Dissertations / Theses on the topic 'Contact filtration'

Contact flocculation filtration using natural cationic polyelectrolytes extracted from seeds of the tree M.oleifera were found to be effective in the treatment of low turbidity waters. The coagulant was dosed immediately prior to the filter inlet, with subsequent flocculation and deposition occurring in the filter bed. This single stage treatment option was considered appropriate for developing countries, due to observed treatment performance, robustness of operation and reduced treatment costs. This work extends and complements previously successful studies on the treatment of medium to high turbidity raw waters using M.oleifera seed. Laboratory studies using twin 100 mm diameter filter columns, were undertaken with the following variables: turbidities of 5-75 NTU; filtration rates of 5-20 m/h; filter depths of 70 and 120 cm; dual and single media beds, and media sizes of 0.50-1.00 mm and 0.85-1.70 mm. Deeper beds and smaller media were found to considerably reduce filtrate turbidity when using M.oleifera seed. The consequent headloss increase was only significant with the higher turbidity waters; dual media beds were most effective on such waters. Turbidity removal was reduced at higher filtration rates (10m/h), due to lower retention times in the bed, and increased detachment of retained particles causing early turbidity breakthrough. Higher filtration rates with another natural coagulant, chitosan, increased turbidity removal and prolonged the time to breakthrough, due to the reduction in surface removal in the filter. At lower loading rates (5 NTU at 5 m/h), removal with M.oleifera seed was comparable with chitosan and aluminium sulphate, with the additional advantage of a lower headloss. Optimisation of the hydraulic variables for a specific coagulant was considered necessary to ensure maximum output and filtrate quality. Field trials on a low turbidity natural raw water indicated that M.oleifera reduced the turbidity by >95% and bacterial numbers by 100% at the optimum dose. Despite the rise in organic matter in the final water, trihalomethane levels were not excessive.

L'élimination de l'acide fulvique (AF) est étudiée par des méthodes physico-chimiques avec des eaux synthétiques contenant de l'AFcommercial (10 mg/l en général). La coagulation-floculation de l'AF par le sulfate d'aluminium (alun), le chlorure ferrique ou le polychlorosulfate d'aluminium (WAC HB) et l'influence de la bentonite et du calcium sont étudiées en Jar-Test. Le WAC HB est efficace dans une large gamme de pH surtout pour pH>7 mais l'alun n'est efficace qu'a pH 6-7 ; le fer reste le coagulant le plus efficace à pH<6. Les matières en suspension peuvent améliorer l'élimination de l'AF. La présence de calcium diminue la dose de réactif nécessaire pour la déstabilisation de l'AF. La complexation entre l'AF et les espèces solubles de l'hydrolyse de réactif et l'adsorption-neutralisation de ces complexes sur le précipite d'hydroxyde sont les mécanismes principaux quand l'AF est coagulé par l'alun ou le fer. L'influence du pH et de la dose d'alun sur l'élimination de l'AF par filtration contact est étudiée avec deux filtres à sable. Les résultats montrent que le pH optimal dépend de la dose de réactif. Le recours à la méthode de filtration sur membrane après Jar-Test afin de choisir la dose et le pH optimaux pour la filtration contact conduirait à des erreurs importantes, alors que ce choix peut être fait par observation des micro-flocs formés en Jar-Test. L'ensemble des considérations (efficacité, Al soluble, etc. ) suggère 5,5-6 comme zone optimale de pH. Deux filtres à sable à flux ascendant ou descendant et un filtre anthracite-sable sont comparés. Le dernier avec de gros grains d'anthracite (d=2,0-2,5 mm) présente les meilleurs résultats en utilisant l'alun comme coagulant et le polyacrylamide comme adjuvant (0,2 mg/l). L'analyse sur des résultats expérimentaux par simulation indique que le dépôt volumineux et sa faible résistance au cisaillement sont les causes principales conduisant à des difficultés pour l'élimination de l'AF par filtration contact.

Le foisonnement des boues activées, conséquence du développement excessif de micro-organismes filamenteux constitue un problème majeur qui limite les performances des stations d'épuration. Parmi les conditions favorisant la croissance filamenteuse, les carences nutritionnelles du micro-environnement bactérien apparaissent déterminantes ; de p1us elles sont responsables des problèmes les plus fréquents. Pour corriger cet état de carence, la recharge artificielle du floc en nourriture est à la base d'une nouvelle technique désignée sous le vocable de zone de contact. Les expérimentations entreprises sur 3 sites réels révèlent l'efficacité et la fiabilité de cette technique qui reste sur le plan économique, compétitive par rapport à d'autres solutions. L'étude approfondie des conditions nutritionnelles des micro-organismes à partir des mesures de biosorption montre que ce paramètre est en relation avec la qualité de la boue (indice de boue). De plus, cette étude fournit de nouveaux. Éléments d'appréciation sur les modes d'action intervenant dans une zone de contact ainsi que sur les critères de dimensionnement à retenir. Les travaux réalisés dans le cadre de cette thèse conduisent à proposer une démarche pragmatique aux gestionnaires de stations d'épuration pour les aider à faire face aux difficultés liées au foisonnement des boues.

Die eingereichte Arbeit ist ein Beitrag, um das Verständnis der Filtration von metallischen Schmelzen für hochwertige Gussprodukte zu erhöhen. Anhand theoretischer und experimenteller Betrachtungen wird besonders die Benetzung zwischen der kontinuierlichen und der dispersen Phase als Einflussfaktor auf Tiefenfiltrationsprozesse untersucht. Rasterkraftmikroskopische Messungen verdeutlichen die Bedeutung der Benetzung auf die Adhäsionsenergie zwischen zwei Feststoffoberflächen. Durch ein entwickeltes Modellsystem konnte bewiesen werden, dass mit steigendem Kontaktwinkel zwischen disperser und kontinuierlicher Phase die Filtrationseffizienz signifikant ansteigt. Aufgrund der wirkenden Haftmechanismen im getesteten Benetzungssystem können sich dendritische Abscheidestrukturen ausbilden, die zur Redispergierung neigen. Ergänzt um eine numerische Simulation am Einzelkollektor, konnte ein Abscheidemodell entwickelt werden. Dieses berücksichtigt erstmals reale Haftenergieverteilungen, simulierte Aufprallenergieverteilungen und die hydrodynamische Hemmung als relevante Parameter für die Tiefenfiltration.

Thin liquid films (TLFs) of water are ubiquitous in daily lives as well as in many industrial processes. They can be formed between two identical phases, as in colloid films between two macroscopic surfaces and foam films between two air bubbles; and between two dissimilar phases, as in wetting films. Stability of the colloids, foams, and wetting films is determined by the surface forces in the TLFs. Depending on the nature of the surfaces involved, the stabilities can be predicted using combinations of three different forces, i.e., the van der Waals, electrical double layer (EDL), and hydrophobic forces. The objective of the present work is to study the roles of these forces in determining the stabilities of the TLFs of water confined between i) an air bubble and a hydrophobic surface and ii) an oil drop and a hydrophobic surface, with particular interest in studying the role of the hydrophobic force. The first part of the study involves the measurement of the surface forces in the TLFs confined between bitumen drops and mineral surfaces. Deformation of bitumen drops has been monitored by interferometry while it approaches a flat surface. By analyzing the spatiotemporal film profiles, both the capillary and hydrodynamic forces have been calculated using the Young-Laplace equation and the Reynolds lubrication approximation, respectively, with the surface forces being determined by subtracting the latter from the former. The results are useful for better understanding the effects of electrolyte and pH on bitumen liberation and recovery by flotation and for developing a filtration model from first principles. The second part of the study involves the surface force measurement in wetting (flotation) films. Surface forces in the TLFs of water on silica surfaces have been measured using the force apparatus for deformable surfaces (FADS) using an air bubble as a force sensor. The measurements have been conducted in the presence of various cationic surfactants such as dodecylamine hydrochloride (DAH), and alkyltrimethylammonium chloride (CnTACl), electrolytes, and polymers. The results show that film stability and hence the kinetics of film thinning can be greatly improved by the control of bubble ζ-potentials, whose role in flotation has long been neglected in flotation studies. Force measurements have also been conducted in the TLFs of water confined between oil drops and hydrophobic surfaces. Stability of this type of film plays an important role in a process of using oil drops rather than air bubbles to collect hydrophobic particles from aqueous phase. The force measurements conducted in the present work show that hydrophobic forces are much stronger in water films formed between oil drops and hydrophobic surfaces than in water films formed between air bubbles and hydrophobic surfaces, which can be attributed to the differences in the Hamaker constants involved.
Doctor of Philosophy
When two macroscopic surfaces in water are brought to a close proximity, a thin liquid film (TLF) is formed in between, with its stability being determined by the surface forces present in the film. TLFs are ubiquitous in daily lives and play a decisive role in many industrial processes such as mineral flotation, food processing, oil extraction, heat transfer, etc. In the present work, the surface forces present in wetting films have been measured by approaching an air bubble (or an oil drop) slowly toward a flat surface while monitoring the curvature changes during film thinning by interferometry and calculating the capillary forces using the Young-Laplace equations. By analyzing the results in view of the Frumkin-Derjaguin isotherm and the extended DLVO theory, it was possible to determine the changes in the van der Waals, electrical double-layer (EDL), and hydrophobic forces during film thinning. The results show that both the EDL and the long-range component of the hydrophobic force control the kinetics of film thinning and rupture while the contact angle formation is controlled by the van der Waals force and the short-range hydrophobic force. It has been found also that n-alkane drops form substantially larger contact angles than air bubbles on a hydrophobic surface due to the fact that the van der Waals force is attractive in the drop-surface interactions while the same is repulsive in the bubble-surface interactions. These observations have a profound implication in flotation, that is, oil drops can recover hydrophobic particles from an aqueous phase better than air bubbles.

This thesis describes possibilities removal of iron and manganese from the water. The first part of the thesis describes the sources and forms of iron and manganese in water, the health limits and possibilities removal of iron and manganese from the water. Contact filtration and materials used for contact removing of iron and manganese are described in more detail. The second part describes using materials Birm, Greensand and Semidol in practise. There i also described the experimental removing of iron and manganese by these three materials.

Abstract The aim of the present study was to increase the understanding of how the cell surface properties affect the performance of unit operations used in primary protein purification. In particular, the purpose was to develop, set up and apply methods for studies of cell surface properties and cell interactions. A method for microbial cell surface fingerprinting using surface plasmon resonance (SPR) is suggested. Four different Escherichia coli strains were used as model cells. Cell surface fingerprints were generated by registration of the interaction between the cells and four different surfaces, with different physical and chemical properties, when a cell suspension was flown over the surface. Significant differences in fingerprint pattern between some of the strains were observed. The physical properties of the cell surfaces were determined using microelectrophoresis, contact angle measurements and aqueous two-phase partitioning and were compared with the SPR fingerprints. The generated cell surface fingerprints and the physical property data were evaluated with multivariate data analysis that showed that the cells were separated into individual groups in a similar way using principal component analysis plots (PCA). Studies of the behaviour of the model cells on stirred cell filtration and in an interaction test with different expanded bed adsorption (EBA) adsorbents were performed. It could be concluded that especially one of the strains behaved differently. Differences in the properties of the model cells were indicated by microelectrophoresis and aqueous two-phase partitioning which to some extent correlated with observed differences in behaviour during filtration and in an interaction test with EBA adsorbents. The impact of high-pressure homogenisation of E. coli cell extract was examined, with a lab scale and a pilot scale technique. The DNA-fragmentation, visualised with agarose gel electrophoresis, and the resulting change in viscosity was analysed. A short homogenisation time resulted in increased viscosity of the process solution that correlated with increased concentration of released non-fragmented DNA. With longer homogenisation time the viscosity decreased with increasing degree of DNA-fragmentation. The results show that strain dependant cell surface properties of E. coli may have an impact on several primary steps in downstream processing.
QC 20101129

Abstract

The aim of the present study was to increase the understanding of how the cell surface properties affect the performance of unit operations used in primary protein purification. In particular, the purpose was to develop, set up and apply methods for studies of cell surface properties and cell interactions.

A method for microbial cell surface fingerprinting using surface plasmon resonance (SPR) is suggested. Four different Escherichia coli strains were used as model cells. Cell surface fingerprints were generated by registration of the interaction between the cells and four different surfaces, with different physical and chemical properties, when a cell suspension was flown over the surface. Significant differences in fingerprint pattern between some of the strains were observed. The physical properties of the cell surfaces were determined using microelectrophoresis, contact angle measurements and aqueous two-phase partitioning and were compared with the SPR fingerprints. The generated cell surface fingerprints and the physical property data were evaluated with multivariate data analysis that showed that the cells were separated into individual groups in a similar way using principal component analysis plots (PCA).

Studies of the behaviour of the model cells on stirred cell filtration and in an interaction test with different expanded bed adsorption (EBA) adsorbents were performed. It could be concluded that especially one of the strains behaved differently. Differences in the properties of the model cells were indicated by microelectrophoresis and aqueous two-phase partitioning which to some extent correlated with observed differences in behaviour during filtration and in an interaction test with EBA adsorbents.

The impact of high-pressure homogenisation of E. coli cell extract was examined, with a lab scale and a pilot scale technique. The DNA-fragmentation, visualised with agarose gel electrophoresis, and the resulting change in viscosity was analysed. A short homogenisation time resulted in increased viscosity of the process solution that correlated with increased concentration of released non-fragmented DNA. With longer homogenisation time the viscosity decreased with increasing degree of DNA-fragmentation.

The results show that strain dependant cell surface properties of E. coli may have an impact on several primary steps in downstream processing.

En marge d'expériences actuelles visant à développer une méthodologie analytique sur la pharmacocinétique-pharmacodynamique de la N-acétyl-cystéine (NAC) en prévention de la néphropathie liée à l'exposition aux substances de contraste (NESC), une mesure de la clairance des substances de contraste a été mise au point comme marqueur de filtration glomérulaire (FG) étant donné que celles-ci sont totalement éliminées par FG. Ainsi, la mesure de la FG a été déterminée par la clairance de l'iohexol, substance de contraste utilisée en imagerie médicale. L'originalité de ce projet est triple: (1) mesurer la clairance de l'iohexol (Omnipaque) chez des patients recevant également de l'iodixanol (Visipaque), substance de contraste de plus en plus utilisée; (2) explorer la mesure de la clairance d'iodixanol et (3) utiliser la spectrométrie de masse couplée à la chromatographie liquide, qui depuis les dernières années s'est taillée une place de plus en plus importante, pour le dosage de l'iohexol et de l'iodixanol. Le projet actuel s'est déroulé chez 17 sujets avec divers niveaux de fonction rénale devant subir des examens d'imagerie avec des substances de contraste. Une dose-traceur d'iohexol (5 ml) a été co-administrée avec l'iodixanol (environ 95 ml). Des spécimens sanguins ont été obtenus 0, 1, 2, 3, 4, 8 et 24 heures post-imagerie pour mesurer les clairances de l'iohexol et de l'iodixanol. Le comportement des autres marqueurs conventionnels de FG, soit le taux créatinine plasmatique et la clairance de la créatinine, ainsi que la clairance de la cystatine C et la clairance d'iodixanol ont été comparés à la clairance d'iohexol. Par conséquent, un protocole scientifique par HPLC-MSD Tof a été développé afin de séparer et de quantifier les molécules iohexol et iodixanol co-administrées dans le plasma des sujets. Les mesures des taux plasmatiques de ces deux molécules ont permis de déterminer par des calculs pharmacocinétiques que la clairance de l'iohexol discrimine bien la fonction rénale des sujets avec une fonction rénale normale de ceux avec une fonction rénale diminuée. De plus, il a été démontré qu'une seule mesure post-4 heures est suffisante pour diagnostiquer l'état de la fonction rénale d'un patient qui a subi une intervention demandant une exposition aux substances de contraste. Les corrélations entre la clairance de l'iohexol et d'autres marqueurs conventionnels de FG ainsi que celle de l'iodixanol ont illustré que la clairance de la créatinine calculée soit par l'équation MDRD (r = 0,714 et p = 0,001) ou par Cockcroft et Gault (r = 0,518 et p = 0,033) et la clairance de la cystatine C (r = 0,671 et p = 0,003) corrèlaient de manière significative avec l'étalon d'or, soit la clairance de l'iohexol. C'est pourquoi, il pourrait être possible de se fier à la mesure de la clairance de l'iohexol comme meilleur marqueur de FG afin de prévenir, de diagnostiquer et de traiter la NESC. De plus, des expériences scientifiques en recherche fondamentale pourront enfin être menées pour déterminer la relation pharmacodynamique- pharmacocinétique de la N-acétylcystéine dans la prévention de la NESC à l'aide de la mesure de la clairance de l'iohexol comme marqueur fiable de la FG. Enfin, les mécanismes d'action qui interviennent dans la NESC pourront être mieux évalués.

Three membrane bioreactors, a low flux filter (LFF), a diafilter (DF), and an ion-exchange (IE) membrane bioreactor were used to treat water polluted with 50 ppm-N nitrate. The three systems were compared in terms of removal efficiency of nitrate, operational complexity, and overall quality of the treated water. In the low flux filter (LFF) membrane bioreactor an hemo-dialysis hollow fiber module was used and operated continuously for 29 days with a constant flux of permeate. The performance of the system was constant during the span of the experiment, which demonstrated that when the module was operated under constant low flux of permeate, the membrane filtration process was not affected by fouling. The removal rate of the LFF was 100% since the treated effluent did not contain nitrate or nitrite. The volumetric denitrification rate was 240 g-N day-1 m-3, which is within the range of denitrification rates obtained in tubular membrane modules. The treated effluent contained acetate, the carbon source of the biological process, and other inorganic nutrients, which showed that operating this ultrafiltration module at controlled flux did not improve the retention of these substances in the bioreactor. The same hemo-dialysis hollow fiber module employed in the LFF system was used in the diafilter (DF) membrane bioreactor. In the DF system, however, the membrane module was used as a contactor that separated the treated water and the bioreactor system, which allowed the transfer of solutes through the membrane porous structure and supported the growth of a biofilm on the membrane surface. The nitrate removal rate of the DF system increased from 76% to 91% during the 17 days assay. Unfortunately, this improvement could be attributed to microbial contamination of the water circuit because significant concentrations of the carbon source, acetate, nutrients, and nitrate were found in the treated effluent. The volumetric denitrification rate of the system was 200 g-N day-1 m-3, and the surface denitrification rate was lower than values previously reported for contactor membrane bioreactors. The results hereby presented do not evidence any advantage of operating the Filtral 20 ® membrane module as a contactor instead of as a filter such as in the LFF system. On the other hand, the third system herein presented, the IE membrane bioreactor, demonstrated several advantages of a contactor configuration but with a non-porous ion exchange membrane module in place of the Filtral 20 ®. As in a contactor system, the anion membrane provided a surface for biofilm growth, facilitated the transport of nitrate, and prevented mixing of treated water and bioreactor medium. Compared to the two previous systems, the most remarkable result of the IE was the reduction of secondary pollution in the treated water. The concentrations of phosphate and ethanol were zero and less than 1% of the concentration in the bioreactor, respectively. In addition, the IE system was less complex than the two other systems because the ion exchange membrane is non-porous. Therefore, unlike with porous contactors, it was not necessary to control the flux of treated water that could be lost through the bioreactor. The average surface denitrification rate of the IE system was 7.0 g-N day-1 m-2, which is higher than what had been reported for other contactor denitrification systems. However, because of the low surface to volume ratio of the membrane module that was used, the volumetric denitrification rate of the IE system was low, equivalent to 65 g-N day-1 m-3.
Master of Science

In the present work, novel dewatering aids and a novel centrifuge configuration were developed and applied for the purpose of dewatering fine particles. Three different types dewatering reagents were tested in different filtration and centrifugation units. These chemicals included low-HLB surfactants, naturally occurring lipids, and modified lipids. Most of these reagents are insoluble in water; therefore, they were used in solutions of appropriate solvents, such as light hydrocarbon oils and short-chain alcohols. The role of these reagents was to increase the hydrophobicity of the coal and selected mineral particles (chalcopyrite, sphalerite, galena, talc, clay, phosphate, PCC and silica) for the dewatering. In the presence of these reagents, the water contact angles on the coal samples were increased up to 90o. According to the Laplace equation, an increase in contact angle with the surfactant addition should decrease the capillary pressure in a filter cake, which should in turn increase the rate of dewatering and help reduce the cake moisture. The use of the novel dewatering aids causes a decrease in the surface tension of water and an increase in the porosity of the cake, both of which also contribute to improved dewatering. A series of batch-scale dewatering tests were conducted on a variety of the coal and mineral samples using the novel dewatering aids. The results obtained with a Buchner funnel and air pressure filters showed that cake moistures could be reduced substantially, the extent of which depends on the particle size, cake thickness, drying time, reagent dosage, conditioning time, reagent type, sample aging, water chemistry, etc. It was determined that use of the novel dewatering aids could reduce the cake formation time by a significant degree due to the increased kinetics of dewatering. At the same time, the use of the dewatering aids reduced the cake moistures by allowing the water trapped in smaller capillaries of the filter cake. It was found that final cake moistures could be reduced by 50% of what can be normally achieved without using the reagents. However, the moisture reduction becomes difficult with increasing cake thickness. This problem can be minimized by applying a mechanical vibration to the cake, spraying a short-chain alcohol on the cake and by adding a small amount of an appropriate coagulant, such as alum and CaCl2 to the coal and mineral slurries. The novel dewatering aids were also tested using several different continuous filters, including a drum filter, disc filter and horizontal belt filter (HBF). The results obtained with these continuous filtration devices were consistent with those obtained from the batch filters. Depending on the coal and mineral samples and the type of the reagent, 40 to 60% reductions in moisture were readily achieved. When using vacuum disc filters, the cake thickness increased substantially in the presence of the novel dewatering aids, which could be attributed to the increased kinetics of dewatering. A dual vacuum system was developed in the present work in order to be able to control the cake thickness, which was necessary to achieve lower cake moistures. It was based on using a lower vacuum pressure during the cake formation time, while a full vacuum pressure was used during the drying cycle time. Thus, use of the dual vacuum system allowed the disc filter to be used in conjunction with the novel dewatering aids. Its performance was similar to that of HBF, which is designed to control cake thickness and cake formation time independently. The effectiveness of using the novel dewatering aids were also tested in a full-continuous pilot plant, in which coal samples were cleaned by a flotation column before the flotation product was subjected to the disc filter. The tests were conducted with and without using novel dewatering aids. These results were consistent with those obtained from the laboratory and batch-scale tests. The novel centrifuge developed in the present work was a unit, which combined a gravity force and air pressure. The new centrifuge was based on increasing the pressure drop across the filter cake formed on the surface of the medium (centrifuge wall). This provision made it possible to take advantage of Darcy s law and improve the removal of capillary water, which should help lower the cake moisture. A series of tests were conducted on several fine coal and mineral particles and obtained more than 50% moisture reduction even at very fine particle size (2 mm x 0). Based on the test results obtained in the present work, two proof-of-concept (POC) plants have been designed. The first was for the recovery of cyclone overflows that are currently being discarded in Virginia, and the other was for the recovery of fines from a pond in southern West Virginia. The former was designed based on the results of the plant tests conducted in the present work. Cost vs. benefit analyses were conducted on the two POC plants. The results showed very favorable internal rates of return when using the novel dewatering aids. Surface chemistry studies were conducted on the coal samples based on the results obtained in the present investigation. These consisted mainly of the surface characterization of the coal samples (surface mineral composition, surface area, zeta potential, x-ray photoelectron microscopy (XPS)), acid-base interactions of the solids and liquids, dewatering kinetic tests, contact angle measurements of the coal samples and surface force measurements using AFM. In addition, carbon coating on a silica plate using palsed laser deposition (PLD) and Langmuir-Blodgett (LB) film deposition tests were conducted on the sample to better understand the surfactant adsorption and dewatering processes. The test results showed that the moisture reductions on the fine particles agree well with the surface chemistry results.
Ph. D.

The LignoBoost process is a valuable supplement to the Kraft process. It can increase the pulp production rate of a Kraft mill and it enables lignin separation from black liquor with a high degree of purity. However, residual xylan in black liquor has been observed to increase filtration resistance of lignin during the LignoBoost process. In order to uncover underlying mechanisms, this thesis investigates the potential influence of xylan during lignin precipitation and filtration, which are the two main steps of the LignoBoost process. For this purpose experiments based on a model system were designed. Model liquors consisted of lignin and xylan as the only organic compounds and contained lower salt concentrations (4.2-5.9 wt%) compared to black liquor. Furthermore, reference liquors were prepared without xylan addition. Precipitation mechanisms were studied in the onset precipitation region (i.e. alkaline regime) by in-situ focused beam reflectance measurements (FBRM) during step-by-step acidic precipitation of the model liquor. It was found that the onset precipitation pH does not change with the presence of xylan as all liquors started precipitation around pH 9.15. The filtration process was investigated on model liquors that had been precipitated by fast acidification to acidic regimes (pH 6.5-2.87). The use of FBRM during acid precipitation of model liquors suggested that temperature had a significant influence on the chord length distribution (CLD) of the particles. In all filtration experiments, a decrease in CLD was observed when the temperature was changed from 80 °C to 25 °C. Moreover, this thermal instability of particles seemed to be higher when added xylan was present in the liquor. The investigation of the resulting filer cakes with HPLC showed that xylan was evenly distributed through the cake. Further findings on the influence of xylan were impeded due to variations in ionic strength in the model liquors. It was found that the effect of ionic strength on filtration properties and particle sizes overshadows the effect of xylan. Higher ionic strength was observed to yield a lower filtration resistance, a higher solidosty, larger particles and lower solid surface area, as investigated by filtration measurements, laser diffraction and BET analysis. Finally, xylan was fluorescently tagged (i.e. dyed) with Remazol Brilliant Blue R to investigate xylan position in the ligninxylan filer cake, using a confocal fluorescence microscope. However, due to the autofluorescence of lignin as well as low emission intensity of the synthesized dyed xylan, xylan could not been tracked within the lignin particle. Nevertheless, valuable insight was gained into the preparation of dyed xylan and the bond stability.

Les géo-structures telles que les barrages et les digues sont soumises à des écoulements hydrauliques variant dans le temps et dans l'espace. L'eau qui traverse ces milieux poreux peut entraîner le détachement et le transport de certaines particules des sols constituant les structures et leurs fondations. Ce problème est généralement appelé "érosion interne". Le terme suffusion, un type d'érosion interne, se réfère au détachement et au transport de particules les plus fines à traversune matrice de sol poreuse plus grossière en raison d'un écoulement hydraulique. L'évolution temporelle de la suffusion peut modifier les propriétés hydrauliques et mécaniques des sols et peut entraîner des changements importants dans le comportement de telles structures pouvant aller jusqu’à leur effondrement. Ce travail de thèse tente de contribuer à la conception et à la durabilité des ouvrages en ingénierie géotechnique et hydraulique en mettant un accent particulier sur les barrages, les levées et les digues. Il a été consacré à développer un modèle numérique de suffusion en introduisant d’une part le couplage des phénomènes hydrauliques et mécaniques et d’autre part le couplage des phénomènes d'érosion et de filtration
Geo-structures such as dams and levees or dikes are subjected to seepage varying in time and space. The water flowing through these porous media can lead to the detachment and transport of part of the soil particles within the structures or their foundations. This problem is usually called internal erosion. The term suffusion, one type of internal erosion, refers to the detachment and transport of finer particles through a coarser porous soil matrix due to seepage flow. Suffusion can modify with time the hydraulic and mechanical properties of the soils and may trigger significant damage on such structures and lead eventually to their collapse. This research attempts to contribute to the design and sustainability of geotechnical and hydraulic engineering structures, with a particular focus on embankment dams, levees, and dikes. It aims to develop a numerical model of suffusion by introducing, on the one hand, the coupling of the hydraulic and mechanical phenomena and, on the other hand, the coupling of erosion and filtration

The first part of the thesis is focused on the problems related to sludge and evaluates sludge disposal from waste treatment plants. The thesis mentions factors influencing method selection of sludge disposal as well as it compares sludge disposal in the Czech Republic and in the other states of the EU. It describes a complete waste treatment line and sludge disposal in the area of sludge treatment and disposal. It deals with sludge disintegration and describes the most effective methods of disintegration. The second part of the thesis describes an experimental part of disintegration of waste treatment sludge. An experiment was conducted in the school laboratory in a way of thermal disintegration in the double-surface pressure tank. The disintegration was conducted to temperatures of 60 °C, 90 °C, 120 °C, 150 °C, and 180 °C. We monitored dependence of the sludge dry residue content on disintegration temperature as well as content of suspended solids in liquid fraction (FUGAT). It was possible to choose optimal temperature of disintegration in accordance with processed results.

L’arceau interventionnel est un système d’imagerie rayons X temps réel. Il dispose d’une option tomographique qui, grâce à une rotation de l’arceau autour du patient, permet d’acquérir des images en coupes dont la résolution en contraste est plus faible que celle des tomodensitomètres diagnostiques, rendant l’information clinique des tissus mous du cerveau inexploitable. Nous proposons un nouveau mode d’acquisition et de reconstruction tomographiques sur arceau interventionnel pour l’amélioration de la détection des faibles contrastes en imagerie interventionnelle des tissus mous de la tête. Afin d’émuler un filtre « bow-tie » (en nœud papillon), une double acquisition est envisagée. Les spécificités de la double acquisition imposent la conception d’un algorithme de reconstruction itérative dédié, incluant le filtre rampe dans l’énergie de minimisation. En bifurquant des approches par rétro-projection filtrée vers celles par filtration des rétro-projections, une méthode de reconstruction directe, alternative à la précédente, est proposée pour les acquisitions doubles. Pour une acquisition simple, la méthode est assurée de faire aussi bien que l’algorithme de rétro-projection filtrée quel que soit l’échantillonnage angulaire en géométrie planaire, et offre une approximation alternative à l’algorithme de Feldkamp-Davis-Kress en géométrie conique. Nous montrons qu’avec peu ou pas de modifications aux schémas précédents, les deux méthodes de reconstruction (itérative et directe) s’adaptent bien à la reconstruction de régions d’intérêt, à laquelle l’acquisition double reste étroitement liée à travers son acquisition tronquée
Interventional C-arm systems are real-time X-ray imaging systems, that can perform tomographic acquisitions by rotating the C-arm around the patient ; however, C-arm cone-beam computed tomography (CBCT) achieves a lower contrast resolution than diagnostic CT, which is necessary in order to benefit from the clinical information of soft tissues in the brain. We propose a new C-arm CBCT acquisition and reconstruction framework to increase low-contrast detection in brain soft-tissue imaging. In order to emulate a bow-tie filter, a dualrotation acquisition is proposed. To account for all the specificities of the dual-rotation acquisition, a dedicated iterative reconstruction algorithm is designed, that includes the ramp filter in the cost function. By switching from filtered backprojection (FBP) to backprojection-filtration (BPF) reconstruction methods, we propose an alternative, direct reconstruction method for dual-rotation acquisitions. For single-rotation acquisitions, the method ensures to perform as good as FBP with arbitrarily coarse angular sampling in planar geometries, and provides a different approximation from the Feldkamp-Davis-Kress (FDK) algorithm in the cone-beam geometry. Although we used it to emulate a virtual bow-tie, our dual-rotation acquisition framework is intrinsically related to region-of-interest (ROI) imaging through the truncated acquisition. With few or no modification of the proposed reconstruction methods, we successfully addressed the problem of ROI imaging in the context of dual-rotation acquisitions

碩士
逢甲大學
水利工程與資源保育學系
104
With the gradual economic development, human often unknowingly created water pollution. In Taiwan, water pollution can be divided into two kinds - point source and non-point source. In urban area, point source pollution will be treated by waste water treatment systems, or sewage treatment plants and so on, but for point source in rural area, it has not yet taken seriously, especially some inappropriate dispose inside the catchment of a reservoir, or hillside development, which create pollution not effectively collected and treated. In this study, we focus on the small-scale domestic waste water at outskirts of non-urban areas or in remote mountainous area with low population density. We follow the natural way, called Eco-Engineering, and try to utilize on-site material to purify inadequate waste water disposal which causing river pollution. We tested a method called gravel contact combined with sand filtration system to the treatment of small-scale domestic sewage. For comparison, a gravel contact without sand filtration system was also tested as a reference to explore which one has a better purifying effect. In order to facilitate the experiment, we use sanitary sewage of Feng Chia University as tested subjects which with BOD about 21.9mg/L is much larger than the statistical data of catchment samples with about 7.48mg/L. Because the design of two systems is different, therefore, using the same hydraulic retention time of 96 hours as a benchmark for comparing two systems. For gravel contact combined with sand filtration system of our experiments, the average SS removal rate was 99.6%, the average concentration removal rate of COD was 83.6%, the average concentration removal rate of NH3 was 94.7%. For domestic sewage treatment of pure gravel contact, the average of SS concentration removal rate was 100%, the average of COD concentration removal rate was 70.8%, the average of NH3 concentration removal rate was 97.8%. For different water-quality targets, each system/method may have advantages and disadvantages, but gravel contact combined with sand filtration system has a shorter channel design. Therefore, for the same hydraulic residence time, the difference between the two shows that the gravel contact combined with sand filtration system was better than the pure gravel contact. The tests were last for 168 hours in our experiments, but for a site design it will be too long to reach. As for designing a shorter system, removal results can be seen for DO improvement for 3 hours hydraulic retention time, SS was 1 hour, NH3 was 72 hours, COD was up to 6 hours. If a single design parameter, hydraulic retention time(HRT), is used for designing a gravel contact combined with sand filtration system, HRT can be designed for between 3-6 hours, no need to cycle through, and was possible to remove large amounts of sewage. The pure gravel contact system without changing any design in our experiments, the water quality of its effluents were in compliance with the EPA set of effluent standards. As a conclusion, in a remote and small catchment area with limited funding and irregular terrain, for treating domestic sewage decentralized, our systems can greatly improve the domestic waste water for recycling back to nature.

Die eingereichte Arbeit ist ein Beitrag, um das Verständnis der Filtration von metallischen Schmelzen für hochwertige Gussprodukte zu erhöhen. Anhand theoretischer und experimenteller Betrachtungen wird besonders die Benetzung zwischen der kontinuierlichen und der dispersen Phase als Einflussfaktor auf Tiefenfiltrationsprozesse untersucht. Rasterkraftmikroskopische Messungen verdeutlichen die Bedeutung der Benetzung auf die Adhäsionsenergie zwischen zwei Feststoffoberflächen. Durch ein entwickeltes Modellsystem konnte bewiesen werden, dass mit steigendem Kontaktwinkel zwischen disperser und kontinuierlicher Phase die Filtrationseffizienz signifikant ansteigt. Aufgrund der wirkenden Haftmechanismen im getesteten Benetzungssystem können sich dendritische Abscheidestrukturen ausbilden, die zur Redispergierung neigen. Ergänzt um eine numerische Simulation am Einzelkollektor, konnte ein Abscheidemodell entwickelt werden. Dieses berücksichtigt erstmals reale Haftenergieverteilungen, simulierte Aufprallenergieverteilungen und die hydrodynamische Hemmung als relevante Parameter für die Tiefenfiltration.:Inhaltsverzeichnis III Danksagung VII Eidesstattliche Erklärung IX 1 Einleitung 1 2 Grundlagen 4 2.1 Metallschmelzefiltration 4 2.2 Benetzbarkeit 18 2.3 Wechselwirkungskräfte zwischen Feststoffen 25 2.4 Tiefenfiltration 34 2.4.1 Transportmechanismen 42 2.4.1.1 Sedimentation 43 2.4.1.2 Trägheit 44 2.4.1.3 Sperreffekt 44 2.4.1.4 Strömungseffekte 45 2.4.2 Haftmechanismen 49 2.5 Einzelkollektormodell 53 3 Materialien und Methoden 57 3.1 Charakterisierung verwendeter Feststoffe 57 3.1.1 Aluminiumoxid 59 3.1.2 Polytetrafluorethylen 62 3.1.3 Beschichtung des Aluminiumoxids 64 3.2 Keramische Filterstrukturen 65 3.2.1 Schaumfilter 65 3.2.2 Einzelkollektoren 72 3.3 Eigenschaften der kontinuierlichen Phase 74 3.4 Versuchsanlagen und Analytik 74 3.4.1 Filtrationsanlagen 75 3.4.2 Einzelkollektorversuchsstand 77 3.4.3 Analytik 80 3.5 Versuchsdurchführung 82 3.5.1 Kleine Filtrationsversuchsanlage 83 3.5.2 Einzelkollektorversuchsstand 86 3.5.3 Statistische Versuchsplanung 88 4 Entwicklung eines Abscheidemodells für Partikel in flüssigen Medien mithilfe numerischer Simulationen 93 4.1 Beschreibung der numerischen Strömungssimulation 94 4.2 Einfluss der hydrodynamischen Hemmung auf den Partikelaufprall 98 4.3 Experimentelle Ermittlung der Haftenergie 105 4.4 Berechnung der Haftwahrscheinlichkeit (Hiller-Zahl) 109 5 Modellhafte Untersuchungen mithilfe des Einzelkollektorkonzeptes 114 5.1 Grundlagenuntersuchungen zum Einzelkollektorkonzept 115 5.2 Parameterstudie zum Abscheideverhalten beim Einzelkollektoraufbau 119 6 Ergebnisse der Filtrationsversuche 128 6.1 Einfluss der Benetzung auf die Filtrationseffizienz 128 6.2 Einfluss der Fluidgeschwindigkeit und des Benetzungszustandes auf die Filtrationseffizienz 134 6.3 Redispergierungseffekte in keramischen Schaumfiltern 139 6.4 Einfluss der relativen Dichte auf die Filtrationseffizienz im komplett hydrophoben System 146 6.5 Vergleich der numerisch modellierten und der experimentell ermittelten Filtrationseffizienz 150 7 Zusammenfassung 155 8 Ausblick 159 9 Symbolverzeichnis 161 Lateinische Symbole 161 Symbol 161 Einheit 161 Bedeutung 161 Griechische Symbole 165 Indizes 166 Abkürzungen 167 10 Literaturverzeichnis 168 11 Anhang 189 11.1 Herstellung Polytetrafluorethylen Pulver 189 11.2 Berechnung der vdW-Kräfte und der Kapillarkräfte basierend auf Kapitel 2.3 190 11.3 Rezeptur zur Herstellung der Dynasylan-Beschichtung 192 11.4 Ergebnistabelle der statistischen Versuchsplanung am Einzelkollektorsystem 193

The phenomenon of particle retention in granular materials has a wide range of implications. For agricultural operations, these particles can be contaminants transported through the ground that can eventually reach to aquifers, consequently contaminating the water. In oil reservoirs, these particles can be clays that get detached from the rock and migrate with the flow after a change of pressure, plugging the reservoir with the consequent reduction in permeability. These particles can also be traceable nanoparticles, introduced in the reservoir with the purpose of identifying bypassed oil. For all these reasons it is important to understand the mechanisms that contribute to the transport and retention of these particles. In this dissertation the retention of micro and nano size particles was investigated. In saturated model sediments (sphere packs), we analyzed the retention of particles by the mechanism of straining (size exclusion). The analysis focused on experiments reported in the literature in which particles smaller than the smallest pore throats were retained in the sediment. The analysis yields a mechanistic explanation of these observations, by indentifying the retention sites as gaps between pairs of sediment grains. A predictive model was developed that yields a relationship between the straining rate constant and particle size in agreement with the experimental observations. In unsaturated granular materials, the relative contributions of grain surfaces, interfacial areas and contact lines between phases to the retention of colloidal size particles were investigated. An important part of this analysis was the identification and calculation of the length of the contact lines between phases. This estimation of contact line lengths in porous media is the first of its kind. The algorithm developed to compute contact line length yielded values consistent with observations from beads pack and real rocks, which were obtained independently from analysis of high resolution images. Additionally, the predictions of interfacial areas in granular materials were consistent with an established thermodynamic theory of multiphase flow in porous media. Since there is a close relationship between interfacial areas and contact lines this supports the accuracy of the contact line length estimations. Predictions of contact line length and interfacial area in model sediments, combined with experimental values of retention of colloidal size particles in columns of glass beads suggested that it is plausible for interfacial area and contact line to contribute in the same proportion to the retention of particles. The mechanism of retention of surface treated nanoparticles in sedimentary rocks was also investigated, where it was found that retention is reversible and dominated by attractive van der Waals forces between the particles and the rock’s grain surfaces. The intricate combination of factors that affect retention makes the clear identification of the mechanism responsible for trapping a complex task. The work presented in this dissertation provides significant insight into the retention mechanisms in relevant scenarios.
text

Submitted in fulfillment of the requirements for the degree of Master of Engineering in Chemical Engineering, Durban University of Technology. Durban. South Africa, 2015.
Several areas in the world such as the United States of America, Sri Lanka, China, Argentina, Canada, Tanzania, Kenya, South Africa and many others have a problem of high fluoride content in drinking water. Generally fluoride levels above 1.5 ppm in water may result in dental and skeletal fluorosis in humans depending on quantity consumed (Fan et al., 2003; Meenakshi, 2004). Remote rural areas where there are no water treatment facilities are more vulnerable to this problem. Adsorbents such as activated alumina and FR-10 resin seem to have a potential for successful application in rural areas. These methods however require pre-treatment if the feed has high turbidity. A membrane based system called woven fabric microfiltration gravity filter (WFMFGF) developed by Durban University of Technology proved to be suitable for turbidity removal. The main objective of this research was to develop a small water treatment system for fluoride removal. The small water treatment system developed in this study consists of WFMFGF for pre-treatment and an adsorption column. The WFMFGF is made up of a 40 L container packed with 15 immersed flat sheet membrane elements. The operation of the WFMFGF is in batch mode, driven by varying static head. The static head variation results in flow rate variation through the system. This in turn result in variation of contact time, velocity as well as pressure drop in the fluoride removal unit. Specific objectives of the study were: (1) to establish the maximum and minimum flow rates through the WFMFGF system, the total run time before cleaning is required and the best cleaning method for this particular membrane system. (2) to evaluate and compare the performance of activated alumina and FR-10 resin on varying contact time, velocity and pressure drop on the fluoride removal unit. The adsorbents were also compared on adsorption capacity, cost and ease of operation. The minimum and maximum flow rates through the WFMFGF were found to be 5 l/hr and 100 l/hr respectively. It was found that the system can be run for more than a month before requiring cleaning. The suitable cleaning method was found to be soaking the membranes in 0.0225 percent sodium hypochlorite solution overnight and brushing them using a plastic brush. The comparison of the performance of FR-10 resin to activated alumina found that the adsorbents gave equal performance based on the given criteria. FR-10 resin had higher adsorption capacity, gave good quality treated water even with shorter contact time and operated at wider velocity range. Activated alumina on the other hand had an advantage of lower costs, lower pressure drop and ease of use. According to Pontius (1990), the performance of activated alumina can be improved by intermittent operation. Point of use (POU) systems are generally operated intermittently. This improves the fluoride removal efficiency of activated alumina giving it more advantage over FR-10 resin. Based on this activated alumina was selected as the best adsorbent for the system. After the adsorbent was selected, the adsorption column was designed. The column operation regime was 3.5 minutes minimum contact time and 1.17 to 7.8 m/hr velocity range. The activated alumina adsorption capacity was 1.53mg/g. The column had an inside diameter of 70 mm. It was packed with activated alumina to a bed height of 400 mm. The column inlet and outlet pipes were made of PVC with a standard pipe size of 20 mm outside diameter. A valve at the column inlet pipe allowed water to flow through the system.

Thesis (M. Sc.)--University of Alberta, 2010.
Title from pdf file main screen (viewed on Jan. 21, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Biological filtration (Biofiltration) processes have been used first in Europe and then in North America for decades, however currently there is not a good overall parameter to guide biofiltration design and operation except adopting parameters from traditional particle- removal filtration process. On the basis of the biofilm model developed by Rittmann and McCarty (1980a) and the pseudo-analytical solution for the model, Zhang and Huck (1996a) obtained an analytical solution for PF (plug flow) reactors (which can be used for biofilters approximately) after demonstrating that axial dispersion could be reasonably ignored and developed a new parameter, X*, which incorporates considerations of physical contact time, filter media particle size, kinetics, etc. A small-scale application on peers’ engineering/research data by Huck (1999) demonstrated it was a better indicator than other parameters for biofiltration performance. By collecting, screening and investigating literature on AOC, BDOC and odorous compounds removal by biofiltration process, this thesis applied the X* concept to the collected investigations to assess process performances among different target parameters, different filters and different investigations. To the author’s knowledge, this is the first such attempted comprehensive comparison of literature studies, interpreted in terms of a common parameter (X*). The wide ranges of particle sizes, EBCTs, temperatures and high diversity of pre-treatment and operation conditions for the collected cases were considered to be able to well represent biofiltration practices for studied removal targets. No significant relationship between EBCTs and removal percentages were found, indicating that EBCT alone is not able to guide biofiltration design and operation. Based on kinetics parameter comparison, BDOC removal-X* relationship was established. A new parameter, θα, was developed in this thesis to refer to estimated X* values only considering EBCT and particle size. θα parameter values were estimated by comparison of ratios of θα products ((θα)’) based on the properly chosen calculation bases. Distribution of the θα values for temperature-favored (i.e. temperature ≥15°C) AOC and BDOC removal biofiltration processes matched the established removal-X* relationship reasonably. Given the exploratory nature of this research and the complexity of attempting quantitations, fits were assessed based on visual comparison. With the assistance of supporting information and by adopting available temperature activity coefficients, temperature-adjustment coefficients for θα values were determined for the different temperature ranges. Temperature-adjusted AOC and BDOC removal-θα relationships were developed and temperature-adjusted θα parameter values for AOC and BDOC removal were also estimated. Comparisons were conducted, showing fair matches based on visual examinations, for most of the temperature ranges. No relationships were found between ozone dosages and AOC/BDOC removal percentages and the statistical analysis indicated there was significant difference of removal efficiencies between ozonated and non-ozonated influents for biofilters, suggesting ozonation may not only increase the amount of BOM for following biofilter and increase the biodegradability of bulk water; it may also increase the biodegradability of AOC and BDOC themselves. It may not be realistic to obtain the estimated θα values for MIB and geosmin removal by biofiltration. However, plotting θα product vs. removal percentage for the collected MIB and geosmin removal cases shows more positive co-relationships than EBCT-removal percentage relationships visually. A utilization factor η was proposed to guide biofilter design and operation and to assess “over-design” and “under-operated”. Biofilter over-design or under-operated is common for the collected cases. In general, examining X* (or θα, a parameter incorporating the physical components of X*) provided useful information in terms of evaluation and prediction of biodegradable organic compounds removal by biofiltration, which confirms that X* is a better parameter for biofiltration design and operation than other parameters, such as EBCT.

Yes
Acute kidney injury (AKI) can occur rarely in patients exposed to iodinated contrast and result in contrast-induced AKI (CI-AKI). A key risk factor is the presence of pre-existing chronic kidney disease (CKD), therefore it is important to assess patient risk and obtain kidney function measurement prior to administration. Point of care (PoC) testing provides an alternative strategy but there remains uncertainty, with respect to diagnostic accuracy and clinical utility. A device study compared three PoC analysers (Nova StatSensor, Abbott i-STAT, Radiometer ABL800 FLEX) with a reference laboratory standard (Roche Cobas 8000 series, enzymatic creatinine). Three hundred adult patients attending a UK hospital phlebotomy department were recruited to have additional blood samples for analysis on the PoC devices. The ABL800 FLEX had the strongest concordance with laboratory measured serum creatinine (mean bias=-0.86, 95% limits of agreement = -9.6 to 7.9) followed by the i-STAT (average bias=3.88, 95% limits of agreement = -8.8 to 16.6) and StatSensor (average bias=3.56, 95% limits of agreement = -27.7 to 34.8). In risk classification, the ABL800 FLEX and i-STAT identified all patients with an eGFR≤30, whereas the StatSensor resulted in a small number of missed high-risk cases (n=4/13) and also operated outside of the established performance goals. The screening of patients at risk of CI-AKI may be feasible with PoC technology. However in this study it was identified that the analyser concordance with the laboratory reference varies. It is proposed that further research exploring PoC implementation in imaging department pathways is needed.
Yorkshire and Humber Academic Health Science Network (Grant Number: YHP0318)