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Membrane wetting, scaling and low flux are challenging obstacles for membrane distillation (MD). However, the lack of advanced membranes capable of achieving both high flux and high wetting/scaling resistance constrains MD potential applications. Herein, a dense Janus membrane (JM) was facilely developed by co-depositing a dense PVA/PDA layer on a highly porous PTFE substrate to overcome this dilemma and systematically compared with omniphobic PTFE substrates with varied pore sizes for the first time. Results showed that, unlike flux-resistance "trade-off" observed for PTFE substrates, dense JM effectively resisted 0.4 mM SDS at a high flux of 56.8 LMH and retarded membrane scaling by 20 mM oversaturated gypsum. Robust wetting resistance was primarily attributed to the sieving effect of the sub-nanometer surface layer, which greatly protected substrate from SDS adsorption and feed intrusion, and was less affected by severe surface concentration polarization and relatively low substrate LEP than PTFE substrates. Strongly polar PVA/PDA layer provided a much more thermodynamically unfavorable continuous interface for gypsum adhesion than PTFE substrates, which played a key role in determining anti-scaling behavior. In contrast, gypsum still tended to rapidly cause membrane scaling in stagnant zones within PTFE substrates when flux was increased. This study shall provide new insights in designing high-performance membranes for robust hypersaline wastewater treatment, and highlighting dense JMs with a macroporous substrate and a highly hydrophilic dense surface layer as ideal alternatives. [Display omitted] [ABSTRACT FROM AUTHOR]

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously. Unlabelled Image • Maximum concentration of Zn ions generated in the electrolytic was obtained at a potential difference of 2 volts. • The use of Zn2+ improved anti-scaling capacity of the membrane when treating brackish water • Scaling of the membrane in the pilot plant was minimized with the use of commercial anti-scalant as well as Zn ions. • SEM and OM analyses showed that deposits on the membrane surface were minimized with the use of both anti-scalants tested [ABSTRACT FROM AUTHOR]

β-cyclodextrin (β-CD) and tannic acid (TA) together as an organic phase and zeolitic imidazolate framework-8 (ZIF-8) as an additive can be used along with trimesoyl chloride (TMC) as a monomer to synthesize nanofiltration (NF) membranes. Those membranes have better separation performance and provide higher flux. In this study, a new NF membrane was synthesized using them to investigate the effects of monomer concentration, substrate morphology, and reaction temperature on membrane performance. The results showed that when the concentrations of both β-CD and TA were 1 wt%, the membranes had the highest selectivity (2.99) for monovalent and divalent salts. A 10-fold increase in TMC concentration (0.05 to 0.5 wt%) optimized membrane selectivity and flux. When both spongy and cavernous structures were present in the substrate, the membranes could achieve >85 % removal of monovalent and divalent salts. After the introduction of ZIF-8, the roughness of the membrane increased, and the removal rate of monovalent salts decreased significantly, resulting in a salt selectivity of 7.97 and a flux up to 27.81 ± 1.17 L/(m2 h). The growth of ZIF-8 on the membrane surface was assisted by an increase in the reaction temperature. • The selectivity for monovalent and divalent salts of synthesized membrane reached 7.97. • The substrate with both spongy and cavernous structures aided in the removal of monovalent and divalent salts. • Increasing the synthesizing temperature from 20 to 70 °C promoted ZIF-8 growth on membrane surfaces. [ABSTRACT FROM AUTHOR]

A major problem for the operation of membrane based water treatment systems is fouling of the membrane surface. Within industrial modules, such as spiral wound modules, feed spacers are necessary to separate adjacent membrane layers. Engineering of feed spacers with novel characteristics is an attractive option for reducing fouling within the module, for instance by increasing surface shear forces. This paper reviews the characteristics of feed spacers which are important in fouling and efforts to design novel feed spacers with anti-fouling characteristics, such as by addition of surface coatings, modified feed spacer design and geometric considerations, 3D printing and use of electrically conductive feed spacers. This paper also provides a brief review of techniques available to assess aspects of feed spacer design. It is seen that appropriate feed spacer design can do much to mitigate fouling in membrane modules, but continued effort is needed toward enhancement of high flux and low-pressure drop in membrane modules. [ABSTRACT FROM AUTHOR]

A simple theoretical method for maximizing efficiency via real-time balancing of direct contact membrane distillation (DCMD) systems is presented. The method is applicable under variable operating conditions. Balancing involves measuring only the flow rates of feed stream out of the module and the cold water flow into the module, as well as the salinity of the feed. A valve or variable frequency drive is used to set the condensate water flow into the module so that the heat capacity rates of the hot and cold streams are equal. This method is much simpler and more general than what is proposed in the literature, which generally requires more measurements and a complicated expression. Balancing leads to 20–50% improvement in efficiency (GOR) compared to equal inflow of both feed and pure water streams, which is the common practice. Real-time balancing is particularly useful for variations in feed salinity, whereas the improvement by real-time balancing is low for changes in system top or bottom temperatures. [ABSTRACT FROM AUTHOR]

Fouling and scaling is one of the major challenges in membrane distillation process. This study investigates the utilizing of thermal rejected brine produced from multi-stage flash distillation (MSF) to minimize fouling and scaling on membranes in direct contact membrane distillation (DCMD) settings. The effect of operating parameters on permeate flux and the extent of scaling during long time operation was considered and compared when real seawater and reject thermal brine were used. The deposit morphology of scaling was observed using different analytical methods, including scanning electron microscopy and contact angle measurement. Thermal brine showed enhanced performance in terms of flux and scaling compared to seawater. It was found that flux is reduced by 8% compared to 12–20% when the feed to the DCMD was brine was used as compared to seawater. In addition, thermal brine feed showed better anti-fouling behavior compared to the fresh seawater which contains different organic and inorganic contaminants. Furthermore, utilizing waste heat contained in the thermal brine to raise the temperature of the feed was advantageous in increasing the energy efficiency of DCMD process. [ABSTRACT FROM AUTHOR]

Herein, we describe the performance (i.e., flux and rejection) of commercially-available, thin film composite brackish water RO (BWRO), seawater RO (SWRO) and high-pressure RO (HPRO) membranes operating at pressures from 14 bar (200 psi) to 207 bar (3000 psi). For each membrane material, we elucidate the impacts to performance using a porous metal frit and woven tricot mesh permeate carrier materials from commercial HPRO, SWRO, BWRO and tap water RO (TWRO) membrane modules. The water permeability of all tested membranes declines with increasing pressure, whereas rejection behaves differently for different combinations of membrane type and permeate carrier. Cross-sectional SEM and FIB-SEM images confirm permanent reduction of the polysulfone support membrane thickness (38% to 60%) as well as collapse of support membrane skin layer pores – both of which may contribute to the observed performance decline. Also, at ultra-high pressures, permeate carrier materials with higher porosity cause greater embossing and, ultimately, coating film damage (defect formation) that leads to increased salt passage (loss of salt rejection). In contrast, the permeate carriers with lower porosity still lost water permeability, but maintained higher rejection. Finally, all of the observed compaction/embossing-related performance decline occurs within about 60 min after a membrane coupon was exposed to ultra-high pressure. [Display omitted] • Compaction decreases water and salt permeability via skin layer pore collapse. • Embossing leads to micron-scale defects, which increases salt passage. • It is not clear that spiral wound elements are the right form factor for UHPRO. • Spiral wound support membrane, permeate carrier & feed spacer need re-design. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) based desalination is one of the most important and widely recognized technologies for production of fresh water from saline water. Since its conception and initiation, a significant development has been witnessed in this technology w.r.t. materials, synthesis techniques, modification and modules over the last few decades. The working of a RO plant inclusive of the pretreatment and post-treatment procedures has been briefly discussed in the article. The main objective of this review is to highlight the historical milestones achieved in RO technology in terms of membrane performance, the developments seen over the last few years and the challenges perceived. The material properties of the membrane dominate the performance of a RO process. The emergence of nano-technology and biomimetic RO membranes as the futuristic tools is capable of revolutionizing the entire RO process. Hence the development of nano-structured membranes involving thin film nano-composite membranes, carbon-nanotube membranes and aquaporin-based membranes has been focussed in detail. The problems associated with a RO process such as scaling, brine disposal and boron removal are briefed and the measures adopted to address the same have been discussed. [ABSTRACT FROM AUTHOR]

Abstract: Recent years have witnessed the emergence of detonation nanodiamonds (DNDs) as a new member of the nanocarbon family. This paper reports the immobilization of DNDs within a hydrophobic membrane for desalination applications. A dispersion of DNDs in polyvinylidene fluoride polymer was injected through a hydrophobic membrane, which incorporated the DNDs within the membrane. Embedding only a minimal quantity of (approximately 2%) the nanocarbon favorably altered the water vapor–membrane interactions to enhance water vapor permeability while preventing liquid penetration into the membrane pores thereby enhancing water vapor flux. Overall, desalination was consistently better with DND immobilized membrane than with conventional polypropylene, with flux enhancement as high as 118% in the sweep gas membrane distillation mode. [Copyright &y& Elsevier]

Abstract: In the present study, a monolithic alumina coated microfiltration ceramic membrane was used for solid particulate removal and nutrient recovery from anaerobic digester complex effluent streams. The aim was to test the effect of the cake layer developed by the solids, on the surface of the membrane channels, to the filterability of these materials. The solid content ranged between 2.6g/L to 15.1g/L. During practical application, two processing techniques targeting the enhanced recovery of the materials of interest including ammonia, phosphate, calcium bicarbonate and volatile fatty acids, namely dewatering and diafiltration, were used. These had an immediate effect on the solid content (PDS 13μm to 3.97μm) enhancing the filterability of the effluents. Their processability was evaluated in terms of flux, cross flow velocity, membrane resistance and cake resistance. An important finding of this study is the nonalignment of the flux rates to the cake resistance, explained by the formation of a compressible, permeable cake layer that allowed the continuous operation of the system, under constant low pressure conditions (TMP 15psi). Permeate flux remained constant to 120L/m2 h when applying diafiltration, while when dewatering process is used the permeate flux remained constant at 115.4L/m2 h. [Copyright &y& Elsevier]

Mineral scaling by sparingly soluble gypsum (CaSO 4 ∙2H 2 O) is a persistent challenge to membrane distillation (MD). The underlying relationship between the thermodynamic state of the precipitating solution and the point of flux decline due to rapid mineral growth remains unclear. In this work, a series of experiments along with a semi-empirical model are executed to examine the thermodynamic state of the feed solution at the feed/membrane interface to evaluate and compare the critical point of scaling. The experiments were deliberately designed in a way to decouple the influence of feed temperature and vapor flux. The thermodynamic state of the precipitating solution at the membrane interface is evaluated using the saturation index and the nucleation energy barrier derived from the chemical potential difference between the dissolved ions and the gypsum mineral. The model is rooted in established heat and mass transfer relationships and reflects the testing conditions used to carry out the experiments. The model is built upon experimental results across a range of operational conditions, with the bulk feed solution temperature ranging from 50 to 80 °C (at a constant flux) and the trans-membrane water flux ranging from 10 to 40 L m−2 h−1 (at a constant feed temperature). It was observed that interfacial saturation index calculated at the induction point was not consistent across different experiments, confirming that gypsum scaling in MD is controlled by kinetics instead of thermodynamics. We also found that temperature plays a more important role than vapor flux in affecting the critical recovery. Lastly, we also provide theoretical reasoning to support the experimental observation that gypsum scaling in MD is largely dominated by heterogeneous nucleation onto the membrane surface. • The impacts of temperature and flux on gypsum scaling are experimentally decoupled. • Interfacial saturation index alone cannot predict the onset of gypsum scaling. • Temperature has a stronger impact than flux on critical water recovery. [ABSTRACT FROM AUTHOR]

Abstract: Gradual reduction of steady state permeate flux (throughput) over a period of time often mars the performance of nanofiltration process. In the present study, nanofiltration of two-component dye and NaCl mixture containing Reactive Black 5 and C.I Reactive yellow 160 was carried out in a flat sheet membrane module with hydrophilized polyamide membrane (molecular weight cut off 400) over a range of operating conditions. Results indicate that the flux decline with time could be significantly mitigated under low frequency (34±3kHz) ultrasonic irradiation when compared with the conventional unassisted nanofiltration. Various filtration resistances were determined using a simple resistance-in-series model, which revealed that concentration polarization resistance could be effectively decreased by ultrasonic irradiation. Effect of several parameters such as mode of irradiation (viz. continuous and intermittent), trans-membrane pressure and temperature were studied and discussed with respect to existing theories. The power consumption of the high pressure plunger pump at different feed pressures and the ultrasonic power transferred to the water bath at three different temperatures were estimated. More than 96% of color, and 65% TDS were removed from the treated water accompanied by a marked reduction of COD. The process allowed the production of permeate stream with great reutilization possibilities. [Copyright &y& Elsevier]

Abstract: One significant challenge to membrane filtration technologies is membrane fouling causing pressure drop, flux decline and eventually significant cost of membrane replacement. The objective of this research was to determine the impact of metabolic activity as measured in adenosine triphosphate (ATP) concentration of the pure culture of biofoulants on the membrane biofilm metabolic activity, biofilm formation rate, and operational flux decline. Our results showed that after 10–12h of filtration, the biofilm ATP levels reach an equilibrium concentration (avg. 8amol/cell) and do not appear to be related to biofoulant ATP levels from cells harvested in the late exponential growth phase regardless of initial ATP level. However, the bacterial growth phase affected the ATP activity of cells and membrane biofilms formed from biofoulants in the lag and stationary phases of growth contained similar levels of activity, and the exponential phase cells resulted in significant higher activity. Flux decline does not appear to be related to metabolic activity of the biofoulant or biofilm following 24h of filtration but notably, there was much less flux decline when the biofoulant cells were inactive. [Copyright &y& Elsevier]

Abstract: This study is focused on the physical filtration characteristics of a flatsheet membrane bioreactor (MBR) operated under a novel filtration mode. The objective of this research was to demonstrate the possibility of running an MBR with high MLSS concentration for prolonged periods without frequent blocking of the membranes. Current MBR designs, mostly dictated by the manufacturers, have restrictions on the level of MLSS due to fouling. It has been observed that this restraint can be eliminated by applying high shear rates for better removal of cake layer from membrane surface. A pilot scale MBR was setup at the inlet works of a domestic sewage treatment plant. The system was dynamically modeled and calibrated for flux, hydraulic permeability, transmembrane pressure using the in-series resistance model. Resistance components were experimentally determined and compared against the results of dynamic simulations. Intrinsic membrane resistance (Rm) and fouling resistance (Rf) were the major components contributing to total resistance with fractions of 69% (Rm/Rt) and 30% (Rf/Rt) respectively. It was found that cake resistance did not have major impact on the total resistance which was linked to the high aeration intensity. Proposed model was validated by experiments which indicated its potential use on other MBR systems. [Copyright &y& Elsevier]

Abstract: In this research, the structure optimized BP-ANN model was applied to simulate the permeate flux as a function of mixed liquor suspended, temperature, dissolved oxygen, hydraulic retention time, transmembrane pressure and operating time during dead-end microfiltration of activated sludge suspensions and its supernatant from sequencing batch reactor (SBR). This artificial neural network approach was also used to model the chemical oxygen demand (COD) concentration of effluent from SBR. The results showed that the structure optimized single hidden layer neural networks was able to accurately simulate the dynamic behavior of permeate flux and the COD concentration for SBR activated sludge process, and this BP-ANN model possessed higher accuracy than that of C. M. Silva''s predictive model and linear multi-regression model. [Copyright &y& Elsevier]

Abstract: The blend membranes of sodium alginate (SA)/dextrin were prepared by solution casting method followed by crosslinking with glutaraldehyde and used for the separation of water+isopropanol mixtures at 30°C. Pervaporation (PV) separation characteristics were studied for the different water compositions (10–50mass%) in the water+isopropanol feed mixtures through the prepared blend membranes. The crosslinked and un-crosslinked membranes were characterized by FTIR, DSC and surface morphology of membranes studied by SEM. The membrane performance was studied by calculating the flux and selectivity. Sorption studies were carried out to evaluate the extent of interaction and the degree of swelling of the membranes in pure liquids as well as in binary mixtures. The observed flux was higher for crosslinked SA/dextrin blend membranes, compared to plain crosslinked SA membrane; nevertheless, the selectivity was also higher for SA/dextrin (40:60mass%), SA/dextrin (50:50mass%) and SA/dextrin (60:40mass%) blend membranes compared to the plain crosslinked SA membrane. [Copyright &y& Elsevier]

Abstract: Two supported liquid membranes (SLMs) containing two different carriers but formed by the same polymer support polyvinylidene difluoride ( PVDF ) and the same organic phase (xylene), were used to realize the facilitated transport of vanadium ions (VO2 +) from the concentrated acid solutions. The SLM support was a micro porous PVDF polymer film of thickness 100µm with pore size 0.45µm which has been impregnated with a solution of xylene containing 0.01M of one of the carriers, the Di-(2-ethylhexyl) phosphoric acid ( D2EHPA ) or the Trioctylphosphine oxide ( TOPO ). The permeabilities P and the initial fluxes J 0 for the transport of the VO2 + ions were calculated from the proposed kinetic model for the two SLMs used. These two macroscopic parameters depend on both the concentration of the carrier (T) and that of the substrate (S) to be transported. The proposed mechanism indicates the formation of a complex (1/1) carrier–substrate (TS), and the migration of this complex through the organic phase of the SLM, is the rate-determining step in the transport mechanism. The initial flux J 0 is related to the initial substrate concentration C 0 in the feed phase by a saturation law, which allowed the determination of the apparent diffusion coefficients D* and the association constants K ass of the complexes (TS), formed in the organic phase of the two studied SLMs. These results clearly indicate that the values of these two microscopic parameters (D* and K ass), depend certainly on the acidity of the medium and probably the concentration of co-ions NO3 −. [Copyright &y& Elsevier]

Abstract: The drying of middle distillate (MD), from which diesel fuel is made, by Pervaporation (PV) was experimentally investigated in a laboratory plant applying organic membranes. The work was conducted in cooperation with a refinery in which MD is catalytically desulphurized by hydrogenation. The H2S formed is separated by steam stripping. The resulting water content in the MD is removed by decanting and subsequent vacuum drying. The objective was to investigate whether drying to low ppm water content is technically possible by the process of PV and to find out about the feasibility of replacing the vacuum drying by PV to save energy. The drying to low ppm water content was accomplished successfully. Permeate total and pure water fluxes are reported. Economic estimations compared vacuum drying costs taken from an existing plant with a design for a full scale multi-module PV plant. The run time of a plant for the point, at which energy savings make up for higher investment costs is estimated. [Copyright &y& Elsevier]

Abstract: A major stumbling block in polyamide thin film composite RO membrane performance is its incompatibility with chlorine and oxidizing agents. The amide bond of the membrane is highly vulnerable to chlorine attack. Two reactions are possible with chlorine exposure i.e. N–H bond chlorination and/or aromatic ring chlorination. In this way, chlorine may cause degradation/modification in the membrane leading to deterioration in performance. However, low concentration of chlorine up to a certain time may give synergistic effect on membrane and improve its performance. Chlorine solution, if exposed to membrane for certain time gives enhancement in trans-membrane flux of the membrane. The same solution if exposed for more time deteriorates ultra-thin polyamide layer of TFC membrane. Conspicuously, the membrane with poor salt rejection and flux benefited more as compared to the membrane with better performance. In the present study, membranes with different salt rejection and flux were taken and exposed to the inorganic chlorine solution. The inorganic chlorine solutions were made by dissolving sodium hypochlorite in pH buffer. The different solutions were made by varying pH to investigate the pH dependence. The membrane samples were kept in solution for different time durations. The exposure time was monitored and the exposure level was taken in terms of ppm h (ppm chlorine solution exposed to membrane for a fixed time in h). With the same chlorine concentration, effect of varying pH was studied. Spiral wound TFC membrane modules were also subjected to chlorine solution to study its effect. [Copyright &y& Elsevier]

Abstract: MBR-technology has become a standard technology for waste-water treatment. Worldwide more than 5000 MBR plants are under operation. Most of them are quite small plants but more and bigger plants are under construction. The investment costs can be compared with conventional plants in case that the effluent requirements are the same. But MBR technology has further advantages. In this paper, the benefits of MPE technology at some full-scale MBR plants are shown. These results will be used to demonstrate the possibility CAPEX and OPEX savings that can occur if new MBRs are designed with MPE-technology. [Copyright &y& Elsevier]

Abstract: On principle of polymer blend phase separation, PVDF/PVA hollow fiber membranes were prepared using phase inversion method. The membrane morphology and performance varied with the blending ratio. The PVDF/PVA blends showed incompatibility by the results of dynamic mechanical analysis (DMA) and infrared attenuated total reflection (FTIR-ATR) sampling technique. Based on bursting pressure and tensile strengths results, we suggest that the mechanical properties of PVDF/PVA blend membranes are worse than that of PVDF membrane. PVA can improve the hydrophilicity of PVDF/PVA hollow fiber membranes, which could be illuminated by the decrease in contact angle, the increase in equilibrium water content (EWC) and the variety in dynamic moisture regain. The pure water flux increases while the rejection ratio decreases with PVA content increasing. Moreover, PVA can improve the anti-fouling property of PVDF/PVA hollow fiber membranes, which could be illuminated by the result of increase coefficient of resistance. [Copyright &y& Elsevier]

Abstract: Kaolin porous support ceramic was prepared from kaolin. The characterization of the porous properties and structure of the support synthesis was carried out by scanning electron microscopy (SEM), absorption rate, shrinkage rate and Hg-porosimetry methods. The pore size distribution showed a unimodal pore size distribution with an average pore size of about 0.9µm. The reliability of support was measured by filtration tests and removal of heavy metals. Filtration studies using porous tubular supports were performed for solutions containing methylene blue and Evans blue. The study of the liquid filtration and flow through these supports showed that the methylene blue rejection rate was 99% while the Evans blue rate reached 90% for a 90minute filtration time under a pressure of 2bar. We beforehand tested the flow rate for each support with distilled water and the results show that the support of kaolin gave a flux for distilled water of 31.0L/h at the pressure of 2bar. At a pressure of 3.5bar an increase in the distilled water flux through the support was observed. The rejection rate of cadmium ions was more significant. A rejection rate of 99.99% using a 10−4 mol/L solution of this heavy metal for two-hour treatment time was obtained. [Copyright &y& Elsevier]

Abstract: A system coupling photocatalytic oxidation of titanium dioxide particles separated by non-woven membrane for the degradation of 4-chlorophenol in an aqueous solution was studied. Non-woven membranes with three different pore sizes were applied to compare their specific flux and permeate turbidity. The results showed that when the pore size was slightly smaller than secondary particles of photocatalyst, higher specific flux and lower turbidity permeate were obtained. Four different applied fluxes, 0.25, 0.5, 1.0 and 2.0 m3/m2/d, were used with a 2.0 μm pore size non-woven membrane in a continuous system. The results revealed that the transmembrane pressure (TMP) was less than 10 kPa in all applied fluxes, due to the formation of a porous dynamic cake layer on the surface of the membrane. Based on the filtration characteristics of non-woven membranes, we found that cake formation, rather than pore blocking or pore narrowing, was the dominant factor. This phenomenon also resulted in permeate turbidity ranging from 0.5 to 1.5 NTU and non-detectable concentration of TiO2 in the permeate. At the same time the experimental results indicated that the concentrations of TOC and 4-chlorophenol decreased with decreasing applied flux, and that the concentration of chloride ions increased with decreasing applied flux in a 4-chlorophenol photodegradation test. It showed that 4-chlorophenol could be effectively degraded by this hybrid system with lower TMP and stable applied flux. [Copyright &y& Elsevier]

Abstract: In order to determine the suitability of an ultrafiltration membrane module (Omexell™ SFP2660) to different feed waters, the filtrate quality and the operation status of the module were studied comparatively when it was fed with raw seawater, coagulated seawater and cooling tower blowdown (CTB) respectively. The results indicated that (1) under a flux of 60–65 L·m−2·h−1, the UF membrane module was suitable for the three kinds of feed water; (2) when fed with the CTB and operated at an increased flux (90 L·m−2·h−1), the module could still keep stable production while the filtrate quality became a little poorer (turbidity ≥0.1 NTU) and the transmembrane resistance went a bit higher (transmembrane pressure, ≥0.15 bar); (3) due to low concentration of organic matter (total organic carbon, <2 mg/L) in the feed water, the residual contamination in the membrane is little; and (4) feed water temperature had a great effect on the silt density index of the filtrate. So the membrane module could not only adapt to the three kinds of feed water, but it also endured the fluctuation of feed water turbidity (7–300 NTU) and flux (60–90 L·m−2·h−1), whereas stabilized and clarified feed water provided by the coagulation process will benefit the membrane module for long-term operation. [Copyright &y& Elsevier]

Abstract: Membrane processes have been used as a key technology for water reclamation and reuse of secondary effluent discharged from municipal wastewater treatment plants. However, its extensive practices are limited due to membrane fouling. To control and manage the membrane fouling properly, pretreatment methods were compared and evaluated. Prior to direct membrane filtration of secondary effluent, the effect of coagulation with alum and ferric sulfate on membrane fouling was investigated using two different ultrafiltration membranes (YM30 and PM30). Membrane filterability was enhanced by addition of alum and ferric sulfate respectively. This was due to the effective destabilization of colloidal particles, which was confirmed by measuring particle size distribution. Soluble foulants present in secondary effluents were entrapped to coagulated flocs. This reduced the concentration of soluble foulants, which lead to a decrease in Rf values. The hydrophobic membrane (PM30) showed high flux declines, whereas the hydrophilic membrane (YM30) showed relatively low flux decline. For the purpose of controlling membrane fouling, a pretreatment using coagulation is more efficient for hydrophobic than hydrophilic membranes. This could give us a good criterion for selecting membrane materials for water reuse practices. [Copyright &y& Elsevier]

Abstract: By-products obtained from red currant processing still contain large amounts of useful components, e.g. pectin. Pectin was extracted from red currant marc with water at a solid/liquid ratio of 1:10. To reduce the operating costs of further possessing, we concentrated the pectin solution by membrane separation, i.e. nanofiltration (NF) and reverse osmosis (RO). The objectives of our work were to study the effects of the operating pressure and cross-volume flow rate on the flux and on the membrane separation concentration ratio in order to establish the optimum operating conditions and to evaluate the contributions of the fouling, cake and membrane resistances to the overall resistance. Flat-sheet RO and a spiral-wound NF membrane were applied in the work. The conductivity, the color, the viscosity and the TSS of the permeate and the concentrate were followed during the measurements. Concentration by RO resulted in an increase of the TSS content to 4.28°Brix; for NF the corresponding level was 8.88°Brix. The membrane resistance and the fouling resistance were the determinant relative to the gel resistance. [Copyright &y& Elsevier]

The design of membrane distillation modules is an important issue that must be addressed for it to be practically implemented. Herein, a combination of the design of experiments (DOE) and computational fluid dynamics (CFD) was developed to evaluate the interaction between variables of module geometry and how they affect the performance of a direct contact membrane distillation (DCMD) process. A three-dimensional CFD model was developed to calculate flux, the performance ratio (PR), and the permeate-to-feed ratio (ϕ p) as functions of the height, length, and width of the channel in a plate-and-frame DCMD module. The CFD model was validated using experimental results in a laboratory DCMD system. Based on a DOE with a central composite design (CCD), CFD simulations were carried out, and response values were obtained for each combination. The results show that length is the most important factor affecting flux, and height is the most important factor affecting PR and ϕ p. However, the effect of module width was not significant compared with that of the other variables. Based on the results, a set of regression models were developed to estimate flux, the PR, and ϕ p , and these estimations match the CFD simulation results well. Using the derived models, the dimensions of the DCMD module were optimized to simultaneously increase water productivity and energy efficiency. • The CFD model of the direct contact membrane distillation (DCMD) module was investigated using a combination of CFD and design of experiment (DOE). • DCMD module optimization was attempted by simulating CFD model for flux, the performance ratio (PR), and the permeate-to-feed ratio (ϕ p). • The length of the module was the most influential factor on the flux, and the height of the module had the most influence on the PR and ϕ p. • This study demonstrates that the dimensions of DCMD module can be optimized using a combination of CFD and DOE. [ABSTRACT FROM AUTHOR]

Abstract: Sesame seeds contain important proteins like globulin, albumin, prolamine and glutelin. Sesame protein hydrolysate is also thought to be an important source of nutritional supplement. The work in this study was carried out to assess the feasibility of concentrating sesame protein hydrolysate by ultrafiltration (UF) and to obtain the effects of different operating parameters like transmembrane pressure (TMP), feed concentration and solution pH on UF flux and rejection. No studies regarding the application of UF in treating sesame protein hydrolysate have been reported in the literature elsewhere. A polyether sulfone (PES) membrane of 5 kDa molecular weight cut-off was used for this study. Results of investigation show the membrane fouling to be quite dominant, though in most of the cases, water flux could be recovered by following the suggested cleaning methodology. Capillary electrophoresis was carried out for feed characterization with an objective to obtain molecular weight distribution. Solute rejection with a 5 kDa PES membrane was found to lie within the range of 50–70% depending upon the operating condition—an observation which is commensurate with the molecular weight distribution results obtained through capillary electrophoresis. Minimum flux and maximum permeate concentration (i.e. minimum rejection) were obtained at the isoelectric point of the sesame protein hydrolysate. Adequate explanations for all the observations reported in this study were cited in appropriate places. The investigation clearly proved that UF could be used as an effective tool for concentration of sesame protein hydrolysate after proper choice of operating conditions. [Copyright &y& Elsevier]

Abstract: The variation of quality and fouling properties of wwtp effluent over time influences the performance of ultrafiltration (UF) plants. This research reports three experiments in which the specific ultrafiltration resistance (SUR) measurement is applied to obtain more insight in quality variation an impact on UF performance. Firstly the overall performance (flux, recovery and trans-membrane pressure) of a UF pilot was compared with the SUR values of the feedwater. Secondly the effect of pre treatment was investigated. At last the relation between the slopes of filtration cycles of a UF installation and SUR measurements of feedwater were compared. The results clearly indicate that the overall performance of the UF pilot depends on the SUR values of the feedwater. The SUR values should be less than 10×1012 m−2 for a stable UF performance. Also the effect of pre treatment depends on the SUR values of raw wwtp effluent. Very low SUR values (∼4×1012 m−2) mean less effect compared to higher SUR values. The relation and correlation between SUR values of feed water and single filtration cycles of UF installations depends on the condition of the membranes in the units. Using fouled membranes the variation of SUR values corresponds to higher TMP variations than using cleaner membranes. [Copyright &y& Elsevier]

Abstract: An investigation was conducted to determine the feasibility of using reverse osmosis (RO) membranes to treat water containing up to 50% (by volume) oil. The effect of varying the feed pressure, pH and temperature on separation performance of two thin film composite polyamide RO membranes was evaluated. In experiments involving contaminated water with up to 30% oil, high permeate quality was attained with more than 99% oil rejection being achieved. In some circumstances, oil contamination resulted in an increase in membrane flux and, as an example, at 50% oil contamination, an increase in membrane flux of 40% was observed. However, membrane permeate quality was deteriorating at these high concentrations. The product water quality improved significantly with decreasing feedwater pH and temperature effects on permeate quality were found to be minimal. It was observed that increased feedwater pressure leads to a significant improvement in permeate quality in terms of the total organic carbon (TOC). In this paper the observations from a comprehensive set of experiments are discussed in relation to the practicalities of using RO processes for oily water treatment. [Copyright &y& Elsevier]

Abstract: This paper aims to examine the separation of ultrafine titanium dioxide (TiO2) ptotocatalyst from its aqueous suspensions and its reuse by cross-flow ultrafiltration (CFU) process. Initially, the effects of various parameters, such as feed concentration, transmembrane pressure, cross-flow velocity, pH, electrolyte and membrane molecular weight cut-off (MWCO) on the flux were investigated. Thereafter, the activity of reused photocatalyst for dye wastewater by CFU and coagulation processes was compared respectively. The results of this investigation reveal that: (1) a complete separation of TiO2 from its aqueous suspensions can be obtained by an ultratfiltration process compared to coagulation process; (2) it is more efficient to maintain high activity of the separated TiO2 by CFU process than that of coagulation process. Therefore, the combined slurry photoreactor and CFU process in this study can be an attractive option for controlling pollutants in water. [Copyright &y& Elsevier]

Abstract: The demand for clean water is currently increasing because of the decreasing sources of drinking water the stringent environmental legislation and the rigorous quality demands. Nanofiltration may be a solution for the effective separation of anionic detergents from used water or wastewater. In this work the removal of an anionic surfactant cleaning agent by nanofiltration was investigated. The nanofiltration of aqueous solutions of the anionic surfactant was examined at detergent concentrations of 0.5, 1.0 and 5.0g L−1 at 20, 30 and 40°C and at 20, 30 and 40 bar. Statistical evaluation of the data revealed that the retention was principally affected by the temperature. The highest retention was observed at 20°C. Increase of both pressure and temperature increased the flux, but the impact of pressure was higher than that of temperature. The highest flux was measured at 40°C. There was no appreciable difference between 30 and 40 bar. The fouling index, calculated by fitting a power function to the measured data, was mainly affected by the temperature: it decreased with increasing temperature. The ideal parameters for the best retention and a reasonable flux were found to be 20°C and 30 bar and for the minimal fouling were 30°C and 30 bar. [Copyright &y& Elsevier]

Abstract: In this study the effects of operating parameters on the ultrafiltration of metal working fluids were considered and the optimum conditions for filtration were estimated. In order to reduce the number of experiments an experimental design method (Taguchi) was applied. Seven parameters including pH, oil concentration, temperature, salt (NaCl, CaCl2), feed velocity, and pressure were studied at three levels (low, medium, and high). The oil was water soluble cutting oil and the membrane was an ultrafiltration membrane (C100F) which was supplied by the NADIR Company. The filtration was done at total recycle conditions. During the experiment samples from feed and permeate were collected in order to measure the retention of oil, the zeta potential, and the oil drop size. The obtained results showed a flux increase with increasing pH. The highest flux was achieved at alkaline conditions but the highest retention was observed when the pH was acidic (lower limit in experiment). It was also observed that the zeta potential was mostly affected by pH and CaCl2. The biggest zeta potential resulted in the lowest permeate flux. The drop size measurement showed that a bigger drop size usually gave a higher flux. The effect (increase in flux) of salt addition implied that at acidic conditions the effect was smaller than at alkaline conditions. As a conclusion, an alkaline pH, a high pressure, a high temperature and a low amount of CaCl2 gave the optimum conditions. [Copyright &y& Elsevier]

Abstract: Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m2 surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m2/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation. [Copyright &y& Elsevier]

Abstract: In this paper, a linear multi-regression model was used to study the degree of influence of various operating conditions on the permeation flux of deionized water and bovine serum albumin (BSA) solutions in the ranges of 0.04–0.16 MPa and 20–30°C during dead-end microfiltration. In the experiment, two kinds of membrane were used. One was a PVDF membrane with pore size of 0.1 μm, and the other was a PTFE membrane with a pore size of 0.2 μm. Experimental and analytical results showed that temperature, pressure and concentration had a significant influence on the microfiltration membrane flux. For deionized water, the flux increased with increasing temperature and pressure, and the relative degree of influence of temperature and pressure on the microfiltration membrane flux was different, 2% and 98%, respectively. The relationship was Jw =−6.57+0.27 T +133.27 P. For BSA solutions, the flux increased with increasing temperature and pressure, while decreased with increasing concentration. The degree of influence of pressure, temperature and concentration on the permeation flux was 69%, 18%, 13%, respectively, and the relationship was J =−1.28+0.22 T +33.11 P −1.04 C. Therefore the relative importance of pressure on the membrane flux was much greater than that of temperature or concentration. [Copyright &y& Elsevier]

Abstract: An adjustable parameter k was introduced in an original model based on Darcy’s Law to increase its accuracy, and a new semi-empirical model predicting permeate flux for dead-end microfiltration (MF) systems was proposed. The adjustable parameter k was validated in laboratory experiments by using two different suspensions (kaolin and yeast). The membranes adopted in this research included flat PES and PVDF with 0.2μ and 0.1μ average pore size respectively. The experiments showed that this adjustable parameter was almost independent of operating conditions pressure, concentration and temperature), but depended on the character of the cake formed on the membrane surface and on the type of membrane. The average values of k for yeast and kaolin are 4.15 and 1.10 respectively. The results showed good agreement between model prediction and experimental observations. [Copyright &y& Elsevier]

Abstract: Interpenetrating network (IPN) membrane of HTPB-based polyurethane urea (PUU) and poly (methyl methacrylate) (PMMA) was developed and used in the pervaporation separation of water–dimethyl formamide (DMF) mixtures of different compositions. From these data the permeation flux, separation selectivity, degree of swelling were calculated at 25, 40 and 60°C. At a higher temperature, the permeation of diffusing molecules through the membrane becomes easier, resulting in an increase of DMF flux. Again with the increase in PMMA content in the membrane the DMF flux and separation selectivity values are increased due to the presence of more polar groups of PMMA. The membrane showed more selectivity towards DMF than water. The highest DMF flux of 0.231 kg/m2.h was obtained for the PUU-PMMA-3 membrane at a temperature of 60°C for 80% DMF in the feed. [Copyright &y& Elsevier]

Abstract: The static adsorption test showed that hydrophobic organics adsorbed much more quickly than hydrophilic organics. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption ratio [C(t)/C(e)] was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions. The rate of flux decline for the hydrophobic membrane was significantly greater than for the hydrophilic membrane, regardless of pretreatment conditions. The pretreatment of raw water significantly reduced the fouling of the membrane. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. After this flux decline, the permeate flux decreased in the pore volume. This implies that all four mechanisms are valid when applying these filtration models. When the pretreatment coagulation applied, the kinetic constants, Ks , Ki , and Kc , showed lower values than UF alone process. Therefore, applying coagulation process before membrane filtration was found to be very effective in fouling reduction as well as critical flux increase due to the increase in particle size. For UF process alone, Ks was lower for the hydrophobic membrane, while Ki and Kc were higher for the hydrophilic membrane. That is, the result showed that decrease in the pore volume, which was caused by the particle deposition into the internal pore, was greater with the hydrophobic membrane than with the hydrophilic membrane. [Copyright &y& Elsevier]