Filtration Properties Of Membranes Research Articles

Performance of an aerobic granular sludge membrane filtration in a full-scale industrial plant.

This study quantifies the hydraulic performance of a pilot-scale ultrafiltration system integrated into a full-scale industrial aerobic granular sludge (AGS) plant. The treatment plant consisted of parallel AGS reactors, Bio1 and Bio2, with similar initial granular sludge properties. During the 3-month filtration test, a chemical oxygen demand (COD) overloading episode took place, affecting the settling properties, morphology, and microbial community composition in both reactors. The impact on Bio2 was more severe than on Bio1, with higher maximal sludge volume index values, a complete loss of granulation, and the excessive appearance of filamentous bacteria extending from the flocs. The membrane filtration properties of both sludges, with these different sludge qualities, were compared. The permeability in Bio1 varied between 190.8 ± 23.3 and 158.9 ± 19.2 L·m-2·h-1·bar-1, which was 50% higher than in Bio2 (89.9 ± 5.8 L·m-2·h-1·bar-1). A lab-scale filtration experiment using a flux-step protocol showed a lower fouling rate for Bio1 in comparison with Bio2. The membrane resistance due to pore blocking was three times higher in Bio2 than in Bio1. This study shows the positive impact of granular biomass on the long-term membrane filtration properties and stresses the importance of granular sludge stability during reactor operation.

Enhanced methane production coupled with livestock wastewater treatment using anaerobic membrane bioreactor: Performance and membrane filtration properties

The present study introduced a new method for enhanced biomethane production and pollution control of swine wastewater (SW) using anaerobic membrane bioreactor (AnMBR). Results confirmed 35 °C as the optimum temperature for enhanced anaerobic digestion which resulted in relatively higher methane production rate and potential. In AnMBR system, robust pollutants removal and conversion rate were achieved under various hydraulic retention time (HRT) ranging from 20 to 10 days, while the highest methane yield (0.24 L/g-CODremoved) and microbial activity (6.65 mg-COD/g-VSS·h) were recorded at HRT of 15 days. Reduction of HRT to 10 days resulted in serious membrane fouling due to accumulation of extracellularpolymericsubstances(EPS) and cake layer on the membrane. However, cake layer as the dominant membrane foulant could be effectively removed through periodic physical backwash to recover the membrane permeability. Overall, the suggested AnMBR is a promising technology to enhance SW treatment and energy recovery.

High‐Temperature Bearable Polysulfonamide/Polyurethane Composite Nanofibers’ Membranes for Filtration Application

AbstractPolysulfonamide (PSA)‐based membranes are widely used for high‐temperature filtration. PSA/polyurethane (TPU) composite membranes that can withstand a temperature exceeding 200 °C are fabricated by an electrospinning method. The effects of PSA/TPU mass ratio on the morphology and properties of the prepared composite membranes are investigated to obtain nanofibers with different diameters. These composite membranes are characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and differential scanning calorimetry, and mechanical and filtration properties of membranes are also investigated. The maximum stress and elongation at break of PSA/TPU nanofibers’ membranes reach 13.66 ±1.43 MPa and 75.01 ± 3.78%, respectively, when the PSA/TPU mass ratio is 3:7. Moreover, filtration results show high filtration efficiency (>99%) and low pressure drop for diethyl‐hexyl‐sebacat (DEHS) and sodium chloride (NaCl) aerosol particles at 4 m3 h−1 airflow velocity. Therefore, PSA/TPU composite membranes are a promising candidate for high‐temperature filtration applications.

Development of novel nanocomposite polyurethane ultrafiltration membranes based on multiwalled carbon nanotubes functionalized with PAMAM dendrimer

ABSTRACT Novel biodegradable nanocomposite membranes were prepared using a chemo-enzymatic route. Polyester-urethane-urea matrix was obtained from poly(ε-caprolactone) diol, isophorone diisocyanate (IPDI), and hexamethylene diamine (HMDA) as a chain extender. Nanocomposites (0.5% wt/wt) were synthesized by in situ polymerization using reinforced multi-walled carbon nanotubes (MWNTs) grafted with two distinct-generation dendritic poly(amidoamine) (PAMAM). Membranes were prepared by the so-called inversion phase method, using N,N dimethylformamide as solvent and water as non-solvent. The effect of the amine group content into filler in the mechanical and filtration properties of membranes was evaluated. It was observed that the content of amine groups in the dendrimer-modified MWNTs provides sites for hydrogen bonding interactions in the matrix, which influence mechanical properties such as toughness and extensibility, and the porous morphology of the membrane. Additionally, it was observed that PAMAM grafted MWNTs may interact with soft segments of PU, modifying the filtering properties of membranes.

Yeast Cell Cake Characterization in Alcohol Solution for Efficient Microfiltration.

Microfiltration is widely used to remove microbial cells from the fermentation broth in the downstream processing of biotechnological products. Because filtration behaviors are strongly affected by the characteristics of the microbial cell cake formed on the surface of the membrane, insights into the cake structure facilitate the design and operation of filter equipment and membranes. In the alcohol fermentation process using a yeast strain, the cake characteristics are considered to be complicated because yeast cells are strongly influenced by external factors such as filtration pressure and alcohol concentration. In this study, we evaluated the membrane filtration properties, in particular the cake characteristics of a yeast suspension containing alcohol. Microfiltration experiments were performed in the dead-end filtration mode using yeast suspensions with several ethanol concentrations (0–20 wt%) under constant pressure. Flux decline behaviors caused by yeast cake were put in a similar form for 0–15 wt% ethanol concentrations. In contrast, a severe flux decline was observed for the suspension with 20 wt% ethanol concentration. It was also observed that in the membrane filtration of yeast cells with 20 wt% ethanol concentration, the cake structure became denser and the filtration resistance remarkably increased because of cellular destruction. Furthermore, the yeast cake exhibited a high compressibility in the solution containing a 20 wt% ethanol concentration. Therefore, the filtration rate of the alcoholic fermentation broth is not significantly improved by increased pressure due to the increase in the cake resistance.

Enhanced Methane Production Coupled with Livestock Wastewater Treatment Using Anaerobic Membrane Bioreactor: Performance and Membrane Filtration Properties

Enhanced Methane Production Coupled with Livestock Wastewater Treatment Using Anaerobic Membrane Bioreactor: Performance and Membrane Filtration Properties

Cultivation of aerobic granular sludge for the treatment of food-processing wastewater and the impact on membrane filtration properties.

A laboratory-scale sequencing batch reactor was operated for approximately 300 days, divided into four periods based on the feeding strategy, to develop stable aerobic granular sludge (AGS) while treating chocolate processing wastewater. Application of a prolonged mixed anaerobic feeding was not sufficient to develop AGS and reach stable reactor performance. Through the application of a partially non-mixed and a partially mixed feeding strategy, the reactor performance was increased and stable AGS formation was established characterized by low diluted sludge volume index (D)SVI DSVI10,30) values of 78 ± 27 mL·g-1 and 52 ± 17 mL·g-1, respectively, and a capillary suction time/mixed liquor suspended solids value of 0.9 sec·(g·L-1)-1. The membrane bioreactor (MBR) filtration tests showed a reduction of the fouling rate (FR) and an increase of the sustainable flux (SF0.5) for AGS compared to flocs treating the same industrial wastewater. The SF0.5 (FR > 0.5 mbar·min-1) for the flocs was 10 L·(m2·h)-1 while for AGS the SF0.5 is higher than 45 L·(m2·h)-1 because the FR did not exceed 0.1 mbar·min-1. Additionally, the AGS showed reduced irreversible fouling tendencies due to pore blocking. Our results underline the need for an increased substrate gradient during anaerobic feeding for the development and long-term maintenance of AGS under minimum wash-out conditions. The AGS-MBR filtration performance also shows strong advantages compared to a floccular MBR system due to a high increase of the SF0.5 and reduced reversible and irreversible fouling.

Analyzing the effect of nanofiber orientation on membrane filtration properties with the progressive increase in its thickness: a numerical and experimental approach

One of the merits of modeling is that the computer-generated data is used in optimizing equipment and experimental designs, eliminating the costs associated with scaling up by experimentation. In this work, the filtration performance of nanofibers aligned diversely within virtual webs was numerically analyzed using Star CCM + and Ansys Fluent software. This knowledge was then used to fabricate two distinctly oriented nanofiber membranes via free surface electrospinning. Their filtration performance was studied by capillary flow porometry technology using POROLUX™ 100. The results of this were in agreement with the simulation work.

The influence of solid retention time on IFAS-MBR systems: analysis of system behavior

ABSTRACTA University of Cape Town Integrated Fixed-Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant was operated at different values of the sludge retention time (SRT). Three SRTs were investigated at different durations: indefinitely, 30 and 15 days. The organic carbon, nitrogen and phosphorus removal, kinetic/stoichiometric parameters, membrane fouling tendency and sludge filtration properties were assessed. The findings showed that by decreasing the SRT, the pilot plant could maintain excellent carbon removal efficiencies throughout the experiments. In contrast, the biological carbon removal showed a slight nitrification and was slightly affected by the decrease of the SRT, showing high performance (approximately 91%, on average). Thus, the biofilm might have helped sustain the nitrification throughout the experiments. The average phosphorus removal performance increased slightly with a decrease in SRT, achieving the maximum efficiency (61.5%) at a SRT of 15 days. After a 30-day SRT, an increase in resistance due to pore blocking and a general worsening of the membrane filtration properties occurred.

Moving bed membrane bioreactors for carbon and nutrient removal: The effect of C/N variation

In this paper, an experimental campaign was carried out on a University of Cape Town Integrated Fixed Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant. The aim of the study was to evaluate the effect of the influent C/N ratio on the system performance in terms of organic carbon, nitrogen and phosphorus removal, biomass viability (through respirometry), activated sludge features and membrane filtration properties. The experiments were organized into three phases, characterized by a variation of the C/N ratio (namely, Phase I: C/N=5, Phase II: C/N=10; Phase III: C/N=2). The results highlighted that the system performance was significantly affected by C/N ratio. The removal efficiencies were satisfactory for C/N ratio equal to 10 and 5, with average removal in Phases I and II of 98–98%, 53–69% and 67–87% for COD, nitrogen and phosphorus, respectively. Conversely, with a C/N ratio of 2, a significant worsening of the pilot plant performance was observed, with average COD, nitrogen and phosphorus removal equal to 70%, 44% and 26%, respectively, much lower compared to the previous phases. Respirometry highlighted a significant decrease of bacterial activity when the C/N was reduced to 2, even if the biofilm seemed to be more resilient in terms of activity compared to the activated sludge.

Investigation of Titanium-Dioxide Coatings on Membrane Filtration Properties

Investigation of Titanium-Dioxide Coatings on Membrane Filtration Properties

Filtration properties of membranes with active graphene oxide layer

Filtration properties of membranes with active graphene oxide layer

嫌気条件下における活性汚泥の膜濾過特性の変化と有機酸の産生

嫌気条件下における活性汚泥の膜濾過特性の変化と有機酸の産生

Fabrication of novel porous membrane from biobased water-soluble polymer (hydroxypropylcellulose)

Herein, a novel polymeric porous membrane was developed, without the use of any organic solvent in the initial dope solution and using a biobased polymer derived from cellulose: Hydroxypropylcellulose (HPC). HPC was dissolved in water (20wt%) and the phase separation was induced by increasing the temperature above the Lower Critical Solution Temperature (LCST) of the polymer solution, around 40°C in the concentration range concerned in this study. To fix the membrane morphology and to prevent any resolubilization in water during filtration tests, a chemical crosslinking was performed using Glutaraldehyde. The phase diagram of HPC/water system was first studied and not only the cloud point but also the spinodal curves were determined using optical transmission techniques. It was exhibited that HPC phase diagram is very weakly dependent on concentration up to large concentrations and that the metastable region is very small, i.e. the cloud point and the spinodal curves are very close in a large range of concentration. The membrane stability was tested in water and some organic solvents, thus demonstrating the efficiency of the chemical crosslinking during membrane formation. The swelling and mechanical properties of HPC membranes were also investigated depending on the operating condition during membrane formation, showing that the temperature ramp during the membrane formation, from initial to final temperature, have a significant effect on the crosslinking efficiency and hence on the swelling properties. Finally, adding a porogen (PEG200) into the collodion, filtration tests were performed and exhibited that the membrane filtration properties depend on the temperature ramp as well, showing higher water flux for the highest temperature ramp tested.

Morphological Analysis of Membranes of PES/Commercial Clay

The separation membrane processes are still fresh, but have had a lot of attention because they present attractive, such as low energy consumption, greater operating flexibility and better quality in the final product. Obtaining membranes incorporating clay is attracting interest because it improves the membrane filtration properties. In this study, pure polymer membranes were produced from poly (ether sulfone) and clays Cloisite Na and 20A, the levels of 1, 3 and 5% from the phase inversion technique using the dimethylformamide solvent. XRD results indicated the presence of a peak at both at about 15.8° compositions indicating that the systems are possibly intercalated and/or microcomposites structures. SEM results showed that the membranes with clay showed different behavior in relation to pure PES membranes. They apparently exhibited a surface without pores with exception of membrane with 5 wt.% Na Cloisite, which showed pores on its surface.

Effect of polydopamine deposition conditions on polysulfone ultrafiltration membrane properties and threshold flux during oil/water emulsion filtration

Surface modification of porous membranes for water filtration has been extensively reported in the literature to improve fouling resistance. However, surface modification can significantly change the membrane filtration properties, sometimes resulting in more severe fouling than with the original, unmodified membrane. This study focused on demonstrating surface modification strategies and membrane comparison strategies to better understand the complex, competing phenomena occurring when membranes are surface modified. Polysulfone ultrafiltration membranes were modified with polydopamine (PDA) at different initial dopamine concentrations and deposition times. Membrane properties, including surface hydrophilicity, roughness, and zeta potential, were characterized. PDA coatings significantly increased surface hydrophilicity, but they did not markedly change the surface roughness or zeta potential. The threshold flux during oil/water emulsion filtration was determined and used as a fouling parameter for membranes modified with PDA at various modification conditions. The threshold flux increased when PDA was deposited at low initial dopamine concentrations or short coating times. However, PDA deposition at high initial dopamine concentrations or long coating times decreased the threshold flux, suggesting that a tradeoff exists between increased hydrophilicity and reduced pore size due to surface modification. An increase in membrane surface hydrophilicity was observed at all PDA deposition conditions, which tends to reduce foulant adhesion and increase threshold flux. However, extensive PDA coating significantly decreased membrane pure water permeance, suggesting that some membrane pores may have been narrowed or blocked, increasing local permeate flux through the remaining pores in the PDA-modified membranes. This higher local flux would exacerbate fouling and decrease threshold flux. Comparing unmodified and PDA-modified membranes having similar pure water permeance values, the PDA-modified membranes had higher threshold fluxes than the unmodified membranes.

Carbon and nutrient biological removal in a University of Cape Town membrane bioreactor: Analysis of a pilot plant operated under two different C/N ratios

The effect of the carbon-to-nitrogen (C/N) ratio variation in a University of Cape Town Membrane bioreactor (UCT-MBR) was investigated. The experimental campaign was divided into two phases, each characterized by a different C/N ratio (namely, 10 and 5, Phase I and Phase II, respectively). The UCT-MBR pilot plant was analysed in terms of carbon and nutrients removal, biomass respiratory activity, activated sludge features and membrane fouling. The results highlighted that the nutrients removal was significantly affected by the decrease of the C/N ratio during the Phase II. The biological carbon removal was also affected by the low C/N value during the Phase II. Indeed, the average biological COD removal efficiency was equal to 72.9% during the Phase II, while the average value was 82.8% in the Phase I. The respirometric batch test suggested that both heterotrophic and autotrophic species were severely affected by the lower C/N ratio in the Phase II. Moreover, a decrease of the membrane filtration properties was observed during the Phase II, mainly due to the worsening of the activated sludge features, which enhanced the increase of SMP production.

Modified alumina nanofiber membranes for protein separation

Large-scale purification/separation of bio-substances is a key technology required for rapid production of biological substances in bioengineering. Membrane filtration is a new separation process and has potential to be used for concentration (removal of solvent), desalting (removal of low molecular weight compounds), clarification (removal of particles), and fractionation (protein-protein separation). In this study, we developed an efficient membrane for protein separation based on ceramic nanofibers. Alumina nanofibers were prepared on a porous support and formed large flow passages. The radical changes in membrane structure provided new ceramic membranes with a large porosity (more than 70%) due to the replacement of bulk particles with fine fibers as building components. The pore size had an average of 11nm and pure water flux was approximately 360Lh−1m−2bar−1. Further surface modification with a self-assembled monolayer of (3-aminopropyl) triethoxysilane enhanced the membrane filtration properties. Characterization with SEM, FTIR, contact angle, and proteins separation tests indicated that the fibril layers uniformly spread on the surface of the porous support. Moreover, the membrane surface was changed from hydrophilic to hydrophobic after silane groups were grafted. It demonstrated that the silane-grafted alumina fiber membrane can reject 100% BSA protein and 92% cellulase protein. It was also able to retain 75% trypsin protein while maintaining a permeation flux of 48Lh−1m−2bar−1.

Effects of cationic polyelectrolyte on filterability and fouling reduction of submerged membrane bioreactor (MBR)

Organic and inorganic polyelectrolytes are commonly used as coagulants or flocculants in membrane bioreactor to enhance the filtration properties of membranes. The main objective of this study was to determine the effectiveness of organic cationic polyelectrolyte (CPE) addition on filterability of various membranes and to investigate the influences on fouling of membranes. First, batch tests were performed to determine the optimum polyelectrolyte concentration at which the highest soluble microbial products (SMPs) removal was observed. Then, short-term filtration test were conducted. Cellulose acetate, polyethersulfone, mixed ester, polycarbonate (CA, PES, ME, PC) membranes with two different pore sizes (0.45–0.40 and 0.22–0.20 μm) were used in submerged MBR experiments. Permeate flux decline at constant vacuum was observed with time. Protein and carbohydrate analysis were performed in the permeate samples. Filtration resistances were determined for each membrane. Cake resistance was observed to be the most significant fouling mechanism for all membranes. Polyelectrolyte addition decreased the cake resistance. The effect of polyelectrolyte on pore resistance was relatively insignificant. The results showed that addition of polyelectrolyte had significant impact on sustainable filtration time.

Integrated Nanofiltration and Upflow Anaerobic Sludge Blanket Treatment of Textile Wastewater for In‐Plant Reuse

The filtration characteristics of simulated dyeing effluents containing Acid Orange 7, sodium sulfate, and a pH buffer made of acetic acid and sodium acetate is described using a commercially available nanofiltration membrane. The original membrane filtration properties were characterized with deionized water to provide a baseline of membrane performance. At high volumetric concentration of the test solutions, greater than 98% rejection of dye and sodium sulfate were obtained. Rejection of buffering chemicals was approximately 50% in all experiments, giving a permeate water not suitable for reuse in most dyeing operations. The final composite concentrate had a chemical oxygen demand (COD) value > 2000 mg/L. No problems were encountered with anaerobic treatment of the concentrate obtained from the dyeing wastewater. Adjusting the sulfate concentration to give COD-to-sulfate ratios to 2.9, 5.4, and 18.2 in the reactor feed had no significant alterations in the performance of the upflow anaerobic sludge blanket reactor.