and crossflow velocity, being higher for higher crossflow velocity or lower feed concentration. Critical flux was also dependent on membrane type, being lower for hydrophobic membranes. Although the transmembrane pressure was higher for the larger pore size membrane, no significant difference in critical flux was observed among different pore size membranes. © 1999 Society of Chemical Industry     

A pilot scale study of reverse osmosis for the purification of condensate arising from distillery stillage concentration plant

Reverse osmosis (RO) is an interesting process to eliminate small organic solutes (carboxylic acids and alcohols) from distillery condensates before recycling them into the fermentation step. This work investigates the influence of transmembrane pressure, pH and volume reduction factor (VRF) on the efficiency of reverse osmosis treatment of condensate from distillery stillage concentration at pilot scale using three pre-selected membranes (CPA2 and ESPA2 from Hydranautics, BW30 from DOW). Performances were assessed according to permeate flux, solutes rejection and abatement of fermentation inhibition. Transmembrane pressure increase leads to an increase of these three parameters with a plateau for rejections and abatement at 20 bar; however, in order to comply with membranes manufacturer's recommendations and to limit or delay polarization and fouling, it was decided to keep the permeate flux below a value of 30 L h⁻¹ m⁻². This corresponded to a maximum pressure of 10 bar for CPA2 and ESPA2 membranes and 25 bar for BW30 membrane. pH increase leads to a diminution of permeate flux and an increase of carboxylic acids rejection whatever the membrane; nevertheless, no abatement of fermentation inhibition is observed. Increasing VRF provokes a decrease of the permeate flux. Although local rejections are stable, the mean rejection assessed with the raw condensate (feed) and the mean permeate decreases. However, the fermentation inhibition remains under 10% up to a VRF of 8. BW30 membrane exhibits the highest rejections and inhibition abatement. On the basis of the pilot scale results with the BW30 membrane, a preliminary estimation of the membrane area is proposed for an industrial plant with 100 m³ h⁻¹ of condensate flow rate and the optimized parameters (pressure 25 bar, no pH modification, VRF 4 and 8).     

Treatment of oily wastewater using low cost ceramic membrane: Comparative assessment of pore blocking and artificial neural network models

This work addresses the performance and modeling of the separation of oil-in-water (o/w) emulsions using low cost ceramic membrane that was prepared from inorganic precursors such as kaolin, quartz, feldspar, sodium carbonate, boric acid and sodium metasilicate. Synthetic o/w emulsions constituting 125 and 250 mg/L oil concentrations were subjected to microfiltration (MF) using this membrane in batch mode of operation with varying trans-membrane pressure differentials (ΔP) ranging from 68.95 to 275.8 kPa. The membrane exhibited 98.8% oil rejection efficiency and 5.36 × 10⁻⁶ m³/m² s permeate flux after 60 min of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L initial oil concentration. These experimental investigations confirmed the applicability of the prepared membrane in the treatment of o/w emulsions to yield permeate streams that can meet stricter environmental legislations (<10 mg/L). Subsequently, the experimental flux data has been subjected to modeling study using both conventional pore blocking models as well as back propagation-based multi-layer feed forward artificial neural network (ANN) model. Amongst several pore blocking models, the cake filtration model has been evaluated to be the best to represent the fouling phenomena. ANN has been found to perform better than the cake filtration model for the permeate flux prediction with marginally lower error values.     

Membrane fouling and chemical cleaning in water recycling applications

Fouling and subsequent chemical cleaning are two important issues for sustainable operation of nanofiltration (NF) membranes in water treatment and reuse applications. Fouling strongly depends on the feed water quality, especially the nature of the foulants and ionic composition of the feed water. Consequently, appropriate selection of the chemical cleaning solutions can be seen as a critical factor for effective fouling control. In this study, membrane fouling and chemical cleaning under condition typical to that in water recycling applications were investigated. Fouling conditions were achieved over approximately 18 h with foulant cocktails containing five model foulants namely humic acids, bovine serum albumin, sodium alginate, and two silica colloids in a background electrolyte solution. These model foulants were selected to represent four distinctive modes of fouling: humic acid, protein, polysaccharide, and colloidal fouling. Three chemical cleaning solutions (alkaline solution at pH 11, sodium dodecyl sulphate (SDS), and a combination of both) were evaluated for permeate flux recovery efficiency. The results indicated that with the same mass of foulant, organic fouling was considerably more severe as compared to colloidal fouling. While organic fouling caused a considerable increase in the membrane surface hydrophobicity as indicated by contact angle measurement, hydrophobicity of silica colloidal fouled membrane remained almost the same. Furthermore, a mechanistic correlation amongst cleaning efficiency, characteristics of the model foulants, and the cleaning reagents could be established. Chemical cleaning of all organically fouled membranes by a 10 mM SDS solution particularly at pH 11 resulted in good flux recovery. However, notable flux decline after SDS cleaning of organically fouled membranes was observed indicating that SDS was effective at breaking the organic foulant—Ca²⁺ complex but was not able to effectively dissolve and completely remove these organic foulants. Although a lower permeate flux recovery was obtained with a caustic solution (pH 11) in the absence of SDS, the permeate flux after cleaning was stable. In contrast, the chemical cleaning solutions used in this study showed low effectiveness against colloidal fouling. It is also interesting to note that membrane fouling and chemical cleaning could permanently alter the hydrophobicity of the membrane surface.     

Flux Characteristics of Oil Separation from O/W Emulsions using Highly Hydrophilic UF Membrane in Narrow Channel

Flux characteristics of oil separation from O/W emulsions using highly hydrophilic polymeric UF membrane has been investigated. The effect of using sub-millimeter filtration channel on both unsteady and steady state permeate flux is evaluated. The time-dependent flux characteristics indicated that membrane fouling has proceeded mainly according to the intermediate pore blocking mechanism modified for crossflow filtration. The steady state flux increased initially with the transmembrane pressure (TMP), then reached a plateau at a relatively low TMP of ～15 kPa, beyond which a steady operation was achieved, and there were practically no advantages of increasing the TMP. The pressure independent limiting flux increased with increasing the crossflow velocity and was found to scale with the membrane surface shear rate to the power of 0.35. The data were modeled satisfactorily using a dimensionally consistent semi-empirical model with R² value of 0.96.     

Influence of filtration conditions on the performance of nanofiltration and reverse osmosis membranes in dairy wastewater treatment

Filtration performance and fouling of nanofiltration (NF) and reverse osmosis (RO) membranes in the treatment of dairy industry wastewater were investigated. Two series of experiments were performed. The first one involved a NF membrane (TFC-S) for treating the chemical-biological treatment plant effluents. The second one used a RO membrane (TFC-HR) for treating the original effluents from the dairy industry. The permeate flux was higher at higher transmembrane pressures and higher feed flowrates. The curves of permeate flux exhibited a slower increase while the feed flowrate decreased and the pressure increased. Membrane fouling resulted in permeate flux decline with increasing the feed COD concentration. Furthermore, the flux decline due to the COD increase was found higher at higher pressures for both NF and RO membranes.     

Enantiomeric Separation of Tryptophan by Ultrafiltration Using the BSA Solution System

Abstract

The optical resolution of racemic tryptophan was performed by ultrafiltration using the BSA solution system. The pH of the feed solution had a strong influence on the complexation constants between BSA and tryptophan, especially for L-tryptophan. The complexation constant for L-tryptophan reached a maximum value at pH 9 (K _L = 110,000), varying by 2 orders of magnitude in the range from pH 6 (K _L = 1000) to pH 11 (K _L = 21,000). Smaller variations of the complexation constant of D-tryptophan were observed. Based on these data, the recovery and the purity of the permeate were optimized by a proper control of the physicochemical parameters of the feed solution (essentially pH and initial concentrations). In one stage, 91% purity with a 89% recovery of D-tryptophan has been easily obtained with a high permeation rate (6.3 × 10^?4 mol·m^?2s^?1 at 1.5 bar).     

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.     

Harvesting of Cyanobacterium Arthrospira platensis Using Inorganic Filtration Membranes

Abstract

The present work deals with the concentration and the separation of Arthrospira platensis from a diluted culture medium. Among the different ways to operate this liquid/solid separation, this paper is focused on the membrane alternative. The general framework of this experimental study is the MELISSA project from the European Space Agency (ESA) for the development of life support systems in Space. The performances of fourteen inorganic membranes (microfiltration and ultrafiltration) were evaluated. According to the results, the operating conditions and the influence of phycocyanin and exopolysaccharides on the fouling phenomenon were investigated on the best membrane. A critical aspect to monitor along the process is the quality of the product in terms of composition of the main cell macro‐components, such as proteins and exopolysaccharides. The ultrafiltration membrane ATZ‐50 kD exhibited the best permeation flux and cleanability. An increase of fluid velocity and transmembrane pressure is energy‐consuming. A good compromise between this consideration and the gain in terms of permeation flux is close to 3 m · s^?1 and 2 · 10⁵ Pa with the selected membrane and with a cyanobacteria suspension concentration ranging from 50 mg · L^?1 to 1 g · L^?1.     

Application of Vibratory System to Improve the Critical Flux in Submerged Hollow Fiber MF Process

Submerged hollow fiber membrane system is widely used in water and wastewater treatment plants. One of the major problems of the microfiltration/ultrafiltration (MF/UF) process is membrane fouling. Few techniques have been developed to reduce membrane fouling and increase critical flux of the filtration process. In this study, membrane vibration was applied to improve the critical flux in a submerged hollow fiber MF system. A bench scale unit was especially built for this purpose and different vibrating speed was tested. The effect of the feed concentration and vibrating speed on the critical flux measurement were investigated. The critical flux was measured at different vibrating speeds varied from 0–500 oscillation per minute (opm) (5.83 Hz). The lowest critical flux was 15 L·m^?2·h^?1 when no membrane vibration was used and then increased gradually from 27 to 56 L·m^?2·h^?1 when the vibrating speed increased from 100 to 500 opm (8.35 Hz). A sharp drop in the critical flux was noticed when the concentration of feed suspension doubled from 5 g/L to 10 g/L. However, the increase in the critical flux was insignificant at higher feed concentration even when a high membrane vibrating speed was applied. This signifies that there is a limit for flux improvement in a vibratory system which is strongly dependent on the feed concentration.