Dissertations / Theses: 'Filtration'

7

Hasan, Faisal S. "Upflow sand-roughing filtration." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/34972.

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Slow sand filtration requires low turbidity water for effective operation. In most cases this means pretreating the raw water to reduce its turbidity. Lately horizontal gravel filters have become very popular as a means of pretreatment. They are simple to operate, have a large mass storage capacity, and can cope with high turbidity shock loads. However, cleaning them can be a problem. An alternative pretreatment, which this study is concerned with, is upflow sand roughing filtration. It has the potential advantages of simple design, ease of operation and cleaning, and low area requirements. A study of upflow versus downflow was done using two small filter columns. The results showed that although downflow exhibited a better turbidity removal than upflow, upflow allowed longer filter runs and better utilisation of bed depth. This was in agreement with earlier findings. The effect of backwash water quality was also investigated. Both filters were run in upflow direction; one was washed with tap water, the other with polluted raw water. The results suggested, unexpectedly, that a filter washed repeatedly with polluted water produced slightly better turbidity removal than one washed with tap water. This indicated some form of maturation, which could be biological in nature, taking place. Experiments with horizontal gravel filters clearly showed the importance of biological mechanisms in maturation. Four new filter columns, 50mm in diameter, were constructed. These allowed further investigation of the effect of bed depth. Backwash rate and duration were investigated to find an optimum. Very little of the wash water was required to clean the filters, the majority being required to flush the turbidity out of the system. The long-term effect of backwash on filters was investigated, as was the effect of wash water quality. Tap water, raw water and raw water polluted with settled sewage were used to wash the filters. The results indicated that the filters washed with raw water and polluted water proved to be as good as regards turbidity removal as those washed with tap water. This suggested that raw water backwash could be used effectively for washing upflow roughing filters.

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8

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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9

Yukseler, Hande. "Biological And Chemical Sludge Filtration." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608608/index.pdf.

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Up to date, sludge filterability has been characterized by the Ruth&rsquo s classical filtration theory and quantified by the well-known parameter specific cake resistance (SCR). However, the complexity of the actual phenomenon is clearly underestimated by the classical filtration theory and SCR is often not satisfactory in describing filterability. Although many scientific studies were conducted for a better analysis and understanding of the filtration theory, still a practically applicable solution to replace the classical theory for a better description of filterability has not been proposed yet. In the present study, blocking filtration laws proposed by Hermans and Bred&eacute e, dating back to 1936, which have been extensively used in the membrane literature for the analysis of fouling phenomenon and the multiphase filtration theory developed by Willis and Tosun (1980) highlighting the importance of the cake-septum interface in determining the overall filtration rate have been adopted for the analysis of filterability of sludge systems. Firstly, the inadequacy of the classical filtration theory in characterizing the filterability of real sludge systems and also the lack of the currently used methodology in simulating filtration operation was highlighted. Secondly, to better understand the effect of slurry characteristics and operational conditions on filtration, model slurries of spherical and incompressible Meliodent particles were formed. Finally, a methodology was developed with the gathered filtration data to assess the filterability of the sludge systems by both theories. The results clearly show that both approaches were superior to the classical approach in terms of characterizing the filterability of sludge systems. While blocking laws yielded a slurry specific characterization parameter to replace the commonly used SCR, the multiphase theory provided a better understanding of the physical reality of the overall process.

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10

Tuori, Timo. "Enhancing filtration by electroacoustic means." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/12211.

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Fouling of filter media and physico-chemical properties of suspensions decrease the efficiency of filtration devices in a wide range of process industries. Environmental protection causes increasing demand to clean effluent waters to higher standards and to recycle process waters more completely. Conventional deliquoring processes are mainly based on a single driving force, usually gravity, underpressure or pressure. Today, multiforce deliquoring processes based on a combination of ultrasonic and/or other nonmechanical forces, like an electric field, are being developed. These new technological applications, namely electro-acoustic deliquoring techniques, will most probably enable higher deliquoring rates and final solid contents than conventional methods have been able to yield. Results from an experimental study of electric and/or ultrasonic field assisted filtrations are presented in this thesis. Both electric and ultrasonic fields can reduce fouling of the filtration medium and have a significant influence on filtration capacity. The extent of filtration improvement is affected mostly by particle size, surface charge, acoustic frequency, intensity and field strengths. Theoretical examinations of the use of electric and/or ultrasonic fields to enhance filtration efficiency are laid out. Some aspects regarding orthokinetic interaction in acoustic agglomeration have been considered, and energy consumptions of the filtrations of different suspensions used in experiments were also determined. Using electric field as a pre-treatment, biolfiber suspension filtration can be enhanced 4-fold and energy consumption of electric field enhancing the filtration (kWh kg1 separated water; product final dry solid content 23 % by mass) was only about 17 % of the total energy consumption of conventional vacuum filtration. Pre-treatment units can be connected to the filtration unit, for instance before the filter drum. Possible pre-treatment apparatuses could be electroflotation equipment or a pre-treatment tube technique introduced in this Ph.D. Thesis…

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11

Sheppard, Stuart Vincent. "Leucocyte filtration and cardiac surgery." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310490.

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12

Baril, Catherine. "Filtration réactive à haute température." Mémoire, Université de Sherbrooke, 2002. http://savoirs.usherbrooke.ca/handle/11143/1146.

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Ce projet de maîtrise visait à filtrer des particules à haute température et à dégrader des oxydes d'azote dans une seule unité. Les particules et les oxydes d'azote sont deux des six polluants principaux selon l' Environmental Protection Agency des États-Unis et ils sont tous les deux régis par des réglementations environnementales dans plusieurs pays. La projection de particules par plasma d'air, les procédés d'incinération, de gazéification et de combustion produisent ces deux types de polluants. Il devient alors avantageux des points de vue économique, technique et économie d'espace d'éliminer ces deux substances dans une même opération. Suite à une revue de la littérature, un filtre rigide en céramique a été sélectionné pour effectuer la filtration à haute température. La méthode de réduction catalytique sélective a été choisie pour la dégradation des NOx. L'agent réducteur utilisé a été le propane et la zéolite ZSM-5 activée par du cuivre a été adoptée comme catalyseur."--Résumé abrégé par UMI

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13

Krupp, Armin Ulrich. "Mathematical modelling of membrane filtration." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:ae6dd9e4-a862-4476-a8d9-35156848297f.

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In this thesis, we consider four different problems in membrane filtration, using a different mathematical approach in each instance. We account for the fluid-driven deformation of a filtercake using nonlinear poroelasticity in Chapter 2. By considering feeds with very high and very low particle concentrations, we introduce a quasi-static caking model that provides a suitable approximation to the full model for the physically realistic concentration regimes. We illustrate the agreements and differences between our model and the existing conventional cake-filtration law. In Chapter 3, we introduce a stochastic model for membrane filtration based on the quantised nature of the particles and show how it can be applied for feeds with different particle types and membranes with an interconnected pore structure. This allows us to understand the relation between the effects of clogging on the level of an individual pore and on the macroscopic level of the entire membrane. We conclude by explaining the transition between the discrete and continuous model based on the Fokker--Planck equation. In Chapter 4, we consider the inverse problem of determining the underlying filtration law from the spreading speed of a particle-laden gravity current. We first couple the theory of gravity currents with the stochastic model developed in Chapter~3 to determine a filtration law from a given set of experiments. We then generalise this idea for the porous medium equation, where we show that the position of the front follows a power law for the conventional filtration laws, which allows us to infer the clogging law in certain instances. We conclude the thesis by showing in Chapter 5 how we can combine experimental measurements for the clogging of a depth filter and simple fluid dynamics to accurately predict the pressure distribution in a multi-capsule depth filter during a filtration run.

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14

Herterich, James George. "Mathematical models in water filtration." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:73036408-fbc5-497a-a99f-b8da3dbca0a5.

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Membrane filtration is a simple concept for water purification: water containing particulate contaminants is forced through a semi-permeable membrane that rejects the particulates leaving clean water to flow out. Nevertheless, there are many complex features of membrane filtration, the most important of which is the accumulation of the particulates at the membrane surface. This leads ultimately to fouling of the membrane and a reduction in the efficiency of the process. Concentration polarization is the precursor of fouling, that is, a high concentration of contaminants develops in front of the membrane without the contaminants attaching to each other or the membrane surface. However, several types of acute membrane fouling develop from the layer formed in concentration polarization, including internal fouling, pore blocking and caking. Addressing these and related problems has been at the forefront of membrane research since the process' inception. In this thesis we develop mathematical models of aspects of crossflow and directflow filtration operating at constant flux. We begin by addressing questions related to the initial stages of concentration polarization in crossflow systems. In particular, we study the influence of particulates on the viscosity of the filtrate, and show how the filtration efficiency may be improved by tailoring the wall permeability to reduce the effects of osmosis. We then address the development of membrane fouling and caking in directflow systems: the transmembrane pressure difference, the possibility of elastic deformations during filtration, and the influence of these on the development of fouling and caking are all considered. We show that even small elastic effects can worsen fouling and suggest how the process can be operated to avoid this. We then discuss further opportunities for mathematical modelling in this area.

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15

Leguillon, Virginie. "Filtration des émulsions lipidiques injectables." Paris 5, 1996. http://www.theses.fr/1996PA05P141.

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16

GHIDAGLIA, CLAUDE. "Filtration en profondeur de particules." Paris 6, 1994. http://www.theses.fr/1994PA066371.

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Nous etudions la filtration de particules entrainees par un ecoulement a faible nombre de reynolds dans un empilement desordonne de spheres de verre de meme taille. Nous pouvons visualiser la trajectoire des particules car l'indice de refraction du fluide est ajuste avec celui du verre. L'influence de la structure geometrique du filtre et les effets hydrodynamiques sont etudies plus particulierement. Les mesures portent sur les distributions statistiques des profondeurs de penetration des particules dans le milieu. Des experiences systematiques en fonction de la taille des particules nous ont permis de mettre en evidence deux types de sites de capture: sites de constriction de taille inferieure a celle des particules et sites ou la capture est due a des effets hydrodynamiques. D'autre part, nous avons observe que des particules injectees par paquets penetrent plus loin dans le filtre que si elles sont injectees une a une. Par comparaison avec des experiences sans ecoulement, nous avons pu montrer que cet effet de concentration inattendu est du aux interactions hydrodynamiques entre les particules qui en se propageant modifient le champ local de vitesse dans le milieu. L'etude numerique consiste en une simulation monte carlo ou l'espace des pores est modelise par un reseau carre a deux dimensions de tubes de rayon aleatoire. Les vitesses locales sont calculees par application de la loi de poiseuille et la loi de propagation des particules est probabiliste: la probabilite pour une particule de choisir un pore est proportionnelle au debit dans ce pore. La modelisation de l'effet de concentration des particules qui augmente leur profondeur de penetration consiste a definir un rayon d'interaction hydrodynamique entre particules de l'ordre d'une ou deux longueurs de pore. Une particule capturee peut etre liberee par le passage alentour d'une autre particule situee a une distance inferieure a ce rayon d'interaction

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17

Baril, Catherine. "Filtration réactive à haute température." Sherbrooke : Université de Sherbrooke, 2002.

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18

Sanchez, Erin. "Filtration Efficiency of Surgical Masks." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1760.

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Surgical masks are intended to be used to prevent transmission of disease from a health care worker to a patient. Often times, they are relied upon by health care workers for their own protection. In light of recent developments regarding preparation for health care worker response to global infectious diseases such as H1N1 Influenza, health care workers may experience a false sense of security when wearing surgical masks. The goal of this study was to evaluate the filtration efficiency of a double strap tie-on surgical mask. The manufacturer asserts a >95% efficiency with a 0.1 um challenge aerosol under FDA testing procedures. The NIOSH Title 42 CFR Part 84 certification criteria call for testing at a rate of 85 lpm representing a human moderate to heavy work load breathing rate. Three sizes of monodispersed aerosols (polystyrene latex beads: 0.5 um, 1.0 um, 2.0 um) were used. The specific aims were to measure the collection efficiencies of this mask for the various particle sizes. Two tests were performed. In the first, masks were affixed to a dummy head and the edges of the mask were not sealed. In the second, the edges of the masks were sealed to the head using silicone sealant, so all penetration was through the filtering material of the mask. Differences in upstream and downstream particle concentrations were measured. Thus, penetration by leakage around the mask and through the filtering material was measured. The experimental set up involved passing the aerosol from the nebulizer through a diffusion dryer and Kr-85 charge equilibrator ensuring a dry charge neutralized aerosol cloud for detection by a LASAIR particle counter. The analysis revealed that the filtration efficiency for 0.5 um particles ranged from 3% to 43% for the unsealed masks and 42% to 51% for the sealed. For 1.0 um particles, the efficiency was 58% to 75% for unsealed and 71% to 84% for sealed masks. For 2.0 um, the efficiency was 58% to 79% for unsealed masks and 69% to 85% for the sealed masks. The data were statistically significant and indicated that surgical masks were associated with very low filtration efficiency. This suggests that they may be inadequate against airborne viruses and bacteria.

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19

Mullins, Benjamin James, and n/a. "Study of Capture, Fibre Wetting and Flow Processes in Wet Filtration and Liquid Aerosol Filtration." Griffith University. School of Environmental Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040919.124658.

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This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.

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20

Fournet, Frédéric. "Étude d'un cycle de filtration - lavage - essorage - centrifuge : Application à la filtration de l'acide salicylique." Vandoeuvre-les-Nancy, INPL, 1988. http://www.theses.fr/1988NAN10134.

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Étude expérimentale et modélisation des paramètres hydrodynamiques influençant un cycle de filtration centrifuge sur essoreuse discontinue. L'acide salicylique est choisi pour sa granulométrie et la forme de ses particules. Les paramètres plus particulièrement étudiés sont : la formation du gâteau, la perméation (ou lavage) et l'essorage (le drainage) et la cinétique de l'essorage. Chacune de ces opérations est étudiée théoriquement en vue d'une modélisation. Trois types d'essais expérimentaux sont réalisés : sous champ gravitant, sous champ centrifuge sur dispositif de laboratoire et essais à l'échelle du pilote sur essoreuse Rousselet de diamètre 400 mm

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21

Munholand, Luke. "Filtration à haute température avec des chandelles céramiques = High temperature filtration with ceramic candle filters." Sherbrooke : Université de Sherbrooke, 2001.

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22

Fournet, Frédéric. "Etude d'un cycle de filtration-lavage-essorage-centrifuge application à la filtration de l'acide salicylique /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37613693s.

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23

Mullins, Benjamin James. "Study of Capture, Fibre Wetting and Flow Processes in Wet Filtration and Liquid Aerosol Filtration." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/365591.

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This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) School of Environmental Engineering Faculty of Environmental Sciences Full Text

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24

Kong, Deyi. "A modelling study of filtration mechanisms for micron-particles filtration in fibrous diesel particulate filters." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/130563/9/Deyi%20Kong%20Thesis.pdf.

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Diesel exhaust has a particle size less than 10 µm; for the visualisation of micron-particles’ motion, the numerical method is applied. A coupled lattice Boltzmann method and discrete element method is implemented to investigate the mechanism that governs particle-gas flows and particle fouling in idealised 2D fibrous DPFs. The open-source library, Mechsys, is validated and then implemented for idealised filter configurations. The initial parameters of simulations are filter configurations, initial velocities of fluid, the density of the particles, porosity of the filters, with the particle diameter being 10 µm. These results consider the numbers of particle deposition, filtration time, pressure drop, and location of particle deposition. The results have shown that the different filter configurations have different filtration performances for different velocities or densities. The filters of 75% porosity have better than 90% porosity filtration performance for 10 µm particles.

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25

Jeffcoat, Stuart Blakely. "The importance of hydrophobicity/hydrophilicity on particle removal in deep bed filtration and macroscopic filtration modeling." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20149.

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26

Foreman, Gordon P. "Slow Rate Sand Filtration With and Without Clinoptilolite: A Comparison of Water Quality and Filtration Economics." DigitalCommons@USU, 1985. https://digitalcommons.usu.edu/etd/2896.

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Slow rate sand filtration (SSF) amended with a 20 em surface layer of clinoptilolite, a natural zeolite, was compared to SSF with no amendment in a field scale SSF facility treating 85 m3/d of water. Parameters examined included turbidity, coliforms, and ammonium removal. The control filter with sand and the experimental filter amended with the zeolite were also compared with respect to duration of filter cycle, cold weather operation, and economics. Amended and unamended filters were appr oximately equivalent with respect to ammonium and coliform removal at 10° C. The zeolite amended cell was superior to the unamended cell with respect to coliform and turbidity removal at 3° C. The zeolite amended cell had filter cycle durations four times longer and operation and maintenance costs 25% lower than the unamended cell. Laboratory column studies were also conducted to compare a control column of construction sand to a homogeneous sand-zeolite mixture. and to SSF amended with zeolite or coarse sand. Construction sand and clinoptilolite were very similar in metal removal efficiency. Head loss developed most rapidly in the SSF column with construction sand only. Head loss developed more slowly resulting in longer filter cycles when the SSF was amended with a zeolite or coarse sand surface layer. A homogeneous sand-clinoptilolite mixture had filter cycles longer than construction sand, but shorter than SSF amended with a coarse surface medium. Batch reactor tests were utilized to compare adsorption of reovirus to sand and clinoptilolite. Reovirus adsorption was approximately equivalent for the two media.

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27

Monzón, Montebello Andrea. "Aerobic biotrickling filtration for biogas desulfurization." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/126525.

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Es va gestionar l'operació d'un biofiltre percolador (BTF) durant un període total de 990 dies per a la dessulfuració d'un biogàs sintètic contenint 2,000 ppmv d’H2S (≈ 50 g S-H2S·m-3·h-1), utilitzant un material de rebliment aleatori (anelles Pall d'acer inoxidable). Després de l'optimització de l'operació a pH neutre, es va estudiar l'eliminació simultània de metilmercaptà (CH3SH) i H2S. A continuació es va executar la transició ininterrompuda des de 440 dies a pH neutre (6.0 – 6.5) a 550 dies a pH àcid (2.50 – 2.75). Paral·lelament es van desenvolupar eines per a la monitorització en línia d’H2S, sulfur dissolt total (TDS = H2S(aq) + HS- + S2-) i sulfat (SO42-), aplicant elèctrodes selectius d'ions (ISEs). Es va emprar un ISE de membrana cristal·lina en el sistema analític proposat, que consisteix en un analitzador per injecció de flux (FIA) per anàlisi de TDS integrat com a detector en un analitzador de flux continu amb una etapa prèvia de difusió de gas (GD-CFA) per l’anàlisi d’H2S, el qual es va mostrar idoni per a la monitorització en línia del BTF. Es va realitzar l'estudi preliminar de la determinació en línia de SO42- utilitzant un ISE de membrana líquida polimèrica, preparada amb un ionòfor comercial. No obstant això, es va obtenir baixa selectivitat per al SO42- en presència d'anions interferents, el que desaconsella l'aplicació dels elèctrodes construïts. Es van optimitzar paràmetres operacionals del BTF a pH neutre, com ara la taxa d'aeració, la velocitat de percolació (TLV) i el temps de residència hidràulica (HRT), obtenint una mínima producció de sofre elemental (S0). També es va estudiar la resposta del BTF enfront del temps de contacte del gas (EBRT) i de la càrrega aplicada (LR) d’H2S. La capacitat d'eliminació (EC) màxima va ser de 135 g S-H2S·m-3·h-1. Per a un EBRT de referència de 131 s, l'eficàcia d'eliminació (RE) va ser superior al 99%. Es va investigar l'eliminació simultània de CH3SH i H2S a pH neutre, a concentracions normalment trobades en biogàs (2,000 ppmv d’H2S i 10 – 75 ppmv de CH3SH). Les màximes EC trobades van ser de 1.8 g S-CH3SH·m-3·h-1 i 100 g S-H2S·m-3·h-1. La presència natural de CH3SH en el biogàs va ser considerada beneficiosa per l’efecte de descolmatació del llit produït pel consum de S0 per reacció química amb CH3SH. Finalment, es va caracteritzar l'operació a llarg termini del BTF sota condicions àcides de pH en funció del EBRT i la LR, obtenint una ECmax de 220 g S-H2S·m-3·h-1. Es va estudiar el perfil d'eliminació d’H2S i es va avaluar la velocitat d'oxidació del S0 acumulat dintre del llit durant episodis periòdics d'inanició. Els resultats indiquen que el primer terç del llit és responsable pel 70 – 80% del total eliminat d’H2S. L'oxidació de S0 a SO42- se suggereix com una estratègia de control contra la colmatació del llit per sofre. Tot i la important quantitat de S0 produït a pH àcid, la capacitat de dessulfuració global del BTF va ser comparable a l'obtinguda anteriorment a pH neutre. The performance of an aerobic biotrickling filter (BTF) was assessed during a total period of 990 days on the desulfurization of a synthetic biogas containing 2,000 ppmv of H2S (≈50 g S-H2S·m-3·h-1), using a metallic random packing material (stainless steel Pall rings). After the optimization of the operation at neutral pH, the simultaneous removal of methylmercaptan (CH3SH) and H2S was studied. Afterwards, the uninterrupted transition from 440 days at neutral pH (6.0 – 6.5) to 550 days at acidic pH (2.50 – 2.75) was performed. In parallel, sensing tools for the on-line monitoring of H2S, total dissolved sulfide (TDS = H2S(aq) + HS- + S2-) and sulfate (SO42-) were developed applying ion-selective electrodes (ISEs). An ISE of crystalline membrane was used in the proposed analytical system, consisting in a flow injection analyzer (FIA) for TDS detection integrated as a detector into a continuous flow analyzer with a gas diffusion step (GD-CFA) for H2S detection, which was proven to be reliable for on-line monitoring of the BTF. The preliminary study on the on-line determination of SO42- was performed by an ISE of polymeric liquid membrane, prepared with a commercial ionophore. However, low selectivity to SO42- was found in the presence of interfering anions, discouraging the application of constructed electrodes. Operational parameters of the BTF were optimized under neutral pH, such as the aeration rate, the trickling liquid velocity (TLV) and the hydraulic residence time (HRT), achieving a minimum elemental sulfur (S0) production. Also, the behavior of the BTF was studied as a function of the empty bed residence time (EBRT) and the H2S loading rate (LR). A maximum elimination capacity (EC) of 135 g S-H2S·m-3·h-1 was found. Removal efficiency (RE) above 99% was obtained at the reference EBRT of 131 s. The simultaneous removal of CH3SH and H2S was investigated at neutral pH, for concentrations commonly found in biogas (2,000 ppmv of H2S and 10 – 75 ppmv of CH3SH). Maximum ECs were 1.8 g S-CH3SH·m-3·h-1 and 100 g S-H2S·m-3·h-1. The natural presence of CH3SH in biogas was considered beneficial because of the unclogging effect produced by the consumption of S0 by chemical reaction with CH3SH. Finally, the BTF long-term operation under acidic pH was characterized in terms of EBRT and LR, obtaining an ECmax of 220 g S-H2S·m-3·h-1. The H2S removal profile was assessed and the oxidation rate of S0 accumulated inside the filter bed was evaluated by periodical H2S starvation episodes. Results indicate that the first third of the filter bed is responsible for 70 to 80% of the total H2S removal. Oxidation of S0 to SO42- was suggested as a S-clogging control strategy under acidic conditions. Despite the important amount of S0 produced under acidic pH, overall BTF desulfurizing capacity was comparable to that obtained previously under neutral pH.

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28

Bruasse, Laurent. "Stabilité et filtration de Harder-Narasimhan." Phd thesis, Université de Provence - Aix-Marseille I, 2001. http://tel.archives-ouvertes.fr/tel-00004129.

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Née sur les variétés algébriques, la notion de stabilité s'est ensuite généralisée aux variétés kähleriennes, puis, au variétés holomorphes compactes grâce à l'utilisation des métriques de Gauduchon. L'étude du comportement des fibrés (ou des faisceaux) non semi-stables n'a été faite de façon complète que dans le cas algébrique à travers la notion de filtration de Harder-Narasimhan (FHN). Nous poursuivons ici cette étude pour des variétés holomorphes compactes quelconques. Nous montrons qu'il est possible de définir le sous-faisceau de pente maximale d'un fibré vectoriel complexe. Ce sous-faisceau est obtenu comme limite au sens des sous-fibrés holomorphes faibles, notion déjà utilisée par Uhlenbeck et Yau pour la correspondance de Kobayashi-Hitchin, qui nous donne ici ``la bonne notion de convergence''. Nous démontrons l'existence d'une FHN dans ce cadre. Nous généralisons ensuite le résultat aux faisceaux cohérents sans-torsion. On est alors confronté à des problèmes de convergence liés à la non compacité de la base (lieu où le faisceau est localement libre). Nous montrons ensuite comment ces méthodes s'appliquent à une famille de fibrés (ou une famille plate de faisceaux sans-torsion) définie sur une déformation de variété holomorphe compacte pour obtenir des résultats d'existence de sous-faisceaux limites de type Bishop. On obtient par là-même une nouvelle démonstration de l'ouverture de la stabilité en déformation qui n'utilise pas la difficile correspondance de Kobayashi-Hitchin. Dans une deuxième partie, nous donnons des conditions équivalentes de simplicité et de stabilité pour les fibrés tangents des surfaces holomorphes compactes de la classe $VII$. Nous obtenons, en particulier, un exemple de déformation de surface à coquille sphérique globale qui illustre la non ouverture de la non semi-stabilité en déformation.

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29

Twumasi, Ebenezer. "Molecular filtration : the study of adsorbents." Licentiate thesis, KTH, Byggnadsmaterial, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32075.

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Adsorbent materials for gas purification have been studied and developed for application in many areas. It is known that a single adsorbent may not adequately control multiple contaminants. Therefore, the development of adsorbent materials has accelerated over the past two decades, and is today an area attracting a lot of attention. In view of the global environmental movement for clean air, the development of improved sorbents will help address new challenges that cannot efficiently be met with the generic sorbents that are presently commercially available. On the other hand, the utilization of these new sorbents for specific applications within the area of molecular filtration remains largely unexplored. This thesis presents a synthesis of new sorbent materials, and the characterization and application of these materials for molecular filtration. Commercial adsorbents have been used for benchmarking for the pore properties, the applicability, and the performance of these new adsorbents. A double metal-silica adsorbent has been synthesized. The preparation procedure is based on the use of sodium silicate coagulated with various ratios of magnesium and calcium salts which yields micro-meso porous structures in the resulting material. The results show that molar ratios of Mg/Ca influence the pore parameters as well as the structure and morphology. The bimodal pore size can be tailored by controlling the Mg/Ca ratio. The effect of thermal treatment on pore parameters of these adsorbents has been investigated. The results show that heat treatment had a notable effect on the pore parameters, and that the pore structure was thermally stable even at 600°C. A synthesis method has also been developed for the preparation of carbon-silica composites. The method involves a number of routes, which can be summarised as addition of activated carbon particles to (I) the paste, (II) the salt solution, or (III) with the sodium silicate solution. In route II and III the activated carbon is present also before coagulation. The routes presented here leads to carbon-silica composites possessing high micro porosity, meso porosity as well as large surface areas. The increase in micro porosity and surface areas was linear with carbon content. The results shows further that pore size distribution may be tailored based on the route of addition of the carbon particles. Following route I and III a wide pore size (1-30nm) was obtained where as by route II a narrow pore size (1-4nm) was observed. KOH or KMnO4 modified MgCa adsorbent varieties were also prepared. The impregnationwas performed by either a direct synthesis or post-synthesis procedure. Potassium hydroxide and potassium permanganate have been chosen as impregnate chemicals. Results revealed that theimpregnate amount significantly affected both the structural and the gas adsorption characteristics of the impregnated MgCa adsorbents. The properties of double- metal adsorbents, impregnated adsorbents and carbon-silica composites were characterized by various methods (X-ray diffraction, scanning electron microscopy, thermo gravimetric analysis, and nitrogen adsorption at 77K) to study the material structure and morphology, thermal stability, ignition temperature and porous parameters with regard to surface area, pore size, pore size distribution and porosity volume, which is important for optimizing their use in many practical application. The up-take performance of adsorbents for dynamic adsorption of SO2, H2S and toluene was performed in a system similar to the setup usedin ASHRAE 145.1. Finally the applicability and performance of the impregnated modified MgCa-silica adsorbents and composites have been evaluated for H2S, SO2 and toluene adsorption and compared to some commercial adsorbent materials. Results revealed that a potassium permanganate modified MgCa-adsorbent has a H2S adsorption capacity in the range of 0.08-3.19 wt % at 50% efficiency, and that the uptake capacity was relative to the amount of potassiumpermanganate loading. Moreover, KOH modified MgCa-adsorbent shows highest SO2 adsorption capacity (1.7 wt %) which is 3.47 times higher than commercial alumina impregnate with potassium permanganate (0.49 wt %). Carbon-silica composites on the other hand shows adsorption of toluene and high adsorption capacity was obtained when carbon content was 45 wt %. The results further shows that a composite with 45 wt % carbon and obtained via route I present the highest toluene adsorption capacity ( 27.6 wt % relative to carbon content) at 0% efficiency. The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1-30nm) bimodal pore system consisting of extensive mesopore channels (2-30nm) as well as large surface area. These capacity values of carbon-silica composites are competitive to results obtained for commercial coconut based carbon (31 wt %), and better than commercial alumina-carbon composite. QC 20110405

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30

Ying, Tung-Yu. "Magnetically-seeded filtration of colloidal particles." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/20229.

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31

Kunjikutty, Sobhalatha Panangattu. "Floodplain filtration for treating municipal wastewaters." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100641.

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The effectiveness of a cheap, low-tech, environmentally and technically favorable treatment of secondary treated municipal wastewater by contaminant removal through a floodplain-soil filter was evaluated using floodplain-simulating field lysimeters, packed with a sandy soil in 2002 and sand in 2003 and 2004. Secondary treated wastewaters from Vaudreuil (2002 and 2003) and Pincourt (2004) Wastewater Treatment Plants were used as influent. This was applied at rates of 0.06, 0.19, and 0.31 m3 m-2 d -1 to vegetated lysimeters, and at a rate of 0.19 m3 m-2 d-1 to bare-soil lysimeters. Removal of NH4+-N, NO3--N, and COD from the influent was studied in all three years. Irrespective of flow rate or year, the system removed 62~84%, 96~99%, and 6~67% of TKN, NH4+-N, and COD, respectively, from the influent. Under 0.19 m3 m-2 d-1 flow rate, vegetated systems removed slightly more of these constituents from the influent, than did bare-soil lysimeters. Organic degradation mainly occurred in the top 0.1 m soil depth. Degradation of organic and inorganic influent nitrogen increased NO3--N levels in the effluent. Only minimal increases in soil-N levels and N2O emissions occurred with increasing application rates. The nitrogen mass balance accounted for 85&sim;98% (2003) and 67&sim;96% (2004) of input nitrogen (through leaching, soil retention, and N2O emissions), the remaining portion being attributable to vegetative effects and volatilization of non-N2O nitrogenous gases. The under established vegetation on the lysimeters reduced nitrogen leaching through soil, being 6% (2003) and 60% (2004) more effective than bare soil. Effluent water quality improved with decreasing levels of heavy metals. Compared to influent levels, in vegetated lysimeters, under all flow rates, mean effluent As, Cd, Cu, Ni, Pb, and Zn levels had dropped by 58%, 9%, 3%, 37%, 63%, and 52% in 2003, and by 20%, 63%, 5%, 23%, 18%, 57%, and 79% for As, Cd, Cr, Cu, Ni, Pb, and Zn, in 2004. In both years, similar decreases in heavy metal levels occurred in the bare soil lysimeters. Across all flow rates and influent concentrations, soil heavy metal levels increased. In 2004, even low heavy metal content influent further increased (6&sim;179%) their accumulation in soil. As inputs of heavy metals to the soil increased with the increase in application rates, their associated times to reach maximum permissible limits also decreased. LEACHN simulation of NO3--N in leachate arising from wastewater application, showed lowered levels with increasing flow rates, due to enhanced denitrification in the resulting anoxic upper soil zones. The simulation under continuous wastewater application at different range of nitrogen concentrations (low, medium, high) showed an increase of NO 3--N levels in the leachate with increasing N-levels. For all flow rates, and under tropical or humid conditions, the effluent NO 3--N levels remained below permissible limits for the low-N content wastewater applications. Intermittent applications, under all wastewater N-contents and flow rates, reduced NO3--N levels in the leachate by 51&sim;89% compared to continuous wastewater application, and permissible limits were not exceeded. Hence, wastewater with high levels of nitrogenous compounds, as occurs in most developing countries, could be treated by land under an intermittent application pattern, allowing a considerable reduction in nitrate pollution.

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32

Rajapakse, Jayasiri Pemathilake. "Pre-filtration of high turbidity waters." Thesis, University College London (University of London), 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497127.

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33

Miao, Lin. "The gas filtration properties of needlefelts." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352964.

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34

Payne, Simon Daniel. "Experimental studies of diesel particulate filtration." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610170.

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35

Kakutkina, NA, and MM Mbarawa. "Transition Processes in Filtration Gas Combustion." Plenum Publishing Corporation, 2004. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001750.

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Methane Summary The behavior of gas filtration combustion waves in the low-velocity regime has been studied experimentally with variation in the parameters of the gas flow and porous medium. It is shown that in transition processes there may be quenching or formation of a stable combustion-wave structure that does not correspond to the initial or final conditions. A nontrivial type of transition process accompanied by spatial transfer of the combustion zone is found.

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36

Mignard, Dimitri. "Mass transport studies in membrane filtration." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/12654.

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First, a programme to model concentration polarisation was written using the finite difference approach developed by Ilias and Govind. It was validated with experiments using Centrisystem C-300 and C-400 cartridges and BSA solutions (1-5 g/L), and experimental data from Yeh and Cheng with an H1P30-20 Amicon cartridge and Dextran T-500. The next step was to incorporate fouling into this model. To calculate the configurational Derjaguin-Landau-Vervey-Overbeek (DLVO) forces and the resulting osmotic pressures, large use was made of the work of Bowen et al. Concentration dependent diffusivities were calculated from the generalised Stokes-Einstein equation, and used in the transport equation to describe the concentration polarisation profile. It was shown that, when the transport equation did not have a solution at the membrane (or membrane + cake) surface, and that concentration was greater than the highest-concentration local maximum for the diffusivity, coagulation would occur. In this case, a monolayer of globular protein was assumed to deposit, and concentration polarisation was recalculated with this additional resistance. Experiments with 1g/L BSA solutions and Amicon H1P30-20, for a range of transmembrane pressure, ionic strengths and pH, were compared with the model predictions. Both showed that fouling increased with ionic strength away from the Iso-Electric Point of BSA (IEP), and decreased with zeta potential. Simulation also showed that fouling could decrease with increased ionic strength around the IEP, in accordance with classical results. Total resistance to flux from experiments and simulation were in a similar range, although the lack of data relating zeta potentials and pH prevented further comparison. The model would also determine the critical pressure above which fouling occurred. However, observed values were significantly lower than predicted. Direct adsorption of the BSA onto the polysulfone membrane or the effect of high local pore velocities may both explain these discrepancies.

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37

Vengadasalam, Kirijen. "Computational modelling of coalescence filtration process." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/17323/.

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The low water-diesel interfacial tensions arising in biodiesels pose a problem for fuel filters designed to separate water contamination from diesel fuel. Such filters operate by passing the fuel through a fibrous non-woven material with the aim of capturing small water droplets on the fibres and holding them while further droplets coalesce with the captured droplets until the droplets are large enough to be carried away from the fibres and subsequently settle out of the fuel by gravity. The coalescence process is however less effective at lower interfacial tensions. The main purpose of this research is to explore the mechanisms at work in a coalescence filter by developing and applying computer simulations of the process, and to understand the effects of fibre properties such as wettability, size and separation on the filtration performance. Following a detailed review of the relevant literature, a macroscopic simulation of the flow within a filter housing is first presented, using finite element analysis via COMSOL Multiphysics to establish the main flow patterns through the filter system. The filter medium itself in this model is treated as a continuous porous medium. The flow at the pore/fibre scale is then analysed by means of a multiphase lattice Boltzmann method based on the multicomponent Shan-Chen model. The wettability of the fibres is incorporated through specification of a fluid density at the solid surfaces, allowing easy control of the local contact angle. The code developed is tested against previously published and validated finite volume/volume-of-fluid simulations of free droplet coalescence, with good agreement seen in the predicted dynamics. The interactions between individual water droplets and fibres is explored, in particular to establish critical conditions (flow speed, fibre contact angle, droplet/fibre size, droplet-fibre separation, fuel viscosity etc.) under which droplets carried by the flow can be captured by fibres, and the conditions under which droplets are released from fibres. The results confirm the difficulties in achieving rapid and effective coalescence when the interfacial tension is low, and reveal the sensitivity of the droplet-fibre dynamics to the contact angle on the fibres and the relative size of the droplets and fibres. In particular larger fibres are not effective for small droplets, so small fibres are essential in the filtration process. Also investigated are the dynamics of multiple droplets with arrays of fibres representing the filtration media. It is found that higher contact angles ( > 120°) lead to lower capture efficiency compared to lower contact angle, while contact angles less than 106° tend to produce a small variation in capture efficiency and capture most of the droplets at a filter porosity of 0.87. It is concluded that the inlet layer of the filter should have fibres with 78° contact angle and the exit layer fibres with contact angle 106°.

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38

Wu, Nan. "Filtration de nanoparticules par procédés membranaires." Ecole centrale de Marseille, 2013. http://www.theses.fr/2013ECDM0017.

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39

Andan, Saravanan. "Modeling of Drainage in Coalescence Filtration." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1268145371.

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40

Raghavan, Bharath Kumar. "Nanofiber Filter Media for Air Filtration." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1279744866.

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41

Farmerie, Sarah Mace. "Stormwater filtration properties of pervious concrete." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025013.

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42

Khan, Muhammad Waleed. "Dynamic filtration at soil-geotextile interfaces." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39882/.

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The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Geotextiles often perform well under steady state conditions like those found in dams. However, when the soil-geotextile interface is subjected to dynamic loading, the requirements for successful filtering are uncertain and/ or conservative as the controlling factors are not well understood in these circumstances. There are few filter design criteria available for dynamic flow conditions. These criteria do not properly address the internal instability of soils for which the rearrangement of particles adjacent to the filter interface is complex. Unstable soils may exist in roadway bases adjacent to pavement edge drain. Therefore, this research work was carried out to better understand the filtration behaviour of non-woven geotextiles with internally stable and unstable soils beneath roads. To carry out the filtration tests, a flexible wall gradient ratio (GR) apparatus was developed. The GR tests were performed to investigate the effect of different factors on the filtration performance of the soil-geotextile interface under dynamic conditions. The factors included hydraulic gradient, vertical stress and frequency of loading, soil gradation and geotextile properties. Test results were interpreted in terms of head loss within the soil and across the geotextile, GR values, permeability ratio, mass and gradation of particles passed through geotextiles, microscopic images of geotextiles after test, partial geotextile clogging levels and hydrometer sieve analyses of soil samples to compare the gradation of samples after test with the original gradation. All the tests were performed under a hydraulic gradient of five. The internal stability of soil samples were evaluated by three geometric criteria. The test results showed that a high hydraulic gradient has the ability to lead to the internal instability of soils which resulted in migration of fines towards the geotextiles. The dynamic loading resulted in increase of soil migration within the base soil as well as washing out of soil particles through geotextiles. No significant effect of increase in frequency and vertical stress was observed on filtration behaviour of soil-geotextile combinations. The geotextile pore size was found to be the main factor controlling the filtration behaviour as compared to other geotextile properties. The Kenney and Lau (1985) and the Kezdi (1979) criteria predicted well the internal instability of soils under dynamic conditions. In this research study, a new method was suggested which is able to measure the pore sizes along the entire thickness of geotextiles. The filtration tests showed that geotextiles having the same large openings but different pore size distributions may result in different filtration performances. Based on the test results, filter design criteria were suggested for piping and blinding limits which were compared with the existing design criteria. These new filter criteria were found to be more appropriate in terms of piping and blinding limit states.

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43

Romo, Romero Ricardo. "Filtration enlargement with applications to finance." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLE012/document.

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Cette thèse se compose de quatre parties indépendantes. Le fil conducteur de celle-ci est le grossissement de filtration. Dans la première partie, nous présentons des résultats classiques de grossissement de filtration en temps discret. Nous étudions quelques exemples dans le cadre du grossissement initial de filtration. Dans le cadre du grossissement progressif nous donnons des conditions pour obtenir la propriété d'immersion des martingales. Nous donnons également diverses caractérisations des pseudo temps d'arrêt et nous énonçons des propriétés pour les temps honnêtes.Dans la deuxième partie, nous nous intéressons à la détermination du prix de produits à annuités variables dans le cadre de l'assurance vie. Pour cela nous considérons deux modèles, dans ces deux modèles nous considérons que le marché est incomplet et nous adoptons l'approche par prix d'indifférence. Dans le premier modèle nous supposons que l'assuré procède à des retraits aléatoires et nous calculons la prime d'indifférence par des méthodes standards en contrôle stochastique. Nous sommes conduits à résoudre des équations différentielles stochastiques rétrogrades (EDSR) avec un saut. Nous fournissons un théorème de vérification et nous donnons les stratégies optimales associées à nos problèmes de contrôle. De ceux-ci, nous tirons une méthode de calcul pour obtenir la prime d'indifférence. Dans le second modèle nous proposons la même approche que dans le premier modèle mais nous supposons que l'assuré effectue des retraits qui correspondent au pire cas pour l'assureur. Nous sommes alors amenés à traiter un problème de max-min.Dans la troisième partie, nous étudions la relation des solutions d'EDSR dans deux filtrations différentes. Nous étudions alors la relation entre ces deux solutions. Nous appliquons ces résultats pour obtenir le prix d'indifférence dans les deux filtrations, c'est-à-dire le prix auquel un agent aurait le même niveau d'utilité attendue en utilisant des informations supplémentaires.Dans la quatrième partie, nous considérons des équations différentielles stochastiques rétrogrades avancées (EDSRAs) avec un saut. Nous étudions l'existence et l'unicité d'une solution à ces EDSRAs. Pour cela nous utilisons la décomposition des processus à sauts liée au grossissement progressif de filtration pour nous ramener à l'étude d'EDSRAs browniennes avant et après le temps de saut This thesis consists of four independent parts. The topic in common is the filtration enlargement.In the first part, we present classical results for filtration enlargement in discrete time. We study some examples in initial enlargement of filtration. For the progressive enlargement of filtration, we give conditions for immersion martingale property. We also provide various characterizations of pseudo-stopping times and properties for honest times.In the second part, we are interested in determining the indifference price for variable annuities products. For this we consider two models, in both models we suppose that the market is incomplete and we adopt the approach of indifference price. In the first model we assume that the insured performs random withdrawals. Following indifference pricing theory, we define indifference fee rate for the insurer as a solution of an equation involving two stochastic control problems. Relating these problems to backward stochastic differential equations with a jump, we provide a verification theorem and give the optimal strategies associated to our control problems. From these, we derive a computation method to get indifference fee rates. We conclude this part with numerical illustrations of indifference fees sensibilities with respect to parameters.In the second model we propose the same approach as in the first model but we assume that the insured makes withdrawals that match the worst case for the insurer. In the third part, we study the relation of the solutions of BSDEsin two filtrations. As an application, one of our goals is to find theindifference price of information, i.e. the price at which an agentwould have the same expected utility level using extra informationas by not doing so. In the fourth part, we investigate advanced backward stochastic differential equations (ABSDE) with a jump. We study the existence and uniqueness of the solution to these ABSDEs. For this we relate the solution of the ABSDEs wth jumps to Brownian ABSDEs associated to the original ABSDE before and after the time jump

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44

Chateauneuf-Randon, Sixtine de. "Membranes d'hydrogel pour une filtration sélective." Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS255.

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Les hydrogels sont des matériaux polymères hydrophiles qui retiennent de grandes quantités d’eau tout en conservant une structure tridimensionnelle, ce qui les rend adaptés à des applications biomédicales et de filtration. Ce manuscrit se concentre sur les membranes d’hydrogels fabriquées à partir de polyéthylène glycol diacrylate (PEGDA) réticulé par UV en présence de chaînes de polyéthylène glycol (PEG) et d’un photoamorceur. Les membranes PEGDA/PEG sont sélectionnées pour leur robustesse mécanique et leur perméabilité élevée qui peut être ajustée en fonction de la concentration et de la masse molaire du PEG. Une caractéristique importante de ces membranes est que les chaînes de PEG restent piégées dans la matrice, permettant ainsi de les fonctionnaliser pour une filtration sélective. Notre étude montre que les membranes PEGDA/PEG peuvent retenir sélectivement de petites molécules formant des liaisons hydrogène. Nous fonctionnalisons également les membranes avec de l’acide polyacrylique (PAA) pour les rendre sélectives aux colorants chargés positivement. Les membranes PEGDA/PEG/PAA s’avèrent efficaces pour la rétention du bleu de méthylène et de la rhoda- mine B. La sélectivité de ces membranes est réversible par ajustement du pH, permettant ainsi de les rincer et de les réutiliser. L’analyse structurelle des membranes par diffusion de neutrons aux petits angles (SANS) révèle que les chaînes de PEG conservent une structure gaussienne dans la matrice de PEGDA, mais avec des rayons de giration et des longueurs de corrélation plus élevés qu’en solution, suggérant des contraintes topologiques comme des greffages chimiques ou des enchevêtrements. Une observation clé est que le rapport surface/volume de la matrice de PEGDA diminue avec l’ajout de PEG, indiquant la formation de cavités plus grandes, ce qui explique l’augmentation de la perméabilité observée. Lorsque la concentration en PEG dépasse une certaine valeur critique (C∗), le rapport surface/volume augmente, suggérant une diminution de la taille des cavités d’eau et, par conséquent, de la perméabilité. Nous développons également un modèle théorique pour prédire la perméabilité des hydrogels PEGDA/PEG en fonction de la masse molaire et de la concentration en PEG pour C < C∗, qui correspond bien aux mesures expérimentales Hydrogels are hydrophilic polymer materials that retain large amounts of water while maintaining a three- dimensional structure, making them suitable for biomedical and filtration applications. This manuscript focuses on hydrogel membranes made from polyethylene glycol diacrylate (PEGDA) crosslinked by UV in the presence of polyethylene glycol (PEG) chains and a photoinitiator. PEGDA/PEG membranes are selected for their me- chanical robustness and high permeability, which can be adjusted based on the concentration and molecular weight of PEG. An important feature of these membranes is that the PEG chains remain trapped in the ma- trix, allowing them to be functionalized for selective filtration. Our study shows that PEGDA/PEG membranes can selectively retain small molecules forming hydrogen bonds. We also functionalize the membranes with polyacrylic acid (PAA) to make them selective for positively charged dyes. PEGDA/PEG/PAA membranes prove effective in retaining methylene blue and rhodamine B. The selectivity of these membranes is reversible by adjusting the pH, allowing them to be rinsed and reused. Structural analysis of the membranes by small- angle neutron scattering (SANS) reveals that the PEG chains maintain a local gaussian structure within the PEGDA matrix, but with larger radii of gyration and correlation lengths than in solution, suggesting topolo- gical constraints such as chemical grafting or entanglements. A key observation is that the surface-to-volume ratio of the PEGDA matrix decreases with the addition of PEG, indicating the formation of larger cavities, which explains the observed increase in permeability. When the PEG concentration exceeds a certain critical value (C∗), the surface-to-volume ratio increases, suggesting a decrease in the size of the water cavities and consequently in permeability. We also develop a theoretical model to predict the permeability of PEGDA/PEG hydrogels as a function of the molecular weight and concentration of PEG for C < C∗, which corresponds well with experimental measurements

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Iessa, Hassan. "Concentrating food materials using electrokinetically enhanced filtration (EKEF) : impact on filtration efficiency, quality compounds and power consumption." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3483.

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Countries around the world are suffering from many problems caused by the misuse of their resources either by using non-renewable ones or destroying the valuable features of the resources that are available. Some of the most important challenges facing humanity are related to food and energy security. Food security includes many aspects besides providing people with an adequate amount of safe and healthy food; it also includes improving food processing to produce acceptable, high quality food products with reduced losses of nutrients, carbon footprint and using fewer resources in the production/packaging processes. Dried and concentrated foods have become an important category in the food products marketplace. Many of the usual traditional methods require very high energy inputs. These methods may also have significant negative impacts on the foodstuffs, especially their chemical properties, such as loss of essential nutrients, as well as their appearance, aromas and flavour. This project aimed to combine the electrokinetic phenomenon of electro-osmosis with the traditional functions of filtration to form a process of electrokinetically enhanced filtration (EKEF). This process is based on using electrokinetic effects to enhance conventional filtration technologies to concentrate foodstuffs at low temperature which saves energy, time, and product constituents associated with product quality, especially the temperature-sensitive components such as Vitamin C, fruit/vegetable colours and key aromas. This study is concerned with factors affecting the efficiency of the EKEF process after its application to concentrate orange juice (14% dry matter content, pH=3.6) and malt extract (20% dry matter content, pH=4.55), and monitoring the changes that occur in indicators of food quality, such as the change in pH value, vitamin C content, colour, dry matter as well as the energy inputs to facilitate the EKEF. The process of electrokinetics was combined with micro-filtration (MF) to speed up the process and save time and energy. This is carried out in an EKEF-rig which was designed to meet the project needs with an ability to change all the dependent parameters to find the optimum conditions to run this application. Applying EKEF improved the filtration process and achieved net dewatering efficiencies up to 7.43% and 4.86% for orange juice and 10.68% and 6.26% for malt extract after 5.5hrs of processing under 30V and 15V respectively; and increased dry matter content from 14% to ii 33.09% and 29.52% for orange juice and from 20% to 34.2% and 32.14% for malt extract after 5.5hrs under 30V and 15V respectively. The maximum dry matter content was 28.75% and 29.63% under the control condition after the same time for orange juice and malt extract respectively. Results showed that the performance of the EKEF process was dependent upon several parameters such as the sample’s conductivity, applied voltage used, applied pressure, initial sample’s thickness (the distance between electrodes) and filters pore size; all of these factors had a positive impact on improving the process efficiency except of the initial sample’s thickness which had a negative impact. Regarding the impact on the heat-sensitive food compounds, here represented by vitamin C; applying EKEF for 5.5hours reduced vitamin C retention in the concentrated juice to 41% under 15V and 7% under 30V. The retention of the total filtrate was also influenced by the EKEF process, where it fell to 48% under 15V and 35% under 30V. Vitamin C retention was better under the EKEF process compared with its value under conventional thermal methods, where it needed about 10-15min at 50-75ºC and (3min) at 90ºC to drop to 50% or less (Vikram et al., 2005). EKEF also had a negative impact on the juice colour and pH value. The direction of water flow and the profile of fluid flow between the two electrodes were thoroughly investigated to identify the main filtration outlet and its position; the power consumption of the application was also calculated and compared with power consumption of conventional thermal methods. The EKEF process resulted in a large power consumption addition compared with applying the pressure only; however, the required additional energy needed to achieve the same increase in dewatering efficiency by increasing the pressure only without EK was relatively small. On the other hand, EKEF showed a good efficiency in energy saving compared with the power consumption required in more conventional thermal methods used to evaporate an equal amount of water. This saving was up to 18.35 times and 47.34 times in OJ and ME dewatering respectively.

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Tavares, Marcelo Botini. "Utilização de colunas verticais de filtração em manta e areia como pré-tratamento de filtro lento /." Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/98081.

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Orientador: Edson Pereira Tangerino Banca: Tsunao Matsumoto Banca: Luiz Di Bernardo Resumo: A Filtração Lenta é um processo de tratamento de água que tem como principal característica a eficiente remoção de patógenos, algas e cianobactérias, as quais nos últimos anos têm-se desenvolvido muito nos reservatórios de abastecimento de água devido à eutrofização causada principalmente pelas atividades antrópicas. As cianobactérias produzem substâncias tóxicas conhecidas como cianotoxinas, que causam problemas gástricos, dermatológicos e toxicológicos nos humanos, além de problemas nas estações de tratamento de água. Apesar da eficiência da Filtração Lenta na remoção destes organismos, ela possui restrições quanto à área necessária aos filtros lentos, quanto ao processo de limpeza destes e dos pré-filtros de pedregulho quando utilizados no tratamento. Esta pesquisa teve então como objetivo desenvolver uma pré-filtração ao filtro lento, através das Colunas Verticais de Pré-Filtração, que fosse eficiente na remoção de parâmetros físico-químicos e bacteriológicos e também no procedimento de limpeza, tornando-o mais rápido e menos dispendioso. Este trabalho foi vinculado ao Programa de Pesquisa em Saneamento Básico (PROSAB) de número 5 do ano de 2007. Para tanto, foi utilizada uma instalação piloto de tratamento de água existente na cidade de Ilha Solteira/SP na qual o processo de tratamento foi o de Filtração em Múltiplas Etapas. Nela foram introduzidas quatro colunas verticais de pré-filtração com taxas diferentes entre si. Foram analisados parâmetros de qualidade de água, o período de desenvolvimento da camada biológica e o tempo de colmatação das unidades filtrantes. Como alguns resultados da pesquisa, foram notificados: a rapidez e facilidade no procedimento de limpeza das colunas, além de necessitarem de limpezas menos freqüentes que os pré-filtros de pedregulho; remoção de cerca de 95% de algas... (Resumo completo, clicar acesso eletrônico abaixo) Abstract: Slow filtration is a water treatment process that provides an efficient removal of pathogens, algae and cyanobacteria, which in recent years have been developed in a large amount in water reservoirs due to eutrophication, caused by human habits. The cyanobacteria produces toxic substances known as cyanotoxins, which cause gastric, skin and toxic disorders in humans, as well as problems in water treatment plants. Despite the efficiency of slow sand filtration in removing these bodies, it has restrictions on the required area for slow filters, on their cleaning process or rubble pre-filters cleaning when used in treatment. The objective of this research is developing a pre-filter to filter slowly through vertical columns pre-filtration, which would be efficient in the removal of physical, chemical and bacteriological bodies and also in cleaning process, making it faster and less expensive. This work was linked to the Programa de Pesquisa em Saneamento Básico (PROSAB) of 5th paragraph from the year of 2007. For this, we used an existing pilot plant for water treatment from of Ilha Solteira City - SP in which the process of treatment was Multiple Stages Filtration. Four pre-filtration vertical columns with different rates were introduced. We analyzed parameters of water quality, the period of organic layer development and the filter units clogging time. As some search results have been reported: the speed and ease of the columns cleaning procedure, less requiring of rubble pre-filters frequent cleaning; approximately 95% of algae and cyanobacteria removal by the columns; satisfactory turbidity removal, apparent color and true color, and smaller area required for its installation, because of their vertical shape. Mestre

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Bucherer, Catherine. "Etude comparative de la déformabilité érythrocytaire par viscométrie et filtration mise au point d'une nouvelle méthode de filtration." Grenoble : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375964714.

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Habibi, Sepideh. "Caractérisation multi-échelles d'un système de filtration en présence d'un biofilm." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2014. http://www.theses.fr/2014ECAP0042/document.

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Dans un procédé de filtration, un fluide traverse une membrane (barrière sélective). Une force motrice s’applique entre les deux côtés de la membrane qui peut être un gradient de pression, température ou un potentiel électrique/chimique. Dans les procédés de filtration par un gradient de pression, certains composés du milieu fluide, traversent la membrane alors que d’autres sont retenues sur la surface membranaire. Ces procédés sont très utiles dans différents domaines de l’industrie, notamment en ce qui concerne le traitement des eaux et des effluents, biotechnologie, agroalimentaire et pharmacie. En plus les procédés de filtration offrent des installations plus compactes avec une optimisation des coûts opérationnels comparant avec des procédés traditionnels de séparation notamment distillation et cristallisation. Par ailleurs, ces procédés se réalisent en absence des additifs chimique et changement de la phase. Dans cette étude, on se focalise sur les procédés de microfiltration. L’inconvénient principal de ces procédés est l’accumulation continue de particules/molécules sur la surface de la membrane. Ceci affecte la sélectivité de la membrane, modifie la qualité et la quantité de liquide passant à travers la membrane et conduit à une augmentation des coûts et de l’énergie. Le Colmatage (encrassement) membranaire se produit dans tous les types de procédés membranaires et par conséquent est connu le principal obstacle à l’utilisation répandue de ces procédés. Différentes techniques sont utiles pour surmonter les effets de l’encrassement de la performance de la membrane: le traitement physico-chimique des membranes utilisées, la modification des conditions opératoires (flux tangentiel de la solution d’alimentation sur la surface de la membrane est souvent appliqué pour réduire au minimum l’accumulation de particules), l’utilisation de membranes moins sensibles au colmatage, etc. Tout dépendant de la nature des solutions traitées, les particules déposées sont très variables. Les micro-organismes, des matières organiques naturelles notamment les protéines, les polysaccharides, les substances humides, les oxydes inorganiques et les sels contribuent au colmatage des membranes. Dans les dernières années, un grand nombre d’études expérimentales ont été investis pour comprendre les mécanismes de colmatage. Il a été souligné que les propriétés physico-chimiques de la membrane, la chimie des solutions et les conditions opératoires sont les trois principaux facteurs influant sur les mécanismes de colmatage. En parallèle, les modèles théoriques ont été proposés pour confirmer / décrire les observations expérimentales. La modélisation du colmatage membranaire est un outil essentiel pour évaluer les mécanismes qui le causent. Il permet également prédire la performance du système de filtration et par conséquent trouver des stratégies adaptées pour empêcher la modification de la performance membranaire pendant le procédé de filtration. En général, les modèles de classifient en deux grandes catégories: les modèles de transport de masse qui se concentrent sur le transport de solutés dans le procédé de filtration, et les modèles de colmatage basés sur le blocage des particules/molécules sur la surface ou à l’intérieur de la membrane. Dans la plupart des cas, les modèles dépendent fortement des paramètres empiriques ou semi-empiriques et restent phénoménologique. 1. Avoir une meilleure compréhension des mécanismes du colmatage membranaire lors de la filtration d’un milieu liquide contenant les micro-organismes en suspension. Il est important de souligner que des eaux industrielles et des eaux usées dans plusieurs domaines appartiennent à ce type d’effluents. 2. Proposer un modèle macroscopique décrivant les mécanismes de colmatage observés. [...] During a membrane filtration process, a liquid medium is filtered through a membrane(selective barrier). The applied driving force between two sides of the membrane can be a gradient of pressure, temperature or a chemical/electrical potential.In pressure driven filtration processes (application of a pressure gradient as driving force between two sides of the membrane), certain components of the liquid medium pass through the membrane, while others are retained at the membrane surface. These processes are widely used as separation techniques in different industrial fields like waste water treatment, biotechnology, food and pharmacy. Compared to conventional techniquesof separation (distillation, crystallization, ...), membrane processes offer more compact installations with more optimized operational costs. Moreover, membrane processes are mainly performed in absence of chemical additives and phase change. In this work we focus on the pressure-driven microfiltration membrane processes.The main disadvantage of these processes is the continuous accumulation of particles on the membrane surface. This affects the membrane selectivity, modifies the quality and the quantity of the liquid passing through the membrane and leads to an increase of energy costs. Membrane fouling occurs in all types of membrane processes and therefore is known as the major obstacle for widespread use of these processes. Different techniques are used to overcome the effects of fouling on the membrane performance : physical-chemical treatment of used membranes, modification of the operational conditions (tangential flow of the feed solution to the membrane is often applied for minimizing the particle accumulation to the membrane surface), use of membranes less susceptible to fouling, etc. Depending on the nature of the treated solutions, the deposited particles are highly variable. Microorganisms, natural organic matter such as proteins, polysaccharides, humid substances, inorganic oxides and salts contribute notably to membrane fouling.It should be noted that membrane fouling problem is a multi-physics (hydrodynamics,mass transport, physics, chemistry), multi-scale (different length scales are involved:molecules, pores and membrane surface) and time dependent (evolution of the membrane microstructure and the molecule-surface interactions) phenomena.In the last decades, a huge number of experimental studies have been invested to understand fouling mechanisms. It has been pointed out that membrane physicochemical properties, solution chemistry and operational conditions are the three major factors affecting the fouling mechanisms. In parallel, theoretical models have been proposed to confirm/describe the experimental observations.Modeling of membrane fouling is an essential tool for assessing the fouling mechanisms. It helps predicting the membrane performance and consequently finding adapted strategies to prevent their modification during the filtration process.In general, the models can be classified into two main categories: mass transport models which focus on solute permeation during the filtration process, and fouling models based on particle or solute blocking within the membrane porous structure. In most of the cases, models depend strongly on the empirical or semi-empirical parameters and thus remain phenomenological. Two main objectives have been set for the present work: 1. Get a better understanding of the membrane fouling mechanisms during filtration of a liquid medium containing suspended microorganisms. It should be pointed out that several Industrial streams and wastewaters belong to this kind of effluents.2. Propose a macroscopic model describing the observed fouling mechanisms. [...]

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Schmid, Moura Miguel. "Impact of Filtration on Energy Contract Valuation." St. Gallen, 2008. http://www.biblio.unisg.ch/org/biblio/edoc.nsf/wwwDisplayIdentifier/05609615001/$FILE/05609615001.pdf.

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Frisvold, Frede. "Filtration of aluminium : theory, mechanisms, and experiments." Doctoral thesis, Norwegian University of Science and Technology, Department of Materials Technology, 1990. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2105.

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Dissertations / Theses on the topic 'Filtration'

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