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1
Bali, Rana. "Microfiltration en flux tangentiel : applications et intérêts dans le procédé technologique de transformation de l'orange." Montpellier 1, 1991. http://www.theses.fr/1991MON13522.
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Chen, Jaspe. "Nano-encapsulation de l’amiodarone dans des nanoparticules fonctionnelles pour le ciblage du myocarde et le traitement des arythmies cardiaques." Electronic Thesis or Diss., Angers, 2024. https://dune.univ-angers.fr/documents/dune19169.
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La fibrillation atriale est l’arythmie la plus fréquemment rencontrée et est devenue un enjeu de santé publique croissant. Bien que l’amiodarone soit la plus puissante des molécules antiarythmiques, elle est prescrite seulement en cas de contre-indication ou d’inefficacité des autres antiarythmiques. Son profil pharmacocinétique et son accumulation dans les tissus hautement perfusés et gras est associée à de nombreux effets indésirables lors de traitement chronique. Ainsi, son encapsulation dans des nanocapsules lipidiques fonctionnalisées représente une stratégie prometteuse pour cibler spécifiquement le myocarde et altérer sa biodistribution vers les autres organes. Ce projet met en avant l’importance d’employer des méthodes complémentaires pour la caractérisation fine des formulations multimodales comme celles des nanocapsules lipidiques. La purification des nanocapsules lipidiques par filtration à flux tangentiel a mis en évidence, in vitro et ex vivo, une toxicité associée aux micelles résiduelles présentes dans les formulations initiales de nanocapsules lipidiques. Enfin, ce travail a permis d’initier la fonctionnalisation des nanocapsules lipidiques. Les résultats encourageants démontrent le potentiel de ce peptide antiarythmique comme ligand de ciblage actifAtrial fibrillation is the most encountered arrhythmia and has become an increasingly important public health issue. Although amiodarone is the most potent antiarrhythmic molecule, it is prescribed only in cases of contraindications or ineffectiveness of other antiarrhythmics. Its pharmacokinetic profile and accumulation in highly perfused and fatty tissues are associated with numerous adverse effects during chronic treatment. Therefore, its encapsulation in functionalized lipid nanocapsules represents a promising strategy to specifically target the myocardium and alter its biodistribution to other organs.This project emphasizes the importance of employing complementary methods for the characterization of multimodal formulations such as lipid nanocapsules. The purification of lipid nanocapsules through tangential flow filtration highlighted, both in vitro and ex vivo, a toxicity associated with residual micelles present in the initial formulations of lipid nanocapsules. Finally, this work initiated the functionalization of lipid nanocapsules. The encouraging results demonstrate the potential of this antiarrhythmic peptide as an active targeting ligand
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Espinasse, Benjamin. "APPROCHE THEORIQUE ET EXPERIMENTALE DE LA FILTRATION TANGENTIELLE DE COLLOÏDES : FLUX CRITIQUE ET COLMATAGE." Phd thesis, Université Paul Sabatier - Toulouse III, 2003. http://tel.archives-ouvertes.fr/tel-00201613.
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Si la problématique posée par le colmatage des membranes est ancienne, prévoir et adapter les conditions de filtration pour réduire le colmatage reste essentiel pour un meilleur contrôle du procédé. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique peut être un paramètre clef pour ce contrôle. Dans le cadre de cette étude,nous avons cherché à relier la pression osmotique d'une suspension colloïdale aux valeurs expérimentales du flux critique par le biais de la modélisation du procédé de filtration tangentielle. Une procédure de filtration a été développée pour déterminer de façon précise et rigoureuse le flux critique. Cette méthode permet une détermination continue de la réversibilité de l'accumulation de matière lors d'une diminution de flux permettant ainsi de dissocier expérimentalement la part de diminution de flux due à la pression osmotique et celle due à la résistance irréversible. La caractérisation de la suspension au niveau microscopique (potentiel zêta, taille, etc.) a été complétée par une mesure macroscopique, plus originale, de la pression osmotique particulaire par compression chimique. La pression osmotique de la dispersion colloïdale se révèle être une caractérisation pertinente par rapport à la filtration car relative à la résistance des particules à la surconcentration. Un modèle bidimensionnel adapté calculant les profils de concentration en particules dans un procédé de séparation par membranes est utilisé pour confronter théoriquement les mesures expérimentales de pression osmotique aux valeurs de flux critique. La comparaison des valeurs expérimentales et modélisées de flux critique suggèrent que des hétérogénéités de propriétés physiques de la membrane et des particules doivent être prises en compte. Intégrées dans un modèle descriptif, les distributions de flux permettent d'expliquer les différences entre expérience et simulation de la filtration d'une suspension colloïdale.
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El, Rayess Youssef. "Microfiltration tangentielle appliquée à l'oenologie : compréhension et maîtrise des phénomènes de colmatage." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0089/document.
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La clarification des vins par procédés membranaires en particulier la microfiltration tangentielle a toujours été limitée par le colmatage, générant des flux de perméation faibles incompatibles avec la rentabilité économique. La compréhension, la maîtrise, ainsi que l'anticipation des phénomènes de colmatage font l'objet de ce travail. Dans un premier temps, la contribution individuelle puis en mélange des composés du vin (tannins, pectines, mannoprotéines et levures) au colmatage d'une membrane céramique multicanaux a été évaluée. Une approche fondamentale a permis de proposer des mécanismes de colmatage : la présence des pectines induit les flux de perméation les plus faibles en formant un gel à la surface de la membrane tandis que les levures semblent au contraire avoir un effet protecteur dans le cas d'un vin brut. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique pour l'irréversibilité est un paramètre clef pour contrôler le colmatage. Dans le cas de la filtration de vin, aucun flux critique n'a pu être déterminé ce qui a conduit à définir un critère identifiant une zone de travail où le degré de colmatage reste acceptable. La dernière partie de cette thèse est consacrée à l'étude de la filtration dynamique (RVF) pour une éventuelle application dans le secteur vinicole. Cette technique est testée en présence de deux membranes organiques différentes: PES (hydrophile) et PTFE (hydrophobe). Les observations ont permis de mettre en évidence l'efficacité du système contre le colmatage des membranes PES induite par l'action de l'agitateur. Le colmatage des membranes PTFE est énormément affecté par les interactions molécules/membrane rendant la filtration dynamique inefficace pour lutter contre le colmatage de ces membranesWine clarification by membrane processes mainly cross-flow microfiltration has been limited by membrane fouling generating low permeate fluxes with economic efficiency. Understanding, controlling and anticipation of fouling are the main goals of this work. In a first time, the individual contribution of wine compounds (tannins, pectins, mannoproteins and yeasts) to a multichannel ceramic membrane fouling was evaluated. The fouling mechanisms were analyzed using a fundamental approach. The presence of pectins induce the lowest fluxes by a gel-type formation at the membrane surface while yeasts presence tends to reduce fouling in the case of crude wine (case of mixed components). Because it represents the flux beyond which irreversible fouling appears on the membrane surface, the critical flux for irreversibility is a key parameter to control fouling. No critical flux for irreversibility could be measured, hence a criterion that identifies a range of operating conditions where the degree of fouling remains acceptable was proposed. The last part of this work was devoted to the study of dynamic filtration (RVF) for further application in wine sector. This technique was tested with two different membranes: hydrophilic PES and hydrophobic PTFE. Results have allowed to demonstrate the efficiency of the system to reduce fouling in the case of PES membrane. Fouling of PTFE membrane is greatly influenced by molecules / membrane interaction making dynamic filtration ineffective in reducing of membrane fouling
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Ho, Chia-Chun. "Protection des berges contre l'érosion avec des dispositifs incorporant des géotextiles." Université Joseph Fourier (Grenoble), 2007. http://www.theses.fr/2007GRE10231.
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Dans ce projet, le comportement sous érosion de sols avec les trois conditions de flux a été étudié avec des essais utilisant un équipement développé pour chaque condition. Les résultats révèlent qu'un écoulement souterrain dans la zone de flux unidirectionnel peut provoquer l'érosion interne et qu'une partie des particules de sol entraînées peut passer à travers les ouvertures du géotextile. Le reste de ses particules peut se colmater à géotextile ou s'accumuler derrière le géotextile, formant une couche filtrante naturelle et réduisant la vitesse de l'écoulement. La zone de flux cyclique bidirectionnel peut être identifiée en fonction des conditions de : flux cylique à court terme et à long terme. Les résultats d'essais dans un canal avec des conditions de flux cycliques à court terme révèlent que le sol de la couche supérieure de la zone est soumis à la charge cyclique des vagues, ce qui peut entraîner un excès de pression interstitielle et aboutir à l'écroulement, tandis que le sol dans la couche moyenne peut être érodé par le flux tangentiel et accumulé en aval. Les résultats de flux cyclique bidirectionnel à long terme, pour une période de flux cyclique longue, on ne s'attend donc à aucune érosion. Cependant, quand la vitesse d'infiltration augmente, ils causant un phénomène de boulance et un entraînement considérable de sol ainsi que le tassement de celui-ci. Dans la zone de flux tangentiel a été étudié avec l'instrument d'essai d'érosion parallèle. Une couverture géotextile appropriée sur la surface du revêtement peut non seulement éviter l'érosion, mais aussi former une couche filtrante naturelle au-dessous du géotextile qui empêche que l'érosion du sol continueLn this project, the soil erosion behavior under three flow conditions was studied by tests using the equipment developed respectively. The test result reveals that ground water seepage in the uni-dÎrectional flow zone may cause the internai erosion, and part of the soil particles may be lost through the openings of the geotextile, and the rest may be clogged inside the fibers of the geotextile or accumulated behind the geotextile, forming a natural filter layer and thereby causing the decrease of seepage velocity. Bi-directional cyclic flow zone can be categorized into short term and long-term cyclic flow conditions. The result of large-scale tank test for short term cyclic flow conditions reveals that the soil În the upper layer is subject to the cyclic wave loadings which may trigger higher excess pore pressure and result in collapse, while the soil in the middle layer may be eroded by the tangential flow along the riverbank and accumulated downstream. The test results using bi-directional cyclic flow instrument show that under the long-term bi-directional cyclic flow action, if the cyclic flow period is considerably long, no erosion is expected. However, as long as the seepage velocity increases, it will cause boiling and triggering considerable loss of soil and settlement. Erosion behavior in the tangential flow zone was studied with the parallel erosion test instrument. A suitable geotextile covered on the surface of the revetment cannot only avoid the erosion but also form a natural filter layer underneath the geotextile which prevent the soil from continuous erosion. Once the natural filter layer is completely formed, the revetment will be stabilized
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Karisiddappa, Anoop M. "Study of Filtration Characteristics of Crossflow Filtration for Cable Suspended Robot - Algae Harvester." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1470825680.
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Higino, Jane Sheila. "Influence de la microfiltration en flux tangentiel sur la composition chimique de solutions extractives d'eucaplyptus globulus labill. Et d'atropa belladonna l." Montpellier 1, 1994. http://www.theses.fr/1994MON13506.
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Valentine, Mark Edward. "Fundamental flux enhancement modelling of membrane microfiltration." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:f1b0388e-25b9-4038-be04-360b1414d172.
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Membrane filtration is used in a variety of industries, including water treatment and the food industry. Membrane systems include microfiltration and reverse osmosis processes. Membranes used in reverse osmosis are nonporous or pores at 0.2-2 A. This work will focus on mechanical microfiltration. These filtration systems suffer from an accumulation of the rejected material near the membrane surface. This causes additional resistance to the flow through the membrane (flux), resulting in a decline in the performance of the system. Sparging gas bubbles into the mixture has been shown to improve performance. The flow field promotes the transport of material away from the membrane surface and into the bulk. The goal is to predict the sparging that will achieve the maximum flux. Existing flux prediction models often assume steady shear at the membrane surface but in bubbling regimes the shear stresses are unsteady. In this thesis a model is developed to calculate the flux based not solely on shear but on the behaviour and resistance of suspended particles in a gas-liquid flow field. The bubble shape and flow field is calculated using computation fluid dynamics (CFD). The flow around a bubble in gap between two parallel flat sheet membranes is investigated. The calculated bubble shape correlates well with the results seen in experiments. The bubble rise velocity with respect to gap width is shown to transition between that expected in the literature for extended flow for large gap widths and that for a two dimensional case for smaller gap widths. The transitional region however, does not behave as may be expected. The rise velocity does not monotonically decrease as the gap width is reduced. The particle concentration is found by the solution of the convection-diffusion equation, where the convection velocity terms are given by the results of the CFD calculation. The permeate flux is then calculated using a resistance model giving the enhancement due to the bubble. The model is also applied to single phase crossflow. As the shear stresses are steady in this single-phase flow regime, established membrane shear linked mass-transfer coefficient methods can be employed. Good agreement is found between the model and theory. The flux results obtained when the model is applied to the flow around the bubble show a peak in performance with respect to the gap between the membranes for a given bubble volume. The optimal flux enhancement is found to correlate well with the bubble size compared to the flow area. The results show a bubble width of around 60% of the flow width provides the best flux performance.
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Chan, Robert Chemical Engineering & Industrial Chemistry UNSW. "Fouling mechanisms in the membrane filtration of single and binary protein solutions." Awarded by:University of New South Wales. Chemical Engineering and Industrial Chemistry, 2002. http://handle.unsw.edu.au/1959.4/18832.
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In this study the fouling mechanisms of various microfiltration and ultrafiltration membranes were studied when subjected to crossflow filtration using various protein solutions. Experimentation was carried out using controlled flux experiments and fouling phenomena was investigated via the monitoring of the transmembrane pressure (TMP) and rejection. Electron microscopy was employed to study fouling on microfiltration membranes when single protein solutions were filtered while a novel method involving Matrix-Assisted Laser Desorption Ionisation Mass Spectrometry (MALDI-MS) was developed to qualitatively and quantitatively analyse mixed proteins fouled on ultrafiltration membranes. An apparent critical flux was identified whereby fouling was shown to occur at fluxes where there was no increase in TMP. TMP increase is one of the common indicators of fouling in controlled flux operation. Microfiltration experiments showed that the imposition of the apparent critical flux is accompanied by rapid increases in hydraulic resistance and the membrane wall concentration. Pore blockage and narrowing occurred at somewhat higher fluxes as indicated by increases in the observed rejection. Fouling was not influenced greatly by the addition of electrolytes for microfiltration membranes but observed transmissions were found to be greater than 100% when ultrafiltration membranes were employed. For all membranes used, the actual value of the apparent critical flux was shown to be independent of the salt concentration but dependent on pH. Sub apparent-critical constant flux microfiltration showed the existence of an aggregation/deposition time lag after which the membrane experiences a rapid increase in resistance due to protein aggregates blocking a majority of pores. This phenomenon was shown to be dependent on pH and ionic strength and was concluded to be the product of a balance between electrostatic, solubility and hydrophobic interactions.
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DUBOURG, DERAIN LAURENCE. "Evolution de la fonction renale apres transplantation de rein chez l'enfant." Lyon 1, 1994. http://www.theses.fr/1994LYO1M069.
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Faghihi, Mohammad Hosein. "Effect of Pore Geometry on Membrane Flux Decline due to Pore Constriction by Particles in Ultra and Micro Filtration." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24296.
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Membrane separation is known as an economic and environmental friendly mode of separation and is used in various types of separation processes. The major challenges regarding membrane separation are the internal and external fouling of the membrane which reduces the permeate flux of the membranes by inducing extra resistance to flow.
Synthetic membranes are designed and implemented to separate solutes or particles in a feed stream by rejecting them and permitting the liquid to pass through the membrane pores; however, most of the feed streams, such as wastewaters, contain more than one type of solute. This yields a distribution of particle sizes in the feed. Many wastewaters contain supracolloidal particles (1-100µm). Most membrane separations aim to remove these particles from the feed solution. Wastewaters also contain colloidal particles (0.001-1µm). These particles are less concentrated than supracolloidal particles in the feed but they are more problematic since they are able to penetrate into the membrane pores and cause internal fouling which is the main source of irreversible flux decline.
Fouling mechanisms are traditionally classified into four types. Among these mechanisms, standard pore blocking (pore constriction) refers to internal fouling while the other types model external fouling. On the effect of pore geometry, as a morphological factor, studies to date have been limited to external membrane fouling. However, it is believed that up to 80% of the permeate flux can be affected by pore constriction which is caused by particle penetration and deposition into membrane pores (internal fouling).
The effect of pore geometry, as a factor, in flux decline due pore constriction of membranes was investigated in this work. Pore constriction by particles was approximated by maximum particle deposition onto the interior wall of the pores and simulated using MATLAB image processing toolbox (MIPT). Sixteen different basic geometries were considered for the simulation of pore constriction by particles. These include circular pores, 3 groups of rectangular, triangular and oval geometries at four different aspect ratios (3, 7, 15 and 30) and three combined geometries of star, cross and a rectangle with rounded ends. The simulation of maximum particle deposition onto pore walls was carried out for a range of particle diameters to pore hydraulic diameters (λ) of 0.1 to the complete rejection of the particle by the pore. As the result of the simulation, the ratio of the available pore cross-sectional area after pore constriction to initial pore cross-sectional area (α) and the ratio of pore channel hydraulic diameter after pore constriction to initial pore hydraulic diameter (β) were measured and recorded. It was observed that for λ<0.2 (small particles compared to pore size) some geometries showed the same values of α and β. However, for λ>0.2, other geometries showed different values of α and β. It was also observed that several geometries reject the particle at different λ ratios.
Using the values of α and β, the fluxes of membranes having different pore geometries, after pore constriction by particles, were calculated and compared. These results show that for a very small particle size, compared to pore size, there is no preference for a specific geometry over another; however, for intermediate particle sizes, membranes having triangular and star pore shapes provide higher fluxes compared to other membranes. The effect of pore aspect ratio (PAR) on the flux of membranes after pore constriction was also examined.
In order to compare the combined effect of pore geometry on particle rejection and pore constriction, fluxes of membranes having different pore shapes were compared in light of several pore size distributions (PSDs). For this part of the study, the pore geometries of circular, rectangular, triangular and oval were considered at four PARs. Different values for the hydraulic diameter of the largest rejecting pore (D_(H,LRP)) were observed for different geometries. Rectangular pores showed the largest values of D_(H,LRP), at a constant PAR, which affirms their superior rejection behavior. The overall flux of the membranes after pore constriction was determined by a combination of three effects: the position of D_(H,LRP) in the PSD, the pore constriction behavior of the pore geometry and the shape of the PSD. Generally, for the PSDs for which most of the pores in the membrane physically reject the particles, membranes having rectangular pores showed higher fluxes, due to the greater rejection of particles. However, for PSDs for which a major number of pores are constricted by the particles, membranes with triangular pores offered higher flux after membrane pore constriction. The results of this work indicate a new direction for the design of membranes having defined pore geometries.
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Neal, Peter Ross Chemical Sciences & Engineering Faculty of Engineering UNSW. "An examination of the nature of critical flux and membrane fouling by direct observation." Awarded by:University of New South Wales. School of Chemical Sciences and Engineering, 2006. http://handle.unsw.edu.au/1959.4/30584.
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Securing water in the right quantities at the right quality for the right price is a major issue around the world. Membranes are making an increasingly important contribution to meeting this need; however their performance is limited by fouling. This thesis reports on an investigation into the fouling of systems related to water treatment using the Direct Observation Through the Membrane (DOTM). The investigation focused on the measurement of critical flux and observation of particle behaviour under a variety of conditions and for a number of different particles. The range of meanings attributed to critical flux in the literature was analysed and several proposals made for the improved use of the concept. In particular, critical flux determination techniques were classified by whether they measure resistance changes or particle deposition; leading to the definition of Critical Resistance and Critical Deposition Fluxes. In this thesis the deposition definition is used exclusively. The effect of Reynolds number and spacer orientation on critical flux was correlated for spacer-filled channels. The heterogeneous deposition patterns observed with regions of heavy deposition next to areas of little or no deposition. This pattern was related to the local hydrodynamics of spacer cells (a few mm2 in size). The correlations developed for critical flux in spacer-filled channels were adjusted for submicron particle size and incorporated into a SpiralWound Module (SWM) leaf model and then used to simulate the fouling of SWM leaves under a range of operating conditions and operating policies. The Mass Balance technique of critical flux determination was also briefly assessed. The applicability of critical flux criteria to SWM arrays was discussed. Fouling, particle behaviour and critical flux were also investigated in air-sparged systems. The post-cleaning water flux was found to be enhanced when the membrane is fouled in the presence of bubbles. The rate of flux decline was reduced by bubbles. Critical flux increased with air flowrate, and decreased with increased liquid flowrate and concentration. Bubbles caused particles to periodically deposit on the membrane. Particles were observed to stream past the membrane under the influence of back-diffusive forces. Video clips of particulate fouling are provided.
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Luo, Jianquan. "Traitement d'effluents industriels par filtration membranaire dynamique à fort cisaillement." Compiègne, 2012. http://www.theses.fr/2012COMP2026.
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La filtration membranaire est facile à combiner avec d’autres technologies pour traiter les eaux usées industrielles, en produisant de l'eau réutilisable et en récupérant des composants organiques/inorganiques. Le déclin du flux à cause de la polarisation de concentration et du colmatage de la membrane est une limitation importante dans l'application des technologies membranaires pour traiter les eaux usées. Afin de contrôler le déclin du flux, la filtration membranaire à fort cisaillement a été utilisée pour traiter les eaux usées de nettoyage et laitières dans ce travail. Les comportements du flux, les mécanismes de colmatage, le rôle des polluants et les stratégies de contrôle du colmatage dans le traitement des eaux usées par la filtration membranaire avec un cisaillement amélioré ont été étudiés pour fournir de précieuses informations pour les applications industrielles. Le déclin du flux dans le traitement des eaux usées détergentes par nanofiltration (NF) peut être restreint lorsque la couche de polarisation de concentration tensioactive est éliminée par un taux de cisaillement élevé sur la membrane. L’augmentation du pH a eu un effet positif en augmentant la répulsion électrostatique entre les molécules de surfactant et de la membrane. Le colmatage de la membrane peut être éliminé par un rinçage à l'eau, et la perméabilité membranaire récupérée complètement sans nettoyage chimique. Le colmatage des membranes dans le traitement des eaux usées laitières est plus compliqué. Avec un taux de cisaillement et une pression élevés, un léger déclin du flux dû à l'adsorption des polluants (le lactose, les ions multivalents de sel et leurs agrégats) est observé. Pendant cette phase, le colmatage par adsorption en surface, le rétrécissement et le colmatage des pores, régis par l’interaction de polluants-membrane, sont les mécanismes principaux de réduction du flux. En l'absence de nettoyage chimique, ce colmatage par adsorption peut induire la formation d’un gâteau par des agrégats de protéines et du calcium, ce qui entraîne un fort déclin du flux. Un prétraitement par ultrafiltration (UF) peut réduire le colmatage des membranes de NF à un taux de cisaillement faible à cause de l'élimination des caséines et des protéines de lactosérum, alors qu'il a un effet négatif sur la NF lorsque que le taux de cisaillement est élevé. Nous avons proposé les conditions opératoires suivantes : conditions hydrodynamiques extrêmes et celles d’un flux de seuil (threshold flux). La condition extrême signifie l’application d’un taux de cisaillement élevé et d’une pression de 40 bar, tandis que le fonctionnement au flux de seuil consiste à limiter le flux pour réduire le colmatage (le point au-dessus duquel le flux cesse d'augmenter linéairement avec la pression transmembranaire). Le premier mode donne un flux très élevé et une bonne qualité du perméat, mais le deuxième est intéressant pour des tests de longue durée grâce à un faible déclin du flux. Il peut être conclu qu’en utilisant la filtration dynamique, le déclin du flux peut être parfaitement contrôlé par l’application d’un fort taux de cisaillement sur la membrane. L’opération en conditions extrême avec un nettoyage chimique approprié et l’opération du flux de seuil avec un colmatage faible, sont deux choix possibles pour la filtration dynamique à fort cisaillement. La comparaison et l'applicabilité de ces deux opérations doivent encore être étudiéesMembrane filtration is easy to combine with other technologies to treat industrial wastewater, for the production of reusable water and the reutilization of organic/inorganic components. But flux decline due to concentration polarization and membrane fouling is an important limitation in applying membrane technologies to recycle wastewater. In order to reduce flux decline, shear-enhanced membrane filtration was used to treat detergent and dairy wastewaters in this work. Flux behaviors, fouling mechanisms, foulant roles and control strategies in recycling wastewater by shear-enhanced membrane filtration were investigated to provide useful information for industrial applications. The flux decline in the treatment of detergent wastewater by nanofiltration (NF) could be controlled as the surfactant concentration polarization layer was reduced by high shear rate on the membrane. Increasing feed pH had a positive effect by enhancing electrostatic repulsion between surfactant molecules and membrane. The membrane fouling layer could be broken up by water rinse, and thus membrane permeability could be fully recovered without any chemical cleaning. Membrane fouling in the treatment of dairy wastewater was more complicated. When operating at high shear rate and pressure, after a stable flux period, a slow flux decline caused by surface adsorption of foulants (lactose, multivalent salt ions and their aggregates) occurred. In this adsorption fouling stage, pore narrowing and blocking governed by foulant–membrane interaction were the main fouling mechanisms. In absence of chemical cleaning, this adsorption fouling could induce cake fouling formation by proteins-calcium aggregates, resulting in severe flux decline. Ultrafiltration (UF) pretreatment could reduce NF membrane fouling at low shear rate due to the elimination of caseins and whey proteins, while it had a negative effect on NF of UF permeate at high shear rates. Two new membrane operations, i. E. At extreme hydrodynamic conditions and threshold flux conditions, were proposed. Extreme hydrodynamic conditions consists in high shear rate and high applied pressure (up to 40 bar), while threshold flux operation implies limiting the flux to reduce fouling (the point above which flux ceases to increase linearly with transmembrane pressure). The former had high process efficiency and good permeate quality, but the latter is advantageous in long-term runs due to low flux decline. It can be concluded that, using shear-enhanced membrane filtration, flux decline can be well controlled by its high shear rate on the membrane. Extreme hydrodynamic operation with suitable chemical cleaning and threshold flux operation with low fouling rate, are two possible choices for dynamic shear-enhanced membrane process. The comparison and applicability of these two operations need to be further studied
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Mohaghegh, Motlagh Seyed Amir H. "An Investigation into the Impact of Cell Metabolic Activity on Biofilm Formation and Flux Decline during Cross-flow Filtration of Cellulose Acetate Ultrafiltration Membranes." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310138074.
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Robles, Martínez Ángel. "Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater." Doctoral thesis, Editorial Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/34102.
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El reactor anaerobio de membranas sumergidas (SAnMBR) está considerado como tecnología
candidata para mejorar la sostenibilidad en el sector de la depuración de aguas residuales,
ampliando la aplicabilidad de la biotecnología anaerobia al tratamiento de aguas residuales de
baja carga (v.g. agua residual urbana) o a condiciones medioambientales extremas (v.g. bajas
temperaturas de operación). Esta tecnología alternativa de tratamiento de aguas residuales es
más sostenible que las tecnologías aerobias actuales ya que el agua residual se transforma en
una fuente renovable de energía y nutrientes, proporcionando además un recurso de agua
reutilizable. SAnMBR no sólo presenta las principales ventajas de los reactores de membranas
(i.e. efluente de alta calidad, y pocas necesidades de espacio), sino que también presenta las
principales ventajas de los procesos anaerobios. En este sentido, la tecnología SAnMBR
presenta una baja producción de fangos debido a la baja tasa de crecimiento de los
microorganismos implicados en la degradación de la materia orgánica, presenta una baja
demanda energética debido a la ausencia de aireación, y permite la generación de metano, el
cual representa una fuente de energía renovable que mejora el balance energético neto del
sistema. Cabe destacar el potencial de recuperación de nutrientes del agua residual bien cuando
el efluente es destinado a irrigación directamente, o bien cuando debe ser tratado previamente
mediante tecnologías de recuperación de nutrientes.
El objetivo principal de esta tesis doctoral es evaluar la viabilidad de la tecnología SAnMBR
como núcleo en el tratamiento de aguas residuales urbanas a temperatura ambiente. Por lo tanto,
esta tesis se centra en las siguientes tareas: (1) implementación, calibración y puesta en marcha
del sistema de instrumentación, control y automatización requerido; (2) identificación de los
parámetros de operación clave que afectan al proceso de filtración; (3) modelación y simulación
del proceso de filtración; y (4) desarrollo de estrategias de control para la optimización del
proceso de filtración minimizando los costes de operación.
En este trabajo de investigación se propone un sistema de instrumentación, control y
automatización para SAnMBR, el cual fue esencial para alcanzar un comportamiento adecuado
y estable del sistema frente a posibles perturbaciones. El comportamiento de las membranas fue
comparable a sistemas MBR aerobios a escala industrial. Tras más de dos años de operación
ininterrumpida, no se detectaron problemas significativos asociados al ensuciamiento
irreversible de las membranas, incluso operando a elevadas concentraciones de sólidos en el
licor mezcla (valores de hasta 25 g·L-1
). En este trabajo se presenta un modelo de filtración
(basado en el modelo de resistencias en serie) que permitió simular de forma adecuada el proceso de filtración. Por otra parte, se propone un control supervisor basado en un sistema
experto que consiguió reducir el consumo energético asociado a la limpieza física de las
membranas, un bajo porcentaje de tiempo destinado a la limpieza física respecto al total de
operación, y, en general, un menor coste operacional del proceso de filtración.
Esta tesis doctoral está integrada en un proyecto nacional de investigación, subvencionado por
el Ministerio de Ciencia e Innovación (MICINN), con título ¿Modelación de la aplicación de la
tecnología de membranas para la valorización energética de la materia orgánica del agua
residual y la minimización de los fangos producidos¿ (MICINN, proyecto CTM2008-06809-
C02-01/02). Para obtener resultados representativos que puedan ser extrapolados a plantas
reales, esta tesis doctoral se ha llevado a cabo utilizando un sistema SAnMBR que incorpora
módulos comerciales de membrana de fibra hueca. Además, esta planta es alimentada con el
efluente del pre-tratamiento de la EDAR del Barranco del Carraixet (Valencia, España).Robles Martínez, Á. (2013). Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34102
Alfresco
Premiado
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Uzal, Nigmet. "Recovery And Reuse Of Indigo Dyeing Wastewater Using Membrane Technology." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609000/index.pdf.
Full textAbstract:
The objective of this study is to develop a membrane-based generic treatment scheme for wastewaters of indigo dyeing process of denim industry, based on water reuse. For this purpose, firstly the performances of microfiltration (MF), coagulation, and ultrafiltration (UF) processes were evaluated as pretreatment alternatives and the best pretreatment alternatives appeared to be single stage 5 µm MF and sequential 5 µ
m MF followed by 100 kDa UF providing high permeation rate and high color retention. These two pretreatment alternatives were compared based on the performance of nanofiltration (NF) using NF 270 membrane, and the best pretreatment process was evaluated as 5 µ
m MF that provided 87-92% color and 10% chemical oxygen demand (COD) retention. After the pretreatment tests, three different NF (NF 270, NF 90, Dow Filmtec, USA and NF 99, Alfa Laval, Denmark) and two different reverse osmosis (RO) membranes (HR 98 PP and CA 995 PE, Alfa Laval, Denmark) were tested to produce reusable water. Permeate COD and color performances of the tested NF and RO membranes were similar and satisfactory in meeting the relevant reuse criteria, while permeate conductivity was satisfactory only for HR 98 PP RO membrane and for NF 90 membrane. On the other hand, NF 270 membrane was superior to the other membranes in terms of permeation rate. For NF 270 membrane
cumulative color, COD and conductivity retentions were found to be 93 %, 92 %, and 60 %, respectively. When the developed process chain (5µ
m MF+ NF 270) was also tested for a dilute indigo dyeing wastewater, it was found out that the developed scheme works similarly and is generic for indigo dyeing wastewaters.
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Marelli, Luana Maria. "Desenvolvimento e estudo de um reator UASB com unidade de filtração, utilizado para o tratamento de esgoto sanitário." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-01032007-140140/.
Full textAbstract:
Para o tratamento de esgoto sanitário foi desenvolvido e estudado um reator UASB (Upflow Anaerobic Sludge Blanket), associado com unidade de filtração. O estudo se iniciou pela operação do reator UASB durante 642 dias, onde a fase líquida afluente e efluente foi monitorada. Em seguida uma unidade de filtração foi acoplada ao reator UASB e foram avaliados as características de filtração, o desempenho do tratamento e a eficiência do processo de limpeza química de três filtros. Os materiais poliméricos utilizados como filtros foram o polipropileno, o poliéster e o geossintético de poliéster, com diâmetro médio de poros de um mícron (1μm). As características de filtração avaliadas foram o fluxo do permeado e os mecanismos de obstrução de cada material polimérico (resistência à filtração: total, do material, da camada de biossólidos e de entupimento). O desempenho global do sistema de tratamento foi avaliado em termos de remoção de demanda química de oxigênio (DQO) e de sólidos suspensos totais (SST). Para recuperação dos filtros foi utilizada primeiramente a limpeza química com solução ácida (ácido clorídrico-HCl) e em série a limpeza com solução alcalina (hipoclorito de sódio e hidróxido de sódio- NaOCl e NaOH). Dentre os três materiais poliméricos utilizados verificou-se que, o geossintético (poliéster) foi o filtro que apresentou melhores características de filtração e desempenho global, ou seja, com este material a resistência da camada foi predominante (obstrução é reversível), a concentração de sólidos suspensos totais do permeado estabilizou em 25 mg/L e a eficiência média global de remoção da demanda química de oxigênio (DQO) foi de 78%. Dentre os procedimentos de limpeza química utilizada nos três filtros, verificou-se que a solução ácida (HCl) aplicada em série com a solução alcalina (NaOCl e NaOH) apresentou maior eficiência que a limpeza somente com a solução ácida (recuperação do fluxo inicial do permeado acima de 90%).An anaerobic reactor (UASB Upflow Anaerobic Sludge Blanket) coupled to a filtration unit for the treatment of domestic sewage was developed and studied. The study began by operating the UASB reactor for 642 days, during which time the influent and effluent liquid phase were monitored. The filtration unit was then coupled to the UASB reactor and the filtration characteristics, the performance of the treatment, and the efficiency of the cleaning process of three polymeric filters were evaluated. The polymeric materials used for the filters were polypropylene, polyester and geosynthetic polyester, all with an average pore size of one micron (1μm). The filtration characteristics evaluated were the permeate flux and the fouling mechanisms (total filtration resistance of the material and the cake, and clogging) during filtration. The systems overall performance was evaluated in terms of chemical oxygen demand (COD) and removal of total suspended solids (TSS). The filters were cleaned chemically, first with an acid solution (HCl), followed by alkaline solutions (NaOH and NaOCl) applied in series. A comparison of the three filtering materials indicated that the geosynthetic material (polyester) possessed the best overall characteristics of filtration and performance. In other words, i.e., cake resistance (reversible fouling) predominated with this material, the concentration of total suspended solids (TSS) in the permeate stabilized at 25 mg/L, and the overall removal efficiency of chemical oxygen demand (COD) was 78%. Of the various chemical cleaning procedures tested on the three polymeric filters, the acid (HCl) and alkaline solutions (NaOH and NaOCl) applied in series provided more efficient flux recovery (over 90% of the initial permeate) than chemical cleaning only with acid (HCl).
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Estime, Nicolas. "Contrôle des propriétés des cristaux d'un principe actif pharmaceutique dans la chaîne précipitation - filtration - séchage : vers un procédé continu." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0069.
Full textAbstract:
Les travaux de cette thèse portent sur le développement d'une méthodologie permettant le passage au continu d'une production de cristaux d'un principe actif pharmaceutique : l'acétyl-L- leucine. Le travail est centré sur l'étape de précipitation et ses interactions avec les procédés en aval de filtration / lavage et séchage. La démarche adoptée fut donc d'abord d'acquérir un ensemble de données analytiques et thermodynamiques sur les produits, sous-produits et cristaux. L'impact de plusieurs paramètres opératoires sur la solubilité du produit fut ainsi mis en évidence. D'autre part, on a montré que l'acétyl-DL- eucine cristallise sous la forme d'un conglomérat. Des études ont ensuite été réalisées sur les procédés en discontinu, notamment sur les étapes de précipitation et de lavages, afin d'identifier les paramètres permettant de contrôler au mieux la qualité finale des cristaux. Enfin, à partir de ces résultats, des essais de précipitation en continu ont pu être réalisés à l'échelle du laboratoire, puis à l'échelle industrielle sur l'ensemble de la chaîne de production du principe actifThis study deals with the development of a methodology allowing to transform a batch precipitation process in a continuous one. The active substance considered is acetyl-L-leucine. The work is focused on the precipitation step but also considers the interactions with the downstream processes of filtration, washing and drying. In a first part, characterization methods of pure and impure solutions of active substance were developed as well as methods for determining the crystals properties (purity, size, size distribution, shape, ...). Then the solubility of the product was investigated and the influence of parameters such as temperature, pH, impurity concentration, was studied. The crystallization mode of the racemic mixtures was also determined . Finally, batch crystallization was carried out at the laboratory scale in order to determine nucleation kinetics and to understand the main operating parameters influencing the quality of the crystals. For the applied range of concentrations, the induction time was found very small and indicates that the control of the nucleation step is difficult and depends on the mixing of the reactants. The whole continuous process was finally designed and tested, from the initial reactive to the final dry ZPI powder, in industrial site to validate the feasibility of the continuous process
19
Morganti, Teresa Maria. "In situ direct study of filtration and respiration rate of Mediterranean sponges = Estudio in situ de la filtración y la respiración de esponjas mediterráneas." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/397747.
Full textAbstract:
Sponges play important roles in the functioning of marine ecosystem in which they are abundant. These roles range from stabilizers of substrate, to acting as major link between benthic and pelagic realms by filtering large quantities of water and retaining the particles with high efficiency. Despite sponges have been the focus of much interest in the past years our knowledge on sponge physiology is still poorly understood. This study focused on ecophysiology of five of the most prominent sponge species dwelling the coralligenous community in the NW Mediterranean Sea, and employed an energetic approach to understanding the complex interactions between physiological constrains and seasonal fluctuations of environmental factors experienced by the organism under natural conditions. In this thesis, we contributed to the still limited knowledge of energetic mechanisms that regulate seasonal dynamics and elucidated divergent metabolic profiles between high microbial (HMA) and low microbial (LMA) abundance species accordingly to their different adaptive life strategies. For this purpose we examined the in situ feeding, filtering and respiration activity over annual cycle. Firstly, we started by developing a system for quantifying the particulate and dissolved compounds processed by sponges under natural conditions. In terms of feeding, we observed that all species retained plankton at high efficiency and DOC was the main source of carbon. However, the nitrogen fluxes showed a marked different trophic niche between the two groups: HMA species mostly relied on dissolved compound as main source of N, while LMA solely relied on particulate fractions. Interestingly, natural variation of sponge pump did not follow natural temperature changes. During the period of maximum temperature the sponge pump did not reach its maximum values, suggesting that intrinsic mechanism as a decrease in choanocytes during reproductive cycle may regulate this metabolic process. On the other hand respiration clearly showed a seasonal pattern following natural temperature fluctuation. Combined, these results allowed us to estimate the overall energy budget, which appeared to be regulated by an increase of energy demand in summer as well as the availability of dissolved organic carbon fraction in the water column. Our result also showed different limited energetic profiles between HMA and LMA species accordingly to their different feeding strategies. LMA species appeared to procure sufficient energy to meet metabolic requirements for maintenance and growth by filtering suspended particulates, and dissolved fraction represented an additional input of carbon when available. On the contrary the heterotrophic nutrition in the natural environment may be insufficient to meet basal metabolic requirements in HMA species, suggesting other metabolic pathways as relevant for the energy budget of these species.Les esponges juguen un paper important en el funcionament del ecosistemes marins on hi son abundants. Les funcions atribuïdes a les esponges son molt diverses i inclouen entre altres actuar com estabilitzadores del substrat, així com fer de lligam entre la columna d'aigua i el bentos en l'anomenat acoblament bento-pelàgic; aquest procés te lloc mitjançant una captura eficient de partícules i el retorn de compostos modificats per l'activitat metabòlica de les esponges. Tot i que les esponges han estat punt de mira en l'interès científic durant els darrers anys, s'identifica encara una manca de coneixement de la seva fisiologia. Aquesta tesi es centra en l'ecofisiologia de cinc especies d'esponges emblemàtiques del coral·ligen Mediterrani. Utilitzant una aproximació energètica s'ha avaluat les interaccions entre possibles limitacions fisiològiques en les esponges i fluctuacions estacionals en els paràmetres ambientals a les que estan sotmeses en la natura. En aquesta tesi contribuïm al coneixement encara limitat dels mecanismes energètics que regulen la dinàmica estacional de les esponges així com en aportar informació sobre el perfils metabòlics divergents entre les esponges amb alta (HMA) i baixa (LMA) concentració de microbis associats segons les seves diferents estratègies adaptatives. Amb aquest objectiu examinem in situ l'alimentació, la filtració i la respiració al llarg d'un cicle anual. En primer lloc comencem desenvolupant un sistema que permeti la quantificació de compostos particulats i dissolts processats per les esponges en el seu habitat natural. En termes d'alimentació hem observat que totes les especies retenen molt eficientment el plàncton i que el carboni orgànic dissolt (DOC) es la seva principal font de carboni. Respecte als fluxos de nitrogen s'ha trobat diferents nínxols tròfics entre especies amb diferent concentració de microbis associats: especies HMA depenen bàsicament de compostos dissolts com a font de nitrogen mentre que les especies LMA depenen de la fracció particulada. Curiosament, la variació en la tassa de filtració al llarg de l'any no segueix el cicle de temperatura. El període de temperatura mes alta no va coincidir amb les tasses de filtració mes elevades suggerint que altres mecanismes intrínsecs a les esponges, com pot ser una disminució en la quantitat de coanòcits durant el cicle de reproducció, podrien regular el metabolisme de les esponges. Per altra banda la respiració ha mostrat un patró estacional seguint les fluctuacions naturals de la temperatura. La combinació d'aquests resultats ens ha permès estimar el balanç energètic global, aquest sembla estar regulat per un increment en la demanda energètica a l'estiu coincidint amb un increment en la disponibilitat de carboni orgànic dissolt en la columna d'aigua. Els nostres resultats també han mostrat diferencies en el perfil de limitació energètica entre especies HMA i LMA coincidint amb les seves diferents estratègies en la captura de nutrients. Les especies LMA sembla que obtenen suficient energia per cobrir el seu metabolisme a partir de la matèria particulada de l'aigua, essent la fracció dissolta un aportació addicional de carboni. Contràriament en especies HMA la nutrició heterotròfica sembla ser insuficient per cobrir els requeriments metabòlics basals suggerint altres vies metabòliques rellevants per cobrir el balanç energètic.
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Defrance, Laure. "Bioréacteur à membrane pour le traitement des eaux résiduaires : étude du colmatage de membranes minérales et amélioration du flux de perméat par application de techniques hydrodynamiques." Compiègne, 1997. http://www.theses.fr/1997COMP1055.
Full textAbstract:
Le bioréacteur à membrane est un procédé très performant pour l'épuration des eaux résiduaires. La qualité de l'effluent est telle qu'il peut être recyclé pour des utilisations non nobles (chasses d'eau, arrosage des pelouses, eaux de nettoyage industriel). Le coût du traitement est actuellement élevé à cause d'un phénomène général à toute opération de filtration tangentielle : le colmatage de la membrane qui entraîne une diminution du flux de perméat et une consommation énergétique élevée. Une étude sur un pilote placé en situation réelle dans une station d'épuration urbaine a permis de déterminer le fonctionnement optimal du système en fonction de la vitesse de circulation. Pour cela, une comparaison a été effectuée entre la filtration à flux de perméat fixe et la filtration à pression transmembranaire fixée. La première méthode apparaît plus avantageuse puisque le colmatage formé est moins important, tant que l'on se situe en deçà du flux critique. Le flux critique est caractérisé par le fait qu'un colmatage très important dû à la formation d'un dépôt sur la membrane apparaît lorsque ce flux est dépassé. D'autre part, des variations cycliques des paramètres opératoires ont permis de caractériser le dépôt formé au delà du flux critique : sa compressibilité est importante mais réversible, sa cohésion faible. La réversibilité d'un dépôt formé par des boues activées de bioréacteur à membrane diffère de celui formé par des boues activées issues des aérateurs d'une station d'épuration classique. Finalement, deux techniques instationnaires de filtration ont été testées en vue de diminuer le colmatage : les échelons de pression transmembranaire et de vitesse de circulation et les rétro lavages par le perméat. La première engendre une diminution de l'énergie spécifique même avec des boues colmatantes. La seconde n'a pas été efficace car la pression de rétrofiltration était trop faible.
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Lacour, Céline. "Apport de la mesure en continu pour la gestion de la qualité des effluents de temps de pluie en réseau d'assainissement." Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00555629.
Full textAbstract:
L'objectif de ce travail de thèse est de démontrer qu'il est possible d'utiliser des mesures en continu de turbidité pour suivre la pollution particulaire dans les réseaux d'assainissement et d'évaluer l'apport de ces mesures pour la gestion des réseaux en temps réel ou en temps différé. Dans une première partie, la mise en oeuvre de la mesure en continu de turbidité est décrite. Les éléments principaux contribuant à l'incertitude sont identifiés et des méthodes de calcul des incertitudes adaptées sont proposées. Les questions de fiabilité et de représentativité de la mesure de turbidité sont traitées et aboutissent à des solutions d'installation des sondes in situ et à des protocoles de suivi et de maintenance. Enfin, les perturbations affectant le signal sont quantifiées et des méthodes de filtrage sont comparées. La deuxième partie est consacrée à l'analyse du comportement de la turbidité à partir des données acquises sur deux sites du réseau unitaire parisien en 2006. 80 événements pluvieux sont décrits par leurs concentrations moyennes et maximales et par leurs courbes de distribution masse/volume. Ces critères ont été intégrés dans des typologies qui ont ensuite été mises en relation avec des paramètres de débit et de durée de temps sec ayant précédé l'événement. Cette analyse permet de caractériser la variabilité de façon détaillée. La variabilité de la décantabilité des particules a été également étudiée à partir de données provenant de bassins de décantation. Enfin, deux applications sont proposées. La première est une évaluation en temps différé de flux de polluants. Deux modes d'exploitation de prélèvements d'échantillons réalisés sur un nombre fixé d'événements pluvieux sont comparés. L'un n'utilise que les résultats d'analyses des échantillons au laboratoire pour établir une concentration moyenne. L'autre utilise les prélèvements pour établir des relations entre turbidité et paramètres polluants, ensuite appliquées à des mesures en continu de turbidité. Une seconde série d'applications porte sur l'utilisation de la turbidité pour la gestion en temps réel des flux. Deux configurations-types génériques ont été étudiées. Pour chacune, une stratégie utilisant seulement le débit est comparée à une stratégie utilisant turbidité et débit. Les simulations sont effectuées pour de larges gammes de paramétrage des configurations et avec des données réelles de débit et de turbidité en entrée du système. Pour les applications d'évaluation de flux comme de gestion en temps réel, le gain apporté par la turbidité est chiffré et s'avère significatif
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Vroman, Thomas. "Mécanismes de décolmatage de membranes fibres creuses en traitement des eaux : flux critique de rétrolavage et déformation de la membrane pour une amélioration de l'efficacité du rétrolavage." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30013.
Full textAbstract:
Des membranes fibres creuses d’ultrafiltration Kynar® PVDF possédant diverses caractéristiques (perméabilité et propriétés mécaniques) ont été sélectionnées pour étudier les mécanismes de décolmatage dans le cas de filtration de suspensions modèles (dépôt de bentonite ou d’acide humique). L’objectif de ce travail est d’améliorer l’efficacité du rétrolavage en optimisant les matériaux et les conditions opératoires dans le but de réduire le coût énergétique de cette opération.Des mesures expérimentales sous caméra ont permis d'étudier la déformation de la surface externe des fibres creuses lors des opérations sous pression. Ces déformations qui peuvent atteindre 15% lors des étapes de rétrolavage ont été modélisées par la déformation mécanique d'un tube cylindrique à paroi épaisse sous pression. L'étude expérimentale du taux d'élimination de dépôt de bentonite, fonction de la pression de rétrolavage et des différentes membranes ou suspension filtrée, a permis de montrer l'existence d'un flux critique de rétrolavage pour lequel l'efficacité maximum est atteinte. En revanche, le détachement des dépôts d’acide humique qui sont plus adhérant et responsable d'un colmatage irréversible, n’est pas impacté par le flux de rétrolavage mais semble être affecté par la forte déformation (>10%) de surface externe de la fibre. Les mécanismes de décolmatage des dépôts lors du rétrolavage sont donc liés aux contraintes mécaniques (contrainte normale et de cisaillement) s’exerçant à l’interface dépôt-membraneKynar® PVDF ultrafiltration hollow fiber membranes with various properties (permeability and mechanical properties) were selected for the study of fouling removal mechanisms in the case of model suspension filtrations (bentonite and humic acid cake). The aim of this project is to improve backwash efficiency by optimizing materials and operating conditions for an energy-efficient backwash process.The deformation of the external surface of the hollow fiber during pressure operations was measured under camera. The deformation, which can reach 15% during backwash, was numerically calculated using a mechanical deformation model of a thick-walled cylinder under pressure. The experimental study of the bentonite cake removal percentage, as a function of backwash pressure and the different membranes or feed suspension, showed the existence of a critical backwash flux from which the backwash reached its maximal efficiency. However, detachment of humic acid cake, which is more adherent and causes irreversible fouling, is not affected by the backwash flux but seems to be affected by the strong deformation of external surface of the hollow-fiber (>10%). Mechanisms of cake removal during backwash are therefore linked to the mechanical stresses (normal and shear stress) acting at the cake-membrane interface
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Cromey, Tyler. "Effect of elevated temperature on ceramic ultrafiltration of colloidal suspensions." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51778.
Full textAbstract:
The inherent thermal resistance of ceramic membranes allows for treatment of industrial waters at elevated temperatures. Traditionally, the high temperature of wastewater has been an issue compromising the integrity of polymeric membrane systems or requiring the temperature to be lowered for further treatments. In ceramic membrane systems, a decrease in viscosity with increasing temperature, however, can be utilized, which increases the permeate flux. In this study, the fouling of ceramic ultrafiltration by feed solutions containing colloidal silica was evaluated at temperatures between 25 – 90 °C seen in various industries. Ceramic membranes were able to perform well at elevated temperatures up to 90 ºC with sustained mechanical and chemical integrity. Results showed net benefit of filtration at elevated temperatures on permeate flux in spite of increasing total fouling resistance with temperature. When the temperature increased from 25 to 90 °C, there was a 90% increase in steady-state permeate flux. The dominant resistance was physically removable fouling, and the increase in fouling with feed temperature was supported by force balance analyses. This study provides a foundation from which further studies can be developed including pilot-scale testing, use of real wastewater, and the effects of operating conditions.
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Abuhelou, Fayez. "Les variations spatiales et temporelles de l'occurrence et de la distribution de composés aromatiques polycycliques dans un système fluvial affecté par activités industrielles passées." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0233/document.
Full textAbstract:
La contamination en composés aromatiques polycycliques (CAP) a été suivie entre 2014 et 2015 au cours de six campagnes d’échantillonnage sur 8 sites différents entre Auboué et Richemont. Cette section du cours d’eau correspond à la partie aval de la vallée de l’Orne profondément affectée par plus d’un siècle d’activités minières et sidérurgiques qui ont cessé entre 1968 et 2009. L’Orne a donc été le réceptacle de rejets industriels et urbains et a été profondément perturbée dans son hydrodynamisme avec la construction de plusieurs barrages. Dans ce contexte, l’occurrence des 16 hydrocarbures aromatiques polycycliques réglementaires (HAP), de 11 CAP oxygénés (O-CAP) et de 5 CAP azotés (N-CAP) et leur distribution dans les fractions dissoute et particulaire des eaux de l’Orne ont été étudiées en mettant en place des protocoles d’échantillonnage et d’analyse adaptés. Le premier objectif de ce travail a été de comparer les méthodes d’échantillonnage des matières en suspension par filtration et par centrifugation à flux continu sur le terrain. Des différences significatives ont pu être identifiées entre les deux techniques, la filtration amenant à des concentrations en CAP plus élevées du fait d’une plus grande abondance des CAP de bas poids moléculaire. Nous avons pu mettre en évidence le rôle de la fraction fine (< 5µm) et/ou colloïdale plus ou moins retenue par les filtres et qui, de part sa réactivité, piège des CAP. La comparaison des deux méthodes dans différentes situations hydrologiques nous montre que cette rétention n’est pas systématique mais plutôt corrélée à des situations de fort hydrodynamisme. Les deux méthodes d’échantillonnage des matières en suspension ne sont donc pas comparables mais complémentaires. Le suivi saisonnier et multi-sites des eaux de l’Orne montre que la concentration en CAP varie entre 1.6 et 223.7 ng L-1 dans la fraction dissoute et entre 1.5 et 105.5 µg g-1 dans la fraction particulaire avec des variations spatiales de ±35% et ±45% respectivement. Les variations de concentration des CAP dans la fraction dissoute sont importantes d’un site à l’autre lorsque le débit est faible (de 0.5 à 34 m3.s-1). Les concentrations en CAP sont faibles autour de 20 ng.L-1 et spatialement homogènes en périodes de haut débit (> 50 m3.s-1) du fait de la dilution. Les concentrations en CAP dans les matières en suspension varient entre 2.8 to 36.3 µg g-1, et montrent des concentrations stables quelles que soient les situations hydrologiques lorsqu’elles sont collectées par la centrifugeuse de terrain. La fraction dissoute est enrichie en HAP de bas poids moléculaire dans les périodes d’étiage et est marquée par l’occurrence des HAP à 5 et 6 cycles aromatiques au cours des épisodes de crue. Les CAP polaires sont au moins aussi abondants que les HAP dans la fraction dissoute et évoluent de la même façon que les HAP. La part des CAP polaires dans la fraction particulaire est significativement plus basse (de 10 à 20% de l’ensemble des CAP)The spatio-temporal variations of the concentration and distribution of dissolved and particulate polycyclic aromatic compounds (PACs), namely 16 polycyclic aromatic hydrocarbons (PAHs), 11 oxygenated PACs (O-PACs) and 5 nitrogen PACs (N-PACs), were studied in the Orne, a river impacted for more than one century by iron mining and steel-making industry. The first objective of this work was to compare the influence of two different methods of separation of suspended particulate matter (SPM), filtration (FT) and field continuous flow centrifuge (CFC). Results showed that in half of the sampling campaigns, PAC concentrations were 2 to 8 times higher for PAHs and 2 to 10 times higher for O-PAC when SPM were collected by filtration. These differences that were not observed systematically over the six sampling campaigns could be explained by the retention of colloidal matter on glass-fiber filters that appeared as a very reactive phase particularly enriched in low molecular PACs. The two methods were then considered as complementary methods to study SPM. The second objective of this work was to perform a long term monitoring of PAC concentrations and distributions in dissolved and particulate fractions. The results from the six sampling campaigns between May 2014 and September 2015 in eight different sites showed that the PAC concentrations ranged between 1.6 to 223.7 ng L-1 in the dissolved fraction (?PACTD), and between 1,55 to 105,5 µg g-1 in the total particulate fraction, with maximum spatial variation of ±35% and ±45% respectively. The dissolved PACs spatial variations were strongly influenced by the hydrological conditions and less spatial variation was observed during high flow events as the result of dilution and homogenization of pollutants. During low flow events, particulate PACSPM-CFC concentrations were more stable and equivalent in values and distribution to the corresponding PACSPM-FT samples. Overall it was in a range between 2.8 to 36.3 µg g-1. The dominance of dissolved low molecular weight PAHTD in the low flow events decreased during high flow events due to the appearance of penta- and hexa-cyclic PAHs. The dissolved polar PACs were as high as the PAHs contribution and also subjected to seasonal changes, the O-PACs ranged between 5.6 to 90.3 ng L-1 and N-PAHs from 1.0 to 42.5 ng L-1. The particulate polar PACs concentrations and contribution were significantly lower, the highest concentrations of 8,76 µg g-1 and 29,41 µg g-1 was observed during high flow event for O-PACs and during low flow event for N-PAH respectively
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Falahati, Hamid. "The Characterization of Bimodal Droplet Size Distributions in the Ultrafiltration of Highly Concentrated Emulsions Applied to the Production of Biodiesel." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/19585.
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A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor.Natural Sciences and Engineering Research Council of Canada (NSERC)
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Gangloff, Sophie. "Evaluation of the mechanisms of trace elements transport (Pb, Rare Earth Elements,... ) and the elemental and isotopic fractionation (Ca and Sr) at the interface water-soil-plant." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH002/document.
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Ce travail est axé sur l’étude d’un profil de sol et des solutions de sol prélevés sur une parcelle expérimentale couvertes d’épicéas. Tous ces échantillons proviennent du Bassin Versant du Strengbach (Observatoire HydroGéochimique de l’Environnement – OHGE), ont été échantillonnés à différentes profondeurs (5, 10, 30 et 60 cm) et durant la période comprise entre 2009 et 2013.Les caractérisations des extraits des sols par spectroscopie Infra-Rouge ont permis de mettre en évidence les modifications des groupements fonctionnels organiques avec la profondeur et que ces modifications ont une forte incidence sur le comportement des cations (majeurs et traces) dans le sol. Des expérimentations d’ultra-filtration ont permis d’identifier les flux colloïdaux et dissous du carbone organique ainsi que ceux des éléments majeurs et traces présents dans les solutions de sol. L’utilisation conjointe des traceurs isotopiques (87Sr/86Sr et δ44/40Ca) et chimiques (Terres Rares) ont mis en évidence des processus ayant lieu aux interfaces eau-sol-plante, comme le prélèvement racinaire ou l’altération des solsThis work is focused on the study of a profile of soil and soil solutions collected on an experimental plot covered with spruce. All these samples come from the watershed of the Strengbach (environment - OHGE Hydrogeochimique Observatory), were sampled at different depths (5, 10, 30 and 60 cm) and during the period between 2009 and 2013. Characterizations of soil extracts by infrared spectroscopy allowed to highlight changes in the organic functional groups with depth and that these changes have a significant impact on the behaviour of the cations (major and trace) in the soil. Ultrafiltration experiments helped to identify flows of colloidal and dissolved organic carbon as well as those of the major and trace-element present in soil solutions. The joint use of isotope tracers (87Sr / 86Sr and δ44 / 40 Ca) and chemical (Rare Earth Elements) have highlighted processes taking place at the water-soil-plant interface, as the uptake by root or soil alteration
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(11191359), Jessica L. Zuponcic. "Maximizing Pathogen Recovery and Flux in Tangential Flow Filtration Processes to Enable Rapid Detection." Thesis, 2021.
Find full textAbstract:
Bacteria which enter a viable but non-culturable state cannot be concentrated by enrichment. This means they may not reach a detectable concentration for PCR methods - especially in the presence of sample compounds which may act as PCR reaction inhibitors. An alternative strategy for concentration of bacteria from aqueous samples is explored in this work using tangential flow filtration. The effectiveness of this technology to concentrate pathogens from food-derived samples was previously demonstrated; however, losses of bacteria to the filtration system can still be high (i.e. recovery of bacteria is low).
The goal of this research was to maximize recovery of pathogenic microorganisms from hollow fiber filtration processes while also maximizing flux. In this way, high recovery filtration conditions could be selected while keeping filtration time low. It was hypothesized that flux would have relatively lower impact on final recovery of bacteria at high shear rates (27,000 1/s) which are sufficient to remove attached bacteria on surfaces. It was hypothesized that these high shear rates would not cause loss of bacterial viability, and the main cause of bacterial losses during filtration would be accumulation on the membrane surface.
To test these hypotheses, single fiber filter modules (both microfilters and ultrafilters with 0.5 mm inner diameter), were constructed and used to concentrate GFP-producing Escherichia coli at a wide range of flux conditions. Post-concentration, fluorescence micrographs of bisected hollow fibers illustrated patterns of bacterial accumulation along the length of the fiber. A simple recovery model was constructed to predict recovery as a function of flux and shear rate, and predictions were compared against the experimental data.
Both in the experiments and in the simple recovery model developed in this dissertation, recoveries near 90% were achievable at high shear rates when flux was ≤0.5 mL min-1 cm-2. This amounted to a 3-hour filtration time for a 225 mL sample. Compared to a filtration with only 30% recovery, detectable bacteria concentrations could be achieved with lower starting concentrations – ~5 CFU/mL starting concentration versus at least 15 CFU/mL. Given these high recoveries (determined with plating methods on agar) occurred at high pressure and shear conditions, it was determined the filtration did not affect bacterial viability.
In addition to using the model to predict recovery at various shear and flux conditions, it would be helpful to predict module designs or concentration strategies which could improve bacterial recoveries from the filter. One strategy, explored with preliminary data, was to pre-develop a layer of bacteria on the filter surface prior to concentrating samples.
Understanding and reducing the losses of bacteria during tangential flow filtration could enable detection of dilute levels of viable but non-culturable microorganisms; in addition, sensitivity of detection could be improved for quickly concentration culturable microorganisms in food and water samples.
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Pan, Shai-Yu, and 潘帥宇. "A Study on the Critical Flux of Submerged Membrane Filtration System." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/15800007847256813717.
Full textAbstract:
碩士淡江大學
化學工程學系
91
In this study, the influence of operating parameters on a flat-membrane submerged filtration system were investigated. The operating parameters included aeration rate, particle size, suction pressure, feed concentration, inclination angle and molecular pore size. The experimental results were summarized as follow: (1) The operation of single-liquid phase filtration has an easy trend to obtain a critical flux; (2) Increasing aeration rate not only enhance flux but also delay the occurrence of critical flux; (3) A higher feed concentration has a lower value of permeate flux but with a larger flux enhancement by gas slugs; (4) The membrane with a lower solvent permeability has a lower drag force on particle, the particle can be easily sweep away from membrane surface. (5) Base on several aeration rate, the flux of 1600 membrane inclination is higher than that of 900 inclination. The operation at 1600membrane inclination has a higher critical flux because the rejected solutes can be disturbed significantly by the gas flow. (6) According to the analyses of boundary layer resistance and thickness, both the filtrate resistance and concentration boundary layer thickness decrease as the aeration rate increases, and the resistance and thickness of concentration boundary layer of 1600 membrane inclination are smaller then that of 900.
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Wang, Shu-Yu, and 汪書伃. "Inorganic particle removal and filtration flux enhancement in seawater desalination pretreatment." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/qtjh2w.
Full textAbstract:
碩士淡江大學
化學工程與材料工程學系碩士班
102
Using purified Water and inorganic salts to simulate seawater in this study, then add silica powder to simulate inorganic particles in seawater. The first part of this study used microfiltration apparatus analyzing filtration mechanism and quality of filtrate. The experimental results confirm that the enhancement of transmembrane pressure and cross-flow velocity could improve the filtration rate, but the effect of the transmembrane pressure was more obvious than cross-flow velocity.Using high cross-flow velocities to enhance filtration rate under lower pressure was more effectively then higher pressure. Under low pressure, the filtration rate of cross-flow velocity 0.5 m/s to 0.1 m/s was enhanced about 72.3%, but high pressure just increase 34.4%, while the filtration rate under 100 kPa was higher than 20 kPa about more than 130%. The turbidity of filtrate could be reduced to below 0.5 NTU, and SDI15 less than 2, conform to the requirements of the water into the RO. Using of force balance model associated with basic filtration equation could estimate the filtration rate, the relative deviation of filtration rates between estimated results and experimental data is less than 35%. The second part used different filtration membrane, filtration modules or operating mode, trying to get the best method to improve the filtration rate. The experimental results showed that: At high particle concentrations, the membrane pore size could be close to particles size. The filtration flux of hydrophobic membrane was lower than the hydrophilic membrane. In the cross-flow microfiltration system, changing the orientation of module could not improved filtration rate. Putting spacer in the filter channels as turbulence promoters, the increasing shear stress could improve the filtration rate about 2.8 ~ 10%. Intermittent feeding method that every 20 minutes stopping the pump 5 seconds could enhance the filtration rate about 2.8 ~ 10%, but the two-phase flow unable to enhance the filtration rate effectively, because the particle packing becomes more regular and more compact under two-phase flow cause the higher average specific cake filtration resistance. Adding flocculants could effectively improve the filtration rate, but dispersing agent will make filtration rate decrease.In dynamic filtration module, when the distance between vanes and membrane surface equal to 1.5 mm, the shear stress acting on membrane surface caused by vanes rotation could improve the filtration rate 69% while rotational speed was 500 rpm, but when the distance was equal to 0.8 mm, the vanes could scrape the cake to improve the filtration rate 143.3 % while rotational speed was 500 rpm. Using cross-flow filtration empirical formula to estimate the shear stress of dynamic filtration, and establishing the relationship between the radius of vanes, shear sress and filtration rate, moreover, coupled with the power of calculation, could get the results that use two dynamic filtration modules which with the vanes of radius was 0.01m, and with high speed, low vanes distance 0.8 mm, the filtration rate per unit power efficiency can be maximized.
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Lin, Kung-Hsuan, and 林公璿. "Flux Improvement in Membrane Filtration of Suspended Solutions under an Ultrasonic Field." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/05359657713645111606.
Full textAbstract:
碩士元智大學
化學工程學系
91
In this paper, the characteristics of untrasonic waves like cavitation were applied to modify the processes of ultrafilitration (UF) for the separation of W/O emulsions from external phase. This is because the flux decline and serious fouling phenomena occurs in the ultrafiltration of W/O emulsions. The resistance-in-series model was used to determine the role of operating variables in this system. Firstly, we used ultrasound to prepare W/O emulsions, and the optimal conditions were 100 mL of internal phase, 3 vol% of surfactant concentration, the ratio of internal phase to oil phase was 2 : 1, and 93 watt of operating power. Within 5 mins, ultrosound upped the volume of W/O emulsions to 100 %. In the stirred cell, ultrasound can improve the flux during ultrafiltration of PEI solutions and W/O emulsions. In both solutions, the permeate fluxes were enhanced by 80 % and 60 % under an ultrasonic field. In the resistance-in-series model, permeate flux decreases with an increase of the resistances caused by fouling phenomena (solute adsorption, etc.) and concentration polarization/gel layer formation. The correlation equations for estimating those resistances have been developed in this work. It was found that the resistances are functions of the applied pressure, volume ratio of W/O emulsions, operating power, and tip height. Finally, we made use of unstable of W/O emulsions at low pH, and demulsified at 63 watts of operating power under the ultrasonic field.
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Sethi, Sandeep. "Transient permeate flux analysis, cost estimation, and design optimization in crossflow membrane filtration." Thesis, 1997. http://hdl.handle.net/1911/19209.
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A generalized model is formulated to predict the time-dependent permeate flux by extending previous models to include the particle transport mechanisms of Brownian diffusion, shear-induced diffusion, inertial lift and concentrated flowing layers. A new model for estimating the capital costs of membrane plants is developed which incorporates individual cost correlations for different categories of manufactured equipment. The effects of particle size, design, and operating variables on permeate flux and treatment costs are investigated numerically. Optimization problems are formulated and solved to investigate (a) optimal membrane design and system operation, (b) optimal backflushing frequency, and (c) optimal selection of hybrid filtration configurations, over variable raw water quality.
The combined theory predicts an unfavorable particle size, on the order of 10$\sp{-1}\ \mu$m, where net back-transport is at a minimum. This implies minimum permeate fluxes in the size range of 10$\sp{-2}\ \mu$m - 10$\sp{-1}\ \mu$m, depending on the operating time. These results support experimental observations of minima in back-transport (Chellam and Wiesner, 1996) and permeate flux (Fane, 1984). Inside-out hollow fiber geometry is predicted to be favorable for feed suspensions with small particles and/or low concentrations. The constant pressure mode of operation is predicted to yield higher specific permeate fluxes compared to the constant flux mode, particularly for particles which demonstrate mass-transfer limited behavior. Comparisons and parameter estimations made with available experimental data on polydisperse suspensions give solidosity estimates ranging from 0.70 to 0.77.
Membrane design is predicted to be optimized at values of fiber radius (narrow) and length (short) where the permeate fluxes are maximized. Particles affected by mass-transport limitations demonstrate comparatively lower optimal transmembrane pressures. For unfavorable particles, treatment costs are predicted to be minimized at intermediate recoveries and backflushing frequencies. At small capacities, the hybrid hollow fiber ultrafiltration and spiral wound nanofiltration system with higher non-membrane capital costs is predicted to be largely non-optimal compared to hollow fiber nanofiltration. Membrane costs are expected to play a significant role in determining the optimal configuration at large capacities, where the hybrid configuration is predicted to become largely optimal.
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Ho, Chia Chun. "Protection des berges contre l'érosion avec des dispositifs incorporant des géotextiles." Phd thesis, 2007. http://tel.archives-ouvertes.fr/tel-00340582.
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L'érosion des revêtements des digues de rivière peut affecter la stabilité des talus des rives et mettre en danger la sécurité des constructions voisines, et des écoulements de débris peuvent être déclenchés par le sol et les roches érodées de la rive et accumulées dans le lit de rivière. Des travaux d'amélioration sont nécessaires pour augmenter la stabilité des revêtements aussi bien que réduire la possibilité de rupture. Les pratiques actuelles impliquent habituellement la construction d'un épais revêtement en béton, causant des impacts négatifs sur l'environnement et une instabilité des rives sous l'effet de l'érosion à long terme. Afin de remplacer le béton, il est donc crucial de trouver des matériaux de construction respectueux de l'environnement et appropriés à la construction de revêtements sûrs.Les géotextiles, en tant que matériau de protection de rive sont non seulement plus respectueux de l'environnement, mais aussi plus stables à long terme, comparés au béton. Cependant, une mauvaise conception d'un revêtement géotextile peut entraîner une perte considérable du sol de la rive, ce qui peut conduire à la rupture. Aujourd'hui de nombreuses études sur le comportement de revêtements géotextiles soumis à l'érosion ont été réalisées, mais chacune d'entre elles s'est intéressée uniquement à un type d'écoulement. Le comportement réel d'un revêtement géotextile soumis à écoulement est assez compliqué, et suivant le type d'écoulement on définit dans cette étude trois zones : la zone de flux unidirectionnel, la zone de flux cyclique bidirectionnel, et la zone de flux tangentiel.
Dans ce projet, le comportement sous érosion de sols non cohésifs ou peu cohésifs avec les trois conditions de flux mentionnées ci-dessus a été étudié avec des essais utilisant un équipement développé pour chaque condition de flux. Les résultats d'essais révèlent qu'un écoulement souterrain dans la zone de flux unidirectionnel peut provoquer l'érosion interne du sol et qu'une partie des particules de sol entraînées peut passer à travers les ouvertures du géotextile. Le reste de ses particules peut se colmater à l'intérieur des fibres du géotextile ou s'accumuler derrière le géotextile, formant une couche filtrante naturelle et réduisant la vitesse de l'écoulement. Une fois que la vitesse d'écoulement est plus basse que la vitesse critique, l'érosion interne du sol cesse.
La zone de flux cyclique bidirectionnel peut être identifiée en fonction des conditions de flux de : « flux cylique à court terme » et de cycliques à long terme », selon la période du cycle du flux, pour laquelle le comportement du revêtement géotextile diffère lors de l'érosion. Ainsi, deux instruments d'essais ont été développés. Les résultats d'essais dans un canal à vague grandeur nature avec des conditions de flux cycliques à court terme révèlent que le sol de la couche supérieure de la zone de flux cyclique bidirectionnel est soumis à la charge cyclique des vagues, ce qui peut entraîner un excès de pression interstitielle et aboutir à l'écroulement, tandis que le sol dans la couche moyenne peut être érodé par le flux tangentiel le long de la rive et accumulé en aval. En outre, en plus de l'ouverture du géotextile, le taux de couverture des roches sur le géotextile est aussi un facteur clef qui contrôle le ravinement du sol. Les résultats d'essai utilisant l'instrument de flux cyclique bidirectionnel à long terme, pour une période de flux cyclique particulièrement longue (600 secondes/cycle), montrent que la vitesse d'écoulement dans la couche de sol est trop faible pour déplacer les particules de sol, et on ne s'attend donc à aucune érosion. Cependant, quand la vitesse d'infiltration augmente, la contrainte effective dans le sol diminue en raison de l'augmentation de pression de l'écoulement, causant ainsi un phénomène de boulance (boiling) et un entraînement considérable de sol ainsi que le tassement de celui-ci. En plus, la profondeur d'influence avec cette condition de flux est plus grande qu'avec la condition de flux cyclique à court terme. En outre, d'après les valeurs de gradient hydraulique déduites des mesures réalisées avec deux piézomètres installés au-dessus et au-dessous du géotextile, aussi bien que d'après les images de microscopie électronique de fibres du géotextile, on peut constater que l'extension de la zone de colmatage par les particules de sol n'est pas aussi importante que pour des flux unidirectionnels.
Le comportement en érosion dans la zone de flux tangentiel a été étudié avec l'instrument d'essai d'érosion parallèle. Le résultat révèle que le comportement en érosion tangentiel sur la surface de sol peut être défini par la vitesse de flux. Si la vitesse de flux est inférieure que la vitesse critique (vc), aucune érosion n'apparaît. Si la vitesse de flux est entre la vitesse critique et la vitesse de rupture (vf), une érosion permanente se produira à la surface de sol. Si la vitesse d'écoulement est plus grande que la vitesse de rupture, une érosion intense se produira dans le sol et entraînera la rupture du revêtement. De plus, la présence d'un géotextile sur la surface du revêtement a une influence non négligeable sur le comportement en érosion. Les revêtements sans géotextile sur la surface sont soumis à une érosion continue et peuvent finalement s'effondrer en raison d'éboulements en pied de pente. Une couverture géotextile appropriée sur la surface du revêtement peut non seulement éviter l'érosion, mais aussi former une couche filtrante naturelle au-dessous du géotextile qui empêche que l'érosion du sol continue. Une fois que la couche de filtre naturelle est complètement formée, le revêtement est stabilisé.
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"Numerical Modeling of Cake Formation and Permeate Flux Decline in Membrane Filtration Using OpenFOAM." Master's thesis, 2018. http://hdl.handle.net/2286/R.I.49024.
Full textAbstract:
abstract: Membrane filtration is an important technology in industry. In the past few decades, equations have been developed from experimental results to predict cake formation and permeate flux decline in the membrane filtration process. In the current work, the block of particles on membrane surface is achieved by setting surface flux on membrane surface zero. This approach is implemented for both microfiltration and nanofiltration using OpenFOAM. Moreover, a new method to deal with cake resistance for nanofiltration is introduced. Cake resistance is applied to both cake and membrane. To validate the new techniques, results of crossflow microfiltration are compared to theoretical results and results of two crossflow nanofiltration cases are compared to experimental data. In addition, the new techniques are applied to dead end filtration to observe the different structure of the cake and explore the effect of resistance on velocity profile.Dissertation/Thesis
Masters Thesis Mechanical Engineering 2018
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Wu, Shiau-Feng, and 吳効峰. "Effects of air-sparging on particle deposition and filtration flux in cross-flow microfiltration." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/83200748696282334187.
Full textAbstract:
碩士淡江大學
化學工程與材料工程學系碩士班
96
The effects of filtration flux、adhesion probability、cake properties and shear stress by changing liquid velocities、gas velocities and filtration pressures for air-sparging cross-flow microfiltration are studied. A filter membrane made of mixed cellulose ester with a mean pore size of 0.1 μm is used for filtering wide size distribution range particles, PMMA-7G. The flow behavior will change when gas velocity increases. Shear stress can restrain cake mass availability and improve filtration rates under bubble flow, but specific filtration resistance will increase clearly and filtration rates worse than no sparging filtration under slug flow。Because of shear stress increase rapidly。A great of particle decrease above 5μm. Smaller particle move in the void and the porosity become reduce. On the other hand, the cake layer compressed when fluid went past, so the specific filtration resistance increases glaringly. Communion with force analysis, we can find air-sparging force plays important role in filtration process, and we can use simulation analysis to forecast the tendency for particle distribution and adhesion property.
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Cheng, Yun-Hsin, and 鄭運馨. "Flux Enhancement by Backwashing and Gas-sparging in Tubular Membrane Filtration of Protein Solution." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/22233953093812596129.
Full textAbstract:
碩士淡江大學
化學工程與材料工程學系碩士班
96
Inorganic membranes were employed in a cross-flow filtration system for investigating the flux behavior and membrane fouling of BSA solutions. The operating parameters included transmembrane pressure, solution concentration, pH value, liquid velocity, air velocity and backwashing frequency. The filtration resistances were also evaluated and the net permeate flux was considered in order to compare the performances of various operation modes, For varying the pH, the experimental results show that the permeate flux is maximum at pH = 3 and is minimum at pH = 4.9. The BSA particle’s shape and surface charge were determined by the pH value. At pH = 3, the BSA molecules are linear with surface charge, the BSA polarization layer in the filtration has a loose structure results in a lower filtration resistance.. At pH = 4.9, a compact BSA polarization layer’s structure was formed due to the neutral and nearly spherical BSA molecues. Basing on the analysis of net permeate flux, the gas sparging method is better than the backwashing for flux enhancement. The gas sparging can effectively remove the polarization layer and reduce the BSA deposition on the membrane. Furthermore, no permeate is wasted for washing in gas sparging. At pH =3, the flux increment by gas sparging is up to 60%.
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Lee, Sooi Li. "Role of surfactants in filtration and fouling of colloidal silica." Master's thesis, 2014. http://hdl.handle.net/10362/13290.
Full textAbstract:
The EM3E Master is an Education Programme supported by the European Commission, the
European Membrane Society (EMS), the European Membrane House (EMH), and a large international network of industrial companies, research centres and universitiesThe objective of this study is to investigate the influence of three different types of surfactants (i) anionic sodium dodecyl sulphate (SDS), (ii) cationic (hexadecyltrimethylammonium bromide (CTAB), and (iii) non-ionic: Triton X-100 (Polyethylene glycol tert-octylphenyl ether) and the effect of surfactant concentration on ultrafiltration of colloidal silica nanoparticles. Due to the high surface area to volume ratio of nanoparticles, the role of surface interactions on the stability of silica suspensions is enhanced. The effects of adsorption of surfactants are studied by means of static light scattering and zeta potential measurements. The strongest particle-surfactant interaction is observed between oppositely charged CTAB with silica, followed by TX-100 and SDS. An ultrafiltration hollow-fibre membrane is used in a semi-dead end configuration to perform filtration of silica suspension with varying surfactant concentration to critical micelle concentration (CMC) ratio, csurfactant/ccmc in a flux-step mode. The effect of surfactants and process conditions (flux) on filtration process have been compared by evaluating the critical flux and total fouling rate. The occurrence of critical flux and evolution of fouling rates are also strongly affected by the surfactant concentration. This difference in filtration performance is attributed to various competing and complementary mechanisms: electrostatic and hydrophobic interactions between surfactant-membrane surface, electrostatic and hydrophobic interactions between particles as well as the hydrodynamic effect of fluid motion towards the membrane. A comparison of the overall fouling potential for surfactant-silica systems showed that SDS-silica systems showed fouling rates of an order of magnitude higher than those of CTAB-silica and TX100-silica systems at the same csurf/cCMC ratio. This was an unexpected finding, as we would expect stable colloidal systems such as SDS-silica systems would exhibit lower fouling than unstable colloidal systems (e.g. CTAB-silica systems).
European Commission
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Li, Pei-Ming, and 李培銘. "A Study on Fouling and Flux Recovery in Filtration of Protein Solution by Inorganic Membrane." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/81024998161981847979.
Full textAbstract:
碩士淡江大學
化學工程與材料工程學系碩士班
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In this study, the inorganic tubular membranes(1000, 5000 MWCO) were employed in a cross-flow filtration system to investigate the effect of operation conditions, solutions and membrane properties on protein solutions filtration. The way for cleaning the membrane fouling were also discussed. The solution fluxes and solute rejection were measured under various operating parameters such as membrane MWCO, transmembrane pressure, pH value and solution composition. In addition, in this work also calculate experimental resistance value with resistance-in-series model and predicting flux of BSA solution with osmotic pressure model which will compare with experiment flux. Experimental results indicate that the NaOH solution could removal the BSA fouling on the membrane and the required concentration of NaOH solution increase as the feed BSA concentration increases. Under the turbulent flow pattern, the increase in BSA concentration just slightly reduces the flux. For BSA and β-cyclodextrin binary solution, the rejection of β-cyclodextrin varies with the pH value. In the case of 5k Da membrane, the rejection of β-cyclodextrin is higher than 80% at pH=6.87 and less than 30% in pH=10. This is due to the fact that the porosity of the polarization layer of BSA on the membrane surface varies with pH value. Therefore, the present membrane can be applied for the separation of small molecule from BSA solution by choosing a suitable pH value. In resistance-in-series model, fouling resistance value in all solution concentration of BSA are almost the same and far smaller than membrane resistance value. But in β-cyclodextrin solution, the values become higher than membrane. When in binary solution, fouling layer form by BSA on membrane surface could reject β-cyclodextrin transmembrane, so that the pore blocked resistance value can be decreased. In osmotic pressure model, the trend of theoretical flux agree with experiment flux but higher than it. This is could be the osmotic pressure model just only to consider the concentration rise in membrane surface but the influence of fouling layer was neglected.
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Pikwa, Kumnandi. "Development and evaluation of flux enhancement and cleaning strategies of woven fibre microfiltration membranes for raw water treatment in drinking water production." Thesis, 2015. http://hdl.handle.net/10321/1398.
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Thesis submitted in fulfillment of the academic requirement for the degree of (M.Tech.: Chemical Engineering), Durban University of Technology, South Africa, Durban, 2015.Woven Fibre Microfiltration (WFMF) membranes have several advantages over its competitors with respect to durability, making it a favourable alternative for the developing world and operation during rough conditions. Wide application of membrane technology has been limited by membrane fouling. The durability of the WFMF membrane allows more options for flux enhancement and cleaning methods that can be used with the membranes even if they are vigorous. Therefore, the purpose of this work was to develop and evaluate flux enhancement and cleaning strategies for WFMF membranes. Feed samples with high contents of organics and turbidity were required for the study. Based on this, two rivers which are Umkomaasi and Duzi River were identified to satisfy these criteria. A synthetic feed with similar fouling characteristics as the two river water was prepared and used for this study. The synthetic feed solution was made up of 2 g/ℓ of river clay in tap water and 0.5% domestic sewerage was added into the solution accounting for 2% of the total volume. A membrane filtration unit was used for this study. The unit consisted of a pack of five membrane modules which were fully immersed into a 100 litres filtration tank. The system was operated under gravity and the level in the filtration tank was kept constant by a level float. The study focused on evaluating the performance of the woven fibre membrane filtration unit with respect to its fouling propensity to different feed samples. It also evaluated and developed flux enhancement and cleaning strategies and flux restoration after fouling. The results were compared to a base case for flux enhancement and pure water fluxes for cleaning. The WFMF membrane was found to be prone to both internal and external fouling when used in the treatment of raw water (synthetic feed). Internal fouling was found to occur quickly in the first few minutes of filtration and it was the major contributor for the loss of flux from the WFMF membrane. The fouling mechanism responsible for internal fouling was found to be largely pore blocking and pore narrowing due to particle adsorption on/in the membrane pores. The structure (pore size, material and surface layout) of the WFMF membrane was found to be the main cause that made it prone to internal fouling. The IV major fouling of the WFMF membrane was due to internal fouling, a high aeration rate of 30 ℓ/min had minimal effect on the fouling reduction. An aeration rate of 30 ℓ/min improved the average flux by only 36%, where a combination of intermittent backwashing with brushing and intermittent backwashing with aeration (aeration during backwashing only) improved average flux by 187% and 135% respectively. Pre-coating the WFMF membrane with lime reduced the effects of pore plugging and particle adsorption on the membrane and improved the average flux by 66%. The cleaning strategies that were most successful in pure water flux (PWF) recovery were high pressure cleaning and a combination of soaking and brushing the membrane in a 0.1% NaOCl (desired) solution. PWF recovery by these two methods was 97% and 95% respectively. Based on these findings, it was concluded that the WFMF membrane is susceptible to pore plugging by colloidal material and adsorption/attachment by microbiological contaminants which took effect in the first hour of filtration. This led to a 50% loss in flux. Also, a single flux enhancement strategy proved insufficient to maintain a high flux successfully. Therefore, combined flux enhancement strategies yielded the best results.
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Chen, Huaiqun. "Prediction Of Permeate Flux Decline In Crossflow Membrane Filtration Of Colloidal Suspension: A Radial Basis Function Neural Network Approach." Thesis, 2005. http://hdl.handle.net/10125/10427.
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Deveau, Pierre-Alexandre. "Contribution à l'élaboration d'un indice de Dangerosité Potentielle de l'Atmosphère basée sur la photocatalyse en présence de TiO2." Phd thesis, 2007. http://tel.archives-ouvertes.fr/tel-00416422.
Full textAbstract:
Les travaux de thèse présentés s'inscrivent dans la problématique environnementale actuelle. Depuis la fin du siècle dernier, il a été constaté, que l'industrialisation et l'augmentation des émissions de polluants anthropiques en zone troposphérique, ont provoqué la mise en place de phénomènes de pollution photochimique ayant pour conséquences la détérioration de l'atmosphère et de l'environnement. L'étude suivante a pour but de mettre en place un indice de Dangerosité Potentielle de l'Atmosphère visant à prédire l'évolution chimique d'une masse d'air troposphérique et sa capacité à former et à accumuler de l'ozone selon des conditions optimales de réactivités photochimiques. L'étude, l'élaboration et l'évaluation de l'indice ont été effectuées suite au développement d'un système DPA. Ce dernier est composé, d'une part d'un réacteur de photocatalyse sur TiO2 reproduisant partiellement les réactions photochimiques troposphériques existantes et, d'autre part, de deux cellules de mesures atmosphériques basées sur des capteurs semi-conducteurs ou électrochimiques permettant de suivre chimiquement les polluants troposphériques au cours de la photocatalyse.La validation du système DPA a été réalisée en se basant sur l'étude de la photocatalyse avec un polluant cible (toluène) dans une phase gazeuse constituée d'air. Les observations et résultats obtenus ont permis l'élaboration d'un premier indice DPA. Celui-ci est composé de trois sous-indices qui caractérisent respectivement la pollution de fond, la capacité oxydante de l'atmosphère et la formation ainsi que l'accumulation d'ozone. Le mode de calcul de l'indice DPA, pour être validé à l'aide de valeurs expérimentales réelles, a été adapté aux données chimiques des AASQA. Les résultats obtenus montrent que l'indice DPA peut prévoir avec une à deux heures d'avance les augmentations locales des concentrations en ozone.
Après développement et optimisation, l'indice DPA pourrait devenir un outil d'évaluation aussi bien des émissions polluantes urbaines ou industrielles que de la qualité de l'air intérieur.