Filtration Stage Research Articles

Numerical simulation of mixed aerosols deposition behavior on cylindrical cross fibers

In the actual dust removal process, aerosol particles with distinct physical properties often coexist. Most studies on fiber filtration focused on the particles of a single species, resulting in a poor understanding of the deposition behavior of mixed aerosols. In this study, the dynamic deposition behavior of mixed aerosol particles containing silica (SiO2) and polystyrene (PS) on cylindrical cross fibers was numerically studied using a lattice Boltzmann model coupled with discrete element method (LB-DEM). The mutual influences between the dynamic particle transport/deposition and the airflow were considered using immersed moving boundary (IMB) scheme. The mixed particles exhibit different deposit morphology and filtration performance from single particulate species mainly in the dendritic filtration stage, where the mixed particles tend to deposit on the lateral sides rather than the front of fibers. The filtration efficiency and pressure drop of mixed aerosols are not a superposition of the individual components. At high particle Stroke number (St), the synergistic deposition of SiO2 particles and PS particles of low elastic modulus occurs, resulting in filtration efficiencies that are approximately-four times greater than any single particulate species. When St is below 1.0, the filtration efficiency is improved with increasing St, which is similar to that of single species. Moreover, at the same flow velocity, the pressure drop rises faster and the flow is easier to be clogged for mixed particle filtration. The pressure drop rising rates of the mixed filtration at a high St range from 0.013 to 0.020, which is more than three times the rates for PS (0.006) and SiO2 (0.003).

The impact of PET microplastic fibres on PVDF ultrafiltration performance – A short-term assessment of MP fouling in simple and complex matrices

Wastewater treatment plants (WWTPs) are key components for the capture of microplastics (MPs) before they are released into natural waterways. Removal efficiencies as high as 99% may be achieved but sub-micron MPs as well as nanoplastics have been overlooked because of analytical limitations. Furthermore, short MP fibres are of concern because of their low capture rate as well as the lack of understanding of their influence on purification system efficiency. This study has investigated the impact of poly(ethylene terephthalate) (PET) short nanofibres on the performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes during cross-flow operation. Model MP fibres with an average length of 10 ± 7 μm and a diameter of 142 ± 40 nm were prepared via a combination of electrospinning and fine cutting using a cryomicrotome. The manufactured MPs were added to both pure and synthetic domestic wastewater at a concentration of 1 mg.L−1 to determine their impact on the performance of PVDF ultrafiltration membranes. The results show that PET fibres attach to the membrane in a disorganised manner with low pore coverage. The water flux was decreased by 8% for MPs in pure water and no noticeable effect in wastewater after 3 days of filtration. Additionally, the nutrient removal efficiency of the membrane was not altered by the presence of PET MPs. These findings show that MP fibres do not significantly influence the early stages of filtration for a standard concentration of MPs in wastewater treatment plant studies.

Effect of a Polydisperse Hydrosol on the Spectral Properties of Light Scattering by Seawater at Forfard Angles

In this paper we discuss the problem how to analyze the results of spectral volume scattering function measurements in natural waters and artificial ones. Analytical predictions and experimental proves of the remarkable changes in the properties of the light scattering at small angles after a filtration of water sample are presented. It was proposed that a certain correlations in the positions of scattering centers always exist in the water which were resulted in the volume scattering function of any natural water was strong forward peaked. Based on Mie theory the sums of scattering amplitudes and scattering radiances were calculated for a power-law particle size distribution while the maximal radius was varied. The square of the sum of the scattering amplitudes was compared with the value of the classical term. It is shown that in the “blue” a significant compensation of the effect of spatial correlation of particles occurs with an increasing of the maximum radius of particles, starting from the radius is about 0.2 μm. The contribution of the additional term decreases faster at general angles region. The spectral properties of light scattering by seawater during sequential filtration through nucleopore filters with a pore diameter of 2, 1, and 0.45 μm have been measured. The volume scattering function data at scattering angles from 6 to 90 degrees were analyzed. Water samples were taken from the surface of the Black Sea at the beginning of October. The Secchi depths are varied from 16 up to 19m. It was found that after filtration through a filter with pores diameter equaled to 1 μm, the typical deep at 30° of spectral slope of volume scattering function was appeared. Such deep becomes stronger after the next stage of filtration, when diameter of pores was equal to 0.45 µm. It is shown that the angular dependence of the exponent of the spectral slope obtained as a result of processing the experimental data is in consistent with theoretical predictions.

An effective service trust evaluation and preprocessing approach considering multi-user interests in cloud manufacturing

In the cloud manufacturing (CMfg) platform, there are numerous manufacturing services with same or similar functions. Due to the inconsistency of service quality, how to effectively evaluate the quality of services is a fundamental problem in CMfg, and which aims to reduce risk and increase the benefits of users. Under these contexts, this study first constructs a comprehensive three-dimensional trust evaluation system that considers the trust of service demanders, resource providers, and cloud platform operators in CMfg. And then, a manufacturing services trust evaluation and preprocessing model is proposed, and the optimization process is described as following: (1) superior and inferior manufacturing services are identified by the first stage filtration; and (2) inferior manufacturing services are further classified by the second stage filtration. After that, to deal with the concerned problem, an improved multi-objective non-dominated sorting genetic algorithm III (IMO-NSGA-III) is developed to find the Pareto-optimal solutions. Furthermore, nine random instances are designed to show that the proposed IMO-NSGA-III outperforms other three state-of-the-art algorithms in terms of convergence and diversity. Finally, three case studies that comes from an automotive parts assembly company is employed, and the effectiveness of the proposed model and IMO-NSGA-III algorithm is further demonstrated.

Antifouling enhancement of thin-film composite polyamide reverse osmosis membrane by surface immersion deposition and in-situ crosslinking method with NaAlg-GA hydrogel

In order to optimize antifouling performance to organic foulants, a commercial polyamide reverse osmosis membrane of composite polyamide material was modified by surface gelation using sodium alginate (NaAlg) as surface coating agent, which was widely known as a natural polymer and environmentally friendly materials. NaAlg-GA hydrogel layer was successfully deposited on commercial membrane surface by combining immersion coating with in-situ crosslinking method and the chemical structure was verified by FT-IR spectroscopy. SEM and AFM was adopted to analyze the changes of morphology and roughness. Zeta potentiometer, and contact Angle analyzer were all used to analyze the hydrophilicity and charge property of relevant NaAlg modified membranes in detail. Specific separation performance was also evaluated by cross-flow filtration tests. Results from above experiments confirmed that NaAlg modified membranes exhibited a surface with more hydrophilic, smoother and more regular, denser negative charge, slightly improved selectivity and lower permeability. Long-term monitored the performance of 100 ppm NaAlg modified membrane, it was found that the rejection rate fluctuated between 98.96% and 99.17%, and the flux ranged from 25.15 ∼ 26.06 L/m2 h during the whole test period, which fully proved that modified membrane had good durability. BSA pollution experiment results showed that the flux attenuation rate of 100 ppm NaAlg modified membrane decreased from 40.87% to 25.01%, and flux recovery rate of contaminated membrane after washing was as high as 90.8%. In addition, the flux of 100 ppm NaAlg modified membrane exceeded that of unmodified membrane after filtrating 20 h. Moreover, with the extension of time, the cumulative flux loss of modified membrane caused by additional resistance at the initial filtration stage would soon be compensated, and it completely exceeded that of unmodified membrane after 40 h. All above results showed that NaAlg-GA hydrogel layer can effectively improve the antifouling performance.

UV/Fe(II) synergistically activated S(IV) per-treatment on HA-enhanced Ca2+ scaling in NF filtration: Fouling mitigation, mechanisms and correlation analysis of membrane resistance in different filtration stage

The aim of this study was to investigate the feasibility and fouling mitigation mechanisms of UV/Fe(II) synergistically activated sulfite (S(IV)) (UFS) pretreatment to alleviate membrane fouling caused by HA-enhanced Ca2+ scaling. After UFS treatment, hydrophobic substances and carboxyl groups structure were destroyed by the in-situ-generated SO•–4, resulted in a significant reduction of hydrophobic substances ratio and carboxyl group concentration. Due to the formation of more electropositive in-situ-generated Fe(III), the complexation between Ca2+ and carboxyl groups was weakened so that the bulk crystallization size on the membrane surface was greatly reduced. The filter cake enhanced osmotic pressure effect (CEOP) and concentration polarization effect were hence alleviated, as well as the surface roughness. At the microcosmic perspective, as the energy barrier between the membrane and foulants was increased significantly after pretreatment, the anti-foulants adsorption ability of the membrane was enhanced. Correlation analysis showed that the carboxyl concentration and density, HPO ratio, larger particle size (>100 nm) ratio, the Ca2+ concentration in the scaling layer and energy barrier all had a good correlation with the membrane resistance. This research not only provides an advanced oxidation technology that can effectively alleviate the synergistically-fouling effect of HA and Ca2+ of nanofiltration process, but also proposes a guidance for the UV/Fe(II) synergistically activated sulfite.

Effects of Viscosity on Submerged Membrane Microfiltration Systems.

Submerged microfiltration has a wide range of applications in water and wastewater treatment. Membrane fouling is a major problem, resulting in a severe decline in flux, high energy consumption and frequent membrane cleaning and replacement. The effect of viscosity was not previously studied under controlled conditions to relate it to the air scour. Hence, this study investigated the effect of viscosity on membrane fouling during the operation of submerged membrane microfiltration by adding predetermined amounts of glycerol to a kaolin clay suspension. The addition of glycerol increased the viscosity (from 0.001 to 0.003 Pa·s), resulting in a 3-fold higher transmembrane pressure (TMP) development. An increased airflow (air scour) rate by 3 fold (from 0.6 m3/m2/h to 1.8 m3/m2/h), reduced TMP development by 65%. Membrane fouling quickly developed during the initial stage of microfiltration operation. Therefore, special precautions to control fouling during the early stages of filtration could significantly enhance the operation of the microfilter. Higher airflow caused a reduction in average specific cake resistance, whereas higher viscosity increased this value.

Recovery of Water-Soluble Compounds from Tisochrysis lutea.

This work aims at studying the techno-economic feasibility to produce an extract, at a small industrial-production scale, from a Tisochrysis lutea’s paste, in view of cosmetic applications. The paste was first thawed, diluted and centrifuged to get a crude water extract. Then, two successive stages of membrane filtration were carried out: the first one to essentially remove/retain the particles (cellular debris) by microfiltration and the second one to concentrate (ultrafiltration) the soluble compounds of the permeate from the previous step. The robustness of the processing chain has been demonstrated following the production of three similar extracts with more than 30 L input material each. Around 54% of the final extract was composed of proteins and carbohydrates. The final ingredient was assessed for genomic activity and showed multiple positive responses. Finally, an economic analysis was performed, which demonstrated that the major cost is linked to centrifugation step. The total manpower represents the highest cost of the OPEX categories.

Pembuatan Sistem Desalinasi Kapasitas 240 liter/jam di Dusun Bondan Kecamatan Kampung Laut Cilacap

Dusun Bondan is a district located in a tidal area. Various problems arise in Dusun Bondan because of the use of water that doesn’t meet the quality of sanitation water causing several diseases. The water crisis experienced by the residents of Dusun Bondan becomes the worst disaster especially in summer because the water at Dusun Bondan is salty with high total dissolved solids. A water desalination system has been made to produce sanitation water that meets the standard based on Minister of Health Regulation No. 32 of 2017. The methods used to overcome these problems are water source identification, design of desalination system, purchasing, fabrication and testing of desalinated water. The result of the activities is a desalination system which consists of pre-treatment using 4 filtration stages ended with reverse osmosis desalination using a special membrane. The result of desalinated water test shows that the water is odourless, tasteless, and other parameters meet the requirement of the standard.

Pembuatan Sistem Desalinasi Kapasitas 240 liter/jam di Dusun Bondan Kecamatan Kampung Laut Cilacap

Dusun Bondan is a district located in a tidal area. Various problems arise in Dusun Bondan because of the use of water that doesn’t meet the quality of sanitation water causing several diseases. The water crisis experienced by the residents of Dusun Bondan becomes the worst disaster especially in summer because the water at Dusun Bondan is salty with high total dissolved solids. A water desalination system has been made to produce sanitation water that meets the standard based on Minister of Health Regulation No. 32 of 2017. The methods used to overcome these problems are water source identification, design of desalination system, purchasing, fabrication and testing of desalinated water. The result of the activities is a desalination system which consists of pre-treatment using 4 filtration stages ended with reverse osmosis desalination using a special membrane. The result of desalinated water test shows that the water is odourless, tasteless, and other parameters meet the requirement of the standard.

Filtration of subcritical water hydrolysates from red macroalgae byproducts with ultraporous ceramic membranes for oligosaccharide and peptide fractionation

An ultrafiltration-based process for oligosaccharide and peptide fractionation from a macroalgae subcritical water hydrolysate was studied. A wide range of separation results was obtained depending on the membrane pore. 100 kDa cut-off size was enough for hydrolysate clarification with total retention of colloidal materials. Oligosaccharides present in the hydrolysate showed the highest retention with all membranes, glucans mostly, followed by galactans, and finally arabinans. Peptides obtained after subcritical water treatment were some of the lowest rejected compounds, even using a 5 kDa membrane. The increase in temperature from 20 to 50 °C and feed flow rate from 6.6 to 11.2 L/h enhanced permeate flux for 5 kDa membrane, without perturbing the membrane retention. The Hermia's models identified the cake layer resistance as the major fouling resistance in hydrolysate filtrations at 20 °C, but standard pore blockage was the principal fouling mechanism at 50 °C. A fractionation process with sequential filtration stages at 20 °C and TMP = 1.1 bar was examined. Oligosaccharides were fractionated in the retentates of the sequential filtrations with 100, 5 and 1 kDa membranes. The final permeate collected from the 1 kDa membrane was freeze-dried to obtain a peptide-rich solid (71 wt%) that could be used in different applications.

Optimization and evaluation of the effect of impurities on phosphoric acid process performance using design of experiments

In the present work, we aim to investigate the impact of impurities co-existing in phosphate rock on reactive crystallization and filtration stages during the phosphoric acid dihydrate process. The primary influent impurities were identified by simulating the industrial optimal conditions on a laboratory scale and employing a design of experiments strategy; the positive and negative simultaneous effects for each impurity were elucidated and quantified. In addition, 4 mathematical models describing and predicting their effect on filterability, aspect ratio, thickness, and mean diameter of crystals were established. The obtained results conclude that CO2, F−, Al2O3, and SiO2 impose highly significant contributions and are the most influential species governing the process.

Reduction of total dissolved solids of pre-treated flowback water by two-stage nanofiltration: A gel layer based model to predict the system performance and scale up

Huge quantities of water with additives are required in the hydrofracking process employed for shale gas extraction. The flowback water returned to the surface after the operation is rich in total dissolved solids (TDS) and the organics. An appropriate pre-treatment can remove the organics and a suitable membrane system can be used to reduce the TDS. In this work, a commercial nanofiltration flat sheet membrane was used in cross-flow mode to lower the TDS of the pre-treated flowback water. Two stages of nanofiltration were carried out successfully to bring down the TDS to 3.45 g/l for the first stage and 1.85 g/L for the second stage which is below the desired level prescribed by the Bureau of Indian Standards. The membranes showed an overall rejection of 73% for TDS. The maximum rejection of TDS was obtained at 758 kPa transmembrane pressure (TMP) and 120 L/h cross flow rate (CFR) for both the stages. At the optimum operating condition, the membrane showed a flux decline ratio (FDR) of 0.35 and 0.31 along with an initial flux recovery of 80% and 85% for both the stages, respectively indicating the membrane to have a good anti-fouling property. A transient two-component gel layer controlled model was implemented for the quantification of the membrane performance for both the filtration stages. The gel layer thickness after one hour operation was found to be 19.2 µm for stage 1 and 8.8 µm for stage 2 at the optimum operating condition. The operating parameters, cross flow rate and transmembrane pressure drop were optimized using the criteria of the minimum energy consumption. The optimal operating curves were thus generated for a filtration area of 1 m2 and a filtration volume of 10 m3 and for three different final permeate concentrations of 1.2 g/L, 1.5 g/L and 1.8 g/L. Thus, using the predicted curves, one can find out the optimum TMP, CFR and area required for a target permeate concentration after the second stage of filtration where the total specific energy of the system will be minimum.

The influence of filtration velocity on the full-sized fibrous filter performance

Filtration velocity is a fundamental parameter that influences fibrous filtration performance. The previous work focuses on the effect of velocity on filtration performance, mainly using downsized filters, a flat sheet media or numerical methods. In this study, the actual performance of the full-sized fibrous filters was simulated according to standard test procedures, ISO 16890:2016 at different filtration velocities. The experimental findings show that the filtration efficiency increases with increasing velocity as the inertial impaction increases at higher velocity. The initial pressure differential shows an increasing relationship at [Formula: see text] with increasing velocity. The dust cake specific resistance coefficient, K c increases linearly with the velocity at the depth filtration stage and the beginning of transitional filtration stage. K c exhibits a quadratic growth with filtration velocity since the middle stage of transitional filtration and surface filtration. Dust holding capacity would be reduced and the final pressure differential would be increased with the increasing velocity due to the greater force incurred by the higher velocity, causing the filter media to deform and rupture easily. The experimental outcome of this study can be applied directly to industrial and commercial heating, ventilation and air conditioning design in consideration of the filter pressure differential for a lower energy consumption without compromising the efficiency for indoor air quality.

Experimental study on the effect of particle gradation on dewatering performance of geotubes

To clarify the effect of particle gradation of filling soil on the dewatering and consolidation performance of geotubes, the content of four-particle size classes (powder, fine, medium, and coarse) which are commonly used in engineering as the research object was taken. The dewatering rate, soil infiltration and solid-liquid mixing pressure in the bag with time when filling soil with different particles were studied, and the soil loss of the hanging bag was analyzed from the perspective of seepage soil gradation. The research results show that the dewatering process could be divided into the quick dewatering stage, silting stage, and stable stage according to the dewatering rate. According to the performance of soil conservation, it could be divided into the loss stage and reverse filtration stage. Further, based on the effects of powder content, non-uniformity coefficient, and curvature coefficient of soil on the dewatering rate of the hanging bag, a formula for calculating the dewatering rate of geotubes is summarized.

Design-oriented evaluation of the hydrodynamics in a full-scale combined filter-lamella separator for urban stormwater treatment.

The development of compact treatment devices with high removal efficiencies and low space requirements is a key objective of urban stormwater treatment. Thus, many devices utilize a combination of sedimentation and upward flow filtration in a single system. This study, for the first time, evaluates the flow field inside a combined filter-lamella separator via computational fluid dynamics. Herein, three objectives are investigated: (i) the flow field for different structural configurations, (ii) the distribution of particulate matter along the filter bed and (iii) the dynamic clogging in discrete filter zones, which is addressed by a clogging model derived from literature data. The results indicate that a direct combination of a filtration stage with a lamella separator promotes a uniform flow distribution. The distribution of particulate matter along the filter bed varies with configuration and particle size. Clogging, induced by particles in the spectrum <63 μm, creates gradients of hydraulic conductivity along the filter bed. After treating about half of Germany's annual runoff-efficient precipitation at a rainfall intensity of 5 L/(s·ha), the filtration rates increase in the front of the filter bed by +10%. Thus, long-term operating behavior is sensitive to efficient filter utilization in compact treatment devices.

Highly efficient separation of organic substances from high salinity brine by nanofiltration

Efficient separation of organic compounds from the high salinity brines during the treatment of reverse osmosis concentrate (ROC) is highly desirable and also very challengeable for the purpose of zero liquid discharge (ZLD). For the general treatment process, the efficient removal of organic compounds from the NaCl rich solution before the evaporation-crystallization stage is one of the key challenges. In this work, separation of N-(2-hydroxypropyl)morpholine (NMH), 4-morpholineacetate (MHA), the major organic components of ROC in refinery, and monovalent/divalent ions from the high salinity brines by three commercial nanofiltration (NF) membranes, i.e. Desal-5DK, Desal-5DL and NF270 were systematically investigated. The effects of various parameters on the rejection performance of these three NF membranes were experimentally investigated. The results showed that the retentions of NMH and MHA were dominated by flux and pH. Single stage filtration experiments showed that the rejection to NMH and MHA with various operating parameters was high and stable for DK. In comparison, DL and NF270 had higher separation efficiency for monovalent and divalent ions. The experiments determined that the rejections of NMH and MHA were 99.16% and 98.42% under the optimized conditions, respectively, indicating that NF membranes were highly efficient for separating organic compounds from the high salinity brine.

Solvent recovery from photolithography wastes using cellulose ultrafiltration membranes

Solvent recycling and reuse are indispensable for ensuring a sustainable chemical industry and circular economy. In this study we report the fabrication of cellulose ultrafiltration membranes and their application in recovery of propylene glycol methyl ether acetate (PGMEA) used as developer solvent in SU-8 photolithography. Cellulose membranes were fabricated via alkaline hydrolysis of cellulose acetate membranes in aqueous NaOH. Membrane permeance and molecular weight cut-off (MWCO) were tuned via changing cellulose acetate concentration in precursor solution and evaporation of volatile co-solvent, acetone. MWCO of the membranes was found to be smallest in DMSO, followed by water and largest in methanol. The difference was attributed to the different hydrodynamic diameters of the probe molecules in these solvents. SU-8 rejection from its representative developer solutions in PGMEA was assessed in dead-end filtration at up to 80% permeate recovery. After the first filtration, the collected permeate was fed to the same membrane to simulate a two-stage filtration scenario. Rejection was in the range of 87%–89% in a first stage filtration and 79%–80% in a second stage, both operated at 80% permeate recovery. Recycled solvent could be used in photolithography although with some loss of pattern fidelity, possibly owing to remaining SU-8 and photoacid generator in PGMEA. • Cellulose membrane permeance and MWCO tuned between 0.40–23.3 LHM/bar and 4–15 kDa. • Permeance is via pore flow mechanism but is also affected by swelling and steric hindrance. • SU-8 can be recovered from its PGMEA solution and reused in photolithography.

Neobladder creation in patients with chronic kidney disease: A viable diversion strategy.

Renal function impairment is often cited as a contraindication to continent diversion strategies. There is little evidence exploring renal function changes between continent and incontinent surgery in patients with preoperative chronic kidney disease (CKD), in particular CKD3B. This was a retrospective review of two high-volume centers performing robotic assisted radical cystectomy (RARC) with orthotopic neobladder (ONB) or ileal conduit (IC) between 2014 to 2020. Patients were stratified based on CKD estimated glomerular filtration (eGFR) stage, which was estimated via the CKD-EPI equation. Postoperative renal function was compared for up to 60 months postoperative. Surgical, post-surgical, complications, and readmission data were gathered and compared between all patients RESULTS: 522 cystectomy patients, 430 with IC and 125 with ONB, were included. eGFR decline was statistically significant in a matched cohort of IC and ONB patients only at 3 months. There were no statistically significant differences between readmission rates, time to readmission, or complications. 34.6% of stage 3B patients had hydronephrosis on imaging prior to surgery, compared to 11.4%, 22.1% and 21.8% of CKD stage 1, 2, and 3A patients. CKD stage 3B had statistically and clinically improved eGFR through 24 months. ONB surgery may be a viable diversion strategy in patients previously thought to be contraindicated due to low renal function.

Dual-objective for the mechanism of membrane fouling in the early stage of filtration and determination of cleaning frequency: A novel combined model

It is great importance to clarify the mechanism of the membrane fouling in the early stage of filtration. In this study, a novel model based on the loss of effective filtration area was established to predict the variation of the transmembrane pressure (TMP) at the constant flux mode. The coefficient of available membrane filtration area (ω) was adopted to describe the inflection point varying from combined pore blocking and cake filtration mode to individual cake filtration mode. Model simulations could predict reasonably the rise of transmembrane pressure (TMP) with correlation coefficient of R2 > 0.99. The reliability of the model was evaluated under different operating conditions (flux and stirring speeds) and feed concentrations, wherein the flux presented higher contribution to TMP, resistance of cake filtration (Rc) and resistance of intermediate pore blocking (Ri) than others. The accuracy of predictions of the proposed model was higher than other previous models. Moreover, the wide adaptability of the model was validated by using various real wastewater as feed suspensions. Furthermore, the calculation of the timing of the cake layer formation from the proposed model provided an instructional suggestion for the determination of the cleaning frequency. In summary, the proposed model sheds light on the fouling mechanism in the early stage of filtration and provides guidance to the strategy of cleaning protocols in MBR operations.