Settling and consolidation of suspended clay particles are significant issue in many fields such as geotechnical engineering, coastal and hydraulic engineering, and environmental engineering. A comprehensive literature review was conducted on the settling, consolidation and erosion of mixed soil material (cohesive and non-cohesive). Soil beds formed by sedimentation process of loose particles will be either show a segregated or homogeneous in structure, depending on the depositional environment. These sediments initially undergo self-weight consolidation and may be eroded under high flow rate. A number of studies have recently investigated the characteristic of consolidated clay bed in stagnant water. Hence, consolidation parameters were determined using a well-known vertical settling column consolidation test setup. However, limited research studies are available for deposition and consolidation of a mixture of sediment (clay, silt and sand) under flow conditions which are more representative of what happens in nature. A long flume and pump were used to create different turbulent conditions and simulate the natural process... The results for deposition and consolidation of different mixtures under stagnant and turbulence conditions were analyzed and compered in term of compressibility, permeability as well as shear strength. The results of this experimental research program indicated that the flow rate, initial concentration, height of settling and composition of sediment are all important factors that could affect the final bed dry unit weight. Two non-intrusive techniques were applied for measuring the dry unit weight at settling and consolidation stages. Impact echo technique has never been applied to measure the dry unit weight of self-weight consolidation along the vertical stratification of cohesive and non-cohesive particles. Also, a novel conductance sensor has been developed to improve the efficiency of this technique. The limitations of using these techniques will be highlighted in this study.

No description available.

No / In evaluating the resistance of sediment particles to entrainment by the action of the flow in a river, the grain geometry is usually characterized using representative sizes. This approach has been dictated, initially by lack of physical insight, but more recently by the lack of analytical tools able to describe the 3-D nature of surface grain organization on water-worked sediment beds. Laboratory experiments are presented where mixed grain size beds were mobilized under a range of hydraulic and sediment input conditions. Detailed bed topography was measured at various stages. Statistical tools have been adopted which describe the degree of surface organization on water-worked sediment bed surfaces. The degree of particle organization and the bed stability can be evaluated in relative terms using the properties of the probability density distribution of the bed surface elevations and in absolute terms using a properly defined 2-D structure function. The methods described can be applied directly to natural water-worked surfaces given the availability of appropriate bed surface elevation data sets.

A gravimetric survey has proved its usefulness in the Tucson Basin in locating important structural features, their geometric shapes and extensions. Interpretation was made possible through the correlation of available geologic and hydrologic data from water well logs and water table contour maps. Geophysical logs from a recently drilled test well in North Tucson have been interpreted and have confirmed the existence of another promising aquifer, namely, the deformed gravel which underlies the upper basin-fill aquifer. In most cases, it is apparently separated by a thin aquiclude of clay which results in artesian condition in the lower aquifer. Gravity interpretation discloses the presence of buried channels that may be of importance to groundwater exploration. The buried high basement ridges or faulted blocks as interpreted from gravity data add more information to the understanding of the hydrologic behavior of the basin. Deep drilling of test wells, such as the one drilled recently on Orange Grove Road, will be a useful check to the structures interpreted from gravity data. Geophysical logs of bore holes are of utmost importance in correlation of lithologic units and structures in addition to the hydrologic interpretation that is possible from these logs. The Pantano beds as described here are not promising for new groundwater sources that may be used for domestic needs due to the very low permeability and the expected poor quality of the water. Still more information is necessary to determine clear answers to many problems related to the geology and hydrology of this basin.

Ces travaux de recherche s'intéressent à la caractérisation des transferts thermiques dans les milieux fluide-particules, et en particulier, les lits fluidisés au sein desquels un solide divisé est mis en suspension par un fluide. La grande diversité d'échelles spatiales et temporelles dans ces procédés nécessite d'étudier les interactions hydrodynamiques, thermiques et/ou chimiques entre les particules et le fluide à l'aide d'une approche multi-échelles. Une étude des transferts thermiques dans des lits fixes puis fluidisés, est réalisée à deux échelles : locale (Particle Resolved Simulation) et moyennée (Discrete Element Method-Computional Fluids Dynamics). L'étude PRS permet de caractériser les couplages locaux des transferts thermiques entre particules ainsi que la dynamique de ces transferts dans les configurations fluidisées. Une étude comparative entre les échelles met en évidence les limites du modèle DEM-CFD à capter les fluctuations des transferts thermiques observées dans les simulations PRS. Dans un dernier temps, les fermetures du modèle DEM-CFD sont améliorées de manière à réintroduire les fluctuations perdues par le changement d'échelles. / This work aims at characterizing heat transfer into fluid-solid flows, and more particularly fluidized beds, into which a solid phase is suspended by a flowing fluid. The wide range of spatial and temporal scales present in such processes encourage to study hydrodynamic, thermal and/or chemical interactions between the particles and the fluid through a multi-scale strategy. The analysis of thermal interactions was first carried out for fixed bed configurations and then, fluidized beds at two overlapping scales: local (PRS; Particle Resolved Simulation) and mesoscopic (DEMCFD; Discrete Element Method-Computional Fluids Dynamics). The PRS approach accounts for the local coupling of heat transfer between the particles and its dynamics into fluidized beds. A comparative study of the two scales indicated the limits of the DEM-CFD model to capture the heat transfer fluctuations observed into PRS. In a last step, the closure laws for DEM-CFD were improved to reintroduce the fluctuations lost at this scale.

The wall effect is known to present difficulties when attempting to predict the pressure drop over randomly packed beds. The Nuclear Safety Standard Commission, “Kerntechnischer Auss-chuss" (KTA), made considerable efforts to develop an equation which predicts the pressure drop over cylindrical randomly packed beds consisting of mono-sized spheres. The KTA was able to estimate a limiting line, which defines the region for which the wall effect is negligible, however the theoretical basis for this line is unclear. The goal of this investigation was to determine the validity of the KTA limiting line, using an explicit approach. Packed beds were generated using Discrete Element Modelling (DEM), and the flow through the beds simulated using Computational Fluid Dynamics (CFD). STAR-CCM+R was used for both DEM and CFD operations, and the methods developed for this explicit approach were validated with empirical data. The KTA correlation predictions for friction factors were com- pared with the CFD results, as well as the predictions from a few other correlations. The KTA correlation predictions for friction factors did not correspond well with the CFD results at low aspect ratios and low modified Reynolds numbers, due to the influence of the wall effect. The KTA limiting line was found to be valid, but not exact. A new limiting line for the KTA correlation was suggested, however the new limiting line improved little on the existing line and was the result of some major assumptions. In order to improve the determination of the position of the KTA limiting line further, criteria need to be established which determine how small the error in predicted friction factor must be before the KTA correlation can be accepted as accurate. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2014

The wall effect is known to present difficulties when attempting to predict the pressure drop over randomly packed beds. The Nuclear Safety Standard Commission, “Kerntechnischer Auss-chuss" (KTA), made considerable efforts to develop an equation which predicts the pressure drop over cylindrical randomly packed beds consisting of mono-sized spheres. The KTA was able to estimate a limiting line, which defines the region for which the wall effect is negligible, however the theoretical basis for this line is unclear. The goal of this investigation was to determine the validity of the KTA limiting line, using an explicit approach. Packed beds were generated using Discrete Element Modelling (DEM), and the flow through the beds simulated using Computational Fluid Dynamics (CFD). STAR-CCM+R was used for both DEM and CFD operations, and the methods developed for this explicit approach were validated with empirical data. The KTA correlation predictions for friction factors were com- pared with the CFD results, as well as the predictions from a few other correlations. The KTA correlation predictions for friction factors did not correspond well with the CFD results at low aspect ratios and low modified Reynolds numbers, due to the influence of the wall effect. The KTA limiting line was found to be valid, but not exact. A new limiting line for the KTA correlation was suggested, however the new limiting line improved little on the existing line and was the result of some major assumptions. In order to improve the determination of the position of the KTA limiting line further, criteria need to be established which determine how small the error in predicted friction factor must be before the KTA correlation can be accepted as accurate. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2014

<p>Modern, small-scale wastewater treatment faces a twofold challenge: On the one hand requirements from legal authorities regarding removal of eutrophying substances have become more demanding. On the other hand high-quality phosphorus reserves are dwindling, which has raised calls for increased recycling. The problem is acute in the county of Stockholm where about 34 000 households are identified to not possess adequate wastewater treatment facilities. In this master’s thesis, four treatment systems, of which three had some phosphorus recycling potential, were compared using life cycle assessment methodology. The small-scale treatment systems analyzed were infiltration, filter beds with Filtralite® P and Filtra P respectively as filter material and a chemical precipitation system. The system boundaries included the extraction of raw materials, production of materials and components, the construction and operation of the systems as well as deconstruction and recycling of the treatment plants. Apart from impacts on human health and acidification potential, which both proved to be of less relevance to the final results, energy usage, consumption of abiotic resources, global warming potential and eutrophication potential were taken into account in this study.</p><p>The infiltration system attained the most favourable results in all impact categories save eutrophication potential, which was due to both the low usage of energy and resources as well as the system’s high life expectancy. The filter bed system using Filtralite® P demonstrated the best performance in reduction of eutrophying substances. However, the system’s energy demand and emissions of greenhouse gases by far exceeded the other systems’ results in these categories. Both the filter bed system using Filtra P and the chemical precipitation system fared relatively equal in the overall analysis, with moderate impacts in all categories. The nutrient recycling potential was shown to be limited by the waste products’ relatively high heavy metal content. Sludge from chemical precipitation had higher potential for replacement of fertilizer than filter bed material.</p><p>The chemical precipitation system fared best in the overall assessment. Its technical immaturity and limited data foundation put the alternative using Filtra P into second place. The infiltration system’s limited treatment performance and inexistent recycling potential put this alternative into third place. The alternative using Filtralite® P was ruled out entirely because of its high impact on fossil fuel consumption and global warming. Based on this ranking recommendations were made.</p><p>Even though the filter bed materials in this study showed excellent phosphorus removal capacity, further research into alternative filter bed materials will have to be made due to the materials’ environmental impacts in other areas. Focus should be on waste material and natural products (such as shell sand) with low environmental impacts from production. Ways of separating heavy metals from plant nutrients need to be explored if nutrient recycling is to be an aim. This study showed that good phosphorus removal characteristics can lead to an increase in other environmental impacts, which in some cases even may outweigh the positive effects of decreased eutrophication.</p> / <p>Modern, småskalig avloppsreningsteknik står inför två utmaningar. Å ena sidan har kraven från lagstiftaren på rening av eutrofierande ämnen ökat. Problemet är akut i Stockholms län där det finns ca. 34 000 hushåll som inte anses uppfylla reningskraven. Å andra sidan minskar fosforförekomsterna av hög kvalitet i allt större takt, vilket har väckt krav på ökad återföring av växtnäring. I detta examensarbete undersöktes fyra olika reningstekniker, varav tre har en viss återföringspotential, med hjälp av metodik från livscykelanalys. Systemen som undersöktes var infiltration, filterbäddar dels med Filtralite® P och dels med Filtra P som filtermaterial, samt ett kemikaliefällningssystem. Systemgränserna omfattade extraktion av råmaterial, produktion av anläggningsmaterial och –komponenter, uppförande och drift av systemen samt avveckling av anläggningarna och återföring av restmaterial. Förutom påverkan på mänsklig hälsa och försurningspotential, som visade sig vara mindre relevanta för slutresultaten, omfattade analysen även en undersökning av energianvändning, förbrukning av abiotiska resurser, potential för global uppvärmning och eutrofieringspotential.</p><p>Infiltrationslösningen fick de mest fördelaktiga resultatvärden i alla kategorierna förutom eutrofieringspotential, vilket kan förklaras med systemets låga energi- och resursbehov samt dess höga livslängd. Filterbädden med Filtralite® P som filtermaterial uppvisade den största förmågan att reducera eutrofierande substanser. Systemets energibehov och utsläpp av växthusgaser översteg dock de andra systemens resultat i dessa kategorier kraftigt. Både anläggningen med Filtra P och kemikaliefällningslösningen fick liknande resultat, med måttlig påverkan i alla kategorier. Systemens återföringspotential visade sig vara begränsad av restprodukternas höga tungmetallhalt. Kemikaliefällt slam hade högre återföringspotential än filterbäddsmaterial.</p><p>Kemikaliefällning klarade sig totalt sett bäst i studien. Den relativt obeprövade tekniska utformning och det osäkra dataunderlaget ledde till att Filtra P hamnade i rangordningen efter kemikaliefällning. Infiltrationssystemets begränsade reningsförmåga och den obefintliga återföringspotentialen ledde till att alternativet hamnade näst sist. Filtralite® P-alternativet blev placerat sist i rangordningen på grund av dess stora påverkan på förbrukning av fossila bränslen och global uppvärmning. Baserat på rangordningen utfärdades rekommendationer.</p><p>Trots att filtermaterialen som undersöktes i denna studie har en utmärkt fosforreningsförmåga, kommer det att krävas fler studier med avseende på alternativa filtermaterial, eftersom materialens användning av icke-förnybara energikällor är mycket stor vid tillverkningen. Fokus borde ligga på återvunna eller naturliga material (som t.ex. snäcksand) med låg miljöpåverkan vid tillverkning. Om återföring av växtnäring ska bli ett mål inom småskalig avloppsvattenrening, måste effektiva sätt att separera tungmetaller från växtnäringsämnen utforskas. Denna studie visade att goda fosforavskiljningsegenskaper kan medföra att andra typer av miljöpåverkan ökar, vilket i vissa fall kan leda till att de negativa konsekvenserna överväger nyttan av minskad eutrofiering.</p> / <p>Moderne, dezentrale Abwassertechnik steht zwei großen Herausforderungen gegenüber. Zum einen sind die Ansprüche von Seiten des Gesetzgebers gestiegen, die effektivere Abwasserreinigungstechniken erfordern. Zum andern werden Phosphorvorkommen von hoher Qualität zunehmend knapper, was Rufe nach verstärkter Rückführung von Phosphor hat laut werden lassen. Im Verwaltungsbezirk Stockholm, in dem es ungefähr 34 000 Haushalte mit unzureichender Abwasserreinigung gibt, ist das Problem von besonderer Bedeutung. In dieser Diplomarbeit wurden vier Abwasserreinigungssysteme, wovon drei ein gewisses Potential für Phosphorrückführung haben, mit Hilfe einer Ökobilanzierung untersucht. Folgende Systeme wurden untersucht: Eine Infiltrationsanlage, zwei Filterbettsanlagen, eine mit Filtralite® P und eine mit Filtra P als Filtermaterial sowie ein System mit Chemikaliefällung. Die Systemgrenzen umfassten die Gewinnung und Verarbeitung von Rohstoffen, das Errichten der jeweiligen Anlage, deren Betrieb sowie Rückgewinnung und Entsorgung von Restmaterialien. Neben Auswirkungen auf die menschliche Gesundheit und Versauerungspotential, die sich im Nachhinein als weniger relevant erwiesen, wurden Energiebedarf, Verbrauch abiotischer Resourcen, Potential für globale Erwärmung und Eutrophierungspotential untersucht.</p><p>Die niedrigsten Resultate in allen Kategorien außer Eutrophierungspotential wurden vom Infiltrationssystem erreicht. Filtralite® P erwies sich als am leistungsstärksten, was die Reduktion von eutrophierenden Substanzen angeht. Der Energiebedarf und die Emissionen von Treibhausgasen dieser Alternative überstieg die Ergebnisse der anderen Alternativen in diesen Kategorien doch bei weitem. Filtra P und Chemikaliefällung erzielten moderate Auswirkungen in allen Kategorien. Das Potential für die Rückführung von Pflanzennährstoffen wird, wie die Ergebnisse zeigen, vom relativ hohen Schwermetallhalt in den Restprodukten begrenzt.</p><p>Chemikaliefällung ist in dieser Studie die beste Alternative. Filtra P zeigte sich als technisch noch zu wenig ausgereift und die Datenunterlage als zu unvollständig, weswegen diese Alternative an zweiter Stelle steht. Die begrenzte Reinigungsfähigkeit des Infiltrationssystemes und das nicht vorhandene Potential für Rückführung von Phosphor führten dazu, dass diese Lösung an dritter Stelle steht. Das System mit Filtralite® P als Filtermaterial wurde wegen seines großen Verbrauchs von fossilen Brennstoffen für wenig brauchbar befunden und steht damit an letzter Stelle.</p><p>Trotz ihrer hervorragenden phosphorreduzierenden Eigenschaften, wird weitere Forschung im Bereich alternativer Filtermaterialien notwendig werden. Hierbei sollten natürliche Materialien (wie Muschelsand) oder Restprodukte im Mittelpunkt des Interesses stehen, um die Umweltauswirkungen gering zu halten. Wenn die Rückführung von Phosphor ein Ziel der Abwasserreinigung sein soll, müssen Lösungen, Schwermetalle von Pflanzennährstoffen zu trennen, gefunden werden. Diese Studie hat gezeigt, dass gute phosphorreduzierende Eigenschaften zu verstärkten Umweltauswirkungen in anderen Bereichen führen können, welche in manchen Fällen sogar die Vorteile einer verringerten Eutrophierung übersteigen können.</p>

No description available.

Pela primeira vez incêndios florestais são identificados em uma associação de fácies contendo a Flora Dicroidium nos sedimentos avermelhados do Triássico Médio (Ladiniano) na parte sul da Bacia do Paraná (Formação Santa Maria, Rio Grande do Sul). A extensão geográfica dessa assembleia de plantas foi, assim, estendida no Gondwana brasileiro. As análises por petrografia orgânica, fluorescência, microscopia eletrônica de varredura (MEV) e microscopia eletrônica de varredura (tipo field emission gun - MEV-FEG) revelaram a presença recorrente de carvão vegetal (charcoal) na sucessão vertical de fácies relacionadas a um modelo deposicional de fluxos efêmeros de baixa densidade do tipo inunditos. O carvão microscópico (micro-charcoal) ocorre como fragmentos comuns em diferentes fácies, enquanto que o carvão vegetal macroscópico (macro-charcoal) é representado por espécimes tridimensionais de lenhos atribuídos a gimnospermas (Pinaceae?) e por fragmentos achatados, finos e alongados atribuídos a pteridospermas (rachises de Dicroidium?) Os valores médios de reflectância da inertinita entre 2,80-6,61 %Ro medidos nos fragmentos de macro-charcoal evidenciaram processos de queima de alta temperatura, envolvendo tanto incêndios na copa quanto na interface copa-superfície. A recorrência de fragmentos queimados em várias fácies do perfil estudado indica a ocorrência de incêndios regionais que afetaram tanto as comunidades meso-xerófilas distais quanto às associações proximais higro- mesófilas, compostas majoritariamente por espécimes da Flora Dicroidium. A integração dos resultados obtidos a partir das múltiplas análises dos fragmentos de charcoal é consistente com um teor de oxigênio atmosférico superior a 20%. / For the first time wildfires are reported from an association of different facies containing a Dicroidium flora from the Middle Triassic (Ladinian) red beds in the southern part of the Paraná Basin (Santa Maria Formation, Rio Grande do Sul state). The geographical extension of the Dicroidium plant assemblage has thus been extended in the Brazilian Gondwana. Analyses through petrography, fluorescence microscopy, scanning (SEM) and field emission gun scanning electron microscopy (FEG-SEM) revealed recurrent charcoal presence in a vertical facies succession of depositional cycles related to ephemeral prograding low density flows. Microscopic charcoal occurs as common fragments within different facies whereas macroscopic charcoal is represented by tridimensional wood specimens assigned to gymnosperms (Pinaceae?) and by flattened, thin, elongated remains assigned to pteridospermophytes (rachises of Dicroidium?). Average reflectance values between 2.80-6.61 %Ro measured in the macro-charcoals evidenced burning processes of high temperature, involving fires both in the crown and in the crown-surface interface. The recurrence of charcoal in several facies of the studied profile indicates regional wildfires, which affected hinterland, meso-xerophyllous coniferous assemblages and marginal hygro-mesophyllous Dicroidium-like assemblages. The integration of results obtained from the multiple charcoal analyses is consistent with atmospheric oxygen content higher than 20%.