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1
Meng, Xianghao, Shujuan Meng e Yu Liu. "The Limitations in Current Studies of Organic Fouling and Future Prospects". Membranes 11, n. 12 (25 novembre 2021): 922. http://dx.doi.org/10.3390/membranes11120922.
Testo completoAbstract (sommario):
Microfiltration and ultrafiltration for water/wastewater treatment have gained global attention due to their high separation efficiency, while membrane fouling still remains one of their bottlenecks. In such a situation, many researchers attempt to obtain a deep understanding of fouling mechanisms and to develop effective fouling controls. Therefore, this article intends to trigger discussions on the appropriate choice of foulant surrogates and the application of mathematic models to analyze fouling mechanisms in these filtration processes. It has been found that the commonly used foulant surrogate (sodium alginate) cannot ideally represent the organic foulants in practical feed water to explore the fouling mechanisms. More surrogate foulants or extracellular polymeric substance (EPS) extracted from practical source water may be more suitable for use in the studies of membrane fouling problems. On the other hand, the support vector machine (SVM) which focuses on the general trends of filtration data may work as a more powerful simulation tool than traditional empirical models to predict complex filtration behaviors. Careful selection of foulant surrogate substances and the application of accurate mathematical modeling for fouling mechanisms would provide deep insights into the fouling problems.
2
Peiris, R. H., H. Budman, R. L. Legge e C. Moresoli. "Assessing irreversible fouling behavior of membrane foulants in the ultrafiltration of natural water using principal component analysis of fluorescence excitation-emission matrices". Water Supply 11, n. 2 (1 aprile 2011): 179–85. http://dx.doi.org/10.2166/ws.2011.025.
Testo completoAbstract (sommario):
Natural river water is comprised of different foulant components such as natural organic matter and colloidal/particulate matter. Both individual and combined contributions of these foulant components results in different fouling behaviour. The ability to characterize these contributions that lead to reversible and irreversible membrane fouling would be beneficial for the implementation of fouling monitoring and control strategies for membrane-based drinking water treatment operations. A fluorescence excitation-emission matrix and principal component analysis-based approach was able to qualitatively estimate the accumulation of humic substances (HS)-, protein- and colloidal/particulate matter-like foulant components in membranes during the ultrafiltration (UF) of natural river water. A bench-scale flat sheet UF cross-flow set-up and successive permeation and membrane backwashing cycles were used. Analysis of the accumulation of these foulant components revealed that the increased levels of colloidal/particulate matter accumulation in the membranes appeared to have increased the extent of irreversible fouling by HS-like matter whereas lower irreversible fouling by protein-like matter was observed with increased colloidal/particulate matter accumulation. The results also indicate that the combined contributions by these foulants are important in the fouling of membranes during the UF of river water.
3
Xu, Tingting, Jie Song e Guangli Xiu. "Study on the cross-flow ultrafiltration of mixtures of macromolecular organic and inorganic salts". Water Science and Technology 85, n. 6 (24 febbraio 2022): 1754–64. http://dx.doi.org/10.2166/wst.2022.066.
Testo completoAbstract (sommario):
Abstract Ultrafiltration (UF) has been widely applied to water treatment in the past few decades, but severe membrane fouling is one of the most significant obstacles for its further development. In reality, the constituents of feed water are complex, and the fouling behavior could be different from that induced by a single foulant. In this study, the membrane fouling induced by mixed organic foulant (sodium alginate, SA) and inorganic ions under various conditions were investigated. The effects of ion concentration and valence on the combined fouling as well as the rejection performance were examined. The results showed that compared to SA alone, the presence of inorganic ions could aggravate the organic fouling of UF membranes significantly. The fouling became more severe as the ion concentration increased. Also, ions with higher valence tended to exacerbate the fouling compared with monovalent ions. It was also found that the existence of inorganic ions had negligible effects on the rejection of organic molecules, however, the rejection of salts can be improved because of the organic matter. In addition, the analysis of the classic fouling models showed that the complete blocking model is the main fouling mechanism of the mixed SA and inorganic salts.
4
Nghiem, Long Duc, Christiane Espendiller e Gerd Braun. "Influence of organic and colloidal fouling on the removal of sulphamethoxazole by nanofiltration membranes". Water Science and Technology 58, n. 1 (1 luglio 2008): 163–69. http://dx.doi.org/10.2166/wst.2008.647.
Testo completoAbstract (sommario):
This study investigated the effects of organic and colloidal fouling on the removal of a representative micropollutant sulphamethoxazole by two commercially available NF membranes. Alginate, bovine serum albumin and colloidal silica were selected as model foulants to simulate hydrophilic and hydrophobic organic fractions, and colloidal matter that are often found in treated effluent and surface water. Membrane fouling was related to the membrane and foulant characteristics and subsequently the separation behaviour of the micropollutant sulphamethoxazole under different solution pH. On the basis of these results, it was confirmed that membrane fouling is strongly dependent on both the foulant and membrane characteristics. The complex relationship among retention mechanisms, fouling mechanisms and the effects of fouling on retention was systematically delineated. Of the three model foulants selected for this study, colloidal fouling resulted in the most significant reduction in retention of sulphamethoxazole as well as inorganic salts, while flux decline as a result of colloidal fouling was quite moderate. Reduction in retention caused by fouling was attributed to a phenomenon known as cake-enhance concentration polarisation, which was a predominant mechanism of colloidal fouling. In addition, the reported results suggested that the effect of fouling on retention is also membrane pore size dependent.
5
Moyo, Welldone, Machawe M. Motsa, Nhamo Chaukura, Titus A. M. Msagati, Bhekie B. Mamba, Sebastiaan G. J. Heijman e Thabo T. I. Nkambule. "Fundamental fouling mechanisms of dissolved organic matter fractions and their implications on the surface modifications of ceramic nanofiltration membranes: insights from a laboratory scale application". Water Science and Technology 80, n. 9 (1 novembre 2019): 1702–14. http://dx.doi.org/10.2166/wst.2019.419.
Testo completoAbstract (sommario):
Abstract This work reports on the fundamental factors influencing inter-foulant and foulant-membrane interactions during simulated dissolved organic matter removal using ceramic nanofiltration. Fouling tests were performed using sodium alginate (SAL), humic acid (HA) and bovine serum albumin (BSA) as model foulants. Fouling potentials of each foulant and their mixtures were investigated using feed solutions containing fixed concentrations of K+, Na+, Mg2+ and Ca2+ with a total ionic strength of 10 mM. The impact of modification by atomic layer deposition on fouling mitigation was also assessed. The flux decline in the first 100 min for single foulants was 4.16 × 10−2, 2.69 × 10−2 and 1.60 × 10−2 Lm−2 for SAL, HA and BSA, respectively. These results demonstrated that for the single foulants, deposition on the membrane surface in the early stages of filtration was primarily governed by membrane-foulant interactions. Interestingly, cake filtration was the least fouling mechanism in feed solutions composed of BSA and SAL (R2 = 0.519, 0.374 for BSA + SAL and BSA + SAL + HA, respectively) and the most favorable fouling mechanism of feed solution which included HA and SAL (R2 = 0.972). The water contact angle dropped from 58o to 35° after coating, thus improving its anti-fouling properties.
6
Yan, Linlin, Ruixue Li, Yu Song, Yanping Jia, Zheng Li, Lianfa Song e Haifeng Zhang. "Characterization of the Fouling Layer on the Membrane Surface in a Membrane Bioreactor: Evolution of the Foulants’ Composition and Aggregation Ability". Membranes 9, n. 7 (16 luglio 2019): 85. http://dx.doi.org/10.3390/membranes9070085.
Testo completoAbstract (sommario):
In this study, the characteristics of membrane foulants were analyzed with regard to morphology, composition, and aggregation ability during the three stages of transmembrane pressure (TMP) development (fast–slow–fast rise in TMP) in a steady operational membrane bioreactor (MBR). The results obtained show that the fouling layer at the slow TMP-increase stage possessed a higher average roughness (71.27 nm) and increased fractal dimension (2.33), which resulted in a low membrane fouling rate (0.87 kPa/d). A higher extracellular DNA (eDNA) proportion (26.12%) in the extracellular polymeric substances (EPS) resulted in both higher zeta potential (-23.3 mV) and higher hydrophobicity (82.3%) for initial foulants, which induced and increased the protein proportion in the subsequent fouling layer (74.11%). Furthermore, the main composition of the EPS shifted from protein toward polysaccharide dominance in the final fouling layer. The aggregation test confirmed that eDNA was essential for foulant aggregation in the initial fouling layer, whereas ion interaction significantly affected foulant aggregation in the final fouling layer.
7
Ouyang, Rulu, Bin Huang, Chun-Hai Wei, Hongwei Rong, Huarong Yu, Fangshu Qu, Kang Xiao e Xia Huang. "Cake Layer Fouling Potential Characterization for Wastewater Reverse Osmosis via Gradient Filtration". Membranes 12, n. 8 (21 agosto 2022): 810. http://dx.doi.org/10.3390/membranes12080810.
Testo completoAbstract (sommario):
It is of great importance to quantitatively characterize feed fouling potential for the effective and efficient prevention and control of reverse osmosis membrane fouling. A gradient filtration method with microfiltration (MF 0.45 μm) → ultrafiltration (UF 100 kDa) → nanofiltration (NF 300 Da) was proposed to extract the cake layer fouling index, I, of different feed foulants in this study. MF, UF, and NF showed high rejection of model suspended solids (kaolin), colloids (sodium alginate and bovine serum albumin), and dissolved organic matters (humic acid) during constant-pressure individual filtration tests, where the cake layer was the dominant fouling mechanism, with I showing a good linear positive correlation with the foulant concentration. MF → UF → NF gradient filtration tests of synthetic wastewater (i.e., model mixture) showed that combined models were more effective than single models to analyze membrane fouling mechanisms. For each membrane of gradient filtration, I showed a positive correlation with the targeted foulant concentration. Therefore, a quantitative assessment method based on MF → UF → NF gradient filtration, the correlation of combined fouling models, and the calculation of I would be useful for characterizing the fouling potentials of different foulants. This method was further successfully applied for characterizing the fouling potential of real wastewater (i.e., sludge supernatant from a membrane bioreactor treating dyeing and finishing wastewater).
8
Mulyawan, Rizka, e Agam Muarif. "A Review Of Reverse Osmosis Membrane Fouling: Formation and Control". International Journal of Engineering, Science and Information Technology 1, n. 3 (7 luglio 2021): 110–15. http://dx.doi.org/10.52088/ijesty.v1i3.127.
Testo completoAbstract (sommario):
Membrane application in reverse osmosis (RO) membrane is getting more attention especially in producing drinking water. However, RO membrane faces challenges that reduces its performance such as its permeation flux, salt rejection, additional energy demand, lifetime decrease, extra pre-treatment process, cleaning and maintenance. The challenge is the formation of fouling. RO membrane fouling can happen inside or outside the membrane and the characteristics of membrane fouling differs from one type to other types, depending on the nature and location of membrane fouling. There are several types of RO fouling, which are Biofouling, Organic Fouling, Inorganic Fouling and Colloidal Fouling. The causes of RO membrane are different from one to another. The properties and materials of the solution entering RO membrane are important as it affects the type of fouling of RO membrane fouling. All of the RO membrane foulings need to be considered during membrane usage and demand solution to be controlled. In order to control the fouling in Reverse Osmosis membrane, there have been several control solutions discovered to the membrane fouling challenges. The control solutions are specified to each one of the fouling, in spite of wide applications for some of it. The control solutions are pre-treatment, which has many methods such as photo oxidation, coagulation, scale inhibitor, ion exchange resins, granular media and membrane treatment, membrane monitoring, membrane cleaning, surface modification, and material addition to membrane or novel membrane material. With various control solutions discovered, the RO membrane still faces fouling issue and is still demanding some more advanced applicable control solutions.
9
Chang, Z. H., Y. H. Teow, S. P. Yeap e J. Y. Sum. "Membrane Fouling – The Enemy of Forward Osmosis". Journal of Applied Membrane Science & Technology 25, n. 2 (7 luglio 2021): 73–88. http://dx.doi.org/10.11113/amst.v25n2.220.
Testo completoAbstract (sommario):
Forward osmosis (FO) is an osmotically driven membrane separation process. It is potentially applied in various industries for nutrient recovery and water reclamation. Although FO showed a lesser fouling tendency than other pressure-driven membrane processes, the solutes in the feed solution would still deposit on the membrane surface, forming a fouling layer that resists water permeation. For that reason, fouling mitigation is a trending issue in the FO process. A better understanding of the fouling mechanism is required before opting for the appropriate strategy to mitigate it. This article describes the fouling mechanism based on different foulant presented in the feed, followed by a method in relieving fouling in the FO process.
10
Buchori, Luqman, Heru Susanto e Budiyono Budiyono. "SINTESIS MEMBRAN ULTRAFILTRASI NON FOULING UNTUK APLIKASI PEMPROSESAN BAHAN PANGAN". Reaktor 13, n. 1 (3 febbraio 2010): 10. http://dx.doi.org/10.14710/reaktor.13.1.10-15.
Testo completoAbstract (sommario):
Membran ultrafiltrasi (UF) telah terbukti sebagai proses yang menjanjikan untuk aplikasi di bidang pemprosesan bahan pangan. Namun, peristiwa fouling dapat menurunkan kinerja membran secara signifikan. Meskipun banyak metode pengendalian fouling telah diusulkan, dalam banyak kasus kinerja proses sangat dipengaruhi oleh membran sebagai jantung dari proses. Dalam makalah ini pengendalian fouling dilakukan dengan memodifikasi permukaan membran dengan teknik kopolimerisasi foto-grafting. Acrylic acid (AA), acrylamido methylpropane sulfonic acid (AMPS), poly(ethylene glycol) methacrylate (PEGMA), dan N,N-dimethyl-N-(2-methacryloyloxyethyl-N-(3sulfopropyl)ammonium betaine sebagai senyawa zwitterion (ZI) digunakan sebagai monomer fungsional. Pengaruh waktu iradiasi terhadap efektifitas modifikasi telah diamati. Kinerja membran hasil modifikasi kemudian diuji dengan menggunakan berbagai model larutan foulant yang meliputi larutan protein, larutan polisakarida dan larutan polifenol. Hasil penelitian menunjukkan bahwa sifat non fouling membran sangat jelas dapat ditingkatkan baik dengan PEGMA maupun dengan ZI. Secara umum, modifikasi menggunakan PEGMA menunjukkan kinerja yang lebih baik. Larutan polifenol menunjukkan karakter foulant yang paling kuat diantara model foulant.
11
Ma, Chunyan, Chao Yi, Fang Li, Chensi Shen, Zhiwei Wang, Wolfgang Sand e Yanbiao Liu. "Mitigation of Membrane Fouling Using an Electroactive Polyether Sulfone Membrane". Membranes 10, n. 2 (30 gennaio 2020): 21. http://dx.doi.org/10.3390/membranes10020021.
Testo completoAbstract (sommario):
Membrane fouling is the bottleneck limiting the wide application of membrane processes. Herein, we adopted an electroactive polyether sulfone (PES) membrane capable of mitigating fouling by various negatively charged foulants. To evaluate anti-fouling performance and the underlying mechanism of this electroactive PES membrane, three types of model foulants were selected rationally (e.g., bovine serum albumin (BSA) and sodium alginate (SA) as non-migratory foulants, yeast as a proliferative foulant and emulsified oil as a spreadable foulant). Water flux and total organic carbon (TOC) removal efficiency in the filtering process of various foulants were tested under an electric field. Results suggest that under electrochemical assistance, the electroactive PES membrane has an enhanced anti-fouling efficacy. Furthermore, a low electrical field was also effective in mitigating the membrane fouling caused by a mixture of various foulants (containing BSA, SA, yeast and emulsified oil). This result can be attributed to the presence of electrostatic repulsion, which keeps foulants away from the membrane surface. Thereby it hinders the formation of a cake layer and mitigates membrane pore blocking. This work implies that an electrochemical control might provide a promising way to mitigate membrane fouling.
12
Akter, Mahamuda, e Jin-Soo Park. "Fouling and Mitigation Behavior of Foulants on Ion Exchange Membranes with Surface Property in Reverse Electrodialysis". Membranes 13, n. 1 (13 gennaio 2023): 106. http://dx.doi.org/10.3390/membranes13010106.
Testo completoAbstract (sommario):
In this study, two different types of ion exchange membranes are used to investigate the tendency of membrane fouling with respect to surface roughness and hydrophilicity. Commercially available membranes reinforced by electrospun nanofiber have rough and hydrophilic surfaces, and lab-made pore-filling membranes exhibit a smooth and hydrophobic surface. Three different organic surfactants (i.e., cationic, anionic and non-ionic surfactants) are chosen as foulants with similar molecular weights. It is confirmed that membrane fouling by electrical attraction mainly occurs, in which anionic and cationic foulants influence anion and cation exchange membranes, respectively. Thus, less fouling is obtained on both membranes for the non-charged foulant. The membranes with a rough surface show a higher fouling tendency than those with a smooth surface in the short-term continuous fouling tests. However, during the cyclic operations of fouling and mitigation of the commercially available membranes, the irregularities of a rough membrane surface cause a rapid increase in electrical resistance from the beginning of fouling due to excessive adsorption on the surface, but the fouling is easily mitigated due to the hydrophilic surface. On the other hand, the membranes with a smooth surface show alleviated fouling from the beginning of fouling, but the irreversible fouling occurs as foulants accumulate on the hydrophobic surface which causes membrane fouling to be favorable.
13
Azari, Sara, Linda Zou, Emile Cornelissen e Yasushito Mukai. "Facile fouling resistant surface modification of microfiltration cellulose acetate membranes by using amino acid l-DOPA". Water Science and Technology 68, n. 4 (1 agosto 2013): 901–8. http://dx.doi.org/10.2166/wst.2013.292.
Testo completoAbstract (sommario):
A major obstacle in the widespread application of microfiltration membranes in the wet separation processes such as wastewater treatment is the decline of permeates flux as a result of fouling. This study reports on the surface modification of cellulose acetate (CA) microfiltration membrane with amino acid l-3,4-dihydroxy-phenylalanine (l-DOPA) to improve fouling resistance of the membrane. The membrane surface was characterised using Fourier transform infrared spectroscopy (FTIR), water contact angle and zeta potential measurement. Porosity measurement showed a slight decrease in membrane porosity due to coating. Static adsorption experiments revealed an improved resistance of the modified membranes towards the adhesion of bovine serum albumin (BSA) as the model foulant. Dead end membrane filtration tests exhibited that the fouling resistance of the modified membranes was improved. However, the effect of the modification depended on the foulant solution concentration. It is concluded that l-DOPA modification is a convenient and non-destructive approach to enable low-BSA adhesion surface modification of CA microfiltration membranes. Nevertheless, the extent of fouling resistance improvement depends on the foulant concentration.
14
Mahlangu, Oranso Themba, e Bhekie Brilliance Mamba. "Interdependence of Contributing Factors Governing Dead-End Fouling of Nanofiltration Membranes". Membranes 11, n. 1 (12 gennaio 2021): 47. http://dx.doi.org/10.3390/membranes11010047.
Testo completoAbstract (sommario):
Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane–foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid–base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (<15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane–foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.
15
Halvey, Alex Kate, Brian Macdonald, Abhishek Dhyani e Anish Tuteja. "Design of surfaces for controlling hard and soft fouling". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, n. 2138 (24 dicembre 2018): 20180266. http://dx.doi.org/10.1098/rsta.2018.0266.
Testo completoAbstract (sommario):
In this review, we present a framework to guide the design of surfaces which are resistant to solid fouling, based on the modulus and length scale of the fouling material. Solid fouling is defined as the undesired attachment of solid contaminants including ice, clathrates, waxes, inorganic scale, polymers, proteins, dust and biological materials. We first provide an overview of the surface design approaches typically applied across the scope of solid fouling and explain how these disparate research efforts can be united to an extent under a single framework. We discuss how the elastic modulus and the operating length scale of a foulant determine its ability or inability to elastically deform surfaces. When surface deformation occurs, minimization of the substrate elastic modulus is critical for the facile de-bonding of a solid contaminant. Foulants with low modulus or small deposition sizes cannot deform an elastic bulk material and instead de-bond more readily from surfaces with chemistries that minimize their interfacial free energy or induce a particular repellant interaction with the foulant. Overall, we review reported surface design strategies for the reduction in solid fouling, and provide perspective regarding how our framework, together with the modulus and length scale of a foulant, can guide future antifouling surface designs. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology’.
16
Sun, Chunyi, Na Zhang, Fazhan Li, Guoyi Ke, Lianfa Song, Xiaoqian Liu e Shuang Liang. "Quantitative Analysis of Membrane Fouling Mechanisms Involved in Microfiltration of Humic Acid–Protein Mixtures at Different Solution Conditions". Water 10, n. 10 (22 settembre 2018): 1306. http://dx.doi.org/10.3390/w10101306.
Testo completoAbstract (sommario):
A systematical quantitative understanding of different mechanisms, though of fundamental importance for better fouling control, is still unavailable for the microfiltration (MF) of humic acid (HA) and protein mixtures. Based on extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory, the major fouling mechanisms, i.e., Lifshitz–van der Waals (LW), electrostatic (EL), and acid–base (AB) interactions, were for the first time quantitatively analyzed for model HA–bovine serum albumin (BSA) mixtures at different solution conditions. Results indicated that the pH, ionic strength, and calcium ion concentration of the solution significantly affected the physicochemical properties and the interaction energy between the polyethersulfone (PES) membrane and HA–BSA mixtures. The free energy of cohesion of the HA–BSA mixtures was minimum at pH = 3.0, ionic strength = 100 mM, and c(Ca2+) = 1.0 mM. The AB interaction energy was a key contributor to the total interaction energy when the separation distance between the membrane surface and HA–BSA mixtures was less than 3 nm, while the influence of EL interaction energy was of less importance to the total interaction energy. The attractive interaction energies of membrane–foulant and foulant–foulant increased at low pH, high ionic strength, and calcium ion concentration, thus aggravating membrane fouling, which was supported by the fouling experimental results. The obtained findings would provide valuable insights for the quantitative understanding of membrane fouling mechanisms of mixed organics during MF.
17
Yuliani, Anisa, Mahmud Mahmud e Chairul Abdi. "PENINGKATAN KINERJA MEMBRAN ULTRAFILTRASI ALIRAN DEAD-END PADA PENYISIHAN BAHAN ORGANIK DALAM EFLUEN IPAL DOMESTIK DENGAN PRA-PERLAKUAN ADSORPSI". Jernih: Jurnal Tugas Akhir Mahasiswa 2, n. 2 (8 dicembre 2020): 23–28. http://dx.doi.org/10.20527/jernih.v2i2.589.
Testo completoAbstract (sommario):
Salah satu kendala yang membatasi kinerja membran ultrafiltrasi (UF) yaitu fouling membran. Keberadaan Bahan Organik (BO) merupakan salah satu penyebab utama terjadinya fouling membran pada air efluen IPAL Domestik. Oleh karena itu, perlu dilakukan pra-perlakuan adsorpsi karbon aktif untuk mengurangii foulingi dani meningkatkani performai membrani UF. Penelitian ini bertujuan untuk mengetahui proses pengolahan air efluen dengan kondisi terbaik pada proses hibrid adsorpsi dan Ultrafiltrasi (UF) selulosa asetat (SA), serta menganalisis terbentuknya fouling membran pada proses hibrid adsorpsi dan UF-SA. Karbon aktif yang digunakan pada rencana penelitian ini adalah Powdered Activated Carbon (PAC) dengan interval variasi dosis 25 mg/L pada rentang 25 mg/L-200mg/L serta pH 4. Metode yang digunakan pada proses pra-perlakuan adsorpsi menggunakan sistem batch dengan pengadukan adsorpsi 180 rpm selama 240 menit. Kemudian, dialirkan pada membran UF-SA menggunakan sistem aliran dead-end dengan variasi tekanan operasi 1-3 bar dengan interval 0,5 bar pada pH 4 selama 120 menit. Selanjutnya dicari kondisi terbaik proses hibrid adsorpsi dan UF-SA dengan cara mengatur dosis optimum (dinaikkan maupun diturunkan), sehingga didapatkan tiga variasi dosis. Analisis kandungan BO dilakukan melalui pengukuran parameter Dissolved Organic Carbon (DOC), UV254, E4/E6 , dan UV456 menggunakan TOC Analyzer dan Spektrofotometer UV serta karakterisasi membran dengan permeabilitas. Hipotesis dari penelitian ini adalah pra-perlakuani adsorpsii karboni aktifi berpengaruh untuki mereduksii foulingi pada membrani UF-SA, dan model Modified Fouling Index (MFI) dapat menggambarkan pembentukan fouling pada proses hibrid adsorpsi dan UF-SA pada penyisihan air efluen.
18
Che, Sanchuan, Muyi Ye, Kayiu Li, Yang Xie, Pengyou Du e Hunan Deng. "A review of bio-inspired fouling resistance surfaces". Applied and Computational Engineering 7, n. 1 (21 luglio 2023): 478–506. http://dx.doi.org/10.54254/2755-2721/7/20230409.
Testo completoAbstract (sommario):
Solid fouling settlement, defined as the unexpected payment of various types of solid contaminants, including ice, wax, bacteria, and protein, can result in many problems in daily life and production and cause economic and security losses. Despite many traditional methods for reducing foulant to make a more durable and efficient antifouling surface, many artificial surfaces inspired by the natural antifouling material which the environment has selected during the process of evolution, including lotus leaf, pilot whale skin, gecko feet, shark skin, and pitcher plant are developed to resist adhesion of multiple foulants in an efficient and environmentally friendly way. In this review, the mechanism of how surfaces using patterns similar to the natural antifouling surface resist fouling materials is overviewed. Various methods for fouling formation classify the hazard, properties, and characteristics of different fouling materials. The approaches typically applied in designing a surface with high fouling resistance are presented first. After interpreting the theories and models mentioned in the explanation of the fouling resistance property, the textural microstructures, the chemical and physical properties used, and applications for fouling resistance of several bio-inspired fouling resistance surfaces, and how these surfaces can be improved in the future are discussed.
19
Ling, Bowen, Peng Xie, David Ladner e Ilenia Battiato. "Dynamic Modeling of Fouling in Reverse Osmosis Membranes". Membranes 11, n. 5 (10 maggio 2021): 349. http://dx.doi.org/10.3390/membranes11050349.
Testo completoAbstract (sommario):
During reverse osmosis (RO) membrane filtration, performance is dramatically affected by fouling, which concurrently decreases the permeate flux while increasing the energy required to operate the system. Comprehensive design and optimization of RO systems are best served by an understanding of the coupling between membrane shape, local flow field, and fouling; however, current studies focus exclusively on simplified steady-state models that ignore the dynamic coupling between fluid flow, solute transport, and foulant accumulation. We developed a customized solver (SUMs: Stanford University Membrane Solver) under the open source finite volume simulator OpenFOAM to solve transient Navier–Stokes, advection–diffusion, and adsorption–desorption equations for foulant accumulation. We implemented two permeate flux reduction models at the membrane boundary: the resistance-in-series (RIS) model and the effective-pressure-drop (EPD) model. The two models were validated against filtration experiments by comparing the equilibrium flux, pressure drop, and fouling pattern on the membrane. Both models not only predict macroscopic quantities (e.g., permeate flux and pressure drop) but also the fouling pattern developed on the membrane, with a good match with experimental results. Furthermore, the models capture the temporal evolution of foulant accumulation and its coupling with flux reduction.
20
Yang, Haiyan, Xuri Yu, Junxia Liu, Zhiwei Tang, Tianyi Huang, Zhihong Wang, Yiyun Zhong, Zhihong Long e Lin Wang. "A Concise Review of Theoretical Models and Numerical Simulations of Membrane Fouling". Water 14, n. 21 (3 novembre 2022): 3537. http://dx.doi.org/10.3390/w14213537.
Testo completoAbstract (sommario):
Membrane fouling can cause severe flux drops and affect the quality of produced water, which is a major obstacle for membrane applications. Great efforts have been made to examine theoretical models and numerical simulations for fouling behavior and mechanisms in the past decades, but there is a lack of literature providing a systematic summary. This work aims to present a state-of-the-art review of the principles, applicability and advantages of fouling theoretical models (i.e., the concentration polarization, cake layer formation and blocking models), and numerical simulations (i.e., computational fluid dynamics, Monte Carlo simulation, and artificial neural networks) for fouling behavior and mechanisms. Through these models and simulations, the behaviors of foulant particles at the microscopic level are analyzed in detail from the perspective of force, energy, and particle trajectory during the fouling process. The concise summary of fouling modeling in this review gives guidelines for the selection and application of models to simulate the membrane fouling process accurately, and the optimization of the operation in membrane-based processes.
21
Yao, Weihao, Bing Wang e Kaisong Zhang. "Comparative Study of Membrane Fouling with Aeration Shear Stress in Filtration of Different Substances". Membranes 13, n. 11 (1 novembre 2023): 867. http://dx.doi.org/10.3390/membranes13110867.
Testo completoAbstract (sommario):
The formation process of membrane fouling is complex and diverse, which is an important problem that needs to be overcome in membrane applications. In this paper, three foulant systems consisting of humic acid, humic acid plus Ca2+ and humic acid plus Ca2+ plus yeast were selected to compare membrane fouling processes with different aeration intensities. The aim was to establish the quantitative relationship between membrane fouling rate and shear stress, respectively, in a large-scale flat sheet MBR (FSMBR). The shear stress values at different aeration intensities were obtained using computational fluid dynamics (CFD). The membrane fouling rate during the filtration of different substances was measured by performing experiments. The comparison results showed that the membrane fouling rate varied greatly during the filtration of different substances. With the help of particle size distribution, the effect of different shear forces on floc size was further explored. Using the dual control of fouling rate and floc size, the recommended aeration intensity was 6~8 L/(m2·min).
22
Gray, S. R., C. B. Ritchie e B. A. Bolto. "Effect of fractionated NOM on low-pressure membrane flux declines". Water Supply 4, n. 4 (1 dicembre 2004): 189–96. http://dx.doi.org/10.2166/ws.2004.0077.
Testo completoAbstract (sommario):
The membrane fouling characteristics of natural organic matter (NOM) were assessed using single polypropylene hollow fibre membranes of pore size 0.2 μm. The membranes were liquid backwashed every 30 minutes and filtration runs of up to 48 hours (≤8 litres) were conducted. The NOM samples were fractionated into different chemical classes based on their adsorption properties. For the two waters investigated, the hydrophobic components were the major foulant for one water, and the hydrophilics were the major foulant for the other. Interaction between the strongly hydrophobic and weakly hydrophobic fractions was significant for one water, but the extent of interaction between these fractions was minor for the other. The long term membrane fouling characteristics could not always be deduced from short term fouling trials.
23
Gao, Kuo, Hong Yang, Haichen Liu e Bingzhi Dong. "Alleviating Ultrafiltration Membrane Fouling Caused by Effluent Organic Matter Using Pre-Ozonation: A Perspective of EEM and Molecular Weight Distribution". Membranes 13, n. 4 (21 aprile 2023): 452. http://dx.doi.org/10.3390/membranes13040452.
Testo completoAbstract (sommario):
Wastewater reclamation has gradually become an important way to cope with the global water crisis. Ultrafiltration plays an imperative part as a safeguard for the aim but is often limited by membrane fouling. Effluent organic matter (EfOM) has been known to be a major foulant during ultrafiltration. Hence, the primary aim of this study was to investigate the effects of pre-ozonation on the membrane fouling caused by EfOM in secondary wastewater effluents. In addition, the physicochemical property changes of EfOM during pre-ozonation and the subsequent influence on membrane fouling were systemically investigated. The combined fouling model and the morphology of fouled membrane were adopted to scrutinize the fouling alleviation mechanism by pre-ozonation. It was found that membrane fouling by EfOM was dominated by hydraulically reversible fouling. In addition, an obvious fouling reduction was achieved by pre-ozonation with 1.0 mg O3/mg DOC. The resistance results showed that the normalized hydraulically reversible resistance was reduced by ~60%. The water quality analysis indicated that ozone degraded high molecular weight organics such as microbial metabolites and aromatic protein and medium molecular weight organics (humic acid-like) into smaller fractions and formed a looser fouling layer on the membrane surface. Furthermore, pre-ozonation made the cake layer foul towards pore blocking, thereby reducing fouling. In addition, there was a little degradation in the pollutant removal performance with pre-ozonation. The DOC removal rate decreased by more than 18%, while UV254 decreased by more than 20%.
24
Alresheedi, Mohammad T. "Influence of Iron and Magnesium on Fouling Properties of Organic Matter Solution in Membrane Process". Membranes 14, n. 7 (7 luglio 2024): 150. http://dx.doi.org/10.3390/membranes14070150.
Testo completoAbstract (sommario):
Organic matter has been identified as a significant type of foulant in membrane processes for water treatment. Its fouling tendency is highly affected by the presence of ions and inorganics. While the effects of ions addition on organic fouling have been extensively researched in the past, studies on the effect of positively-charged inorganics, such as Fe2+ and Mg2+, on organic fouling are limited. This study investigates the influence of Fe2+ and Mg2+ addition on fouling properties of the Suwannee River Organic Matter (SROM) solution in the MF process, with and without Ca2+ ions. Results showed that increasing the concentration of Fe2+ and Mg2+ from 0–5 mM promoted SROM fouling, and resulted in an increased flux decline up to 33% and 58%, respectively. Cake layer resistance became more dominant with the addition of Fe2+ and Mg2+, and was counted for more than 60% of the fouling. Mg2+, however, caused higher internal pore blocking, and facilitated the formation of a less permeable cake layer, compared to Fe2+. This was evident in the analysis of the cake layer properties and the visualization of the fouling layer. In all cases, SROM fouling with Fe2+ and Mg2+ worsened with the addition of Ca2+ ions. The results of the study indicated the importance of understanding the interaction between organic matter and Fe2+ and Mg2+, which would provide useful insights on their fouling mechanism and control.
25
Blankert, Bastiaan, Bart Van der Bruggen, Amy E. Childress, Noreddine Ghaffour e Johannes S. Vrouwenvelder. "Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration". Membranes 11, n. 7 (22 giugno 2021): 460. http://dx.doi.org/10.3390/membranes11070460.
Testo completoAbstract (sommario):
The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.
26
Lee, Song, Hyeongrak Cho, Yongjun Choi e Sangho Lee. "Application of Optical Coherence Tomography (OCT) to Analyze Membrane Fouling under Intermittent Operation". Membranes 13, n. 4 (30 marzo 2023): 392. http://dx.doi.org/10.3390/membranes13040392.
Testo completoAbstract (sommario):
There is increasing interest in membrane systems powered by renewable energy sources, including solar and wind, that are suitable for decentralized water supply in islands and remote regions. These membrane systems are often operated intermittently with extended shutdown periods to minimize the capacity of the energy storage devices. However, relatively little information is available on the effect of intermittent operation on membrane fouling. In this work, the fouling of pressurized membranes under intermittent operation was investigated using an approach based on optical coherence tomography (OCT), which allows non-destructive and non-invasive examination of membrane fouling. In reverse osmosis (RO), intermittently operated membranes were investigated by OCT-based characterization. Several model foulants such as NaCl and humic acids were used, as well as real seawater. The cross-sectional OCT images of the fouling were visualized as a three-dimensional volume using Image J. The OCT images were used to quantitatively measure the thickness of foulants on the membrane surfaces under different operating conditions. The results showed that intermittent operation retarded the flux decrease due to fouling compared to continuous operation. The OCT analysis showed that the foulant thickness was significantly reduced by the intermittent operation. The decrease in foulant layer thickness was found to occur when the RO process was restarted in intermittent operation.
27
Zhao, Ping, Jian Sheng e Hua Zhang. "Characteristics of the Initial Stage of CaCO3 Crystallization Fouling on Straight Oblique Fin Tube". Advanced Materials Research 671-674 (marzo 2013): 2535–41. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.2535.
Testo completoAbstract (sommario):
To investigate the effect of CaCO3 concentration and velocity on scaling fouling process on plain and SOFT, experiments have been done at different CaCO3 concentration and velocity on the two kind tubes. The results are that the homogeneous nucleation rate and the growth rate are both increase when CaCO3 concentration increases. This make the scaling particle concentration and foulant ions concentration increase, the former gets more scaling on tubes and the later enlarges the heterogeneous nucleation rate and growth rate. Higher velocity decreases the nucleation of scaling, scaling crystal and fouling resistance, but it can prolong the induction period. Higher velocity increases nucleation rate on SOFT first, but the induction period extends and the mass of scaling and fouling resistance decrease. SOFT has a bigger heat transfer coefficient than PT at both clean and fouling conditions and it has smaller fouling resistance even a little more scaling.
28
Teow, Yeit Haan, Boon Seng Ooi, Abdul Latif Ahmad e Jit Kang Lim. "Investigation of Anti-fouling and UV-Cleaning Properties of PVDF/TiO2 Mixed-Matrix Membrane for Humic Acid Removal". Membranes 11, n. 1 (24 dicembre 2020): 16. http://dx.doi.org/10.3390/membranes11010016.
Testo completoAbstract (sommario):
Natural organic matters (NOMs) have been found to be the major foulant in the application of ultrafiltration (UF) for treating surface water. Against this background, although hydrophilicity has been demonstrated to aid fouling mitigation, other parameters such as membrane surface morphology may contribute equally to improved fouling resistance. In this work, with humic acid solution as the model substance, the effects of titanium dioxides (TiO2) types (PC-20, P25, and X500) on membrane anti-fouling and defouling properties were comparatively analysed. The aims are (1) to determine the correlation between membrane surface morphology and membrane fouling and (2) to investigate the anti-fouling and UV-cleaning abilities of PVDF/TiO2 mixed-matrix membranes with different membrane topographies and surface energy conditions. The mixed-matrix membrane with P25 TiO2 exhibited the most significant UV-defouling ability, with a high irreversible flux recovery ratio (IFRR(UV)) of 16.56 after 6 h of UV irradiation, whereas that with X500 TiO2 exhibited both superior anti-fouling and defouling properties due to its smoother surface and its highly reactive surface layer.
29
Kweon, J. H., e D. F. Lawler. "Investigation of membrane fouling by synthetic and natural particles". Water Science and Technology 50, n. 12 (1 dicembre 2004): 279–85. http://dx.doi.org/10.2166/wst.2004.0724.
Testo completoAbstract (sommario):
The biggest impediment for applying membrane processes is fouling that comes from mass flux (such as particle and organic matter) to the membrane surface and its pores. Numerous research articles have indicated that either particles or natural organic matter (NOM) has been the most detrimental foulant. Therefore, the role of particles in membrane fouling was investigated with two synthetic waters (having either particles alone or particles with simple organic matter) and a natural water. Membrane fouling was evaluated with flux decline behavior and direct images from scanning electron microscopy. The results showed that the combined fouling by kaolin and dextran (a simple organic compound selected as a surrogate for NOM) showed no difference from the fouling with only the organic matter. The similarity might stem from the fact that dextran (i.e., polysaccharide) has no ability to be adsorbed on the clay material, so that the polysaccharide behaves the same with respect to the membrane with or without clay material being present. In contrast to kaolin, the natural particles showed a dramatic effect on membrane fouling.
30
Cai, Weiwei, Qiuying Chen, Jingyu Zhang, Yan Li, Wenwen Xie e Jingwei Wang. "Effects of High Salinity on Alginate Fouling during Ultrafiltration of High-Salinity Organic Synthetic Wastewater". Membranes 11, n. 8 (31 luglio 2021): 590. http://dx.doi.org/10.3390/membranes11080590.
Testo completoAbstract (sommario):
Ultrafiltration is widely employed in treating high-salinity organic wastewater for the purpose of retaining particulates, microbes and macromolecules etc. In general, high-salinity wastewater contains diverse types of saline ions at fairly high concentration, which may significantly change foulant properties and subsequent fouling propensity during ultrafiltration. This study filled a knowledge gap by investigating polysaccharide fouling formation affected by various high saline environments, where 2 mol/L Na+ and 0.5–1.0 mol/L Ca2+/Al3+ were employed and the synergistic influences of Na+-Ca2+ and Na+-Al3+ were further unveiled. The results demonstrated that the synergistic influence of Na+-Ca2+ strikingly enlarged the alginate size due to the bridging effects of Ca2+ via binding with carboxyl groups in alginate chains. As compared with pure alginate, the involvement of Na+ aggravated alginate fouling formation, while the subsequent addition of Ca2+ or Al3+ on the basis of Na+ mitigated fouling development. The coexistence of Na+-Ca2+ led to alginate fouling formed mostly in a loose and reversible pattern, accompanied by significant cracks appearing on the cake layer. In contrast, the fouling layer formed by alginate-Na+-Al3+ seemed to be much denser, leading to severer irreversible fouling formation. Notably, the membrane rejection under various high salinity conditions was seriously weakened. Consequently, the current study offered in-depth insights into the development of polysaccharide-associated fouling during ultrafiltration of high-salinity organic wastewater.
31
Xu, Hao, Kang Xiao, Jinlan Yu, Bin Huang, Xiaomao Wang, Shuai Liang, Chunhai Wei, Xianghua Wen e Xia Huang. "A Simple Method to Identify the Dominant Fouling Mechanisms during Membrane Filtration Based on Piecewise Multiple Linear Regression". Membranes 10, n. 8 (29 luglio 2020): 171. http://dx.doi.org/10.3390/membranes10080171.
Testo completoAbstract (sommario):
Membrane fouling is a complicated issue in microfiltration and ultrafiltration. Clearly identifying the dominant fouling mechanisms during the filtration process is of great significance for the phased and targeted control of fouling. To this end, we propose a semi-empirical multiple linear regression model to describe flux decline, incorporating the five fouling mechanisms (the first and second kinds of standard blocking, complete blocking, intermediate blocking, and cake filtration) based on the additivity of the permeate volume contributed by different coexisting mechanisms. A piecewise fitting protocol was established to distinguish the fouling stages and find the significant mechanisms in each stage. This approach was applied to a case study of a microfiltration membrane filtering a model foulant solution composed of polysaccharide, protein, and humic substances, and the model fitting unequivocally revealed that the dominant fouling mechanism evolved in the sequence of initial adaptation, fast adsorption followed by slow adsorption inside the membrane pores, and the gradual growth of a cake/gel layer on the membrane surface. The results were in good agreement with the permeate properties (total organic carbon, ultraviolet absorbance, and fluorescence) during the filtration process. This modeling approach proves to be simple and reliable for identifying the main fouling mechanisms during membrane filtration with statistical confidence.
32
Koo, Chai Hoon, Abdul Wahab Mohammad, Fatihah Suja' e Meor Zainal Meor Talib. "Comparative Assessment of Membrane Fouling Propensity Using Colloidal Silica as Foulant". Applied Mechanics and Materials 209-211 (ottobre 2012): 1995–98. http://dx.doi.org/10.4028/www.scientific.net/amm.209-211.1995.
Testo completoAbstract (sommario):
Other than silt density index (SDI), modified fouling index (MFI) is claimed as one of most useful fouling predictive tools in the practice of reverse osmosis. In this study, the effect of colloidal silica particles on the MFI value with the presence of crossflow sampler (CFS) cell at the upstream of MFI setup was systematically investigated. Colloidal silica with the particle size ranging from 70-100 nm was used as the model foulant in this experiment. The feed silica suspension was 0, 50, and 200 mg/L. The effect of membrane pore size as the test membrane in the dead-end cell on the fouling indices was also studied. Polyvinylidene fluoride (PVDF) membranes with molecular weight cut-offs of 150 and 100 kDa were employed. As predicted, the experiment results demonstrated that the fouling indices increased significantly as the feed silica concentration increased. The CFS-MFI values were always lower than the MFI in all the fouling index tests due to the shear force effect generated under the crossflow filtration mode. The fouling index generated from PVDF100 was higher than that of PVDF150 due to the retention of smaller particles. For this reason, PVDF100 membrane was preferred to be used as the test membrane for fouling index tests using colloidal silica over the PVDF150.
33
Sun, Yuqi, Runze Zhang, Chunyi Sun, Zhipeng Liu, Jian Zhang, Shuang Liang e Xia Wang. "Quantitative Assessment of Interfacial Interactions Governing Ultrafiltration Membrane Fouling by the Mixture of Silica Nanoparticles (SiO2 NPs) and Natural Organic Matter (NOM): Effects of Solution Chemistry". Membranes 13, n. 4 (21 aprile 2023): 449. http://dx.doi.org/10.3390/membranes13040449.
Testo completoAbstract (sommario):
Mixtures of silica nanoparticles (SiO2 NPs) and natural organic matter (NOM) are ubiquitous in natural aquatic environments and pose risks to organisms. Ultrafiltration (UF) membranes can effectively remove SiO2 NP–NOM mixtures. However, the corresponding membrane fouling mechanisms, particularly under different solution conditions, have not yet been studied. In this work, the effect of solution chemistry on polyethersulfone (PES) UF membrane fouling caused by a SiO2 NP–NOM mixture was investigated at different pH levels, ionic strengths, and calcium concentrations. The corresponding membrane fouling mechanisms, i.e., Lifshitz–van der Waals (LW), electrostatic (EL), and acid–base (AB) interactions, were quantitatively evaluated using the extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory. It was found that the extent of membrane fouling increased with decreasing pH, increasing ionic strength, and increasing calcium concentration. The attractive AB interaction between the clean/fouled membrane and foulant was the major fouling mechanism in both the initial adhesion and later cohesion stages, while the attractive LW and repulsive EL interactions were less important. The change of fouling potential with solution chemistry was negatively correlated with the calculated interaction energy, indicating that the UF membrane fouling behavior under different solution conditions can be effectively explained and predicted using the xDLVO theory.
34
Han, Soo-Jin, e Jin-Soo Park. "Understanding Membrane Fouling in Electrically Driven Energy Conversion Devices". Energies 14, n. 1 (3 gennaio 2021): 212. http://dx.doi.org/10.3390/en14010212.
Testo completoAbstract (sommario):
Positively charged (cetylpyridinium chloride), negatively charged (sodium dodecyl sulfate), and non-charged (polyethylene glycol) surfactants are used as potential foulant in reverse electrodialysis systems supplying seawater and river freshwater. Fouling tendency of the foulants to ion-exchange membranes is investigated in terms of the adsorption by electromigration, electrostatic attraction, and macromolecule interaction in reverse electrodialysis systems. According to theoretical prediction of fouling tendency, charged foulants in seawater streams could foul ion-exchange membranes significantly. However, the worst fouling behavior is observed when the charged foulants are present in river streams. As a result of zeta potential measurement, it is found that the Debye length of the charged foulants decreases due to the higher ionic strength of seawater streams and causes to lower net electrostatic effect. It finally results in less fouling tendency in reverse electrodialysis.
35
Gkotsis, Petros K., e Anastasios I. Zouboulis. "Biomass Characteristics and Their Effect on Membrane Bioreactor Fouling". Molecules 24, n. 16 (7 agosto 2019): 2867. http://dx.doi.org/10.3390/molecules24162867.
Testo completoAbstract (sommario):
Biomass characteristics are regarded as particularly influential for fouling in Membrane Bio-Reactors (MBRs). They primarily include the Mixed Liquor Suspended Solids (MLSS), the colloids and the Extracellular Polymeric Substances (EPS). Among them, the soluble part of EPS, which is also known as Soluble Microbial Products (SMP), is the most significant foulant, i.e., it is principally responsible for membrane fouling and affects all fundamental fouling indices, such as the Trans-Membrane Pressure (TMP) and the membrane resistance and permeability. Recent research in the field of MBRs, tends to consider the carbohydrate fraction of SMP (SMPc) the most important characteristic for fouling, mainly due to the hydrophilic and gelling properties, which are exhibited by polysaccharides and allow them to be easily attached on the membrane surface. Other wastewater and biomass characteristics, which affect indirectly membrane fouling, include temperature, viscosity, dissolved oxygen (DO), foaming, hydrophobicity and surface charge. The main methods employed for the characterization and assessment of biomass quality, in terms of filterability and fouling potential, can be divided into direct (such as FDT, SFI, TTF100, MFI, DFCM) or indirect (such as CST, TOC, PSA, RH) methods, and they are shortly presented in this review.
36
Hasegawa, Susumu, Taro Miyoshi, Ryosuke Takagi e Hideto Matsuyama. "Fouling prediction method using TOC and EEM analysis". Water Supply 19, n. 2 (7 giugno 2018): 610–17. http://dx.doi.org/10.2166/ws.2018.108.
Testo completoAbstract (sommario):
Abstract Many studies on membrane fouling have been made and reported, and it has been revealed, based on liquid chromatography organic carbon detection (LC-OCD), that biopolymer is the main foulant in the drinking water treatment process, in which the raw water is taken from a river or a dam. However, measurement by LC-OCD is time-consuming and costly. Therefore, continuous measurement of biopolymer concentration by LC-OCD is not feasible. For this reason, we have not been able to monitor biopolymer continuously and control membrane fouling. The purpose of this study is to find a new fouling index (FR) to control membrane fouling without measuring the biopolymer concentration. Then, we tried to find a correlation between biopolymer and other water components by a multiple regression analysis. As the result, we have suggested the new fouling index (FR) which consists of the sum of the fluorescence intensity within the Region III domain measured by excitation emission matrix (EEM) fluorescence spectroscopy and the concentration of dissolved organic carbon measured by the total organic carbon (TOC) measurement. TOC and EEM are measured easily and continuously. Thus, we can control membrane fouling by monitoring the FR continuously.
37
Peiris, R. H., M. Jaklewicz, H. Budman, R. L. Legge e C. Moresoli. "Characterization of hydraulically reversible and irreversible fouling species in ultrafiltration drinking water treatment systems using fluorescence EEM and LC–OCD measurements". Water Supply 13, n. 5 (1 settembre 2013): 1220–27. http://dx.doi.org/10.2166/ws.2013.130.
Testo completoAbstract (sommario):
The application of the fluorescence excitation-emission matrix (EEM) approach and liquid chromatography–organic carbon detection (LC–OCD) analysis for the characterization of hydraulically reversible and irreversible fouling species, extracted from hollow fiber ultrafiltration (UF) membranes used in drinking water treatment, was demonstrated. Hydraulically reversible and irreversible fouling species were extracted from two pilot UF membrane systems operated in parallel with lake water as the feed. Two membrane cleaning protocols, hydraulic- and chemical-based (NaOCl and citric acid) cleaning, were considered. Colloidal/particulate matter together with protein-like and metal species in water appeared to contribute to the formation of a hydraulically removable fouling layer on the membranes. Hydraulically irreversible fouling, in contrast, was impacted considerably by humic substances (HS) and protein-like matter. The formation of an irreversible fouling layer was also likely influenced by interactions between the colloidal/particulate matter and metal species together with HS and protein-like matter. LC–OCD analysis revealed the presence of predominant levels of lower molecular weight HS-like matter – compared to the HS-like matter commonly present in lake water – in the citric acid extracted foulant fraction. The permeability loss due to hydraulically irreversible UF fouling was considerably greater than the permeability loss due to hydraulically reversible UF fouling. A permanent permeability loss (∼25–35% of the initial permeability) was present even after the application of considerably strong chemical cleaning protocols on both pilot systems. This study indicated that the fluorescence EEM approach can be applied for monitoring and characterization of membrane cleaning procedures and as a potential diagnostic tool for assessing the effectiveness of hydraulic- and chemical-based cleaning protocols employed in UF drinking water treatment operations using rapid off-line measurements. On the other hand, since the LC–OCD analysis technique is a comparatively time consuming method, it may be used for verification of the fluorescence EEM-based results of the foulant fractions.
38
Kweon, J. H., e D. F. Lawler. "Investigation of membrane fouling in ultrafiltration using model organic compounds". Water Science and Technology 51, n. 6-7 (1 marzo 2005): 101–6. http://dx.doi.org/10.2166/wst.2005.0627.
Testo completoAbstract (sommario):
Natural organic matter (NOM) is known to be the worst foulant in the membrane processes, but the complexities of NOM make it difficult to determine its effects on membrane fouling. Therefore, simple organic compounds (surrogates for NOM) were used in this research to investigate the fouling mechanisms in ultrafiltration. Previous research on NOM components in membrane processes indicated that polysaccharides formed an important part of the fouling cake. Three polysaccharides (dextran, alginic acid, and polygalacturonic acid) and a smaller carbohydrate (tannic acid) were evaluated for their removal in softening (the treatment process in the City of Austin). Two polysaccharides (dextran and alginic acid) were selected and further investigated for their effects on membrane fouling. The two raw organic waters (4 mg/L C) showed quite different patterns of flux decline indicating different fouling mechanisms. Softening pretreatment was effective to reduce flux decline of both waters. The SEM images of the fouled membrane clearly showed the shapes of deposited foulants. The high resolution results of the XPS spectra showed substantially different spectra of carbon, C(1s), in the membrane fouled by two raw organic waters. The XPS was beneficial in determining the relative composition of each fouling material on the membrane surface.
39
Meng, Wang, Zhang, Meng, Liu e Wang. "Insights into the Fouling Propensities of Natural Derived Alginate Blocks during the Microfiltration Process". Processes 7, n. 11 (17 novembre 2019): 858. http://dx.doi.org/10.3390/pr7110858.
Testo completoAbstract (sommario):
Membrane technology has been one of the most promising techniques to solve the water problem in future. Unfortunately, it suffers from the fouling problem which is ubiquitous in membrane systems. The origin of the bewilderments of the fouling problem lies in the lack of deep understanding. Recent studies have pointed out that the molecular structure of foulant affects its fouling propensity which has been ignored in the past. In this study, the filtration behaviors of alginate blocks derived from the same source were comprehensively explored. Alginate blocks share the same chemical composition but differ from each other in molecular structure. The alginate was first extracted from natural seaweed using calcium precipitation and ion-exchange methods. Extracted alginate was further fractionized into MG-, MM- and GG-blocks and the characteristics of the three blocks were examined by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) observations, and transparent exopolymer particles’ (TEPs) measurements. Results showed that MG-, MM- and GG-blocks had the same functional groups, but they showed different intermolecular interactions. TEP formation from MG-, MM- and GG-blocks revealed that the molecule crosslinking of them decreased in the order of MM-blocks > GG-blocks > MG-blocks. It was further found from microfiltration tests that these alginate blocks had completely different fouling propensities which can be explained by the TEP formation. TEPs would accumulate on membrane surfaces and worked as a pre-filter to avoid serious pore blocking of membrane. That all suggested that the membrane fouling was closely related to the molecular structure of foulant. It is expected that this study can provide useful insights into the fouling propensities of different types of polysaccharides during filtration processes.
40
Sanguanpak, Samunya, Chart Chiemchaisri, Wilai Chiemchaisri e Kazuo Yamamoto. "Effect of organic fouling on micro-pollutant rejection in membrane bioreactor treating municipal solid waste landfill leachate". Water Science and Technology 72, n. 4 (20 maggio 2015): 561–71. http://dx.doi.org/10.2166/wst.2015.248.
Testo completoAbstract (sommario):
Effect of membrane fouling on the removal of micro-pollutants from municipal solid waste landfill leachate, i.e. 4-methyl-2,6-di-tert-butylphenol (BHT), bisphenol A (BPA), and bis(2-ethylhexyl)phthalate (DEHP), in membrane bioreactor (MBR) was investigated. Modifications of membrane surface properties were analyzed to determine their relationship with their removals. Membrane fouling was simulated with foulants of different particle sizes on cellulose acetate (CA) microfiltration membrane to investigate the effect of foulant characteristics on BHT, BPA, and DEHP retention in the filtration experiment. The rejection efficiencies of the organic micro-pollutants in the MBR were 82–97% by fouled membrane, and 70–90% by cleaned membrane. The fouled membrane provided higher rejection of micro-pollutants from about 5% for BPA and BHT to 19% for DEHP. These improvements were due to the modification of membrane surface characteristics in terms of surface morphology, and contact angle after membrane fouling. The degree of rejection was found to be dependent upon the characteristics of foulant deposited on CA membrane surface. Increasing foulant particle size and its density shifted the mechanism of micro-pollutant rejection from membrane pore narrowing to pore blocking and cake formation while increasing pollutant adsorption capacity onto the foulant layer.
41
Berg, Thilo H. A., Jes C. Knudsen, Richard Ipsen, Frans van den Berg, Hans H. Holst e Alexander Tolkach. "Investigation of Consecutive Fouling and Cleaning Cycles of Ultrafiltration Membranes Used for Whey Processing". International Journal of Food Engineering 10, n. 3 (1 settembre 2014): 367–81. http://dx.doi.org/10.1515/ijfe-2014-0028.
Testo completoAbstract (sommario):
Abstract Development of resistance during multiple foulings and three-step Cleaning-In-Place (CIP) operations, simulating an industrial cleaning regime of polysulfone ultrafiltration membranes, was investigated. The study explored how trans-membrane pressure (150 and 300 kPa) and feed protein concentration (0.9 and 10%) influenced resistance reduction during filtration and flux recovery by the cleaning procedures. New membranes, pre-cleaned with a full CIP cycle, were used for each experiment. Subsequent fouling (simulating production) and CIP were done three times in a row and the development of fouling layer resistance was monitored and evaluated. Results show that filtration performance decreased during the first days of usage, possibly related to build-up of internal fouling. Cleaning success based on flux recovery was negatively influenced by a high protein concentration in the feed, but independent of the trans-membrane pressure during filtration.
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Meng, Shujuan, Hongju Liu, Qian Zhao, Nan Shen e Minmin Zhang. "Filtration Performances of Different Polysaccharides in Microfiltration Process". Processes 7, n. 12 (2 dicembre 2019): 897. http://dx.doi.org/10.3390/pr7120897.
Testo completoAbstract (sommario):
Membrane technology has been widely applied for water treatment, while membrane fouling still remains a big challenge. The polysaccharides in extracellular polymeric substances (EPS) have been known as a significant type of foulant due to their high fouling propensity. However, polysaccharides have many varieties which definitely behave differently in membrane filtration. Therefore, in this study, different polysaccharides alginate sodium and xanthan gum were chosen to study their effects on membrane fouling in a wide concentration range. The results demonstrated that the filtration behaviors of alginate sodium and xanthan gum were completely different, which was due to their different molecular structures. Alginate had a small molecular weight and it was easy for alginate to penetrate membrane pores resulting in pore blocking. A series of concentrations of alginate including 5 mg/L, 10 mg/L, 20 mg/L, 30 mg/L, 40 mg/L, and 50 mg/L were examined and it was found that the permeate flux decline highly depended on the level of alginate in the feed water. While for the filtration of xanthan gum, the same concentration of xanthan gum led to more serious fouling than that observed in alginate, which might be due to its large molecule. In addition, calcium chloride was added in the solutions of both alginate and xanthan gum to examine the influence of a divalent cation on polysaccharide fouling. A “unimodal” peak can be observed in the fouling propensity caused by Ca2+ and alginate with increasing the concentration of alginate. Such a phenomenon was not found in the fouling of xanthan gum and Ca2+ led to more serious fouling for all concentrations of xanthan gum. In light of this, this study gave new insights into the fouling propensities of different polysaccharides.
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Barambu, Nafiu Umar, Muhammad Roil Bilad, Yusuf Wibisono, Juhana Jaafar, Teuku Meurah Indra Mahlia e Asim Laeeq Khan. "Membrane Surface Patterning as a Fouling Mitigation Strategy in Liquid Filtration: A Review". Polymers 11, n. 10 (15 ottobre 2019): 1687. http://dx.doi.org/10.3390/polym11101687.
Testo completoAbstract (sommario):
Membrane fouling is seen as the main culprit that hinders the widespread of membrane application in liquid-based filtration. Therefore, fouling management is key for the successful implementation of membrane processes, and it is done across all magnitudes. For optimum operation, membrane developments and surface modifications have largely been reported, including membrane surface patterning. Membrane surface patterning involves structural modification of the membrane surface to induce secondary flow due to eddies, which mitigate foulant agglomeration and increase the effective surface area for improved permeance and antifouling properties. This paper reviews surface patterning approaches used for fouling mitigation in water and wastewater treatments. The focus is given on the pattern formation methods and their effect on overall process performances.
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Yu, S. L., W. X. Shi, Y. Lu e J. X. Yang. "Characterization and anti-fouling performance of nano-Al2O3/PVDF membrane for Songhua River raw water filtration". Water Science and Technology 64, n. 9 (1 novembre 2011): 1892–97. http://dx.doi.org/10.2166/wst.2011.138.
Testo completoAbstract (sommario):
Polyvinylidene fluoride (PVDF) flat ultrafiltration membranes modified by nano-sized alumina (Al2O3) particles were prepared by phase inversion process and their properties and anti-fouling performances were examined. The influence of three types of natural organic matters on the modified membrane fouling was also studied. Raw water was taken from two different locations, i.e., Harbin and Zhaoyuan, of Songhua River. Dissolved organic compounds in the raw water were fractionated using XAD resins into three fractions, i.e., hydrophobic fraction, transphilic fraction, and hydrophilic fraction (HPI). The three adsorbed compounds were further eluted and dissolved into distilled water respectively to prepare the feed for the fouling tests. All solutions were adjusted to a concentration of 10.6 mg C/L, which equals to the total organic carbon (TOC) of the raw water. Results show that the addition of nano-Al2O3 particulars did not affect the inherent traits of the PVDF membranes, however, its surface hydrophilic properties were improved significantly with the addition of nanoparticles and anti-fouling performance was enhanced as well. The HPIs in the Songhua River were the main foulant, causing more fouling to membrane than hydrophobic and transphilic matters.
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Li, Zihe, Chongde Wu, Jun Huang, Rongqing Zhou e Yao Jin. "Membrane Fouling Behavior of Forward Osmosis for Fruit Juice Concentration". Membranes 11, n. 8 (11 agosto 2021): 611. http://dx.doi.org/10.3390/membranes11080611.
Testo completoAbstract (sommario):
Forward osmosis (FO) technology has a broad application prospect in the field of liquid food concentration because of the complete retention of flavor components and bioactive substances. Membrane fouling is the main obstacle affecting the FO performance and concentration efficiency. This work systematically investigated the membrane fouling behavior of the FO process for fruit juice concentration elucidated by the models of resistance-in-series, xDLVO theory and FTIR analysis. The results show that the AL-FS mode was more suitable for concentrating orange juice. Increasing the cross-flow rate and pretreatment of feed solutions can effectively improve the water flux and reduce the fouling resistance. The ATR-FTIR analysis revealed that the fouling layer of orange juice was mainly composed of proteins and polysaccharides, and the pretreatment of microfiltration can greatly reduce the content of the major foulant. There was an attractive interaction between the FO membrane and orange juice foulants; by eliminating those foulants, the microfiltration pretreatment then weakened such an attractive interaction and effectively prevented the fouling layer from growing, leading to a lower process resistance and, finally, resulting in a great improvement of concentration efficiency.
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Goh, Y. T., J. L. Harris e F. A. Roddick. "Reducing the effect of cyanobacteria in the microfiltration of secondary effluent". Water Science and Technology 62, n. 7 (1 ottobre 2010): 1682–88. http://dx.doi.org/10.2166/wst.2010.482.
Testo completoAbstract (sommario):
Cyanobacterial blooms in the lagoons of sewage treatment plants can severely impact the performance of membrane plants treating the effluent. This paper investigates the impact of Microcystis aeruginosa in a secondary effluent on the microfiltration filterability and cleaning of the membrane. Alum coagulation and dissolved air flotation (DAF) were investigated to remove the algae and so enhance the volume of effluent processed, and their influence on reversible and irreversible fouling. Degree of fouling due to the algal components was found to be in decreasing order of algal cells, algal organic matter and extracellular organic matter. Alum coagulation with 5 mg L−1 as Al3 + led to a substantial increase in permeate volume, an increase in dissolved organic carbon removal, and a foulant layer which protected the membrane from internal fouling but which was hydraulically removable resulting in full flux recovery. Pre-treatment by DAF or 1.5 μm filtration following alum coagulation enhanced the flux rate and permeate volume but exposed the membrane to internal irreversible fouling.
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Jørgensen, Mads Koustrup, e Tuve Mattsson. "Quantifying Charge Effects on Fouling Layer Strength and (Ir)Removability during Cross-Flow Microfiltration". Membranes 11, n. 1 (1 gennaio 2021): 28. http://dx.doi.org/10.3390/membranes11010028.
Testo completoAbstract (sommario):
Fouling of membranes is still an important limiting factor in the application of membrane technology. Therefore, there is still a need for an in-depth understanding of which parameters affect the (ir)removability of fouling layers, as well as the mechanisms behind fouling. In this study, fluid dynamic gauging (FDG) was used to investigate the influence of charge effects between negatively charged foulant particles and cations on cake cohesive strength. Fouling cakes’ thicknesses and cohesive strengths were estimated during membrane operations, where microfiltration (MF) membranes were fouled in a feed-and-bleed cross-flow filtration system with low and highly negatively charged polystyrene–polyacrylic acid core-shell particles. In addition, an added procedure to determine the irremovability of cakes using FDG was also proposed. Comparing layers formed in the presence and absence of calcium ions revealed that layers formed without calcium ions had significantly lower cohesive strength than layers formed in the presence of calcium ions, which is explained by the bridging effect between negatively charged particles and calcium ions. Results also confirmed more cohesive cakes formed by high negative charge particles in the presence of calcium compared to lower negative charge particles. Hence, it was demonstrated that FDG can be used to assess the cohesive strength ((ir)removability) of cake layers, and to study how cake cohesive strength depends on foulant surface charge and ionic composition of the solution.
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Zhang, Wanzhu, Lin Wang e Bingzhi Dong. "Effects of tannic acid on membrane fouling and membrane cleaning in forward osmosis". Water Science and Technology 76, n. 11 (11 settembre 2017): 3160–70. http://dx.doi.org/10.2166/wst.2017.392.
Testo completoAbstract (sommario):
Abstract The fouling behavior during forward osmosis (FO) was investigated. Tannic acid was used as a model organic foulant for natural organic matter analysis since the main characteristics are similar, and calcium ions were added at different concentrations to explore the anti-pollution capability of FO membranes. The initial permeate flux and calcium ions strength were varied in different operating conditions to describe membrane fouling with membrane cleaning methods. The observed flux decline in FO changed dramatically with the type of foulant and the type of draw solution used to provide the osmotic driving force. Calcium ions aggravated membrane fouling and decreased transmembrane flux. Membrane cleaning methods included physical and physicochemical approaches, and there was no obvious difference among the typical cleaning methods (i.e., membrane flushing with different types of cleaning fluids at various crossflow velocities and backwashing with varying osmotic driving forces) with respect to flux recovery. Ultrasonic cleaning damaged the membrane structure and decreased permeate flux, and reverse diffusion of salt from the draw solution to the feed side accelerated after cleaning.
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Pollet, S., C. Guigui e C. Cabassud. "Fouling and its reversibility in relation to flow properties and module design in aerated hollow fibre modules for membrane bioreactors". Water Science and Technology 57, n. 4 (1 marzo 2008): 629–36. http://dx.doi.org/10.2166/wst.2008.113.
Testo completoAbstract (sommario):
Nowadays, most membrane bioreactors are using membranes submerged in the biomass and aeration in the concentrate compartment to limit or to control fouling. An important issue for the design of modules or membrane bundles in MBRs is to understand how the air/liquid flow is behaving and influencing fouling and its reversibility in relationship to the module properties. This paper focuses on an innovative and very specific process, in which HF membranes are put in a cartridge outside the activated sludge tank and a recycling loop is associated to the cartridge in order to decrease concentration of foulant species at the membrane surface and mass transfer resistance. Recycling operates with a very low liquid velocity in the module (a few cm·s−1) which constitutes a specificity of this process in terms of filtration operation. The aim of this study is to characterise two-phase flow and its effects on fouling and fouling reversibility at the scale of a semi-industrial bundle of outside/in hollow fibres, and as a function of bundle properties (packing density, fibre diameter), using specific methods to characterise the flow and fouling effects. Two modules were used showing a different packing density. Filtration was operated at constant permeate flux with clay suspension at 0.65 g·l−1 in the same hydrodynamic conditions. Fouling kinetics and irreversibility were characterised by an adapted step method, and gas and liquid flows were characterised at global scale by residence time distribution analyses and gas hold-up. Fouling velocities are clearly influenced by gas velocity. The proportion of dead to total volume in the module is mainly affected by the liquid flow velocity and module design. The module with the higher fibre diameter and the lower packing density showed better performances in terms of fouling which was correlated with better flow properties.
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Elahi, Arash, e Santanu Chaudhuri. "Computational Fluid Dynamics Modeling of the Filtration of 2D Materials Using Hollow Fiber Membranes". ChemEngineering 7, n. 6 (9 novembre 2023): 108. http://dx.doi.org/10.3390/chemengineering7060108.
Testo completoAbstract (sommario):
The current study presents a computational fluid dynamics (CFDs) model designed to simulate the microfiltration of 2D materials using hollow fiber membranes from their dispersion. Microfiltration has recently been proposed as a cost-effective strategy for 2D material production, involving a dispersion containing a permeating solute (graphene), a fouling material (non-exfoliated graphite), and the solvent. The objective of the model is to investigate the effects of fouling of flat layered structure material (graphite) on the transmembrane pressure (TMP) of the system and the filtration of the permeating solute. COMSOL Multiphysics software was used to numerically solve the coupled Navier–Stokes and mass conservation equations to simulate the flow and mass transfer in the two-dimensional domain. For the TMP calculations, we used the resistance-in-series approach to link the fouling of the foulants to the TMP behavior. The foulant particles were assumed to form a polarization layer and cake on the membrane surface, leading to the increment of the TMP of the system. We also assumed the wettability of the polymeric membrane’s inner wall increases upon fouling due to the flat layered structure of the foulant, which results in the reduction in the TMP. This approach accurately reproduced the experimental TMP behavior with a Mean Absolute Error (MAE) of 0.007 psi. Furthermore, the permeation of the permeating solute was computed by incorporating a fouling-dependent membrane partition coefficient for these particles. The effects of the concentration polarization and cake formation fouling stages on the membrane partition coefficient were encapsulated into our defined model parameters, denoted as α and β, respectively. This formulation of the partition coefficient yielded permeate concentration profiles, which are in excellent agreement with the experiments. For three feed concentrations of 0.05, 0.1, and 0.3 g/L, our model reproduced the experimental permeate concentration profiles with MAEs of 0.0002, 0.0003, and 0.0022 g/L, respectively. The flexibility of this model enables the users to utilize the size and concentration-dependent α and β parameters and optimize their experimental microfiltration setups effectively.