Dissertations / Theses on the topic 'Turbidity'
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Fay, Gemma Louise. "Mathematical modelling of turbidity currents." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:62bb9382-1c50-47f3-8f59-66924cc31760.
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Turbidity currents are one of the primary means of transport of sediment in the ocean. They are fast-moving, destructive fluid flows which are able to entrain sediment from the seabed and accelerate downslope in a process known as `ignition'. In this thesis, we investigate one particular model for turbidity currents; the `Parker model' of Parker, Pantin and Fukushima (1986), which models the current as a continuous sediment stream and consists of four equations for the depth, velocity, sediment concentration and turbulent kinetic energy of the flow. We propose two reduced forms of the model; a one-equation velocity model and a two-equation shallow-water model. Both these models give an insight into the dynamics of a turbidity current propagating downstream and we find the slope profile to be particularly influential. Regions of supercritical and subcritical flow are identified and the model is solved through a combination of asymptotic approximations and numerical solutions. We next consider the dynamics of the four-equation model, which provides a particular focus on Parker's turbulent kinetic energy equation. This equation is found to fail catastrophically and predict complex-valued solutions when the sediment-induced stratification of the current becomes large. We propose a new `transition' model for turbulent kinetic energy which features a switch from an erosional, turbulent regime to a depositional, stably stratified regime. Finally, the transition model is solved for a series of case studies and a numerical parameter study is conducted in an attempt to answer the question `when does a turbidity current become extinct?'.
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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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Edwards, Deborah Anne. "Turbidity currents : dynamics, deposits and reversals." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293760.
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Straub, Kyle M. "Quantifying turbidity current interactions with topography." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40864.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 196-205).
This thesis advances our understanding of how transport properties of turbidity currents are mediated by interactions with seafloor topography, specifically channelized surfaces. Turbidity currents are responsible for crafting the morphology of continental margins. Unfortunately, very few direct observations exists defining turbidity current interactions with submarine channels and canyons because infrequent occurrence, great water depths, and high current velocities make measurements difficult to obtain. To overcome this problem, I utilize reduced scale laboratory experiments, remote sensing of the seafloor and subsurface deposits, and numerical analysis of transport processes. I focus on resolving the topography and composition of the evolving water-sediment interface with additional measurements that characterize the sediment transport and flow fields. I begin by quantifying interactions between turbidity currents and channel-bounding levees. Levees are the primary elements of self-formed channels and act to confine flows within channels, thereby increasing transport efficiency. I quantify the morphology and growth of levees in a submarine channel network offshore Borneo. Levee deposit trends are interpreted using laboratory observations and a morphodynamic model describing levee growth. Channel and levee deposits resulting from interactions between turbidity currents and sinuous submarine channels are then studied using reduced-scale laboratory experiments. Measurements of current superelevation in channel bends are used to illustrate the importance of current runup onto the outer banks of channel bends. This runup resulted in focused overbank flow and production of thick, coarse, steep levees at these sites.
(cont.) Additional laboratory experiments illustrate the importance of current-channel bend interactions to the runout length of turbidity currents. I observed enhanced mixing in channel bends that reduced proximal deposition rates in sinuous channels compared to straight channels. I hypothesize that a wholesale vertical mixing of suspended sediment within turbidity currents at channel bends is a necessary condition for the construction of submarine channels greater than 100 km in length. Finally, I document the deepening of submarine canyons under net depositional conditions using an industry-grade seismic volume from the continental slope offshore Borneo. Interpretation of seismic horizons suggests deposition resulted from sheet-like turbidity currents, highlighting the importance of unconfined currents to the evolution of seascapes.
by Kyle M. Straub.
Ph.D.
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Altinakar, Mustafa Siddik. "Weakly depositing turbidity currents on small slopes." Online version, 1993. http://bibpurl.oclc.org/web/26138.
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Goater, Alexander James Nicholas. "Shallow-layer modelling of submarine turbidity currents." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.566708.
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Turbidity currents are large-scale natural phenomena that consist of suspended sed- iment travelling over an impermeable underlying boundary. We employ a shallow- layer approach to model their dynamics, taking advantage of the fact that their streamwise length is much larger than their vertical height. We frequently consider flows initiated by the instantaneous release of a finite volume of stationary material, known as a 'dam break' configuration. New complete analytical solutions of dam-break flows into a layer of quiescent fluid, or 'tailwater', are found. The tailwater's presence introduces new phenomena: after sufficient time the front of the flow decelerates and an internal bore develops. A model of polydisperse turbidity current motion is developed in which we con- serve interstitial fluid, momentum and particulate. To integrate our model we con- struct a new numerical scheme that is second-order accurate, simple to apply, shock- capturing and non-oscillatory. The scheme is validated by comparison with existing analytical results and employed in three ways. First, the effect that entrainment of ambient fluid and the gradient of the un- derlying boundary have on particle-driven gravity currents is derived through new scaling relationships. These highlight the role that these processes may have in large- scale geophysical flows and indicate why laboratory investigations at much smaller scales may not have needed to include these effects. The turbidity current formed by a lava dome collapse on the Soufriere Hills volcano, Montserrat in July 2003 is modelled next using no fitting parameters. We employ field data to inform our model and validate the output. Agreement is found for the predicted deposit thickness and aspects of the grain size distribution, thus our model effectively captures the key dynamical processes. Finally, new analytical self-similar solutions to entraining gravity currents on inclined planes are presented. We demonstrate that these are attractive solutions of the governing equations after sufficient time.
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Lucchese, Luisa Vieira. "Estudo numérico da sedimentação em correntes de turbidez com evolução do relevo de fundo." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/175016.
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Correntes de densidade são fluxos gravitacionais gerados pela diferença de densidade entre dois fluidos. Correntes de turbidez fazem parte de uma sub-classificação das correntes de densidade, na qual o fluido mais denso tem, na sua composição, partículas em suspensão. Muitos trabalhos numéricos já estudaram a dinâmica das correntes de turbidez, mas, nenhum dos encontrados aplicou mudanças de relevo concomitantes com a simulação, causadas pela sedimentação das próprias partículas da corrente e nem alterou o relevo após a passagem de cada evento em um domínio tridimensional. O presente trabalho pretende analisar a alteração no relevo de fundo causada por uma corrente de turbidez. No código Incompact3d, as equações de Navier-Stokes, Continuidade e Transporte e Difusão são resolvidas em uma malha cartesiana tridimensional. A condição inicial adotada é a de Lock-Exchange. As simulações realizadas utilizaram Simulação Numérica Direta (DNS). O código utiliza um esquema compacto centrado de sexta ordem, em diferenças finitas, para o esquema espacial, e Adams-Bashfort de terceira ordem para o esquema temporal. A validação do código foi realizada comparando-se com trabalhos experimental e numéricos. A análise das diferentes proporções granulométricas mostrou que quanto maior é a quantidade de material grosso na condição inicial, maior será seu depósito para um dado tempo. Em consequência, mais relevante se torna a consideração da alteração do relevo de fundo. Além disso, quanto maior o fator de compactação do sedimento, maior será o erro de não considerar a atualização de fundo. Os resultados também apontaram que os erros médios ao não considerar a atualização do fundo são da ordem de 4% da massa de depósito em 20 tempos adimensionais, para os parâmetros utilizados. Ao se propagar uma corrente de turbidez sobre o depósito de outra, os erros se mostram menores.Gravity currents are gravitational fluxes triggered by density di erence between two fluids. A sub-classification of those are turbidity currents, in which the denser fluid is composed by the lighter fluid plus suspended particles. Many papers had shown turbidity currents dynamics, although none of the papers found had applied changes in the simulated topography due to deposit during the own simulation, neither they had altered a 3D domain topography after each flux, applying the changes caused by the previous current. The present dissertation aims to analyse the turbidity current dynamics alteration caused by the influence of its own deposit, altering the topography during the very simulation. The analysis is conducted in a polidispersed turbidity current. The Incompact3d code solves Navier-Stokes, continuity and transport-di usion equation, in a tridimensional cartesian mesh. Lock-exchange was chosen to be the initial condition. Direct Numerical Simulations (DNS) are performed. Sixth order compact finite-di erence schemes are used on the spatial domain, while third order Adams-Bashfort is applied for the temporal evaluation. Comparisons with numerical and experimental papers were performed for code verification. Results showed the coarser the particles on the starting lock-exchange, the higher its deposit is, and the more the terrain will be altered. Nevertheless, the bigger the compacting factor, the bigger the error of not considering bathymetry alteration. Results also point that the average errors of not considering the update are in order of 4% on the mass deposit, after 20 dimensionless times, for the used parameters. When a current propagates over the deposit of a previous one, these errors are smaller.
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BITTON, LUIZ FERNANDO ROCHA. "VALIDATION OF SIMPLIFIED MATHEMATICAL MODEL FOR TURBIDITY CURRENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12078@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A combinação de modelos numéricos com modelos computacionais tem contribuido muito para o melhor entendimento matemático de fluxos gravitacionais, porém esses modelos não podem substituir a análise através de trabalhos experimentais. O uso de modelos físicos em escala provou ser essencial na validação de equações para modelagem de correntes de turbidez. Com o objetivo de diminuir o nível de dificuldade em modelar numericamente essas correntes e de gerar modelos computacionais de alto desempenho, algumas simplificações foram feitas durante o desenvolvimento das equações de velocidade. Dessa forma, para provar que tais simplificações não iriam alterar os resultados numéricos do modelo, foram realizados inúmeros experimentos, coletando informações sobre a evolução espaço- temporal de velocidades das correntes de turbidez não- confinadas com e sem partículas. Comparando os resultados do modelo numérico com os do modelo físico, foi concluído que, infelizmente, as aproximações influenciaram os resultados. Contudo, os dados e a comparação visual entre as simulações também revelaram alguns resultados encorajadores, os quais estimularão pesquisas futuras para se melhorar a precisão da equação de velocidade utilizada no modelo numérico.
The combination between numerical and computer models has improved dramatically the mathematical understanding of gravity currents; however, these models can not replace the analysis by experimental work. The use of scaled analogue models, or physical models, proved to be essential in validating velocity equations for turbidity currents. In order to reduce the level of difficulty to model mathematically these currents, some approximations were applied during the development of the velocity equation. Therefore, willing to prove that these approximations would not compromise the numerical results, innumerous experiments were performed to acquire a spatio-temporal velocity evolution database for both unconfined particle free and particulate turbidity flows. Comparing the results from the numerical and physical simulations, it was concluded that, unfortunately, the approximations have influenced the numerical results. Nevertheless, the data and visual comparisons between the simulations also revealed some encouraging results, which will stimulate some future research to improve the accuracy of the depth-averaging velocity equation.
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Ho, Viet Luan. "Multi-pulsed turbidity current dynamics and geological implications." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20794/.
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Deposits of turbidity currents - turbidites - commonly exhibit upward-fining grainsize profiles, reflecting deposition from flows with simple rapidly-waxing then progressively-waning velocity structures. However, turbidites with patterns of multiple cycles of inverse-to-normal grading are not uncommon. Such deposits are interpreted as being deposited under the influence of repeated waxing-waning velocity cycles within multi-pulsed turbidity currents and are termed "multi-pulsed turbidites". Multi-pulsed flow can be initiated by sequences of retrogressive submarine failures in which each slumping episode can form a pulse in the velocity structure, or may arise due to the combination of multiple flows at downstream confluences; separate flows may even run into each other over long distances. In the first case, it has been inferred that multi-pulsed deposits might carry signals of flow initiation, with each slump linked to a seismic impulse, and further, that such signals can be recognised in the vertical grading structures of distal turbidites. The focus of this research has been to establish i) how multi-pulsed flow dynamics and associated deposits vary along flow pathways and ii) the degree to which grading structures in turbidites deposited by multi-pulsed flows permit inference of flow initiation mechanisms. Initial experiment modelling of single- and multi-pulsed solute-driven gravity flows shows that internal pulses are necessarily advected forward, eventually merging with the flow head such that multi-pulsed flows transition from being cyclically waxing-waning to waxing on arrival then monotonically waning. This finding implies that initiation signals should be distorted then lost in any deposits along the flow pathway. Accordingly, an interpretational template for the spatial variation in turbidite character along flow pathways was developed, accounting for both pulse merging and flow combination at confluences. Further experiments were conducted to support a scaling analysis to estimate merging lengths; these lengths are shorter than those documented from prototype settings, and may reflect a limitation in the scope of application, arising from experimental constraints. Experiment modelling of single- and multi-pulsed sediment-driven gravity flows confirms the occurrence of the pulse merging phenomenon in turbidity currents. Analysis of associated deposits confirms the downstream spatial transition from multi- to uni-pulsed turbidites, albeit with the point of transition being more proximal in the laboratory deposit than the point of pulse merging. However, the spatial persistence of the complex velocity structure up to the point of merging need not be reflected in the associated deposit. Beyond the merging point, single-pulsed turbidites must always be deposited. Such deposits cannot be used to infer flow initiation mechanisms.
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Hu, Peng. "Coupled modelling of turbidity currents over erodible beds." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2563.
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Turbidity currents are significant due to their role in dictating reservoir sedimentation, the safety of deep sea facilities and the formation of submarine morphological features and turbidites. Interactions exist between turbidity current, sediment transport, bed topography and deformation. However, existing mathematical models have ignored these interactions either partly or completely. Therefore these models can be referred to as decoupled or partially coupled models. Uncertainties arising from these simplifications remain unclear. To help address this, the present study advances modelling capability and understanding of turbidity currents in three areas. First, the significance of the interactions is analysed theoretically. Second, a fully coupled mathematical model, which incorporates explicitly the interactions between turbidity current, sediment transport, bed topography and deformation, is developed and tested. Third, the model is applied to submarine turbidity currents and reservoir turbidity currents. It is demonstrated that the model is a viable tool for effective reservoir sediment management and facilitates an improved understanding of the formation of submarine morphological features. Three issues need to be carefully dealt with in turbidity current modelling: 1) the internal hydraulic jumps, 2) the moving current front, -and 3) the irregular topographies in the field. These necessitate a mathematical model being well-balanced and capable of automatically capturing shock waves and tracking the wet/dry front. But to the writer’s knowledge, these aspects have so far not been simultaneously implemented in existing models of turbidity currents. In this study, the finite volume method is used to solve the governing equations and the slope limited centred scheme (SLIC) is employed to estimate the numerical fluxes, rendering the model capable of automatically capturing shock waves. The weighted surface depth gradient method (WSDGM) is implemented in the SLIC scheme, making the model well-balanced and thus applicable to both regular and irregular topographies. The wellbalanced property is demonstrated by successful reproduction of an initially subaqueous static turbidity volume over an irregular hump, as well as the successful application of the model to a real reservoir. The experimentally observed internal hydraulic jump is satisfactorily reproduced by the model, suggesting the ability of the model to accurately capture shock-waves. The accuracy of the model in reproducing key current variables is also demonstrated as against experimental data. The significance of fully coupled modelling is investigated theoretically using the multipletime- scale theory. This is complemented by numerical simulations of self-accelerating turbidity currents. Fully coupled modelling is shown to be critical for refined quality of turbidity current modelling, especially for those cases featuring rapid bed deformation. Decoupled and partially coupled models may be approximately applicable only to turbidity currents with mild bed deformation. Existing understanding of the formation of submarine morphological features is based mainly on indirect back-estimations, which cannot resolve the physical process. Applying the fully coupled model, the formation processes of canyons, channel-levees and lobes are numerically resolved. It is demonstrated that appropriate bed slope and sediment particle size may favour the formation of channel-levee morphology over submarine fans, as larger Richardson number does. Turbidity currents have been generated in a series of water-sediment regulation experiments in the Yellow River, China, aiming to get as much sediment as possible transported to the downstream and therefore reduce reservoir sedimentation. However, post-experiment analyses are mainly in the form of observed data comparisons. Two events of turbidity currents in the Xiaolangdi reservoir are investigated numerically. The advance of the current front and the sediment transport rate are reproduced by the model fairly well. These suggest the present model as a viable tool for determining the timing for operating the bottom outlets, which is critical for effective reservoir sediment management.
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Harrinauth, Reshma K. "Sedimentation of Organic - Inorganic Composites by Optical Turbidity." Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/281.
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Sedimentation is one of many characterization tools used to test materials in nanotechnology. Characterization of settling behavior is complex as there are many variables which can affect sedimentation. In our research, we focused on sedimentation in colloidal systems with the aid of an optical turbidometer. Nanoparticles of CeO2 (Ceria Oxide) and TiO2 (Titanium Dioxide) are embedded onto a polymeric matrix of a thermally responsive microgel of poly(N-isopropylacrylamide) (PNIPAM) and interpenetrating chains of poly(acrylic acid) to create novel composites. The composites are loaded with the inorganic oxide nanoparticles at different weight percent from a low value of 10 weight % to 75 weight %. The loading of the colloidal particles affects the sedimentation rate. In this thesis a turbidomenter is used to characterize the settling rate, which is an important characteristic for application of these new composites.
TiO2 is a key constituent in many industrial products; cosmetics, paints, ceramics and used in waste water remediation. It is a potent photocatalyst which breaks down almost any organic compound when exposed to ultraviolet light. By combining nanoparticles of TiO2 with microgels of a polymer, the composites can facilitate use and recovery of the catalyst. Gravity settling of these loaded composites provides an easy separation of TiO2 nanoparticles. In this context, characterization of settling plays an important role. CeO2 composites are used to polish oxide coatings in the semiconductor industry and sedimentation of the composite particles is important as it can affect the efficiency of the planarization process. Therefore, measuring sedimentation of these composites is necessary.
In this study, the settling behavior is measured optically for a variety of conditions that differ in loading of inorganic nanoparticles within the microgels, temperature of the solution, and concentration of particles in solution. The overall goal is to understand the sedimentation behavior of these novel composites and facilitate their use in industrial processes.
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Terlaky, Viktor. "Sedimentology, Stratigraphy, Architecture and Origin of Deep-water, Basin-floor Deposits: Middle and Upper Kaza Group, Windermere Supergroup, B.C., Canada." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30378.
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Ancient basin-floor strata are exceptionally well exposed in the Neoproterozoic Windermere Supergroup in the southern Canadian Cordillera. Data from the Castle Creek outcrop, where strata of the upper Kaza Group crop out, and the Mt. Quanstrom outcrop, where the middle Kaza is exposed, form the main dataset for this study. The aim of this study is to describe and interpret the strata starting at the bed scale, followed by stratal element scale, lobe scale and ultimately fan scale.
Strata of the Kaza Group comprise six sedimentary facies representing deposition from a variety of fluid and cohesive sediment gravity flows. These, in turn, populate seven stratal elements that are defined by their basal contact, cross-sectional geometry and internal facies distribution. The lithological characteristics of stratal elements vary little from proximal to more distal settings, but their relative abundance and stacking pattern do, which, then, forms the basis for modeling the internal architecture of lobes.
Lobes typically comprise an assemblage of stratal elements, which then are systematically and predictably arranged in both space (along a single depositional transect) and time (stratigraphically upward). Lobes typically became initiated by channel avulsion. In the proximal part of the system scours up to several meters deep, several tens of meters wide are interpreted to have formed by erosion downflow of the avulsion node. Erosion also charged the flow with fine-grained sediment and on the lateral margins and downflow avulsion splays were deposited. Later flows then exploited the basin-floor topography and on the proximal basin-floor carved a feeder channel, which then fed a downflow depositional lobe. At the mouths of feeder channels flows became dispersed through a network of distributary channels that further downflow shallow and widen until eventually merging laterally in sandstone-rich terminal splays. During the lifespan of a single lobe the feeder channel remains fixed, but the distributary channel network and its associated terminal splays wander, causing them to stack and be intercalated laterally and vertically. Eventually an upstream avulsion terminates local sediment supply, causing a new lobe to be initiated elsewhere on the fan, and the process repeats.
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Di, Domizio Thomas John. "Treatment of Colorado River water with ozone, ferric chloride and Cat-Floc T-2." Thesis, The University of Arizona, 1990. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1990_607_sip1_w.pdf&type=application/pdf.
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Eggenhuisen, Joris Theodoor. "'The interaction between substrate evolution and turbidity current development'." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507691.
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Gladstone, Charlotte. "Experimental and field investigations of sedimentation from turbidity currents." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388252.
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Kwon, Jae-Il. "Simulation of turbidity maximums in the York River, Virginia." W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539616723.
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Two of the most important processes in cohesive sediment transport, erosion rate and settling velocity, were the focus of this study. Settling velocities were estimated by the Owen tube method and the acoustic Doppler velocimeter (ADV) method. A novel erosion model, namely a constant erosion rate model, was implemented in a three-dimensional hydrodynamic eutrophication model (HEM-3D) to simulate the turbidity maximums in the York River system, Virginia. Two one-month periods of model simulations were conducted to mimic typical dry (November--December, 2001) and wet (March--April, 2002) seasons. In order to have enough data to verify the model, four slack water surveys were carried out during each period to measure salinity and total suspended solid (TSS) profiles. Because of the unexpected extremely low freshwater discharge during both those periods, all survey results showed similar salinity and TSS distributions. The estuarine turbidity maximums were abnormally located about 30 km upstream from West Point, with TSS concentrations on the order of 102 mg/L. Laboratory Owen tube experiments showed that the settling velocity was related to the TSS concentration, highlighting the importance of sediment availability on settling velocity and the less important salinity effect. The estimated settling velocities from four sets of ADV field measurements were much higher than that from the Owen tube laboratory experiments and better reproduced the turbidity maxima for slackwater simulations. These suggested that turbulence may have a dominant effect on settling velocity, and the ADV method seems to be an effective and suitable way to estimate the settling velocity in turbulence dominated environments. Based on a newly found erosion behavior, a constant erosion rate model was implemented in a three-dimensional numerical model such that erosion occurs only during accelerating phases of the tide. Specifically, the Four Factor Model was suggested that consists of (i) a reference constant erosion rate, (ii) hydrodynamic effects, (iii) spatial variability of the bed condition, and (iv) temporal variability of the bed condition. The Four Factor Model successfully simulated the turbidity maximums in the York River system.
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Porro, Francesca. "Understanding palynomorph distribution in turbidite systems." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=238813.
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Rothwell, Robin Guy. "Sedimentation on basin plains." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240961.
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Watson, Dale, and dale watson@ecosec com au. "The Regional Distribution and Significance of Stream Turbidity in Victoria." RMIT University. Mathematical and Geospatial Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070206.150045.
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This thesis investigates the distribution and significance of stream turbidity in Victoria; specifically exploring the factors that may have influenced the pattern of regional variation in turbidity, and factors that give it significance in the regional, social, cultural and environmental context. The limits to water availability are set, not only by the quantity of water in storages or streams but, more fundamentally, by acceptable levels of water quality and catchment health. To make effective judgements of water availability managers of water resources need to know the significance of measured natural resource condition in the regional context. Stream turbidity can be considered by the agricultural community as a sign of soil erosion and a loss of agricultural potential, while from the ecological perspective it can be considered a sign of deteriorating river health. Fundamentally, levels of turbidity are closely bound with land use practice and, in the Australian context, turbidity can be considered a measure of the consequences of land management practices on soil erosion and run-off. Measured levels of turbidity in Victoria should be interpreted within the context of a unique history and geography. The spread of European colonisation and the introduction of massive land use change to the Victorian landscape have meant that over most of Victoria current levels of turbidity reflect the effects of over a hundred and fifty years of large scale intervention with its controlling factors. In Victoria current levels of turbidity are interpreted in a cultural context far different from that of early colonists or even of a few decades ago. The concept of Ecologically Sustainable Development which has dominated natural resource management in recent times brings new responsibilities to resource managers. Ecologically sustainable management means that resources must be considered in a more inclusive spatial and temporal context. In the early stage of Victoria's history sustainable management of water meant having enough water left from winter rains to supplement summer supply. However, in recent years, it has begun to have more complex associations; sustainable water use is now, almost universally considered to include maintenance of the environmental health of waterways, and by implication, the environmental health of the whole catchment. In this context, stream turbidity can be considered a useful indicator of catchment health, in particular, because levels of turbidity bear a direct physical relationship to catchment processes. New tools are needed to explore the relationship between land use and water quality at the regional scale. The results of this current research include a regional statistical model of stream turbidity, which is conceptually designed to offer useful predictions of stream turbidity and underpin sustainable resource management. The statistical model was used as input to the development of a unique map display using Geographic Information Systems (GIS). The GIS is used to display the distribution of model predictions over a large region of south-eastern Australia. The practical advantage of this modelling approach is that it provides managers with the ability to identify locations in Victoria where measured water quality differs significantly from modelled water quality and flag them for further investigation. The major project outputs are a map of Victorian Water Quality Monitoring Network (VWQMN) catchments showing catchments in Victoria where measured turbidity differs from model predictions and a raster representation of the state of Victoria in which cell values indicate predicted stream turbidity. Important to this project was the novel use of GIS technology to process large national and regional scale digital data sets using tools developed for catchment scale hydrological models.
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Hossain, Alamgir, and n/a. "CFD investigation for turbidity spikes in drinking water distribution networks." Swinburne University of Technology, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20071102.161744.
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Drinking water distribution networks such as South East Water Ltd. (SEWL), Melbourne Water, Sydney Water, etc. are supposed to transport only dissolved matter rather than a few visible particles. However, it is almost impossible to make the drinking water free from suspended solid particles. The ability to determine the origins of these particles varies between different water supply systems, with possible sources being from catchment, treatment processes, biofilm growth within the water supply pipes, and corrosion products. Improvement of our understanding of the complex hydrodynamic behavior of suspended and/or deposited particles involved in these distribution pipe networks requires mathematical and physical models. Computational Fluid Dynamics (CFD) along with analytical turbulent model is one of the most popular mathematical techniques, which has the ability to predict the behavior of complex flows for such multiphase flow applications.
This study has been completed mainly in two steps. A CFD investigation was carried out to predict the hydrodynamic behavior of turbid particle flowing through a horizontal pipe networks including loop consist of bends and straight pipes. Furthermore, an extended analytical model was re-developed for the liquid-solid system to look at the similar behavior of the solid particles flowing in a turbulent field. These two parallel studies will provide better understandings about the turbidity spikes movements in the distribution networks.
A comprehensive CFD investigation was carried out for particle deposition in a horizontal pipe loop consisting of four 900 bends in a turbulent flow field. A satisfactory agreement was established with the experimental data as validation. This was a steady state multi-particle problem, which helped to understand the deposition characteristics for different particle sizes and densities at upstream and downstream sides of the bends as well as its circumference. Particle concentration was seen high at the bottom wall in the pipe flow before entering the bends, but for the downstream of bend the deposition was not seen high at the bottom as seen in upstream of bend rather inner side of the bend wall (600 skewed from bottom). The larger particles clearly showed deposition near the bottom of the wall except downstream. As expected, the smaller particles showed less tendency of deposition and this was more pronounced at higher velocity. Due to the high stream line curvature and associated centrifugal force acting on the fluid at different depths the particles became well mixed and resulted in homogeneous distribution near the bend regions.
The hydrodynamic behavior of particles flowing in a turbulent unsteady state flowing through a horizontal pipe was also studied to compare with the drinking water distribution networks data. In this numerical simulation six different flow-profiles and particle-load profiles were used to compute particles deposition and re-entrainment into the systems and to identify the conditions of the deposition and suspension mechanisms. Results showed that after a certain length of pipe and period of time after downward velocity gradient, when the velocity was constants over time, the shear stress was sufficiently high enough to cause the particle deposition on and roll along the bottom wall of pipe wall and created a secondary group of particle peak (called kink).
Finally, an extended analytical Turbulent Diffusion Model for liquid-solid phase was developed following an existing gas-liquid turbulence model. This turbulent diffusion model was then compared with the results of the CFD investigation making use of the same boundary conditions. The comparison established good agreement between these two models. The influence of velocity on the particle size distribution was dominant over the influence of the superficial liquid velocity, which was also explained by using the new parameter, velocity ratio. This velocity ratio was defined as the ratio between the free flight and gravitational velocity. Due to some inevitable assumptions used in the analytical model, the results showed typically less deposition as compared with the CFD investigation.
21
Hayes, Sara. "Polyacrylamide Use for Erosion and Turbidity Control on Construction Sites." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-04072003-143620/.
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Sediment is the most widespread pollutant of streams and rivers in North Carolina. Construction sites are a source of accelerated erosion contributing to the sediment problem. This study was conducted to determine if the application of polyacrylamide (PAM) to soil surfaces on construction sites reduces erosion and turbidity. Polyacrylamide has been demonstrated to greatly reduce erosion in furrow irrigation, and there is limited evidence it controls erosion when applied to bare soil. Two PAM products applied at manufacturers recommended rates (11.2 and 1.68 kg ha-1) and one half the recommended rates (5.6 and 0.84 kg ha-1) with and without grass seeding and mulching were tested on three North Carolina Department of Transportation construction sites in Raleigh and near Fayetteville. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 2:1 cut slope, turbidity and sediment loss were significantly decreased with application of seed/mulch. Erosion rates were 20 times greater on bare soil after seven rain events, with or without PAM, compared to treatments receiving seed/mulch. Polyacrylamide applied with seed/mulch produced slight reductions in turbidity and sediment loss in early rain events. At the higher rate, PAM applied directly on a more moderate, 4:1 fill slope decreased sediment loss and turbidity in the first few rain events following application compared to bare soil, with decreases diminishing over time. A sandy fill slope had inconsistent results between PAM treatments but reductions in turbidity and sediment from seed/mulch applications.
22
Wynn, R. B. "Turbidity current processes and deposits on the northwest African Margin." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42073/.
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The Northwest African margin is affected by a wide variety of sedimentary processes, including pelagic/hemipelagic background sedimentation, alongslope bottom currents, and downslope gravity flows. A large section of the margin can be classified as a fine-grained clastic slope apron, although the presence of numerous volcanic islands and seamounts leads to a more complex distribution of sedimentary processes than is accounted for by existing slope apron models. The Moroccan Turbidite System (MTS) is the largest turbidite system on the margin, with a total length of 1500 km. Individual turbidites can be correlated across three interconnected deep-water basins, giving an unprecedented insight into the turbidite depositional architecture of a system with complex seafioor topography and multiple sources. A detailed, core-based study of the turbidite fill in an intraslope basin within the MTS has revealed that sand body architecture is largely controlled by turbidity current volume. Small-volume turbidity currents deposit all of their sand around the mouth of the feeder canyon, whereas large-volume turbidity currents deposit extensive sheet sands across the basin floor. The large-volume, high efficiency flows excavate giant erosional scours at the canyon mouth, leading to development of a channel-lobe transition zone (CLTZ). Comparison with other CLTZ's has revealed that these zones form in association with flow expansion at a canyon/channel mouth, and may also be linked to major breaks in slope. Deep-water sediment waves are widespread on the margin, and display wave heights up to 70 m, and wavelengths up to 2.4 km. The largest sediment-wave fields are found on the continental slope and rise bordering the volcanic Canary Islands. Analysis of an integrated dataset, combined with simple numerical modelling, reveals that the sediment waves are deposited as antidunes beneath unconfined, low-velocity, low concentration turbidity currents.
23
Jastram, John Dietrich. "Improving Turbidity-Based Estimates of Suspended Sediment Concentrations and Loads." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/32514.
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As the impacts of human activities increase sediment transport by aquatic systems the need to accurately quantify this transport becomes paramount. Turbidity is recognized as an effective tool for monitoring suspended sediments in aquatic systems, and with recent technological advances turbidity can be measured in-situ remotely, continuously, and at much finer temporal scales than was previously possible. Although turbidity provides an improved method for estimation of suspended-sediment concentration (SSC), compared to traditional discharge-based methods, there is still significant variability in turbidity-based SSC estimates and in sediment loadings calculated from those estimates. The purpose of this study was to improve the turbidity-based estimation of SSC. Working at two monitoring sites on the Roanoke River in southwestern Virginia, stage, turbidity, and other water-quality parameters and were monitored with in-situ instrumentation, suspended sediments were sampled manually during elevated turbidity events; those samples were analyzed for SSC and for physical properties; rainfall was quantified by geologic source area. The study identified physical properties of the suspended-sediment samples that contribute to SSC-estimation variance and hydrologic variables that contribute to variance in those physical properties. Results indicated that the inclusion of any of the measured physical properties, which included grain-size distributions, specific surface-area, and organic carbon, in turbidity-based SSC estimation models reduces unexplained variance. Further, the use of hydrologic variables, which were measured remotely and on the same temporal scale as turbidity, to represent these physical properties, resulted in a model which was equally as capable of predicting SSC. A square-root transformed turbidity-based SSC estimation model developed for the Roanoke River at Route 117 monitoring station, which included a water level variable, provided 63% less unexplained variance in SSC estimations and 50% narrower 95% prediction intervals for an annual loading estimate, when compared to a simple linear regression using a logarithmic transformation of the response and regressor (turbidity). Unexplained variance and prediction interval width were also reduced using this approach at a second monitoring site, Roanoke River at Thirteenth Street Bridge; the log-based transformation of SSC and regressors was found to be most appropriate at this monitoring station. Furthermore, this study demonstrated the potential for a single model, generated from a pooled set of data from the two monitoring sites, to estimate SSC with less variance than a model generated only from data collected at this single site. When applied at suitable locations, the use of this pooled model approach could provide many benefits to monitoring programs, such as developing SSC-estimation models for multiple sites which individually do not have enough data to generate a robust model or extending the model to monitoring sites between those for which the model was developed and significantly reducing sampling costs for intensive monitoring programs.Master of Science
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Borner, Karoline. "Influence of turbidity on social structure in guppies, Poecilia reticulata." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17622.
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Umweltveränderungen kommen natürlicherweise vor und viele Spezies waren im Laufe ihrer Evolutionsgeschichte davon betroffen. Durch die Aktivitäten des Menschen jedoch finden diese in höherer Geschwindigkeit und größerem Umfang statt und stellen so für viele Spezies eine neue Herausforderung dar. Einen großen Einfluss auf die Umwelt nimmt der Mensch durch Verschmutzung, welche zu Veränderungen der Physiologie der Organismen und deren Verhalten führen und damit Einfluss auf die Populationsdynamik und letztendlich auf die Biodiversität haben kann. In meiner Dissertation untersuchte ich den Einfluss durch Bergbau ausgelöster Trübung auf das Verhalten und die soziale Struktur des Guppys. Er nutzt soziale Interaktionen für eine höhere Effizienz bei der Nahrungssuche und Räubervermeidung. Die Nutzung sei-nes dafür eingesetzten Sehsinns ist bei Trübung stark eingeschränkt. Ich untersuchte die Reaktion Trübung unerfahrener Fische aus Labor und Feld auf Trübung. Es zeigte sich, dass beide ihre sozialen Interaktionen in trübem Wasser verringerten. Eine zusätzliche Markow-Ketten-Analyse ergab aber auch, dass Laborfische Kontakte zu bestimmten In-dividuen der Gruppe verstärkten und Feldfische ihre initiierten Kontakte behielten. An-schließend studierte ich den Unterschied der sozialen Struktur Trübung erfahrener und - unerfahrener Fische. Trübung erfahrene Fische erhöhten die Gesamtzahl der Interaktio-nen, reduzierten jedoch die Anzahl der initiierten Kontakte im Gegensatz zu unerfahre-nen Fischen. Diese Strukturänderung, vermute ich, erhöht den Zusammenhalt und damit den In-formationsfluss im Schwarm. Die Ergebnisse von Folgeversuchen, nämlich der Erhalt der Paarungsanzahl und die effektivere Vermeidung einer Räuberattrappe bei Trübung er-fahrenen Fischen, unterstützen diese Vermutung. Die Arbeit zeigt, dass Guppys in der Lage sind, sich durch Änderung Ihrer sozialen Struktur an trübe Verhältnisse anzupas-sen. Dies könnte auch Einfluss auf ihre Populationsstruktur haben.Most species have been subjected to environmental changes during their evolutionary history. However, due to human activity, environmental changes are currently occurring at higher speeds and on a greater scale, presenting new challenges for many species. Pollution, as a major type of human-induced environmental change, may not only affect physiology but also behaviour, thereby affecting population dynamics and consequently biodiversity. The topic of my dissertation is the effect of turbidity from quarrying on the behaviour and social association pattern of the guppy (Poecilia reticulata). Turbidity impairs the fish’s ability to use visual cues during social interactions, which in turn helps increases efficiency of foraging and avoiding predators. I investigated the initial re-sponse of guppies to turbidity and subsequently tested whether turbidity-experienced vs turbidity-inexperienced populations differ in their social association patterns and how they cope with ecological challenges. Both lab-reared and wild-caught guppies that were inexperienced with turbidity reduced social associations in turbid water in con-trast to turbidity-experienced fish. A Markov chain analysis revealed that lab-reared guppies increased associations with particular neighbours. Similarly, wild-caught gup-pies maintained the number of initiated associations under turbid conditions. The in-crease in non-initiated associations suggests a stronger connectivity within the shoal, leading to higher information transmission in a poor visual environment. Additional results showed that this altered social structure enabled turbidity-experienced fish to maintain the frequency of mating attempts in turbidity and to avoid predation risk. This suggests that guppies have the ability to adjust to turbidity, but with major changes in their social structure, which might have an impact on population dynamics.
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Yuksel, Mete Avni. "Use Of Calcium-alginate As A Coagulant For Low Turbidity Waters." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12609204/index.pdf.
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This study aims to investigate the possibility of using calcium-alginate as a coagulant in low turbidity waters. Jar tests were initially performed with synthetically prepared turbid waters to investigate the effect of alginate and calcium concentrations, alginate&rsquos molecular weight, rapid mixing time and speed (schedule), initial pH and alkalinity of synthetic water on turbidity removal efficiency of calcium-alginate system step by step. Alum as a coagulant was then used in jar tests conducted with synthetic water to compare with calcium-alginate in terms of its turbidity removal efficiency and produced sludge properties. Finally, raw water acquired from water treatment plant was tested for treatability by using calcium-alginate based on previously determined optimum parameters via jar tests. Experiments of calcium-alginate system with synthetic water showed that calcium was a key parameter in coagulation and high molecular weight alginate performed better in turbidity removal. Significant improvements in turbidity removal were observed when mixing schedules were rearranged
especially in case of increasing rapid mixing time following calcium dosing. Calcium-alginate system neither was notably affected by pH or alkalinity nor did significantly change the pH or alkalinity of the medium. Alum worked well in turbidity removal with additional adjustments of pH and alkalinity, however
alum produced higher quantities of sludge than calcium-alginate system. &ldquo
Raw water&ldquo
experiments with calcium-alginate did not result in desired level of turbidity removals due to the excessively different characteristics of this water compared to the synthetically prepared turbid water.
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McMahon, Alexander D. "Influence of turbidity and aeration on the albedo of mountain streams." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58953.
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Stream surface albedo plays a key role in the energy balance of rivers and streams that are exposed to direct solar radiation. Most physically based models assume that stream albedo lies between 0.03 and 0.10, based primarily on measurements from low-gradient streams with low suspended sediment concentrations. Albedo should depend upon solar elevation angle, suspended sediment, aeration, and fraction of direct vs diffuse radiation. However, there is no model available for predicting the dependence of albedo on these factors. This study quantified the dependence of albedo of mountain streams on the controlling factors in order to improve the representation of albedo in energy balance studies. Proxy measures for albedo using digital camera imagery were also developed and assessed. Stream surface albedo was measured at nine sites with a variety of gradients and suspended sediment characteristics in the southern Coast Mountains of British Columbia, Canada. As expected, albedo of low-gradient, non-whitewater (flatwater) streams increased with solar zenith angle, suspended sediment concentration, and proportion of diff use to direct solar radiation, ranging between 0.025 during cloudy periods in clear water to 0.25 for turbid water at zenith angles of less than 20 degrees. Albedo varied with discharge in steep reaches or at channel steps and cascades where flow was visibly aerated, with a range of 0.09 to 0.33. In clear weather, albedo exhibited notable diurnal variability at flatwater sampling sites. For example, during late summer, surface albedo typically fluctuated between 0.08 and 0.15 on a diurnal basis at a flatwater site on the highly turbid, glacier-fed Lillooet River. Physically based representations of albedo should be incorporated into energy balance models in order to improve predictions of stream temperature, especially for future scenarios.Arts, Faculty of
Geography, Department of
Graduate
27
McCullough, Greg. "Determining precision of aquatic turbidity measurement by NOAA-N series AVHRR." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ35075.pdf.
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Amos, Kathryn Jane. "Sustained turbidity cuurents : a study of experimental flow and river effluent." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399807.
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Herrmann, Lukas Karl. "Effects of must turbidity on fermentative aroma development in Sauvignon blanc." Master's thesis, ISA-UL, 2016. http://hdl.handle.net/10400.5/13010.
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Mestrado Vinifera Euromaster - Viticulture and Enology - Instituto Superior de Agronomia - UL / Institut National d'Etudes Superieures Agronomiques de MontpellierIn many ways New Zealand has become an ideal for a New World wine country. With the first commercial Sauvignon blanc only released in 1974, Sauvignon blanc fought its way to become not only the flagship of New Zealand`s wine industry, holding around 66 % of the country’s total grape production at the 2015 harvest, but also made its way to be recognized for its outstanding quality all over the world. For some critics, New Zealand Sauvignon blanc is arguably the best in the world and others called the Marlborough wine region the best place to grow Sauvignon blanc in New Zealand. Even though testimonies like that may be subjective as taste lies on the tongue of the beholder, New Zealand Sauvignon blanc clearly came a way plastered with success leading to an export value of $1.424 billion NZD in 2015. Key to this success is that the industry found a way to distance itself from its French archetype, world famous Sauvignon blanc originated from the Loire valley, and reinvented itself, introducing a unique winestyle that does not need to shy any comparison. In the heart of this winestyle aroma compounds of the thiol group play an important role. Derived during yeast activity during fermentation from non-odorous precursors found in grapejuice, the two most important thiols that have been related with Marlborough Sauvignon blanc are 3MH and 3MHA. These deliver exotic nuances reminiscent of grapefruit, passionfruit, gooseberry, guava and boxtree. Due to the high oxidability of thiols, several strategies have been adapted by the industry to preserve these key compounds and their non-odorous precursors during the processing of grapes, which includes harvesting, transportation, processing and storage. Although a lot of research has been carried out to further understand the relations between precursors, thiols and their preserving, and to be able to continuously contrast New Zealand Sauvignon blanc from competitors, many questions still remain unclear at the present day. One of them is the effect of juice turbidity on aroma development during fermentation. Research has revealed a broad idea on the positive and negative effects, caused by micronutrients and physical parameters of grape solids derived during process steps leading to juice extraction from the berries on fermentation kinetics and general aroma development. To my best knowledge no research has been published to the present day that focuses on the effect of juice turbidity on the thiol development and expression in Sauvignon blanc ferments. This masterthesis in hand, with the title “Effects of must turbidity on fermentative aroma development in Sauvignon blanc” is supposed to give an overview over the state of research on Sauvignon blanc with a further focus on the question about possible effects and practical applications of juice turbidity. Finally, this work tries to improve the small scale winemaking protocol of Plant and Food Research, Blenheim, where this research has been conducted.
N/A
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Miner, Jeffrey G. "Turbidity-mediated predator-prey interactions among piscivores, prey fishes, and zooplankton /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487685204970099.
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Ekanayake, Sarath. "Characteristics of particles contributing to turbidity in potable water distribution networks." Swinburne Research Bank, 2009. http://hdl.handle.net/1959.3/61048.
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Thesis (PhD) - Faculty of Life and Social Sciences, Swinburne University of Technology, 2009.Submitted in full requirement for the degree of Doctor of Philosophy, Faculty of Life and Social Sciences, Swinburne University of Technology - 2009. Typescript. Includes bibliographical references (p. 137-160)
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Krishna, Gowtham. "A numerical model based examination of conditions for ignitive turbidity currents." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025158.
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Verhagen, Iris Thérèse Elise. "Flow-sediment interactions in turbidity currents moving over soft, muddy beds." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/flowsediment-interactions-in-turbidity-currents-moving-over-soft-muddy-beds(2f075e91-414e-4950-81c1-4f8de5ff326e).html.
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Many aquatic environments have soft, muddy substrates, but this important property has largely been ignored in process-based models of turbidity currents. Previous turbidity current studies have focussed on flows over hard or non-cohesive, movable substrates. However, the flume experiments conducted in this study show that soft mud beds interact differently with a passing flow. Flow-bed interaction caused deformation and erosion of the beds and changed the flow structure of the turbidity currents. Subsequently, these changes might impact the geometry of the resulting turbidite deposits. Five different interaction types bet: ween turbidity currents and soft substrates were defined: 1) no interaction, 2) interfacial waves, 3) mixing and erosion, 4) severe mixing and erosion, and 5) leading wave formation. The now geometry and velocity, turbulence and concentration profiles of flows with no flow-bed interaction resembled those of flows over a hard substrate. But with increasing intensity of the flow-bed interaction, the friction at the flow-bed interface and erosion depth increased, tl1e geometry of tl1e front of the flow changed from blunt to pointed, and leading waves increased in size. This resulted in a decrease in the flow velocity, an increase in the height of the maximum velocity, an increase in near-bed turbulence, and an increase in flow concentration. These changes were strongest in the head of the flows, where the highest intensity of flow-bed interaction occurred. To study spatio-temporal changes in the now structure of turbidity currents, a turbidity current model was created using image analysis on videos taken during the experiments. Results of the model indicated a trend in the head velocity of turbidity currents overriding a soft bed, with an initial decrease in flow velocity followed by an increase until a constant flow velocity was reached. The experimental results were summarised in flow-bed interaction phase diagrams which showed a decrease in flow-bed interaction with increasing yield strength of the bed and an increase in flow-bed interaction with an increase in bed shear stress. For the flow-bed concentration ratios used in this study, the bed shear stress had the largest influence on the flow-bed interaction. Fieldwork was conducted in the Gres de PeYra-Cava (France) which focussed on the lower bed boundary characteristics of turbidite deposits with an underlying mud bed. Flat, non-eroded bed boundaries were inferred to result from flows with no interaction with the bed, while wavy, non-eroded boundaries were believed to be an indication for interfacial wave interaction. Flame and loading structures were interpreted as products of mixing and erosion and sediment injections were related to leading waves, although no direct evidence for this was found in the field. Predictions of turbidite deposit geometry and composition based on the results of this study show a large variation in deposit thickness, run-out length and composition which is of great importance to the hydrocarbon industry.
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Tilston, Michael Christopher. "The Role of Particle Size and Concentration in Defining the Flow Structure of Turbidity Currents and the Morphology of their Deposits: Insights from Computed Tomography." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35828.
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Turbidity currents are turbulent particle suspensions that are the primary mechanism for transporting terrestrial sediments to the deep marine, and generate some of the largest depositional features on Earth. However the fluid-particle interactions that sustain these currents are poorly understood, principally due to the technical challenges posed by obtaining accurate velocity and density measurements, which are critical for describing flow behavior and depositional characteristics. Numerous studies have bypassed these issues by using saline density currents, but this negates the ability to link flow processes with depositional features, and it is unclear whether their density structures are representative of particle gravity flows. Consequently, numerous questions remain over the flow conditions that build up a significant part of the deep-marine geologic record.
In this thesis I reports on the flow processes and depositional features of sediment-gravity currents across a broad range of particle sizes and concentrations. The technical challenges of obtaining reliable density data are overcome by running the experimental flows through a medical grade computed tomography (CT) scanner, and pair this data with three-dimensional velocity measurements using an ultrasonic Doppler velocity profiler (UDVP-3D) to get one of the first glimpses of the internal structure of turbidity currents. Unlike previous studies where flow processes are described in terms of the velocity field, this thesis demonstrates that fluid-particle interactions are controlled by momentum characteristics, and that the velocity field is determined largely by the current’s density structure. Moreover, the density structure also exerts a first order control on the morphology of their deposits.
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Sharp, William Frank. "Changes to in-stream turbidity following construction of a forest road in a forested watershed in West Virginia." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5139.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains ix, 79 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 41-46).
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Crookshanks, Sarah. "High-energy sedimentary processes in Kluane Lake, Yukon Territory." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1219.
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Janča, Štěpán. "Zákal vody ve vodovodních sítích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226159.
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The aim of this thesis is to summarize the available knowledge on the occurrence and formation of turbidity in the water supply system and the design and application of methodology for measuring the potential occurrence of turbidity in the water supply. Problems of the current state of the quality of drinking water in public water supply systems, with a focus on the occurrence of cataract formation turbidity legislative change indicators of drinking water in the Czech Republic and abroad, and potential methods of measuring turbidity is discribed in the first part of the thesis. In the second part of the paper is a methodology for measuring the potential of turbidity in the water supply network. The methodology is applied in the case study Hrbová pressure zone, which is part of the distribution network of city Vsetin. The case study of the thesis is a statistical analysis and mathematical model of consumption of pressure zone Hrbová.
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FIGUEIREDO, FABIO PEREIRA. "NUMERICAL AND COMPUTATIONAL SIMULATION OF LOW DENSITY TURBIDITY CURRENTS FOR BASIN SEDIMENTATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15933@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
UNIVERSITY OF LONDON
Correntes de turbidez ocorrem tanto na natureza como em situações criadas pelo homem. Segundo alguns pesquisadores, grande parte das reservas de petróleo conhecidas no mundo estão armazenadas nos reservatórios de hidrocarbonetos formados a partir dos sistemas turbidíticos. Tendo em vista a importância dessas correntes, este trabalho pretende propor um modelo numérico consistente e com baixo custo computacional, capaz de auxiliar na previsão de sedimentação de bacias nos processos de modelagem estratigráfica no contexto do simulador numérico de sedimentação tridimensional com ênfase nos processos deposicionais em ambientes de talude plataforma e bacia, chamado Steno, e validar o modelo numérico proposto através de simulações físicas conduzidas no Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul. O modelo numérico proposto é baseado nas equações de Navier-Stokes, que são resolvidas tirando-se a média na profundidade do perfil de velocidades característico. Além disso, uma aplicação gráfica tridimensional para simulação numérica de correntes de turbidez, chamada Turb3D, foi desenvolvida com base nas equações propostas. O programa possui uma interface gráfica amigável para o usuário no que diz respeito à entrada de dados, solução e visualização dos resultados. Os resultados obtidos mostraram que apesar do modelo numérico possuir um bom desempenho computacional, se comparado com os complexos modelos numéricos existentes, não foi possível reproduzir com precisão a evolução das correntes de turbidez e seus depósitos. Contudo, acredita-se que a abordagem dada ao problema de simulação numérica de correntes de turbidez apresentada neste trabalho pode fornecer bons resultados. Entretanto, é fundamental que seja dada continuidade a pesquisa, de modo que ajustes e melhorias ao modelo proposto possam ser realizadas.
Turbidity currents occur in both natural and man-made situations. In agreement with some researchers, most of the world’s oil reserves are stored in hydrocarbon reservoir built by turbidity systems. Because of the importance of these currents, this work proposes a consistent and efficient numerical method for simulations of turbidity currents for basin sedimentations predictions in the stratigraphic modelling process, which will be incorporated to the numerical simulator of sedimentation 3D called Steno. In order to validate the proposed numerical model experiments were conducted at the Hydraulics Research Institute of Federal University of Rio Grande do Sul. The proposed numerical model is based on Navier-Stokes equations that are solved in the depth-average. Moreover, a three-dimensional graphic application for numerical simulations of turbidity currents called Turb3D was developed. The application user interface provides a common, user-friendly, graphical environment for pre-processing, solution and post-processing. Despite the good computational performance achieved by using this approach, the method presented did not reproduce accurately the evolution of turbidity current and their deposits. However, it is believed that the approach to the numeric simulation of the turbidity current problem given in this work can provide better results, although this research should continue and improvements should be made.
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Parkinson, Samuel. "Advances in computational modelling of turbidity currents using the finite-element method." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30770.
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Turbidity currents are one of the main processes by which sediment is moved from the continental shelf to the deep ocean. They are a potential environmental hazard and they form a significant component of the stratigraphic record. Computational modelling is an important tool for understanding turbidity current dynamics, for augmenting experimental analyses, and for interpreting data that is collected in the field. This work begins by presenting a depth-averaged turbidity current model that is differentiated to facilitate the use of gradient-based optimisation algorithms. These optimisation algorithms are applied in selecting model parameters to best fit model output with data obtained in the field. To the best of the author's knowledge this is the first published work where optimisation of input parameters is applied to turbidity current modelling. The work also presents the first high resolution three-dimensional simulation of a turbidity current using the finite element method. One of the key benefits of the finite element method is the ability to easily accommodate complex domain geometries. As such this model is uniquely capable of producing high resolution simulations of turbidity currents in unconstrained complex domains. Methods of reducing the computational cost of these very expensive simulations are explored. The use of Large Eddy Simulation is shown to provide some improvements at moderate simulation resolutions. Unstructured mesh optimisation is shown to reduce the cost of these simulations by approximately two orders of magnitude when compared to a fixed mesh simulation. The savings afforded by the use of these techniques make the problem tractable using finite elements and will enable simulation of turbidity currents in complex and expansive domains where DNS modelling was previously unachievable.
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Prince, Rachael Anne. "Formation of discoloured water and turbidity in an unfiltered water distribution system." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/36071.
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Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, 2008.A thesis submitted for the degree of Doctor of Philosophy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2008. Typescript. Includes bibliographical references: p. 263-278.
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Crump, Byron C. "Bacterial activity and community structure in the Columbia River estuarine turbidity maxima /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10989.
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Ashraf, Syeda Nishat. "Applicability of coagulation technologies for high-turbidity coal seam gas water treatment." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127500/1/Syeda_Ashraf_Thesis.pdf.
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This project developed new strategies to facilitate reuse of water from the coal seam gas (CSG) industry. Both chemical coagulation and electrocoagulation were examined for their ability to protect downstream reverse osmosis (RO) desalination systems from detrimental fouling and scaling. Electrocoagulation in particular was highly effective at removing dissolved silicates, alkaline earth ions and suspended solids; thus RO operation was expected to be improved. In addition the purification of resultant brine was demonstrated, thus potentially enabling the recovery of salt as a product. It was recommended to scale-up electrocoagulation testing to pilot plant.
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Ortmanis, Andris. "The development of a microcomputer controlled variable pathlength turbidimeter /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65460.
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Eissa, Yehia Abdelmaksoud Abdalla. "Modélisation des rayonnements direct et circumsolaire par ciel clair en environnement désertique." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0009/document.
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Les mesures de l'éclairement solaire direct reçu au sol en incidence normale (DNI) par des pyrhéliomètres ou instruments équivalents incluent l'éclairement provenant de l'angle solide du disque solaire (DNIS) et celui provenant d'une région angulaire circumsolaire plus large, appelé éclairement circumsolaire (CSNI). Les instruments ont des demi-angles d'ouverture équivalents variant entre 2,5° et 5°, soit un ordre de grandeur plus grand que le demi-angle du disque solaire. Quant aux demi-angles des systèmes de production d'énergie concentrant les rayons solaires, ils sont plus grands que le demi-angle du disque solaire, et plus petits que ceux des instruments. Par consequent, le CSNI doit être connu pour une estimation précise du DNI. Cette thèse contribue à la connaissance et à la modélisation des éclairements direct et circumsolaire en milieu désertique par conditions de ciel clair. Après avoir déterminé les propiétés optiques des aérosols les plus influentes, le modèle numérique de transfert radiatif libRadtran a été utilisé pour modéliser le CSNI et le DNIS. Un modèle paramétrique simplifié et très rapide a été développé qui reproduit les résultats de libRadtran. Il estime le ratio circumsolaire (CSR), soit le rapport entre le CSNI et la somme du CSNI et du DNIS, à partir de mesures standards du DNI et de l'éclairement diffus. A partir du DNI mesuré et de CSR modélisé, le CSNI et le DNIS peuvent être estimés pour tout demi-angle entre 0,4° et 5°. Le modèle a été validé pour deux stations de mesure, dans les Emirats Arabes Unis et en AlgérieRoutine measurements of the broadband direct normal irradiance (DNI), i.e. beam irradiance at normal incidence, by means of pyrheliometers or equivalent pyranometric systems include the irradiance originating from within the extent of the solar disc (DNIS) and that from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). Such instruments have equivalent aperture half-angles between 2.5° and 5° which are one order of magnitude greater than the angular radius of the solar disc. The equivalent aperture half-angles of the concentrated solar powered systems are greater than the angular radius of the solar disc, but smaller than that of the measuring systems. Therefore, information on the CSNI should be provided for an improved assessment of the DNI. The objective of this PhD thesis is to contribute to an improved assessment of the beam and circumsolar radiation under cloud-free conditions in a desert environment. After selecting the aerosol optical properties of significance, the radiative transfer model libRadtran was used to model the CSNI and DNIS. A fast and simple parametric model which mimics the libRadtran values is proposed. This model uses standard measurements of the DNI and the diffuse horizontal irradiance as inputs to estimate the circumsolar ratio (CSR) for any aperture half-angle between 0.4° and 5°. The CSR is the ratio of the CSNI to the sum of the CSNI and the DNIS. Knowing the CSR and having the measured DNI, the CSNI and the DNIS can be computed
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Pratt, Elizabeth Anne. "Evaluating Watershed and Stream-Channel Drivers of In-Stream Turbidity in Virginia and North Carolina." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99990.
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Accurately predicting sediment delivery has been a long-standing problem in the field of water resource management. Many different watershed equations and models have been developed such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more, however, these models have not always been able to reliably predict in-stream sediment loads. In this study, two scales, watershed and site level, are used to understand where sediment transported in-stream is being produced. At the watershed scale, USLE was used to estimate sediment yield and then different factors such as connectivity topographic indices were applied as discount factors in an attempt to improve these estimates. The different parameters were then compared to turbidity to determine the level of accuracy of each method. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An implicit assumption of USLE is that runoff is produced on steeper slopes and that sediment production occurs on these hillslopes. However, it was found that flatter-sloped areas were highly correlated with in-stream turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and level of confinement at higher flows were more accurate predictors of in-stream sediment levels. Overall, turbidity and in-stream sediment levels are not well predicted by models that employ USLE. The distribution of runoff source areas, and channel/bank properties appear to be good predictors of sediment production at the watershed scale. These results indicate that sediment production and transport, as conceptualized by common models and equations, often associate sediment source areas with geomorphic and hydrologic processes in ways that are not consistent with the results of this study. Our results show that sediment is most likely being sourced from the channels and in stream areas.Master of Science
Predicting how sediment moves through a watershed has been a long-standing problem in the field of water resource management. There are many equations and models that have been developed to calculated the amount of sediment that exits a watershed; such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more. However, these models have not always been reliable or accurate in their predictions. In this study, two scales, watershed and site level, are used to understand where sediment transported within streams is being produced. At the watershed scale, USLE was used to estimate sediment leaving a system and then different factors, with different approaches to the understanding of sediment movement, were applied as discount factors in an attempt to improve these estimates. The different values that were calculated were then compared to turbidity to determine the level of accuracy of each parameter. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An assumption of USLE is that runoff is produced on steeper slopes and that sediment erosion occurs on these steeper sloped areas. However, it was found that flatter-sloped areas were highly correlated with turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and the level of confinement at higher flows were more accurate predictors of turbidity. Overall, USLE and models that used USLE were not able to predict turbidity. The distribution of runoff source areas and channel/bank properties appear to be good predictors of turbidity at the watershed scale. These results indicate that sediment movement, as conceptualized by common models and equations, often associate sediment source areas with watershed level morphology and hydrology in ways that are not consistent with the results of this study. Our results show that sediment is most likely being produced from the channels and in stream areas.
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Huenemann, Thad William. "INFLUENCE OF TURBIDITY ON FISH DISTRIBUTION, DIET AND FORAGING SUCCESS OF LARGEMOUTH BASS." MSSTATE, 2010. http://sun.library.msstate.edu/ETD-db/theses/available/etd-03142010-211016/.
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Turbidity is an important measurement of water quality, considering it describes water clarity and is an indirect indicator of light transmittance in the water column. Turbidity may impact fish that rely on vision to forage by affecting ability to search for prey. Largemouth bass (LMB; Micropterus salmoides) is a visual predator that may have lower foraging success resulting in reduced growth, reproduction, or survival under conditions of high turbidity. I conducted a field experiment in Wolf Lake, Mississippi to assess impacts of turbidity on diet and distribution and a laboratory experiment with manipulated turbidity levels (0 250 NTU) to assess foraging efficiency of LMB. There were no significant relationships between turbidity and diet or distribution in the field study. However, there were significant effects of turbidity on foraging efficiency in laboratory trials. These results indicate that assessing turbidity is important to manage LMB in systems susceptible to high turbidity levels.
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Brown, Andrew David. "A physical model of the atmospheric aerosol turbidity for daylight modelling in cities." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440904.
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Moran, Paul Aaron. "Modification of a Biosand Water Filter for Household Treatment of High Turbidity Water." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/752.
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One billion of the poorest people in the world today do not have access to improved drinking water. Without treatment, fecal contamination results in an overwhelming disease burden. A long term best practice solution will take decades to implement. In the meantime, approximately 5 million children under five die each year from gastrointestinal diseases. This tragedy can be alleviated by household water treatment. Household Water Treatment and safe Storage systems (HWTS) provide an interim solution. While many low cost and simple technologies exist, none of them are effective against high suspended solids concentrations (>50 NTU). Previous short-term field research by others has considered modifying a BioSand water Filter (BSF), to include pretreatment through an upper sand layer in order to extend the run cycle of the primary filter, enabling complete ripening to occur. In this research program, one control and twelve configurations of modified filters were setup in the laboratory. Water was chemically conditioned to provide worst case scenario treatment by adjusting pH, TDS, and particle dispersion. Sample water was passed through each filter daily, and monitored for DO, turbidity, flow rate, and E. coli concentrations. The results indicate that pretreatment is not necessarily beneficial under all water quality conditions. Recommendations include a description of conditions under which the modification may be beneficial, and optimized pretreatment design criteria. Regardless of water quality conditions, it was found that changing the operational guidelines for filter use can significantly improve treatment efficiency, without complicating the filter design. Design guidelines for an unmodified filter coupled with operational guidelines are provided, in order to obtain sufficient quantities of the best possible water quality under high turbidity conditions. This will enable the BSF to be used in high turbidity conditions and still significantly improve the drinking water quality. It is hoped that this will decrease the disease burden and loss of life in many of the world's poorest communities.
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Collin, Clair. "Biosand filtration of high turbidity water : modified filter design and safe filtrate storage." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50623.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 126-131).
Unsafe drinking water is a major cause of water-related diseases that predominantly affect people living in developing countries. The most prevalent water-related disease is diarrhea, estimated to kill 1.8 million children every year and the second largest cause of childhood death. Today there are many technologies available to treat unsafe water; however, most of these are suited for use with low turbidity source water. The treatment of high turbidity water (>50 NTU) is a challenge that was investigated in this research. Biosand filters, based on an intermittent slow sand filtration process, are an established household scale water treatment technology widely used in developing countries to treat low turbidity drinking water. This research investigates modifications to the biosand filter design to promote effective pathogen and turbidity reduction in high turbidity water. During field tests conducted in Ghana, a modified biosand filter with dual sand layers for added filtration achieved the greatest pathogen and turbidity removals. This design was then optimised through laboratory studies at MIT. The dual sand layer biosand filter supports straining and sedimentation of particulate matter from the feed water in a 3-7 cm deep raised upper sand layer prior to biological treatment and further filtration of the water in a 15-16 cm deep lower sand layer. Field testing of the dual sand layer biosand filter showed this filter achieved 59% turbidity reduction, 38% higher than an unmodified control filter; and at least 85% E. coli and 95% total coliform reductions, comparable in performance to unmodified control filters.
(cont.) Laboratory testing demonstrated minimum average reductions of 93% turbidity, 97% E. coli and 71% total coliform after filter maturation, comparable to unmodified control filter results. Dissolved oxygen concentration profiling in the laboratory indicated sufficient oxygen diffused through the upper sand layer to the lower sand layer to support biological activity in the lower sand layer. Recommendations for future studies and design optimisation have been made. Recontamination of treated water is also a major concern and it is recommended that the biosand filter be used only as required and filtrate collected in a dedicated container with tight fitting lid and tap dispenser.
by Clair Collin.
M.Eng.
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San-YiHuang and 黃三益. "Turbidity Reduction Using Bio-based Polymer." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/53475674086839241808.
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碩士國立成功大學
水利及海洋工程學系碩博士班
101
Due to fragile geology and steep topography, extremely high turbidity, 10,000NTU or higher, water is frequently observed during a storm event. This extremely high turbidity water could lower the efficiency of water treating process in a water treatment plant or even shut down the water supply. To reduce the turbidity, two types of coagulants can be legally used in a water treating process: (1) inorganic coagulants, and (2) polymer coagulants. The former shows lower efficiency for treating high turbidity water. The latter may introduce healthy risk. Therefore, this study focuses on a bio-based polymer, or called chitosan, which is well known as non-toxic material to human beings. Three kinds of samples are used for jar tests: (1) Ottawa standard sand, (2) Kaolin soil (or Kaolinite clay), and (3) the sediment of Chengcing Lake Reservoir. The result shows that the dosage of 0.2mg/L of the bio-based polymer can reduce the turbidity from 52,000NTU to 25NTU, which meets the drinking water standard of 30NTU during high turbidity periods. This result indicates the capability of bio-based polymer to increase the water treating efficiency for extremely high turbidity water.