Constant Transmembrane Pressure Research Articles

Development of a new modeling framework to describe sterile filtration of mRNA-Lipid nanoparticles

Sterile filtration is one of the critical steps in the production of lipid nanoparticle (LNP)-based biotherapeutics. However, LNP fouling can limit the overall capacity of the sterilizing-grade filter. Effective design and control of this unit operation enables a robust manufacturing process. The objective of this study was to examine the sterile filtration of mRNA-LNP through the dual-layer Sartopore 2 XLG membrane during both constant flux and constant transmembrane pressure (TMP) filtration experiments. The complete pore blockage model effectively described the fouling behavior at constant TMP, with the rate of pore blockage decreasing with increasing TMP. However, a novel modification of the complete pore blockage model was needed to describe the fouling behavior during constant flux operation, with the rate of pore blockage found to be a function of both the instantaneous TMP and the TMP gradient. This new model successfully describes the TMP profiles during constant flux operation at multiple fluxes and the flux profiles during constant TMP operation at multiple TMPs, all using the same model parameters. These findings establish a foundational framework that mathematically describes the fouling behavior of mRNA-LNP and can be used to design and optimize sterile filtration processes for this class of biotherapeutic.

Exploring the impact of fouling on permeate flux and quality in ceramic ultrafiltration after treating poultry wastewater, and strategies for effective modelling and mitigation

Ultrafiltration was used to treat the poultry processing industry's wastewater to enhance the water quality, making it suitable for recycling within the process. With the application of a constant transmembrane pressure for the ultrafiltration process, the permeate flux decreased over time, while the permeate quality improved. Mathematical modelling of the flux data and permeate analysis revealed that cake layer formation was responsible for fouling but with some initial pore blocking. The study indicated that higher transmembrane pressure contributed to the formation and compression of the cake layer, resulting in improved permeate quality. Cleaning with water failed to eliminate fouling, but chemical cleaning with acid and base helped to restore the initial permeate flux. The process effectively removed almost all particles (>99 % reduction of turbidity), over 90 % of the chemical oxygen demand, and 40–80 % of total phosphorus. The efficiency of the phosphorus removal was lower for pre-treated wastewater as part of the phosphorus was already removed. Increasing the pressure from 1 to 3 bar significantly improved the removal of chemical oxygen demand, total phosphorus, and lipids by 10 % without negatively impacting the membrane-cleaning process.

Integrating of electrocoagulation process with submerged membrane bioreactor for wastewater treatment under low voltage gradients

Treating and reusing wastewater has become an essential aspect of water management worldwide. However, the increase in emerging pollutants such as polycyclic aromatic hydrocarbons (PAHs), which are presented in wastewater from various sources like industry, roads, and household waste, makes their removal difficult due to their low concentration, stability, and ability to combine with other organic substances. Therefore, treating a low load of wastewater is an attractive option. The study aimed to address membrane fouling in the submerged membrane bioreactor (SMBR) used for wastewater treatment. An aluminum electrocoagulation (EC) device was combined with SMBR as a pre-treatment to reduce fouling. The EC-SMBR process was compared with a conventional SMBR without EC, fed with real grey water. To prevent impeding biological growth, low voltage gradients were utilized in the EC deviceThe comparison was conducted over 60 days with constant transmembrane pressure and infinite solid retention time (SRT). In phase I, when the EC device was operated at a low voltage gradient (0.64 V/cm), no significant improvement in the pollutants removal was observed in terms of color, turbidity, and chemical oxygen demand (COD). Nevertheless, during phase II, a voltage gradient of 1.26 V/cm achieved up to 100%, 99.7%, 92%, 94.1%, and 96.5% removals in the EC-SMBR process in comparison with 95.1%, 95.4%, 85%, 91.7% and 74.2% removals in the SMBR process for turbidity, color, COD, ammonia nitrogen (NH3–N), total phosphorus (TP), respectively. SMBR showed better anionic surfactant (AS) removal than EC-SMBR. A voltage gradient of 0.64 V/cm in the EC unit significantly reduced fouling by 23.7%, while 1.26 V/cm showed inconsistent results. Accumulation of Al ions negatively affected membrane performance. Low voltage gradients in EC can control SMBR fouling if Al concentration is controlled. Future research should investigate EC-SMBR with constant membrane flux for large-scale applications, considering energy consumption and operating costs.

Influence of the pectin and cellulose on the performance of cross-flow microfiltration

The cross-flow microfiltration (CFM) of fruit juices allows obtaining products of high quality by conserving their organoleptic characteristics and microbiological stability during storage. The effect of the main macro-compounds and the transmembrane pressure (TMP) on the process performance with model fluids was evaluated. The model fluids concentration varied between 0.25 and 0.75% for pectin and 0.04 and 0.08% for cellulose. To study the influence of transmembrane pressure (TMP) and concentration on the hydrodynamic properties of the fouling layer ( , diffusivity (D) and the boundary layer thickness ) the Box-Behnken design with three replicas in the center was used. It was found that the CFM process is efficient and commercially feasible when working at a constant TMP of 1.93 bar and at concentrations of pectin and cellulose of 0.25% and 0.0513%, respectively.

Comparison of the formation, filtration performance, and structural characteristic of self-forming dynamic membranes under constant transmembrane pressure and constant filtration flux

The formation and filtration of self-forming dynamic membranes (SFDMs) can be affected by multiple factors, such as the operating conditions and sludge properties in membrane bioreactors. There has been limited research on the effects of the constant transmembrane pressure and constant filtration flux on the stable filtration of dynamic membranes. In the present study, a large-pore stainless steel mesh (70 µm pore size) was used as the support material for dynamic membrane formation to explore the formation, filtration performance, and structural characteristics of two dynamic membranes, P-SFDM (filtration under constant transmembrane pressure) and J-SFDM (filtration under constant flux), with the same initial filtration flux. The results showed that the stable filtration period of J-SFDM went up to 22.5 h, which was significantly longer than that of P-SFDM (5.5 h) with a higher resistance growth speed. The blocking process of the P-SFDM membrane conformed to the complete blocking model, whereas that of the J-SFDM membrane conformed to the standard blocking model in the initial stage and follows the intermediate blocking model in the later stage. Besides, the P-SFDM cake layer had a higher extracellular polymer content and smaller particle size (106 ± 2 mg·g−1 VSS, 546 ± 63 µm) than that of the J-SFDM cake layer (89 ± 3 mg·g−1 VSS, 615 ± 51 µm). During a 39-day continuous long-term operation, the energy consumptions per ton of water for J-SFDM and P-SFDM were 0.14 kw·h·t−1 and 0.19 kw·h·t−1, respectively. The above results show that the J-SFDM has a longer stable filtration period with lower energy consumption per ton of water.

Effect of operation mode on membrane fouling from traditional Chinese medicine water extracts

Membrane technology is a viable alternative to many conventional methods currently used to process traditional Chinese medicine (TCM). However, membrane fouling is a significant obstacle to the application of membrane technology in TCM. In this study, the ultrafiltration (UF) membrane fouling from TCM water extracts under constant transmembrane pressure (TMP) and constant flux operation was studied in connection with critical and threshold flux determinations. Meanwhile, the physicochemical foulant–membrane interactions were analyzed using the extended Derjaguin, Landau, Verwey, and Overbeek (XDLVO) theory. At constant TMP operation, the high pressure resulted in a rapid drop in permeate flux at the start of the filtration period, but the steady-state fluxes did not increase significantly with an increase in TMP. At constant flux operation, the TMP increased somewhat when the permeate flux was below the threshold flux. Fouling was severe above the threshold flux, and the TMP rapidly increased. By displaying fouling resistance as a function of permeate volume, the constant flux operation was compared to a constant TMP operation beginning at the same flux imposed during the constant flux operation. Below the threshold flux, fouling resistance was similar for constant TMP and constant flux operations. However, above the threshold flux, fouling resistance under constant flux operation was much greater than fouling resistance under constant TMP operation. The results of physicochemical interactions showed that there are attractive interactions between hydrophobic membrane and foulants in the TCM water extracts. These interactions should be considered a key factor leading to serious membrane fouling.

Effects of filtration modes on fouling characteristic and microbial community of bio-cake in a membrane bioreactor

This study investigated the effects of filtration modes, i.e., constant transmembrane pressure (TMP) and constant flux mode, on nutrient removal, fouling characteristic and microbial community in a membrane bioreactor. The results showed that filtration mode had minor effects on membrane rejection of COD and nutrients. Membrane fouling rate was higher in constant flux mode than in constant TMP mode. Significantly higher polysaccharide and protein concentrations were found for membrane bio-cake operated under constant flux mode. Fourier transform infrared spectroscopy revealed a significant difference in chemical compositions of SMP and EPS in bio-cake between two filtration modes. Furthermore, constant flux mode had higher portion of α-helix (70.35%) and β-sheet (67.53%), which is related to aggregation and biofilm formation of bacterial cells, in amide I band than those of constant TMP mode (45.67% and 43.44%, respectively). This was corroborated by the fact that thicker bio-cake layer was formed on membrane surface operated under constant flux mode. In addition, excitation-emission matrix fluorescence spectroscopy showed that the fluorescence intensity related to protein-like and humic acid-like substances in constant flux mode were higher than that in constant TMP mode, suggesting their important roles in accelerating membrane fouling. Finally, the microbial communities of bio-cake in constant TMP mode differed significantly from those in constant flux mode. Overall, the results indicated that different contents, characteristics and microbial communities of membrane foulants led to distinct fouling rates between filtration modes.

Critical Flux and Fouling Analysis of PVDF-Mixed Matrix Membranes for Reclamation of Refinery-Produced Wastewater: Effect of Mixed Liquor Suspended Solids Concentration and Aeration.

Fouling tends to cause a significant increase in hydraulic resistance, decreased permeate flux, or increased transmembrane pressure (TMP) when a process is operated under constant TMP or constant flux conditions. To control membrane fouling and maintain sustainable operation, the concept of critical flux has been discussed by several researchers. Various fouling mechanisms, such as macromolecule adsorption, pore plugging, or cake build-up, as well as hydrodynamic conditions, for example aeration, can take place at the membrane surface. This study aimed to investigate the effects of mixed liquor suspended solid (MLSS) concentration and air bubble flow rate (ABFR) on the critical flux and fouling behavior, when treating refinery-produced wastewater. To determine the critical flux values, the experimental flux-steps were the following: (1) the filtration began with a 30 min step duration at a low flux (10 to 20 L/m2h); (2) at the end of this step (after 30 min), the permeate flux was increased, (3) this step was repeated until the TMP did not remain constant at the constant permeate flux, (4) the critical flux was then achieved. A critical flux model with an R2 of 0.9 was, therefore, derived, which indicates that the particle properties were regulated by the suspended solids. The increase of MLSS concentration, from 3 mg/L to 4.5 mg/L, resulted in a decrease of the permeate flux by 18%. Moreover, an increase in ABFR, from 1.2 mL/min to 2.4 mL/min, increased the permeate flux, but this decreased with a greater flow rate of aeration. To assess the stability and reversibility of fouling during critical flux (Jc) determination using a mixed matrix membrane, flux-step methods were utilized. A step height of 14.3 L/m2h and 30 min duration were arbitrarily chosen. The flux increased to 32.5 L/m2h with a slight increase of trans membrane pressure (TMP), while the rate of increase became significant at a higher flux of 143.6 L/m2h, due to fouling. Overall, this study proved that the response of MLSS concentration and aeration affected the membrane performance, based on the critical flux and fouling behavior.

Comparison of the Formation, Filtration Performance, and Structural Characteristic of Self-Forming Dynamic Membranes Under Constant Transmembrane Pressure and Constant Filtration Flux

Comparison of the Formation, Filtration Performance, and Structural Characteristic of Self-Forming Dynamic Membranes Under Constant Transmembrane Pressure and Constant Filtration Flux

Portfolio of beetroot (Beta vulgaris L.) peel extracts concentrated by nanofiltration membrane

Membrane process is an intelligent alternative way of concentration, preferably for organic juices rich in thermolabile natural components. The expectation is to scale up the extraction of desired compounds from agro-industrial wastes through modernized concentration method. Recovery of betalains, phenolic, and antioxidant from beetroot peel extracts was accomplished by nanofiltration membrane (NF 200) at a recirculation flow rate (400 L h-1) and feed temperature (30 ºC) under constant transmembrane pressure (40 bar). Characterization of betaxanthin, betacyanin, phenolic, and antioxidant activity by spectrophotometric analysis revealed that the final samples contain these compounds respectively: 202.25±3.26 mg.L-1, 360.07±8.43 mg.L-1, 987.79±19.18 mg.L-1, 642.06±14.78 mg.L-1 (pure water); 206.62±1.37 mg.L-1, 339.72±2.89 mg.L-1, 972.72±47.49 mg.L-1, 745.97±25.45 mg.L-1 (ethanol-water). Final samples exhibit vivid colour and a considerably large amount of desired compounds compared to crude extracts and could have industrial applications.

Portfolio of beetroot (Beta vulgaris L.) peel extracts concentrated by nanofiltration membrane

Membrane process is an intelligent alternative way of concentration, preferably for organic juices rich in thermolabile natural components. The expectation is to scale up the extraction of desired compounds from agro-industrial wastes through modernized concentration method. Recovery of betalains, phenolic, and antioxidant from beetroot peel extracts was accomplished by nanofiltration membrane (NF 200) at a recirculation flow rate (400 L h -1 ) and feed temperature (30 oC) under constant transmembrane pressure (40 bar). Characterization of betaxanthin, betacyanin, phenolic, and antioxidant activity by spectrophotometric analysis revealed that the final samples contain these compounds respectively: 202.25±3.26 mg.L -1 , 360.07±8.43 mg.L -1 , 987.79±19.18 mg.L -1 , 642.06±14.78 mg.L -1 (pure water); 206.62±1.37 mg.L -1 , 339.72±2.89 mg.L -1 , 972.72±47.49 mg.L -1 , 745.97±25.45 mg.L -1 (ethanol-water). Final samples exhibit vivid colour and a considerably large amount of desired compounds compared to crude extracts and could have industrial applications.

The materials flow and membrane filtration performance in treating the organic fraction of municipal solid waste leachate by a high solid type of submerged anaerobic membrane bioreactor

The anaerobic digestion of leachate from organic fraction of municipal solid waste (OFMSW) is a long-standing challenge. A submerged anaerobic membrane bioreactor (AnMBR) embedding three flat sheet membrane was therefore continuously operated for 63 days to investigate the materials flow and membrane performance. The results obtained show that approximately 90% COD was removed and 86% was converted into methane under an OLR of 5.6 kgCOD/m3·d corresponding to a HRT of 10 days. Under the high solid condition (34.5–61.1 g/L total solids in AnMBR) and flux of 5 and 6 LMH, the membranes was operated practically at constant trans-membrane pressure (TMP). When the membrane was operated at a high flux of 7 LMH the TMP rapid increase occurred in 22 h resulting in a non-recoverable permeability. A sustainable flux was thus identified. This study demonstrated the feasibility of AnMBR treating OFMSW leachate under high solid condition with high flux.

Occurrence of Antibiotics, Antibiotic Resistance Genes and Viral Genomes in Wastewater Effluents and Their Treatment by a Pilot Scale Nanofiltration Unit.

Broad-spectrum fluoroquinolone antibiotics (ciprofloxacin and levofloxacin), carbapenem and fluoroquinolone resistance genes, as well as viral genomes, were detected in grab samples of wastewater effluents. Passive samplers, which are simpler and easier to use and provide information about the concentrations and combination of contaminants present in a certain fluid matrix over time, proved to be extremely promising devices to monitor the presence of the target antibiotics in wastewater effluents. Nanofiltration was tested with a pilot-scale unit installed at a domestic wastewater treatment facility, using a Desal 5DK membrane operated at a constant transmembrane pressure of 6 bar and 70% recovery rate. In a 24 h experimental assay, the variation of the membrane permeance was low (6.3%). High rejections of the target contaminants from the wastewater effluent were obtained by the pilot-scale treatment. Hence, nanofiltration using the Desal 5DK membrane is considered to be a promising treatment to cope with chemical and biological contaminants present in wastewater effluents.

Direct Measurements of Electroviscous Phenomena in Nafion Membranes.

Investigation of electroviscous effects is of interest to technologies that exploit transport of ions through ion exchange membranes, charged capillaries, and porous media. When ions move through such media due to a hydrostatic pressure difference, they interact with the fixed charges, leading to an increased hydraulic resistance. Experimentally this is observed as an apparent increase in the viscosity of the solution. Electroviscous effects are present in all electrochemical membrane-based processes ranging from nanofiltration to fuel-cells and redox flow batteries. Direct measurements of electroviscous effects varying the applied ionic current through Nafion membranes have, to the best of the authors’ knowledge, not yet been reported in literature. In the current study, electroviscous phenomena in different Nafion ion exchange membranes are measured directly with a method where the volume permeation is measured under constant trans-membrane pressure difference while varying the ion current density in the membrane. The direct measurement of the electroviscous effect is compared to the one calculated from the phenomenological transport equations and measured transport coefficients. Within the experimental uncertainty, there is a good agreement between the two values for all membranes tested. We report here an electroviscous effect for all Nafion membranes tested to be .

Tangential Microfiltration of blackberry (Rubus adenotrichus Schltdl.) juice sweetened with stevia (Stevia rebaudiana Bertoni)

The modern consumer values those components that can promote their well-being and help them reduce the risk of diseases the use of steviolglucosides as a sweetener in the formulation of foods is promising. The study evaluated the tangential microfiltration for clarification and conservation of blackberry juice sweetened with dried leaves of stevia. Two ceramic membranes were evaluated. The tests were performed at 35°C in concentration mode at a constant transmembrane pressure and tangential velocity. The formulation of the juice was defined through sensory evaluation tests. Volume, flow permeate, temperature, and pressure input and output were registered. The results of the variables analyzed in the process, as well as the physicochemical characterization of clarified juice, helped define the operating conditions for draw two formulations of microfiltrated juice, sweetened with stevia or sucrose, and thus evaluate the effectiveness of microfiltration as a conservation treatment. Aciduric microorganisms were quantified; molds and yeasts were carried out in the generated pasteurized samples stored at five different temperatures (5, 20, 30, 37, and 45°C). The recovery permeate juice obtained was 84.62%. The permeate Flow (Jp), exhibited higher values ​​at 40L/hm2. Also, the concentration of stevioside and rebaudioside A in the retentate increased with advancing ultrafiltration. A significant variation in color, turbidity, and soluble solids, was observed, unlike the pH. Also, its chemical and microbiological stability is confirmed that allows you to preserve quality during 27 days of storage.

A corrected cake resistance expression by considering the deposition property of different feed suspensions/solutions

ABSTRACT The influence of deposition property to the cake filtration process was considered and the deposition factor was introduced to correct cake resistance for dead-end mode at constant transmembrane pressure. The values of model parameters in the traditional and corrected cake resistance expressions were determined for activated sludge, yeast, kaolin suspensions, and humic acid solution, respectively. The higher adsorption and sedimentation ability will make the deposition factor bigger. In addition, the predictions of the corrected cake resistance expression are in good agreement with experimental data at different TMPs and concentrations. The applicability of the corrected cake resistance expression was also validated.

Mechanism of biofouling enhancement in a membrane bioreactor under constant trans-membrane pressure operation

In a membrane bioreactor, flux and organic loading rate conditions essentially affect membrane fouling. In constant TMP mode, flux and organic loading rate dynamically change, while they are rather static in constant flux mode. This study investigated fouling mechanism in MBR under these different filtration modes. Fouling development was more significant in constant TMP mode than in constant flux mode when MBR was operated under an equal flux condition in average. In constant TMP mode, microbial community in cake sludge was distinct from bulk sludge and had higher abundance of biofilm-forming bacterial group. The cake sludge contained more SMP and LB-EPS with high polysaccharide contents in constant TMP mode. These results suggested that, in constant TMP mode, (i) initially high flux in a filtration cycle enhanced initial deposition of bacterial cells and rapid development of fouling layer, which resulted in distinct microbial community in cake sludge; (ii) the high abundance of the biofilm-forming bacteria in cake sludge and fluctuation of organic loading rate stimulated polysaccharide production, (iii) higher polysaccharide contents in cake layer caused faster development of fouling layer and increase of hydraulic resistance by compression.

Dynamic behavior of unsteady-state membrane gas separation: Modelling of a closed-mode operation for a membrane module

Membrane gas separations under unsteady conditions provide various opportunities for enhancement of separation performance, particularly in niche applications. An original model describing the dynamics of a closed-mode operation in a cross-flow membrane module is developed for optimization of a pulsed-retentate separation technique. The closed-mode operation is a key step of a pulsed retentate process providing an improvement of separation performance compared to a conventional steady-state separation without productivity losses. The closed-mode operation results in the evolution of a composition profile in a membrane module over time under a constant transmembrane pressure while the feed is being continuously admitted, and a permeate is being evacuated with no retentate withdrawal. During this step the highest possible concentration gradient is realized inside the module between the feed inlet and retentate outlet. The developed model reflects the dynamics of establishing the composition profile under closed-mode operation, linking concentrations, coordinates, and time, which is essential for the optimization of the unsteady membrane separation, as well as for the initial period after either the start of the process or the change of conditions. An axial mixing effect is considered taking into account the deviations from a plug flow present in a real process. The mathematical model is verified through a dedicated experimental study of two binary mixtures separation (CO2/N2, and CO2/CH4) employing experimental techniques based on periodic sampling for gas chromatography analysis and in-situ monitoring by mass spectrometry. The case of a more permeable impurity removal from a less permeable main component is considered. An analytical solution is provided for the membrane module with zero retentate flow.

Co-current crossflow microfiltration in a microchannel.

Steady state crossflow microfiltration (CMF) is an important and often necessary means of particle separation and concentration for both industrial and biomedical processes. The factors controlling the performance of CMF have been extensively reviewed. A major factor is transmembrane pressure (TMP). Because microchannels have small height, they tend to have high pressure gradients in the feed-flow direction. In the extreme, these gradients may even reverse the pressure across the membrane (inciting backflow). It is therefore desirable to compensate for the effect of feed-flow on the TMP, aiming at constant transmembrane pressure (cTMP) at a value which maximizes filtrate flux. This is especially critical during filtration of deformable particles (e.g. erythrocytes) through low intrinsic resistance membranes. Filtration flux is generally taken to be directly proportional to TMP, with pressure drop along the channel decreasing in the flow direction. A co-current flow of filtrate in a suitably designed filtrate collecting channel is shown to allow the TMP to remain constant and permit the sieving surface to perform optimally, permitting up to twice as much filtration over that of a naïve configuration. Manipulation of the filtrate channel may be even more beneficial if it prevents backflow that might otherwise occur at the end of a sufficiently long channel. Experiments with erythrocyte suspensions, reported here, validate these concepts.

3D printed composite membranes with enhanced anti-fouling behaviour

The fabrication of three dimensional (3D) printed composite membranes by depositing a thin polyethersulfone (PES) selective layer onto ABS-like 3D printed flat and wavy structured supports is presented here for the first time. The 50 mm disk supports were printed using an industrial 3D printer with both flat and double sinusoidal, i.e. wavy, surface structures. The thin selective layers were deposited onto the 3D supports via vacuum filtration. The resulting flat and wavy composite membranes were characterised and tested in terms of permeance, rejection, and cleanability by filtering oil-in-water emulsions of 0.3−0.5 vol% through a cross-flow (Reynolds number, Re = 100, 500 and 1000) ultrafiltration set-up under a constant transmembrane pressure of 1 bar. Results showed that pure water permeance through the wavy membrane was 30% higher than the flat membrane for Re = 1000. The wavy 3D printed membrane had a 52% higher permeance recovery ratio compared to the flat one after the first filtration cycle, with both membranes having an oil rejection of 96% ± 3%. The wavy 3D composite membrane maintained some level of permeation after 5 complete filtration cycles using only water as the cleaning/rinsing agent, whereas the flat one was completely fouled after the first cycle. Cleaning with NaOCl after the sixth cycle restored ~70% of the initial permeance for the wavy membrane. These results demonstrate that 3D printed wavy composite membranes can be used to significantly improve permeation and cleanability performance, particularly in terms of reducing fouling build-up, i.e. the main obstacle limiting more widespread adoption of membranes in industrial applications.