Ultrafiltration Tests Research Articles

Treatment of Industrial Effluents by MF and UF Ceramic Membranes:Comparative Study using Commercial and Elaborated Tunisian Clay Membranes

Industrial effluents treatment was investigated using ceramic Microfiltration (MF) and Ultrafiltration (UF) tubular membranes. The comparison of performances between commercial ceramic membranes based on alumina material and elaborated ones based on Tunisian clay material was studied. MF and UF tests applied to cuttlefish effluent treatment were carried out respectively with 0.2 μm and 5 nm commercial membranes and 0.18 μm and 15 nm prepared membranes. The results show that for the two processes, the performances in term of permeate flux and quality of the treated wastewater using clay membranes was a little better than that obtained with commercial one.

Comparison of permeate flux and whey protein transmission during successive microfiltration and ultrafiltration of UHT and pasteurized milks

This paper investigates whether UHT skim milk could be a valid fluid model for testing the separation of whey proteins from casein by microfiltration (MF) and of α-Lactalbumin (α-La) from β-Lactoglobulin (β-Lg) by ultrafiltration (UF). To this effect, we have measured permeate fluxes, α-La and β-Lg transmissions during MF concentration tests with pasteurized and UHT skim milks using a dynamic filtration module with rotating ceramic membranes. Then, wheys resulting from these permeates were ultrafiltered at 50 kDa with a rotating disk module while measuring permeate fluxes and α-La and β-Lg transmissions during concentration. Results showed that, in MF, permeate fluxes were slightly higher for UHT milk than for pasteurized milk. Student tests showed that, if α-La transmissions were slightly higher for UHT milk than for pasteurized milk, they were not significantly different. β-Lg transmissions were a little higher for UHT than for pasteurized milk. In UF tests, permeate fluxes were higher at low VRR (volume reduction ratio) for pasteurized whey, but decayed faster than for UHT milk when VRR increased. α-La and β-Lg transmissions in UHT whey were not significantly different from corresponding ones in pasteurized whey. These results show that the lower concentration of native whey proteins in UHT milk does not affect much their transmission and permeate flux, both in MF and in UF.

Recovery and purification of the exopolysaccharide PS-EDIV from Sphingomonas pituitosa DSM 13101

Abstract The separation and purification of the exopolysaccharide PS-EDIV from the culture broth of Sphingomonas pituitosa DSM 13101 was studied. For this purpose a sequence of separation and concentration operations including centrifugation, ultrafiltration and precipitation were used. Cell removal by centrifugation was performed at four different temperatures, showing that at 40 °C clarification was best with a residual biomass concentration of 0.1 g L−1. Subsequently ultrafiltration tests revealed that the cell debris containing polysaccharide solution did not cause any membrane fouling. The observed decrease of permeate flux at high PS-EDIV concentrations was rather attributed to a concentration polarization effect. The polymer solution could be concentrated up to 5 g L−1 whereby 90% of the initial polymer was recovered. In a last recovery step the polymer was precipitated using four different organic solvents: acetone, ethanol, propanol and isopropanol. Isopropanol gave the highest precipitation yield of 81% at a solvent ratio of 9:1 (v/v).

MODELING OF THE PERMEATE FLUX DECLINE DURING MF AND UF CROSSFLOW FILTRATION OF SUGARCANE JUICE

Experimental results on permeate flux decline with time obtained from crossflow microfiltration (MF) and ultrafiltration (UF) tests were compared with those predicted numerically using the two-dimensional convective-diffusion equation. Numerical simulations of the flow and heat transfer were made using the two-dimensional momentum and energy equations. Feed solution consisted of sugarcane clear juice and limed mixed juice to pH of 7.5. Experimental tests were performed in plate and frame module employing three different MF and UF polysulphone membranes (i.e. 1 μm pore size, 25 and 100 kD molecular weight cut-off, MWCO). Influence of process variables viz. transmembrane pressure (TMP) (i.e. 1.0, 1.5 and 2.0 bar) and feed temperature (i.e. 50, 60 and 70 oC) on the flux of permeate were studied. The present study shows that the permeate flux obtained both experimentally and numerically is increased as the transmembrane pressure is increased for all the membranes considered in this study. Moreover, permeate flux has been increased as the feed temperature is increased and decreased with time. Numerical predictions of permeate flux show a reasonable agreement with experimental counterparts.

AN ASSESSMENT OF OPERATIONAL PARAMETERS FOR THE REMOVAL OF CHLOROPHENOLS FROM WASTEWATER

Abstract The occurrence of priority organic pollutants in wastewaters streams and the environment has raised intensive scientific debates about their effects and the possible abatement technologies. This paper presents some results on the performance of ultrafiltration for the removal of 4-chlorophenol and 2.4-dichlorophenol from synthetic wastewaters. A laboratory scale ultrafiltration set-up fitted with 2000 MWCO cellulose acetate membranes was used for the study of ultrafiltration parameters influence (mode of operation, pressure and cleaning conditions) on the removal efficiencies of 4-chlorophenol and 2.4-dichlorophenol present in synthetic wastewaters at different concentrations. The results show that, depending on process parameters and initial pollutant load, it is possible to achieve removal efficiencies of up to 85% for both chlorophenols. The ultrafiltration tests revealed that these pollutants are eliminated during ultrafiltration by different retention phenomena than the ones that usually occur during ultrafiltration. This was confirmed by the permeated fluxes values that remained constant during all the tests.

Linearization of ultrafiltration models: analysis of experimental data from ultrafiltration tests

A great number of models proposed in the literature that describe permeate flux decline with time in ultrafiltration can be linearized to obtain an equation expressed in terms of transmembrane pressure (TMP) divided by permeate flux, ΔP2/J2P, as a function of time. In this work, experimental results from pilot plant ultrafiltration tests are expressed in terms of DP2/J2P vs. time to check their linearity. Regression analysis allowed the determination of the quotient: specific resistance of the gel layer/ gel layer concentration (rc/Cg). Ultrafiltration tests were performed at constant temperature (25°C) and feed concentration (5 g/L) at different feed flow rates (1–3 m/s) and transmembrane pressures (0.1–0.4 MPa) with monotubular ZrO2-TiO2 (molecular weight cut-off: 15 kg/mol) and aqueous solutions of polyethylene glycol (PEG) of 35,000 g/mol.

A study on the multifunction of ferrous chloride in the formation of poly(vinylidene fluoride) ultrafiltration membranes

Ferrous chloride was employed as additive in preparing flat sheet poly(vinylidene fluoride) (PVDF) membranes by phase inversion method, N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant, respectively, the role of ferrous chloride in membrane formation process and its effects on membrane property were investigated. Ultrafiltration tests showed that the introduction of ferrous chloride in casting solution could effectively increase membrane permeability while acceptable separation performance was maintained. The prepared membranes exhibited satisfactory compaction resistant property. Instrumental analysis found certain chemical traces left by ferrous chloride on the membranes: from scanning electron microscopy (SEM) observation, a large number of particulates with diameter of about 0.3 μm were found on membrane cross-section which might be quite related to the compaction resistant behavior; energy dispersive X-ray (EDX) analysis indicated that those particulates were composed of ferric oxide and PVDF chains; X-ray photoelectron spectroscopy (XPS) analysis revealed that the iron element entrapped on membrane surface stayed in three different chemical states: ferric hydroxide (FeOOH), ferric oxide (Fe 2O 3) and another unidentified one, while FeOOH was the main component of them. The presence of FeOOH could not only enhance membrane hydrophilicity but also combine separation and catalyzation as the membrane's two distinct functions.

Ultrafiltration permeate flux decline prediction for gel layer forming solutes using monotubular ceramic membranes

Experimental results on permeate flux decline with time obtained from ultrafiltration tests were compared with those predicted by means of Song and Elimelech's model. Feed solutions consisted of aqueous solutions containing 15 g/L of polyethylene glycol 35 kg/mol. All model parameters were theoretically estimated, except the gel layer concentration that was estimated as described by Lee et al. Experimental tests were performed with monotubular ceramic Tami MSKT membranes from Tami Industries (France). TMP (0.2, 0.3, 0.4 and 0.5 MPa) and crossflow velocity (1, 2 and 3 m/s) were varied. Permeate flux slightly decreased with time for all the experimental conditions tested. The best predictions were obtained for long time scales for a crossflow velocity of 1 m/s. For those experimental conditions the probability of gel layer formation on the membrane surface is the highest. For short time scales, model predictions showed a rapid initial permeate flux decline that was not experimentally observed because it may occur instantly before the first permeate was collected.

Microfiltration/ultrafiltration as pretreatment for reclamation of rinsing waters of indigo dyeing

This paper focuses on the applicability of microfiltration (MF)/ultrafiltration (UF) as a pretreatment to nanofiltration (NF) for the reclamation of rinsing waters of indigo dyeing process. Two different MF alternatives, single 5 μm MF and sequential 5 μm+0.45 μm MF, were evaluated as prefiltration to improve the performance of the proceeding UF stage. UF tests performed after 5 μm MF using 100 kDa, 50 kDa, 20 kDa, 2 kDa and 1 kDa membranes have indicated that all the UF membranes provided the same cumulative color retention of 98–99%. However, in terms of COD retention, UF membranes presented different performances and the highest retentions were by both 50 kDa (56%) and 100 kDa (59%) membranes. As regards permeation rate, 100 kDa and 50 kDa UF membranes appeared to have the highest flux decline due to fouling. When sequential MF (5 μm+0.45 μm) was adopted to decrease this fouling, 0.45 μm MF before UF was found not to provide any significant improvement. Thus, single stage 5 μm MF followed by 100 kDa UF was selected as the best prefiltration train to NF that permits the textile producer to reclaim indigo dyeing wastewater.

Copper recovery by polymer enhanced ultrafiltration (PEUF) and electrochemical regeneration

In this work, the removal of Cu 2+ from a synthetic effluent has been tested by means of polymer enhanced ultrafiltration (PEUF), using partially ethoxylated polyethylenimine (PEPEI) as water-soluble polymer. Overall, the two necessary steps of a hypothetical continuous process, metal retention (in total recirculation and discontinuous mode) and polymer regeneration (in discontinuous mode), have been confronted individually. On the one hand, the values of temperature ( T), transmembrane pressure (Δ P), metal–polymer ratio and pH that maximize both, permeate fluxes and rejection coefficients, have been obtained by ultrafiltration tests, reaching Cu 2+ retention coefficients higher than 97%. On the other hand, the polymer regeneration step has been carried out by the electrochemical technique, which consists in the metal electrodeposition on the cathode of an electrochemical cell. In a first step, cyclic voltammetries have been carried out to assure the polymer does not suffer any oxidation or reduction process. From these tests, a cathodic working potential has been selected to minimize hydrogen evolution reaction (−0.7 V vs. Ag/AgCl). Working at this voltage in deposition tests, a pH of 3.3 has been selected from experiments at different pH values. This pH is less extreme than the pH necessary if this step was carried out chemically (pH 2).

Complexity of ultrafiltration membrane fouling caused by macromolecular dissolved organic compounds in secondary effluents

Recent investigations indicate the relevance of extracellular polymeric substances (EPS) in terms of fouling of low-pressure membranes in advanced wastewater treatment. In this study, the high impact of the macromolecular fraction of effluent organic matter on fouling was confirmed in cross-flow ultrafiltration experiments using secondary effluent with and without autochthonous biopolymers. A method for the extraction of a natural mixture of EPS derived from the bacterium Sinorhizobium sp. is presented. Ultrafiltration of solutions of this bacterial EPS extract revealed a correlation between the concentration of EPS and the loss of permeate flux. However, in ultrafiltration tests using extracted bacterial EPS in a model solution as well as in secondary effluent without autochthonous biopolymers, the extent of membrane fouling was not identical with the fouling provoked by secondary effluent organic matter, although the biopolymer concentrations were comparable. The differences in the fouling behaviour of the extracted bacterial EPS and effluent organic matter are considered to be due to different compositions of the biopolymer fraction in terms of proteins, polysaccharides, and other organic colloids, indicating a particular impact of proteins on ultrafiltration membrane fouling.

Evaluation and comparison of protein ultrafiltration test results: Dead-end stirred cell compared with a cross-flow system

Dead-end stirred cell devices are commonly used in laboratories to characterise ultrafiltration membranes and their separation behaviour. Additionally, protein separation data from such systems are used for process scale-up. Such devices are operated under conditions that are inherently different from those used during the continuous or semi-continuous processing of industrial feed streams. The work presented in this paper compares the rejection behaviour of single protein solutions in a dead-end stirred cell (SC) device with that for a cross-flow system (CF). The effect of ionic strength (20 and 100 mM) and solution pH (4.9, 6.0, 7.1, 8.4 and 11.0) on protein filtration (bovine serum albumin (BSA) and lysozyme (LYZ) from buffered aqueous solutions) behaviour has been investigated using polyethersulfone (PES) membranes with a manufacturer specified molecular weight cut-off (MWCO) of 50 kDa. PES membranes were characterised in terms of dextran MWCO using both the SC and the CF systems. The mode of operation resulted in significant observed differences in the resulting dextran solute rejection curves for the two systems. The observed rejection ( R obs) values for a series of dextran standards were consistently found to be lower for the CF system compared with the SC unit suggesting higher wall concentrations ( C w ) due to concentration polarisation effects in the CF unit. Protein ultrafiltration studies with the 50 kDa PES membranes highlighted important differences in observed protein rejection behaviour despite operation of the two systems at the same transmembrane pressures (25 kPa). Solution pH was found to have little effect on the rejection of both BSA and LYZ. The solute rejection was found to be more sensitive to ionic strength effects for the SC device both during BSA and LYZ filtration. Convective mass transfer coefficients and hence the true rejection coefficients ( R tr) were calculated for both systems using the stagnant film model to understand the influence of hydrodynamic effects on the ultrafiltration behaviour of the two systems. The magnitude of the membrane Peclet number ( Pe) provides a means of comparing hydrodynamic conditions for the two systems and thereby allows differences in observed solute rejection to be better understood.

COMBINING ULTRAFILTRATION PROCESS WITH COAGULATION PRETREATMENT FOR PULP MILL WASTEWATER TREATMENT

Ultrafiltration combined with coagulation pretreatment was used to treat two kraft pulp mill wastewaters from first-stage caustic extraction and alkaline bleaching operations, respectively. Both alum and ferric chloride were tested using standard jar apparatus at different dose, pH and ionic strength conditions. Ultrafiltration tests were conducted using a crossflow flatsheet membrane apparatus operated in the constant transmembrane pressure mode to examine the effects of membrane material, crossflow velocity and transmembrane pressure in terms of permeate flux and treated effluent quality. The results showed that coagulation with both alum and ferric chloride greatly reduced the permeate flux decline rates. In comparison with alum, greater permeate fluxes were obtained with the use of ferric chloride. Among the process parameters examined, coagulant dose was identified as the most important factor affecting the permeate flux. In addition, colour and COD removals were achieved largely by coagulation for alkaline bleaching wastewater while by membrane filtration for caustic extraction wastewater, highlighting the different mechanisms underlying contaminant removal.

Reuse of tannery wastewaters by combination of ultrafiltration and reverse osmosis after a conventional physical-chemical treatment

Due to the high conductivity of the global wastewater from a tannery industry, wastewater reuse is only possible if a reverse osmosis process is implemented in the wastewater treatment. The supernatant of a physical-chemical treatment is still very polluted, containing high COD values between 3000 mg/l and 4000 mg/l and conductivities of nearly 20 ms/cm. In this work, a combination of filtration, ultrafiltration and reverse osmosis is evaluated as treatment for the physical-chemically treated wastewater. Filtration was carried out using microfilters as a previous stage to ultrafiltration process. Ultrafiltration tests were performed in a laboratory plant. Organic membranes from Orelis with different cut-offs were tested to optimize the rejection and the permeate flux. Finally, the reverse osmosis step was carried out using an ESPA-1 membrane from Hydranautics. Results showed high COD values in ultrafiltration permeates (between 2000 and 3000 mg/l). A polyethersulfone membrane with cut-off of 30 kD was chosen for the pre-treatment of the reverse osmosis membrane. Permeate fluxes of the reverse osmosis membrane reached 40 l/(m 2h) at 30 bar. Though membrane fouling was not observed during RO experiments, an industrial scale plant should pay special attention to a probable flux decrease due to the scaling if a high conversion is aimed.

Preparation and characterization of novel porous PMMA-SiO 2 hybrid membranes

Poly(methyl methacrylate) (PMMA)-SiO 2 composite membranes were prepared by casting ternary solutions obtained by adding additional amounts of TEOS to PMMA solutions. Methods to obtain an intimate dispersion of the inorganic particles in the PMMA solutions were developed. Various samples of hybrid membranes were prepared by varying some of the preparative parameters such as the PMMA solvent (tetrahydrofuran, and N,N-dimethyl formamide) and the PMMA/TEOS ratio in the ternary solution. Membranes were also cast from a binary solution of PMMA and solvent for comparison. The membranes were characterized by water permeability, scanning electron microscope observations, DSC and TGA analysis and ultrafiltration tests. The effects of the above-mentioned preparative parameters on the structure, thermal behavior, flux and dextran retention properties of the membranes are discussed.

Biological Treatment of Agro‐Industrial Wastewater for the Production of Glucoamylase and Rhizopus Biomass

The present work concerns the biological treatment of a starch wastewater, coupled with the production of microbial biomass and glucoamylase. Every unit operation of the process was tested in a laboratory scale, in order to perform a feasibility analysis. Fermentation tests confirmed that a stirring rate of 300 rpm was the optimum (in the investigated range) as concerns biomass growth and enzyme activity. Ultrafiltration tests showed that the best operating conditions in the investigated range for enzyme recovery were: temperature 25°C, transmembrane pressure 100 kPa, membrane cut off 30 kDa. Diafiltration tests evidenced that an effective enzyme washing (about 85% reduction of chemical oxygen demand) was achieved with 3 volumes of water per volume of feed and no significant enzyme deactivation was observed.

Novel porous poly (vinylidene fluoride) membranes for membrane distillation

Polyvinylidene fluoride (PVDF) membranes were prepared by water immersion of a binary PVDF-solvent solution cast on the outer surface of a porous tubular support. During immersion the free shrinkage of the cast solution was hindered by the support and consequently the nascent membrane was subjected to a stretching action that caused pore formation. A laboratory scale device was realized for casting operation and some preparative parameters were studied to control the deposition of the PVDF solution on the porous support. Membranes were characterized through scanning electron microscope observations, air permeability measurements, ultrafiltration tests and membrane distillation experiments. These latter were carried out with a laboratory unit fed with 3 w/v% aqueous NaCl solution at 69°C. The membranes were housed in a tubular cell with the feed flowing on the shell side and the sweeping air in the membrane lumen. The effect of feed and gas velocity on the membrane performance was investigated and the obtained results were compared with those of commercial tubular membranes tested on the same unit. The influence of casting parameters on the morphology and permeation properties of the membranes was also studied.

Novel porous membranes from chemically modified poly(vinylidene fluoride)

Porous membranes were prepared by immersion in pure water or in water–NaOH baths of poly(vinylidene fluoride) solutions in different types of solvent ( N, N-dimethylformamide or 1-methyl-2-pyrrolidone or triethylphosphate). Membranes were characterized through ultrafiltration tests, scanning electron microscope observations and vibrational spectroscopy (FT-Raman and FT-IR) measurements. The presence of NaOH in the immersion bath caused not only chemical dehydrofluorination of the polymer but also affected the membrane formation thus leading to membranes with different structures, permeability and retention properties. Membrane prepared by coagulation in NaOH rich bath were treated with NaOCl and H 2O 2 to attack the double bonds and to obtain membrane with improved hydrophilicity.

Tertiary treatment of a secondary effluent by the coupling of coagulation-adsorption-ultrafiltration for reuse

We considered the treatment of secondary effluent by coagulation-adsorption coupled with ultrafiltration. Tests were performed on the secondary effluent of the wastewater treatment plant at Staoueli (Algeria) where the average chemical oxygen demand (COD) was 46 (mg O 2/L) and turbidity, 16 NTU. The ultrafiltration tests were made with mineral tubular CARBOSEP membranes — M5 (10 kg/ mol), M2 (15 kg/mol) — in the dynamic mode with a transmembrane pressure Δ P = 1 bar and cross flow velocity = 3 m/s. The reagents were calcium chloride (as coagulant agent) and powder activated carbon. Coagulation improved the ultrafiltration performances significantly. In the first step, the optimal conditions for coagulation were determined considering the best elimination of turbidity as well as organic matter. In the second step, the efficiency of different processes (coagulation, adsorption, ultrafiltration) was compared when used alone or in combination. The coagulation test showed a COD elimination equal to 12 mg/L at pH = 6.5 for a concentration of CaCl 2 = 50 mg/L and a turbidity equal to 3 NTU.

Polymer assisted ultrafiltration for copper?citric acid chelate removal from wash solutions of contaminated soil

The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using Polymer-Assisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu2+ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH ≤ 2. Maximum bonding capacity (saturation condition) was 0.625 mg Cu2+ per mg citric acid, meaning 2 mol Cu2+ per mol citric acid. Complexation tests in the system polyethylenimine–citric acid–copper showed that the polymer is able to complex the copper–citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu2+ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.