Dissertations / Theses on the topic 'Settling velocity'

Studies on sediment transport rates are of great importance in fields such as offshore engineering and basic sedimentology. Within this context, this investigation is concerned with the initial motion of non-cohesive biogenic sediments under unidirectional flow conditions. Relevant publications on boundary layer flows and sediment transport are reviewed. The experiments were conducted in a recirculating laboratory flume fitted with a trolley onto which loose sediment grains were placed. Experiments were conducted using this and a laser-doppler anemometer (LDA), Streamflo current meter and a video camera. A semi-quantitative motion criterion was applied to the experiments in order to investigate the motion of two well-sorted biogenic sediments (<i>Mytilus edulis</i> and <i>Cardium edule</i>). The data were processed and analysed using digital and analogue techniques. The sediment samples were also examined in terms of grain size and settling characteristics. Detailed flow experiments were made of four unidirectional flows. Gaussian statistics were derived from these velocity-time series data sets which provided a comparison for the threshold data. Data were compared with theoretical and empirical relationships proposed by other investigators. A number of recommendations for future research have been put forward.

A methodology has been developed to measure the chemical constituents associated with the settling velocity fractions that comprise a wastewater settling velocity profile (SVP). 31 wastewater samples were collected from fifteen different catchments in England and Wales. For each catchment, settling velocity and associated chemical constituent profiles were determined. The results are mainly for Suspended Solids (SS), Chemical Oxygen Demand (COD), Phosphorus (P) and Total Kjeadahl Nitrogen (TKN), however these are supplemented by the results from 5 events for a suite of heavy metals. COD, P, Hg, Mn and Pb were found to be predominantly associated with the solid phase and TKN, Al, Cu and Fe with the liquor phase of the wastewater samples. The results in the thesis are expressed as mass of pollutant (g) per mass total SS (kg). COD and P were found to be mainly associated with the sinkers and had a particular affinity for solids with settling velocities in the range 0.9-9.03mm/sec. TKN was mainly associated with the soluble phase, however of the solids that did settle, a peak was found to be associated within the settling velocity range 0.9-9.03mm/sec. The relationships identified for COD and P were generally found to be unaffected by flow conditions and catchment characteristics. However, TKN was found to be affected by catchment type. Data on the distribution of heavy metals was limited, and no specific relationships with solids were identified. 16 mean pollutant profiles are presented in the thesis. Presentation of the data in this form will enable the results to be of use in the design of sedimentation devices to predict removal efficiencies for solids and associated pollutants. The findings of the research may also be applied to modelling tools to provide further characteristics on the solids that are modelled than is currently used. This would enhance the overall performance of tools used in integrated catchment modelling.

Primary sedimentation involves the separation of solids and liquid in primary settling tanks (PSTs) of wastewater treatment systems. These physical processes are described by various settling conditions such as discrete and flocculent settling, along with other phenomena such as flocculation, coagulation, ammonification or hydrolysis. The modelling of primary sedimentation has often been overlooked because (i) it involves various intricacies that are difficult to replicate and (ii) primary sedimentation has been assumed to be an input to most of the main unit process models, including the activated sludge (AS) system and the anaerobic digestion (AD) models. Though there has been a wide range of proposed mathematical models to describe how PSTs function, the need to correctly disaggregate the total suspended solids (TSS) into realistic fractions of unbiodegradable particulate organics (UPO), biodegradable particulate organics (BPO) and inorganic settleable solids (ISS), remains. This is because PST models that are unable to correctly split the TSS into its characteristic components make incorrect assumptions. These assumptions lead to inconsistencies in predicting the compositions of the primary sludge (PS) that is fed to the AD unit and the settled wastewater (settled WW) that is treated in the AS system. Hence, it becomes difficult to correctly simulate the entire system (plant-wide) towards a holistic evaluation of system strategies. In this study, a realistic PST model was developed, with characterized settling velocity groups, within a plant-wide setting, for municipal wastewater. This involved the improvement of a current TSS-based model into a more accurate and realistic model that could account for the settling of raw wastewater particles. The model was therefore expected to predict the composition of the PS that is treated in the AD system and the composition of the settled WW that is going to the AS unit processes. This could be achieved by splitting the TSS into UPO, BPO and ISS fractions. In developing preparation of such a realistic PST model, the following objectives were established: 1. Disaggregate the TSS into realistic UPO, BPO and ISS fractions, by means of discrete particle settling modelling (Kowlesser, 2014) and the particle settling velocity distribution (PSVD) approach of Bachis et al. (2015). 2. Verify that the model is internally consistent with wastewater treatment plant (WWTP) data, by means of mathematical material mass balances and other specific scenarios. 3. Demonstrate the application and impact of such a model by performing steady state plant-wide simulations. Using the discrete particle settling approach of Kowlesser (2014), a discrete particle settling model was developed in Microsoft Excel and implemented into a dynamic PST framework in WEST® (Vanhooren et al., 2003). The discrete particle settling model was described using steady state and dynamic calculations and the insights obtained from these calculations were implemented in the current TSS-based PST model of Bachis et al. (2015). This was performed towards developing the University of Cape Town Primary Sedimentation Unit (UCTPSU). The influent raw wastewater TSS was fractionated into UPO, BPO and ISS fractions and settling proportions of these fractions were assigned to five settling velocity groups. In addition, a distinct settling velocity was assigned to each settling velocity group. Previous studies data from WRC (1984) and Ekama (2017), were used in the discrete particle settling model, which was able to reproduce PS and settled WW outputs, through steady state and dynamic calculations and under strict material mass balances. As a result, UPO, BPO and ISS settling proportions as well as settling velocities, were extracted from these calculations and used as input parameters into the UCTPSU model. This dynamic model was rigorously verified to be internally consistent with regards to strict material mass balances. The verification scenarios also included variations of high and low settling velocities as well as a combination of both high and low velocities and checking that the model was behaving as expected. The application and impact of the UCTPSU model were demonstrated using plant-wide scenarios in proposing a preliminary integration, under steady state conditions. It showed how incorrect disaggregation of the TSS into UPO, BPO and ISS fractions can lead to incorrect predictions in terms of the settled WW composition, the AS system capacity, the effluent quality, as well as the energy consumption and generation in the AS system and AD unit respectively. The investigation also revealed the need to measure key wastewater parameters such as particle settling velocities and the unbiodegradable particulate COD fraction, when it comes to realistically modelling of primary sedimentation of municipal wastewater, with the view of optimizing plant operations and tactical decision making. The study thereafter recommended the need to conduct an extensive experimental campaign to measure in-situ diurnal data, mainly in terms of settling velocities and settling proportions of UPO, BPO and ISS. It was also suggested to use the settleometer as a tool to extract these settling velocities and settling proportions, after performing biodegradability tests. As such, the data collected from the experimental campaign and the biodegradability tests could be used in calibrating the UCTPSU model and validation could be undertaken by means of full plant scale data.

A procedure has been developed which measures the settling velocity distribution of particles within a complete sewage sample. The development of the test method included observations of particle and liquid interaction using both synthetic media and sewage. Comparison studies with two other currently used settling velocity test procedures was undertaken. The method is suitable for use with either DWF or storm sewage. Information relating to the catchment characteristics of 35 No. wastewater treatment works was collected from the privatised water companies in England and Wales. 29 No. of these sites were used in an experimental programme to determine the settling velocity grading of 33 No. sewage samples. The collected data were analysed in an attempt to relate the settling velocity distribution to the characteristics of the contributing catchment. Statistical analysis of the catchment data and the measured settling velocity distributions was undertaken. A curve fitting exercise using an S-shaped curve which had the same physical characteristics as the settling velocity distributions was performed. None of these analyses found evidence that the settling velocity distribution of sewage had a significant relationship with the chosen catchment characteristics. The regression equations produced from the statistical analysis cannot be used to assist in the design of separation devices. However, a grading curve envelope was produced, the limits of which were clearly defined for the measured data set. There was no evidence of a relationship between settling velocity grading and the characteristics of the contributing catchment, particularly the catchment area. The present empirical approach to settling tank design cannot be improved upon at present by considering the variation in catchment parameters. This study has provided a basis for future research into the settling velocity measurement and should be of benefit to future workers within this field.

Stokes’ law that is traditionally used for modeling the sedimentation of flocs, incorrectly assumes that the floc is solid and spherical. Consequently the settling rates of flocs cannot be estimated using the Stokes law. The application of fractal dimensions to study the internal structure and settling of flocs formed in lime softening process was investigated. An optical microscope with motorized stage was used to measure the fractal dimensions of lime softening flocs directly on their images in 2 and 3D space. The fractal dimensions of the lime softening flocs were 1.15-1.27 for floc boundary, 1.49-1.90 for cross-sectional area and 2.55-2.99 for floc volume. Free settling tests were used for indirect determination of 3D fractal dimension. The measured settling velocity of flocs ranged from 0.1 to 7.1 mm/s (average: 2.37 mm/s) for the flocs with equivalent diameters from 10µm to 260µm (average: 124 µm). Floc settling model incorporating variable floc fractal dimensions as well as variable primary particle size was found to describe the settling velocity of large (>60 µm) lime softening flocs better than Stokes’ law. Settling velocities of smaller flocs (<60 µm) could still be quite well predicted by the Stokes’ law. The variation of fractal dimensions with lime floc size in this study indicated that two mechanisms are involved in the formation of these flocs: cluster-cluster aggregation for small flocs (>60 µm) and diffusion-limited aggregation for large flocs (<60 µm). Therefore, the relationship between the floc fractal dimension and floc size appears to be determined by floc aggregation mechanisms. The settling velocity of lime softening flocs was also modeled by a general model that assumes multiple normally distributed fractal dimensions for each floc size. The settling velocities were in the range of 0-10mm/s and in good agreement with measured settling velocities (0.1-7.1mm/s). The Stokes’ law overestimates the settling velocity of lime flocs. It seems that the settling velocity of flocs is mainly controlled by aggregation mechanisms and forming large floc does not guarantee improved sedimentation. The multifractal analysis of lime softening flocs showed that these aggregates are multifractal and a spectrum of fractal dimensions is required to describe the structure of an individual floc.

Les dessableurs font partie du prétraitement de la plupart des stations de récupération des ressources de l'eau (StaRRE). Ces unités de dessablage servent à protéger les équipements et les procédés aval ainsi qu'à maintenir la performance des traitements primaire et secondaire. Même si ces unités jouent un rôle crucial, un manque criant au niveau des connaissances sur les caractéristiques des particules de grit sur leur comportement et sur la modélisation des dessableurs est observé. Ce manque implique une définition incorrecte des particules de grit, l'inexistence d'un protocole standard d'échantillonnage et de caractérisation des particules autour d'un dessableur, et l'utilisation de modèles simples basés sur un % d'enlèvement constant. Le premier objectif de la thèse est de développer une méthode de caractérisation de la vitesse de chute des particules, variable clé du processus de sédimentation. Cet objectif peut être divisé en plusieurs sous-objectifs. Un premier sous objectif est de concevoir un protocole d'échantillonnage spécifique pour les sites expérimentaux échantillonnés. Un deuxième sous objectif est de comparer les méthodes actuellement utilisées pour caractériser les particules de grit de proposer une méthode de caractérisation pour les particules mentionnées autour des unités de dessablage. Le deuxième objectif de la thèse est de développer un modèle dynamique basé sur la distribution de vitesse de chute des particules (DVCP). Le modèle est appliqué à deux différents cas d'études avec différentes conceptions de dessableur (vortex et aéré) et de capacités de traitement. Dans les deux cas, le modèle est calibré et validé avec succès. Il s'agit d'un modèle puissant permettant de prédire la concentration des solides à la sortie des dessableurs et la quantité de solides enlevés (particules de grit ) en fonction de la dynamique des solides et du débit à l'entrée du dessableur. Les résultats obtenus dans le cadre de ce doctorat ont permis de présenter une nouvelle approche expérimentale pour la caractérisation des particules de grit ainsi que, pour la première fois, un modèle dynamique des unités de dessablage basé sur la DVCP. Les deux nouveaux outils ont été testés avec succès.<br>Grit chambers can be found at the headworks of most water resource recovery facilities (WRRFs) to protect equipment and the processes downstream and maintain the performance of primary and secondary treatments. Even though they play a crucial role, there is a lack of knowledge on grit characteristics and grit chamber behaviour and modelling. This leads to an improper grit de nition, a non-existing standard protocol of sampling and characterization, a non-existing standard protocol to evaluate the performance of the system and only simple models based on a static %-removal. Given the fact that particle settling is the governing process of grit particle removal, that a vast diversity of sampling and characterization methods is existing, and modelling has been limited to very simple static %-removal based equations, two main objectives in the context of this study are pursued. The rst objective aims for a characterization method taking into account the key parameter of the settling process, i.e. particle settling velocity. It is divided in multiple subobjectives. First, the establishment of a site-speci c sampling protocol to obtain representative samples from the water around the studied grit chambers. Then, the currently used methods to characterize grit particles and wastewater are compared and adapted prior to the proposal of a characterization method. The second objective of this study is to present a new dynamic model based on particle settling velocity distributions (PSVD). The model is tested on two di erent case studies with di erent grit chamber designs (vortex and aerated) and treatment capacities. In both cases, the model was successfully calibrated and validated showing a powerful model to predict the solids concentration at the outlet and solids removal at the under ow (i.e. grit particles) of a grit chamber depending on the inlet dynamics. Summarizing, the results of this PhD study are a new experimental characterization and, for the rst time, a dynamic model, based on PSVD. Both new tools have been successfully tested at full-scale.

Hydrocyclone density-driven particle separation may offer up improved settling performance for wastewater treatment facilities experiencing poor settleability. Hydrocyclones are fed mixed liquor through the feed inlet and experience a centrifugal motion that separates solids based on density. The variation in hydrocyclone nozzle sizes will report different calculated hydraulic and mass split percentages for the overflow and underflow. Previous research conducted with hydrocyclones have at multiple full-scale facilities used a 10 m3/hr hydrocyclone to promote better settleability as well as aid the formation of aerobic granular sludge (AGS). There has been a multitude of settling improvement experiments and initiatives for full scale wastewater treatment. However, little research has been produced utilizing larger hydrocyclones (20 m3/hr) at a full-scale wastewater treatment facility during continuous operation. Two Hampton Roads Sanitation District (HRSD) plants served as sites for this research: James River (JR) Wastewater Treatment Plant located in Newport News, VA and Urbanna (UB) Wastewater Treatment Plant located in Urbanna, VA. Both treatment facilities have utilized the hydrocyclone for more than two years, to fulfill wasting requirements. The JR plant operates the hydrocyclone continuously for wasting purposes, while UB only uses the hydrocyclone for approximately 30-45 minutes per day. In order to evaluate the effectiveness of the hydrocyclone and its overall impact on settleability at the JR plant, eight hydrocyclones were installed. JR samples were taken from the underflow sample port (representing a mixture of underflow samples representing the number of hydrocyclones operational at the sample time) and overflow samples were taken from the outfall point of a single hydrocyclone. The UB plant only operated one 5 m3/hr hydrocyclone on Treatment Train 1 during wasting operations, while Treatment Train 2 served as the control train for the duration of this research. Hydrocyclone performance at JR was assessed through direct measurement of hydraulic and mass split of the underflow and overflow components, initial settling velocity (ISV), sludge volume index (SVI), and SVI5/SVI30 ratio. UB hydrocyclone and settling performance was measured by ISV, SVI5, SVI30, and SVI5/SVI30 ratios during different comparison experiments: hydrocyclone vs. no hydrocyclone, hydrocyclone vs. polymer addition, and hydrocyclone with polymer addition to Train 1 vs. polymer-only addition to Train 2. Nutrient concentrations from both treatment trains were collected and analyzed to determine any significant changes based on hydrocyclone use. T-test statistical analysis, and a dose response analysis included direct measurements of the ISV, SVI5, SVI30, mass split percentages, along with the effect of polymer with and without the use of a mechanical selector. Hydrocyclone settleability measurements at JR over time revealed a statistically significant positive correlation with the ISV, SVI5, and SVI30 measurements of the aeration effluent. Therefore, the hydrocyclone statistically had a strong impact on three settling parameters that are instrumental in determining overall settling efficiency. Statistically, no strong correlation was determined between the hydrocyclone operation and the total phosphorus (TP) concentration in the secondary effluent, or the ferric addition to the secondary clarifiers. The dose response based on the underflow ISV rate provided understanding of the nozzle comparison and the effect it provided to the underflow sample. Hydrocyclone performance at UB was hindered by the re-seed of Train 1 (inDENSE™) due to over wasting, and most of the data were not representative. Before the re-seed, hydrocyclone performance was improving the overall settleability of the mixed liquor in comparison to Train 2 (Control). All settling parameters measured were in favor of the hydrocyclone operation. After the re-seed the plant mixed liquor changed microbial populations for a brief time and was not representative of the overall treatment efficacy. The hydrocyclone did provide a quicker settling velocity than the polymer addition when the polymer addition was steady, and through both polymeric spikes. Polymeric addition to both trains, while inDENSE™ train still employing the hydrocyclone did not provide any conclusive data as to whether polymer addition with the use of a hydrocyclone was more effective than polymer-only addition. Nutrient profiles from UB did not provide any change in NH4-N, NO3-N, NO2-N, or PO4-P, with the hydrocyclone being operational or not on the secondary clarifier effluent.<br>Master of Science<br>Wastewater treatment facilities rely on settling tests to be indicators for plant settling performance. A way to improve plant settling is to separate the sludge on a density basis and retain the dense sludge in the system for better performance downstream, while the less dense sludge is taken out of the system. By implementing a mechanical device that can ensure the separation of dense material and be retained in the system can aide in improved plant settling performance by improving settling parameter measurements. With the ability of using a mechanical device (a hydrocyclone) to physically separate sludge on a density-basis, it will improve settling measurements of the plants taken by operators on a daily basis.

An instrument has been developed to observe the settling of individual flocs in turbid water in order to to measure size and settling velocity spectra of estuarine cohesive suspended sediments. INSSEV - IN Situ SEttling Velocity instrument - is bed mounted and comprises a computer controlled decelerator chamber that collects a sample of water from which some of the suspended matter is allowed to enter the top of a settling column. The settling flocs are viewed using a miniature video system. Subsequent analysis of video tapes provides direct measurements of size and settling velocity of individual flocs down to 20 um. From this information floc effective density is estimated. The main feature of the instrument is its ability to video flocs in situ irrespective of the concentration in the estuary, with as little disturbance to their hydrodynamic environment as possible. In addition to size and settling velocity distributions, data analysis developed for the instrument produces spectra of concentration and settling flux with respect to size, settling velocity or effective density. This is the first time that these parameters have been measured in situ. Field testing in the Tamar Estuary, South West England, and the Elbe Estuary, Germany, has given useful results in flow velocities up to 0.6 m s-1 and in concentrations up to 400 mg l-1 INSSEV was used in the 1993 Elbe Intercalibration Experiment where nearly all types of instrumentation for the in situ determination of estuarine floc size and/or settling velocity were deployed over several tidal cycles. From observations in the turbidity maximum of the Tamar Estuary, INSSEV data has shown significant changes in floc population characteristics during the tidal cycle, the most important being changes in floc effective density. A strong relationship between floc effective density and ambient turbulence characteristics is shown.

Novel settling characteristic metrics were developed based on the fundamental mechanisms of coagulation, flocculation, and settling. The settling metrics determined parameters that are essential in monitoring and optimizing the activated sludge process without the need for expensive or specialized equipment. Current settling characteristic measurements that don't require specialized instruments such as sludge volume index (SVI) or initial settling velocity (ISV), have no fundamental basis in solid-liquid separation and only indicate whether settling is good or bad without providing information as to limitations present in a sludge matrix. Furthermore, the emergence of aerobic granulation as a potential pathway to mitigate solid-separation issues further stresses the need for new settling characteristic metrics to enable integration of the new technology with the current infrastructure. The granule or intrinsic aggregate fraction in different types was of sludge was quantified by simulating different surface overflow rates (SOR). The technique named Intrinsic Settling Classes (ISC) was able to separate granules and floc by simulating high SOR values due to the lack of a flocculation time needed for granules. The method had to be performed in a discrete settling environment to characterize a range of flocculation behavior and was able to classify the granular portion of five different types of sludge. ISC was proven to accurately (±2%) determine the granule fraction and discrete particle distribution. The major significance of the test is its ability to show if a system is producing particles that will eventually grow to become granules. This methodology proved to be very valuable in obtaining information as to the granular fraction of sludge and the granular production of a system. Flocculent settling (stokesian) was found to be predominant within ideally operating clarifiers, and the shift to 'slower' hindered settling (non-stokesian) causes both failure and poor effluent quality. Therefore, a new metric for settling characteristics was developed and classified as Limit of Stokesian Settling (LOSS). The technique consisted of determining the total suspended solids (TSS) concentration at which mixed liquor settling characteristics transition from stokesian to non–stokesian settling. An image analytical technique was developed with the aid of MATLAB to identify this transition. The MATLAB tool analyzed RGB images from video, and identified the presence of an interface by a dramatic shift in the Red indices. LOSS data for Secondary activated-sludge systems were analyzed for a period of 60 days at the Blue Plains Advanced Wastewater Treatment Plant. LOSS numbers collected experimentally were validated with the Takacs et al. (1991) settling model. When compared to flux curves with small changes in the sludge concentration matrix, LOSS was found to be faster at characterizing the hindered settling velocity and was less erratic. Simple batch experiments based on the critical settling velocity (CSV) selection were used as the basis for the development of two novel parameters: threshold of flocculation/flocculation limitation (TOF/a), and floc strength. TOF quantified the minimum solids concentration needed to form large flocs and was directly linked to collision efficiency. In hybrid systems, an exponential fitting on a CSV matrix was proposed to quantify the collision efficiency of flocs (a). Shear studies were conducted to quantify floc strength. The methods were applied to a wide spectrum of sludge types to show the broad applicability and sensitivity of the novel methods. Three different activated sludge systems from the Blue Plains AWWTP were monitored for a 1 year period to explore the relationship between effluent suspended solids (ESS) and activated sludge settling and flocculation behavior. Novel metrics based on the transitional solids concentration (TOF, and LOSS) were also collected weekly. A pilot clarifier and settling column were run and filmed to determine floc morphological properties. SVI was found to lose sensitivity (r < 0.20) when characterizing ISV above a hindered settling rate of 3 m h-1. ISV and LOSS had a strong correlation (r = 0.71), but ISV was subject to change, depending on the solids concentration. Two sludge matrix limitations influencing ESS were characterized by transition concentrations; pinpoint floc formation, and loose floc formation. Pinpoint flocs had TOF values above 400 mg TSS L-1; loose floc formation sludge had TOF and LOSS values below 400 mg TSS L-1 and 900 mg TSS L-1, respectively. TOF was found to correlate with the particle size distribution while LOSS correlated to the settling velocity distribution. The use of both TOF and LOSS is a quick and effective way to characterize limitations affecting ESS.<br>Ph. D.

Hydraulic fracturing is a process for the extraction of hydrocarbons from underground formations. It involves pumping a specialized fluid into the wellbore under high pressures to form and support fractures in the rock. Fracturing stimulates the well to increase the production of oil and the natural gas which are the pillars of the energy economy. Key to this process is the use of proppants, which are solid materials used to keep the fractures open. Understanding the transport of proppant particles through a fluid is important to improve the efficiency and reduce environmental impact of fracturing. An increase of the settling velocity for instance, will impede the hydraulic fracturing process by reducing well productivity, or necessitate use of chemical additives. This thesis presents a theoretical investigation of the settling velocity of proppant particles. The effect of different parameters on the settling velocity were studied by manipulating the main factors that can influence particle transport. These include size of the particle (300 μm- 2000 μm), sphericity, density (1200 kg/m3-3500 kg/m3) and concentration. These typical values were obtained from commercially available proppants currently used in industry. Various correlations were investigated, assuming the carrier (fracturing) fluid to be an ideal Newtonian and as a power law (non-Newtonian) fluid. This will help predict the settling velocity for proppant particles in order to increase well productivity, and improve hydraulic fracturing efficiency. The models show that changing the carrier fluid viscosity and particle properties such as diameter, density, sphericity, and concentration leads to a significant change in the proppant settling velocity. For instance, reduction in particle size, density, and sphericity tend to reduce the settling velocity, while increasing the concentration of the particles and the fluid viscosity reduce the settling velocity.

This study focuses on deposition processes from sediment laden buoyant river plumes in deltaic regions. The goal is to experimentally examine the effects of various physical phenomena influencing the rate at which sediment is removed from the plume. Previous laboratory and field measurements have suggested that, at times, sedimentation can take place at rates higher than that expected from individual particle settling (i.e., C{W}_{s}). Two potential drivers of enhanced sedimentation are flocculation and interfacial instabilities. We experimentally measured the sediment fluxes from each of these processes using two sets of laboratory experiments that investigate two different modes of instability, one driven by sediment settling and one driven by fluid shear. The settling-driven and shear-driven instability sets of experiments were carried out in a stagnant stratification tank and a stratification flume respectively. In both sets, continuous interface monitoring and concentration measurement were made to observe developments of instabilities and their effects on the removal of sediment. Floc size was measured during the experiments using a separate floc camera setup and image analysis routines. Results from the stratification tank experiments suggest that the settling-driven gravitational instabilities do occur in the presence of flocs, and that they can produce sedimentation rates higher than those predicted from floc settling. A simple cylinder based force balance approach adopting the concept of critical Grashof number was used to develop a model for the effective settling velocity under settling-driven instabilities that is a function of sediment concentration in the plume only. Results from the stratification flume experiments show that under shear instabilities, the effective settling velocity is greater than the floc settling velocity, and increases with plume velocity and interface mixing. The difference between effective and floc settling velocity was denoted as the shear-induced settling velocity. This settling rate was found to be a strong function of the Richardson number, and was attributed to mixing processes at the interface. Conceptual and empirical analysis shows that the shear-induced settling velocity is proportional to U{Ri}^{-2}. Following the experiments, analyses were made among contributions of different mechanisms on the total deposition rate, and the locations that the various mechanisms may be active in the length of a plume. This analysis leads to a conceptual discretization of a plume into three zones of sedimentation behavior and Richardson number. The first zone is the supercritical near-field plume with intense interface mixing. Zone two represents the subcritical region where interface mixing still occurs, and zone three is the high Richardson number zone where mixing at the interface is effectively nonexistent. In zones one and two, individual floc settling and shear-induced settling mechanisms play the major roles in removing sediment from the plume. While, shear-induced settling rate was found to be maximum near the river mouth, its share of the total settling rate increases in the crossshore direction, since sand and large particulates deposit near the inlet and only small particles (with relatively low settling velocity) remain as the plume propagates. The third zone, starts when the interfacial mixing diminishes and leaking commences.<br>Ph. D.

Transport of suspended particulate matter (SPM) plays a vital role in controlling large-scale processes related to geophysical flows such as dispersal and sinking of organic matter and contaminants to offshore and deep waters, nutrient cycles, food web stability, morphodynamics and sedimentation in both limnetic and pelagic ecosystems. Although it has been recognized that small-scale microbial processes can introduce substantial differences to the way in which SPM moves in natural waters, the extent to which the attached biological matter affects SPM dynamics is still not well characterized. This thesis focuses on quantifying the attached biomass fraction on SPM aggregates and investigating its contribution to SPM flocculation dynamics, which consequently control SPM aggregate geometrical properties and transport. A novel laboratory-based Optical Measurement of Cell Colonization (OMCEC) system and a microbiological-physical model (BFLOC2) are the main achievements of this thesis that allow the analyses of the correlations between environmental conditions, aggregate-attached biomass fraction, cell colonization patterns, aggregate size, fractal dimension and settling velocity. OMCEC is an experimental system that can simultaneously measure the material composition, geometric properties, and motion of individual suspended aggregates in a non-invasive and non-destructive way. OMCEC consists of a full-color high-resolution optical system and real-time algorithms for (i) material segmentation based on light spectra emission analysis, (ii) quantification of various geometrical properties, and (iii) motion detection with micro particle tracking velocimetry (μPTV). OMCEC was applied herein on three types of aggregates: cell-associated minerals, cell-associated microplastics, and three-phase aggregates made of minerals, microplastics, and biological matter. OMCEC application on Saccharomyces cerevisiae-colonized minerals at four sucrose concentrations showed the likelihood of cell colonization to increase with increasing nutrient concentration. The attached biomass fraction was found to increase nonlinearly regarding an increase of aggregate size but almost constant with fractal dimension variation. Cell distribution on mineral surfaces was then analyzed and classified into three colonization patterns: (i) scattered, (ii) well-touched, and (iii) poorly-touched, with the second being predominant. Cell clusters in the well-touched pattern were found to have lower fractal dimension than those in the other patterns. A strong correlation of colonization patterns with aggregate biomass fraction and properties suggests dynamic colonization mechanisms from cell attachment to minerals, to joining of isolated cell clusters, and finally cell growth over the entire aggregate. OMCEC application on microplastics (MPs) being colonized by natural biological matter from Hawkesbury River, NSW, Australia demonstrated that the biomass fraction of MP aggregates has substantial control over their size, shape and, most importantly, their settling velocity. Polyurethane MP aggregates made of 80% biological matter had an average size almost double that of MP aggregates containing 5% biological matter and sank two times slower. Based on our experimental data, we introduce a settling velocity equation that accounts for the shape irregularity and fractal structure of MP aggregates. This equation can capture the settling velocity of both virgin MPs and cell-associated MP aggregates with 7% error and can be applied widely to predict the settling flux of MP aggregates made of different polymers and various types of biological matter. To consider the complex genesis of cell-associated mineral aggregates, the BFLOC2 model was introduced to predict aggregate geometry and settling velocity under simultaneous effects of hydrodynamic and biological processes. While minerals can contribute to aggregate dynamics through collision, aggregation, and breakup, living microorganisms can colonize and establish food web interactions that involve growth and grazing, and modify the aggregate structure. Modeling of cell-associated mineral aggregate dynamics over a wide range of environmental conditions showed that maximum aggregate size, biomass fraction, and settling velocity could occur at different optimal environmental conditions. Unlike mineral aggregates, which have maximum size when shear rates tend to zero, a relative maximum size of cell-associated mineral aggregates can be reached at intermediate shear rates as a result of microbiological processes. The settling velocity was ultimately controlled by aggregate size, fractal dimension, and biomass fraction. The innovative aspect of this thesis is the simultaneous quantification of composition, architecture, and settling velocity of individual aggregates. Therefore, it puts forth the analysis and prediction of cell colonization impacts on dynamics and transport of suspended particulate matter in natural waters. The output of this thesis can be used in natural water monitoring programs to estimate the biological content based on SPM size, capacity dimension, and settling velocity, which can be measured using in-situ methods. Furthermore, the evidence and tools to quantify the sinking and floating of microplastic subjected to bio-fouling can be implemented in microplastics transport models to enable the three-dimension modeling of both low- and high-density microplastics. The BFLOC2 model can be coupled to traditional sediment transport models to better describe the sediment formation dynamics, thus giving a more precise prediction of sedimentation and carbon flux to deep waters and offshore.

The separation of solids from biological wastewater treatment is an important step in the treatment process, as it has a significant impact on effluent water quality. The moving bed biofilm reactor (MBBR) technology is a proven upgrade or replacement wastewater treatment system for carbon and nitrogen removal. However, a challenge of this technology is the characteristics of the effluent solids that results in their poor settlement; with settling being the common method of solids removal. The main objective of this research is to understand and expand the current knowledge on the settling characteristics of MBBR produced solids and the parameters that influence them. In particular, in this dissertation, the impacts are studied of carrier types, biofilm thickness restraint design of carriers, and varying carbonaceous loading rates on MBBR performance, biofilm morphology, biofilm thickness, biofilm mass, biofilm density, biofilm detachment rate, solids production, particle size distribution (PSD) and particle settling velocity distribution (PSVD). With this aim, three MBBR reactors housing three different carrier types were operated with varying loading rates. In order to investigate the effect of carrier geometrical properties on the MBBR system, the conventional, cylindrically-shaped, flat AnoxK™ K5 carrier with protected voids was compared to two newly-designed, saddle-shaped Z-carriers with the fully exposed surface area. Moreover, the AnoxK™ Z-200 carrier was compared to the AnoxK™ Z-400 carrier to evaluate the biofilm thickness restraint design of these carriers, where the Z-200 carrier is designed for greater biofilm thickness-restraint. The Z-200 carrier is designed to limit the biofilm thickness to the level of 200 µm as opposed to 400 µm for the Z-400 carrier. Finally, to investigate the effects of varying carbonaceous loading rates on system removal performance, biofilm characteristics and solids characteristics, further analyses were performed at three different loading rates of 1.5 to 2.5 and 6.0 g-sBOD/m2·d in steady-state conditions. The PSD and the PSVD analyses were combined to relate these two properties. A settling velocity distribution analytical method, the ViCAs, was applied in combination with microscopy imaging and micro-flow imaging to investigate the relation of PSD and settling behaviour of MBBR produced particles. The obtained results have indicated that the carrier type significantly impacted the MBBR performance, biofilm, and particle characteristics. As such, the K5 carrier MBBR system demonstrated a statistically significantly higher carbonaceous removal rate and efficiency (3.8 ± 0.3 g-sBOD/m2·d and 59.9 ± 3.0% sBOD removal), higher biofilm thickness (281.1 ± 8.7 μm), higher biofilm mass per carrier (43.9 ± 1.0 mg), lower biofilm density (65.0 ± 1.5 kg/m3), lower biofilm detachment rate (1.7 ± 0.7 g-TSS/ m2·d) and hence lower solids production (0.7 ± 0.3 g-TSS/d) compared to the two Z-carriers. The Z-carriers' different shape exposes the biofilm to additional shear stress, which could explain why the Z-carriers have thinner and denser biofilm, resulting in higher solids production and lower system performance in comparison with K5. Moreover, the carrier type was also observed to impact the particle characteristics significantly. PSD analysis demonstrated a higher percentage of small particles in the Z-carrier system effluent and hence a significantly lower solids settling efficiency. Therefore, the solids produced in the K5 reactor have shown enhanced settling behaviour, consisting of larger particles with faster settling velocities compared to Z-carriers. This dissertation also investigated the effects of restraint biofilm thickness on MBBR performance by comparing the Z-200 biofilm thickness-restraint carrier to the Z-400 carrier. No significant difference was observed in removal efficiency, biofilm morphology, biofilm density, biofilm detachment rate, and solids production between the Z-200 to the Z-400 carriers. The PSD and the PSVD analyses did not illustrate any significant difference in the particles’ settling behaviour for these two biofilm thickness restraint carriers, indicating that the biofilm thickness-restraint carrier design was not a controlling factor in the settling potential of MBBR produced solids. Finally, this research studied the effect of varying loading rates and demonstrated a positive, strong linear correlation between the measured sBOD loading rate and the removal rate, indicating first-order BOD removal kinetics. The biofilm thickness, biofilm density and biofilm mass decreased when the surface area loading rate (SALR) was increased from 2.5 to 6.0 g-sBOD/m2·d. The solids retention time (SRT) was also shown to decrease by increasing the SALR, where the lowest SRT (1.7 ± 0.1 days) was observed at the highest SALR, with the highest cell viability (81.8 ± 1.7%). Significantly higher biofilm detachment rate and yield were observed at SALR 2.5, with the thickest biofilm and a higher percentage of dead cells. Consequently, a higher fraction of larger and rapidly settling particles was observed at SALR of 2.5 g-sBOD/m2·d, which leads to a significantly better settling behaviour of the MBBR effluent solids. This study expands the current knowledge of MBBR-produced particle characteristics and settling behaviour. A comprehensive understanding of the MBBR system performance and the potential influencing factors on the MBBR produced solids, particle characteristics, and their settleability will lead to optimized MBBR design for future pilot- and full-scale applications of the MBBR.

Sedimentation is a fundamental operation in wastewater treatment works. A rational design of sedimentation tanks is currently achieved by plotting iso-percentile (iso-percentage) concentration removal profiles from flocculent settling data. A major drawback of the graphical iso-percentage method is that the iso-percentile lines are often manually interpolated and are mere hand drawn estimations. This is because the settling behaviour of sludge particles is highly non-linear. The manual analytical process is therefore very tedious, inaccurate and subjective. Hence, an optimised design of sedimentation tanks is necessary in order to eliminate the errors incurred during data analysis. In this study, a mechanistic iso-percentile flocculent model (referred to as the velocity flocculation model) is developed to simulate the behaviour of flocculating colloidal particles in turbid water. This model is based on the physical meanings of flocculent settling particles and on fractal theory. It is formulated to produce automated iso-percentile curves which are fundamental in the design of sedimentation tanks. The iso-percentile model was vertically integrated into a velocity model to produce a model expressing the velocity of particles as a function of removal rate. The velocity model has an obvious advantage over the iso-percentile model in that it is easy to contextualize. It can be reverted back to the iso-percentile trajectory analysis eliminating the need for extensive data interpolation and may in future eliminate the need for settling column analysis altogether. In the current study, the integrated velocity form is used to predict instantaneous flocculent settling velocity of fine suspended particles under near quiescent conditions. This is vital since it is difficult to obtain velocity values in-situ or directly from sedimentation tanks. Model validity and competency was tested by a direct comparison with existing literature models, such as Ozer’s model and Ramatsoma and Chirwa’s model. Model comparison was based on the goodness of fit, the least sum of square errors and mathematical consistency with known flocculent settling behaviour. The newly developed iso-percentile model achieved a more accurate simulation of physical experimental data, did not violate any of the mathematical constraints and yielded lower sum of square errors than originally achieved by Ozer and Ramatsoma and Chirwa. Notably, the proposed velocity model offers a distinctive advantage over conventional interpolated-iso-percentile based models which are prone to numerical errors during interpolation. Its performance (velocity model) was compared against Je and Chang’s velocity model. Higher velocity values were observed for the new model than for Je and Chang’s model implying that empirically based models would tend to under-predict the velocity values. The model developed in this study brings us one step closer to achieving full automation of the settling tank and clarifier design.<br>Dissertation (MEng)--University of Pretoria, 2013.<br>gm2014<br>Chemical Engineering<br>unrestricted

This work reports an investigation of colloidal suspensions during sedimentation in what is known as the intermediate concentration range; one notoriously difficult to study. Two materials were examined: titanium dioxide P25 nanoparticles and magnesium hydroxide. The characterisation of these materials highlighted their high tendency to form aggregates under certain conditions. By the use of laser diffraction, measurements of the cluster size were conducted at under various conditions of shear. The use of sonication energy suggested the identification and classification of two classes of clusters related to their strength: high strength , and low strength clusters. A mathematical model which considered cluster formation and the occurrence of breakage predicted the aggregation and disaggregation kinetics. The approach was based on cluster-cluster interactions rather than particle-particle interactions. The results obtained by particle size analysis were compared with the size obtained using permeability analysis and settling velocity. In both cases the calculated sizes were comparable with the data obtained from size analysis; however, for magnesium hydroxide the predicted cluster size was a little higher and this may be due to the formation of channels giving faster settling. For the titanium dioxide it was noticeable that different mixing strategies exhibited different cluster size, network formation and settling behaviour. Finally, a novel modelling approach based on the presence of clusters rather than particles is presented. It is a combined model which considers the settling curve divided into two zones: a zone below the gel point modelled by a Kynch type approach and a zone above the gel point modelled by consolidation theory. This combined approach was only applicable to the settling data of titanium dioxide, where the settling data encompassed the gel point and the gel point could be identified by consideration of the Richardson and Zaki plots. For magnesium hydroxide, only the consolidation model was needed as all the initial settling concentrations were above the gel point.

This dissertation aims to better understand how floc aggregate characteristics and behaviors are modified under different local conditions and how such alterations impact the floc settling velocity, which is one of the most crucial parameters influencing sediment transport modeling. A series of laboratory experiments were conducted to examine the impact of suspended sediment concentration, mixes of clay and silt, and resuspension process to equilibrium floc size and floc settling velocity. In order to observe floc size evolution, a new floc imaging acquisition was first developed. This new method allows flocs in suspended sediment concentration up to C = 400 mg/L can be imaged non intrusively. This new method was applied in all three individual studies, which are composed of this dissertation. The first chapter investigates the behaviors of flocs under constant and decay suspended sediment concentrations within a steady turbulent suspension. In the constant-concentration set of experiments, floc size time series were measured for 12 h for each of the concentration C = 15, 25, 50, 100, 200, 300, and 400 mg/L. In the decay-concentration experiments, clear water was introduced to the mixing tank, simultaneously the suspension was drained out of the mixing tank at the same rate to make the suspended sediment concentration reduce while the turbulent shear was remained unchanged. The data shows that the equilibrium floc size is a weak, positive function of concentration. For example, in order to increase 20% of floc size (approximate 22 um) the concentration needs to be increased by 700% (going from 50 to 400 mg/L). The data also illustrates that during the decrease of concentration from C = 400 to 50 mg/L, the floc size responses to the changes of concentration in the order of 10 min or less. The second chapter examines how silt particles and clay aggregates interact in a turbulent suspension. Floc sizes and settling velocity of three different suspensions, i.e., pure clay, pure silt, and a mixture of clay and silt, were monitored. The floc size data show that the presence of silt particles does not have significant impacts on clay aggregate sizes. Silt particles, however, get bound up within floc aggregates, which in turn increase the settling velocity of the floc by at least 50%. The third chapter examines whether any changes in floc properties during the deposition and resuspension processes. The floc sizes and shapes in a set of experiments with different consolidation times, concentrations, and shear patterns were measured. The conditions at which the flocs deposited or resuspended were maintained the same. The data reveal that floc size and shape of freshly deposited and after resuspended are unchanged. The erosion rate and concentration is a function of consolidation time and the applied shear stress during the deposition phase. Hence, there is a small reduction in resuspended concentration resulting in a slight decrease in resuspension floc size since floc size is also a function of concentration.<br>Ph. D.

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.

There is a demand to reestablish a healthy coastal ecosystem by rebuilding wetlands with river diversion or dredged sediments in coastal Louisiana. Land building projects using dredged sediments from adjacent canals and river beds, can be used to protect the coastal properties and infrastructure systems from flood and storm surges. To predict the sediment’s long term behavior, math models require input parameters based on sediment engineering properties and material characteristics. Proper characterization is critical for accurate design of coastal restoration projects. The dredge material sedimentation characteristics and their effects on the settlement rate of suspended solid particles and underlying foundation soil depend, among other factors, on the grain size distribution of the dredged material, salinity of the composite slurry, and slurry solid particles concentration. This research evaluated the effects of grain size distribution, salinity, and initial solids concentration on the sedimentation characteristics of fine grained dredged sediments in Coastal Louisiana.

Durante a floculação, a agitação promove dois efeitos simultaneamente, a agregação e a ruptura. A ruptura ocorre devido à atuação de forças de cisalhamento sobre os flocos. O aumento da agitação com, conseqüentemente, aumento do gradiente de velocidade médio, em água com flocos formados, promove o aumento das forças de cisalhamento e a degradação parcial ou total dos mesmos, em poucos segundos. Retornando à condição anterior de agitação, pode ocorrer o recrescimento dos flocos. Através de ensaios em reatores estáticos (em equipamento de jarteste) foram estudados os efeitos da ruptura e da refloculação na sedimentação dos flocos, para velocidades de sedimentação entre 0,9 e 7,0 cm/min. A água de estudo foi preparada com caulinita, resultando turbidez de 100 uT, e coagulada com sulfato de alumínio. Foram realizadas as etapas de coagulação, mistura rápida, floculação, ruptura (G=75, 150 e 250 \'S POT.-1\') e refloculação (G=25, 20 e 15 \'S POT.-1\'). A ruptura, em poucos segundos, prejudicou a remoção dos flocos por sedimentação. Quanto maior o gradiente de velocidade na ruptura, maiores foram os valores da turbidez remanescente do sobrenadante, mesmo após a refloculação. A refloculação, mesmo nos primeiros minutos, diminuiu a turbidez remanescente do sobrenadante se comparada a logo após a ruptura. Quanto menor o gradiente de velocidade durante a refloculação, menores foram os valores da turbidez remanescente do sobrenadante. Apenas para velocidades de sedimentação, gradientes de velocidade de ruptura e gradientes de velocidade de refloculação menores ou iguais a 2,5 cm/min, 75 \'S POT.-1\' e 15 \'S POT.-1\', respectivamente, foi possível obter sobrenadante com valores de turbidez remanescente similares aos encontrados inicialmente, sem ruptura.<br>During the flocculation, the shear rate promotes two effects simultaneously, growth and breakage of flocs. The break up of flocs is caused as a result of disruptive forces. The increase of the shear rate in water with formed flocs increases the disruptive forces and it also can break the flocs partial or totally in a few seconds. Restoring the previous low shear conditions, flocs can grow back. By using the jar test equipment, the effects of breakage and reflocullation on the efficiency of floc sedimentation were studied, using settling velocities between 0.9 e 7.0 cm/min. Water of study was prepared with groundwater and kaolin, resulting a turbidity of approximately 100 NTU. Coagulation was performed by using aluminum sulfate. Coagulation, flocculation, breakage (G=75, 150 e 250 \'S POT.-1\') and reflocculation tests were carried out. In a few seconds the breakage of flocs hindered the settling removal of turbidity. The higher the average shear rate in the break-up, the higher result the residual turbidity even after the reflocculation. In the first minutes, the reflocculation decreased the residual turbidity after sedimentation if compared to the residual turbidity just after the break-up and sedimentation. The lower the average shear rate during the reflocculation, the lower result the supernatant values of residual turbidity. Supernatant could only be obtained with the value of residual turbidity similar to the values found initially (without breakage of flocs) for the settling velocity, the average velocity gradient of break-up and the average velocity gradient of reflocculation equal or less than 2.5 cm/min, 75 \'S POT.-1\' e 15 \'S POT.-1\', respectively.

Settling phenomenon of solid particles immersed in a turbulent fluid has been investigated, in a condition of free-stream turbulence. Since structures formed onto this condition are complex, it is difficult to predict exactly how particles move. It is thus appropriate to conduct deepen studies of the phenomenon and carry out simulations to describe particles’ settling velocity. In order to define a new correlation for the evaluation of particles’ settling velocity, different literature correlations and parameters have been exploited. Langevin dynamics has been used to describe fluid’s motion, and by considering several forces acting on particles (buoyancy, drag, gravitational and virtual mass), it has been possible to evaluate their settling velocity, through a computational approach. Data have been obtained by varying characteristic properties, such as kinetic energy, its rate of dissipation, and physical properties of fluid and particles. Aiming to find a reliable correlation which best explains the settling phenomenon, results in output from simulations have been compared with that deriving from proposed correlation. Encouraging results have been obtained over the range of operating conditions examined.

To minimize coastal land loss and create new land, dredged sediment has been in use in coastal Louisiana during the last several years. Engineering properties and material characteristics of dredged material are input parameters in several mathematical models used to predict the long-term hydrodynamic behavior of the coast. Therefore, proper characterization of the dredged material is of utmost importance in the correct design of coastal restoration and land creation projects. The sedimentation characteristics of the dredged material, among other factors, depends on the (a) grain size distribution of the dredged material, (b) salinity (fresh, brackish, or saltwater environment) of the composite slurry, and (c) concentration of the solid particles in the slurry. In this research, dredged sediments obtained from actual coastal restoration projects were characterized. Furthermore, the effects of grain size distribution, salinity and solid particle concentration on sedimentation characteristics have been evaluated.

The urban sprawl creates a gap between producers and consumers and the a sustainable circuitof nutrients and energy is difficult to maintain. Many times the waste that is created in urbanareas is not reused and the circuit is lost. In this project, wastewater treatment is looked atwith the view point that resource recovery is possible through energy production and reuse ofnutrients. In order to optimally run each process step at a wastewater treatment plant forimproved resource recovery, more knowledge is needed in order to not disregard the finaleffluent quality. The goal of this project was to develop a model in MATLAB/Simulink for achemically enhanced primary clarifier at a wastewater treatment plant. The potential ofproducing more biogas and reducing the aeration energy needed in the biological treatmentstep was looked at by focusing on describing the settling velocity of suspended solids.Experimental analysis on settling properties for solids was performed on sampled wastewaterentering the primary settler after changing the addition of chemicals prior in the process line.The wastewater samples were homogenized and then rapidly vacuum pumped up in a column.The solids in the column could thereafter settle and was retained in a cup at the bottom. Themass of total suspended solids (TSS) was classified in five different settling velocity classes,each class assigned a characteristic settling velocity. The experimental procedure followed theViCA's protocol (French acronym for Settling Velocity for Wastewater). A settler, much likethe secondary settler in the Benchmark Simulation Model No. 2 (BSM2), a 10 layer nonreactivetank was modeled. The mass balance in each layer of the settler was decided by thevertical solid flux in the tank and built on the characteristic settling velocity gained from theexperiments. Re-circulation of excess sludge from the subsequent steps at the plant showed toeffect the settling properties of the sludge in the primary settler. The components of TSSshowed to have the largest effect on the distribution of settling velocity. The variation in doseof both coagulant and cationic polymer prior the primary settling tank showed to effect theparticle settling distribution somewhat. A first simulation with an applicable dynamic influentscenario was run. Despite any proper calibration the model gave fairly good predictions ofmeasured TSS in the effluent and sludge outtake water.<br>När urbana områden växer uppstår svårigheter i att bibehålla ett hållbart kretslopp av energioch näringsämnen. Avståndet mellan producent och konsument ökar och många gångeråteranvänds inte det avfall som städerna producerar och det hållbara kretsloppet bryts. Dettaprojekt har fokuserat på resursåteranvändningen i avloppsvattenhanteringen genommöjligheterna som finns i energiproduktion i form av biogas samt återanvändning avnäringsämnen genom slamåterförsel. Mer kunskap behövs inom varje processteg för attoptimalt använda avloppsreningsverk för förbättrad resurs-återvinning så att inte utgåendevattenkvalitet blir lidande. Målet med projektet var att utveckla en modell iMATLAB/Simulink för primärsedimentering med kemisk fällning. Experimentelltanalyserades sedimentationsegenskaperna hos primärslam genom provtagning avavloppsvatten inkommande till försedimenteringen efter tillsatser av fällnings-kemikalier.Proverna homogeniserades och vakuumpumpades sedan snabbt upp i en kolonn. Detpartikulära materialet i kolonnen kunde därefter sedimentera och fångades upp i en kopp ibotten. Den sedimenterade massan av totalt suspenderat material (TSS) klassificerades i femolika sedimenteringshastighetsklasser och varje klass tilldelades en karakteristisksedimentationshastighet Det experimentella förfarandet följde ViCA’s protokoll (franskförkortning för sedimentationshastigheter för avloppsvatten). En modell av ensedimentationstank, ungefär som för sekundär-sedimenteringen i Benchmark SimulationModel No. 2 (BSM2), utvecklades som en 10 lager icke reaktiv tank. Massbalansen i varjelager bestämdes av det vertikala flödet av partiklar och beräknades med de experimentelltframtagna karakteristiska sedimentationshastigheterna. Återcirkulering av överskottsslam frånde efterföljande reningsstegen visade sig ha stor påverkan på slammetssedimentationsegenskaper i försedimenteringen. Typen av TSS-komponenter hade den störstainverkan på fördelningen av sedimentationshastigheter. Variationen i dos av bådefällningskemikalie och katjonspolymer före primär-sedimenteringstanken hade en visspåverkan på fördelningen. En första simulering med ett sannolikt dynamisk inflödesscenariokördes. Utan någon riktig kalibrering av modellen gav den ändå en relativt realistisk prognospå TSS i utgående vatten och i slamuttaget.<br>I samarbete med forskningsgruppen ModelEAU, Quebec, Kanada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The settling vessels are equipment destined to solid-liquid separation; usually have continuous operation, with a circular section, presenting one conic and one cylindrical part. The solid particle splitting with small granular becomes difficult through the operation of conventional sedimentation. An expedient very used in the industry is the flocculant substance addition, whose objective is to promote the precipitation of particles, in which decantation speed is upper than the single one. The present work aim the study of the burst operational conditions that influence the formation and the stability of these aggregates, the flake and the effect of pH and the concentration of flocculant in the capacity of conventional settling vessel, which area of the transversal remains constant, considering this operational conditions. The experiments were made using a kaolin suspension, with pH adjustment and iron sulfate as flocculant. It was made batch sedimentation tests to find great points of pH and flocculant concentration on sedimentation and calculate the maxim rate of sedimentation by Kynch (1952) method. The experimental design results in a great pH of 7,5 and flocculant concentration of 0,0031mL/g of kaulim; using the flocculation process the diameter particle raised of 5,06 to 311_m; the batch sedimentation experiments were very efficient in spite of simplicity, obtaining a good adjustment of experimental data by constitutive equations of TILLER e LEU (1980) for pression and permeability; the area of transversal section had an influence in sedimentation velocity, the biggest one provide a bigger velocity, indicating a wall effect in the process; calculating the settling vessel capacity by Kynch (1952) method, a great performance was showed up with flocculation process, showing its importance in sedimentation of very small particles, and this study ended in a suggestion of a procedure to a continuous operation of a conventional settling vessel with suspensions previously flocculated.<br>A sedimentação é uma das operações unitárias mais utilizadas na indústria química. Nela, as fases sólida e líquida são separadas devido à diferença de peso. Para o caso de partículas sólidas muito pequenas, a eficiência de separação diminui drasticamente, inviabilizando a separação com padrões aceitáveis, tornando-se então necessária a pesquisa de métodos para otimização da eficiência de separação. Uma maneira de contornar tal situação consiste na adição de agentes floculantes, cuja ação consiste em produzir estruturas complexas (flocos) com os quais as partículas sólidas interagem e podem ser adsorvidas. Tais estruturas possuem peso suficientemente alto para promover a separação de forma adequada. Os objetivos desse trabalho foram estudar as variáveis que afetam o desempenho de sedimentadores convencionais operando com suspensões previamente floculadas, tais como o pH e a massa de material floculante e apresentar um procedimento para sedimentação contínua com floculação utilizando o sedimentador convencional. Os experimentos foram conduzidos utilizando-se suspensões aquosas de caulim, com ajuste de pH, floculada com sulfato férrico. Foram feitos experimentos em batelada em proveta para encontrar os pontos ótimos de pH e concentração de floculante na sedimentação; experimentos em batelada em proveta e no sedimentador para determinação da taxa máxima de sedimentação pelos métodos de Kynch (1952) e Tiller e Chen (1988). O planejamento experimental resultou em um pH ótimo de operação de 7,5 e concentração ótima de floculante de 0,0031mL/g de caulim; utilizando o processo de floculação conseguiu-se um aumento do diâmetro médio da partícula de 2,9 para 311_m; os ensaios de proveta se mostraram muito eficientes apesar da simplicidade, pois obteve-se um bom ajuste dos resultados experimentais pelas equações constitutivas de TILLER e LEU (1980) para pressão e permeabilidade; houve uma influência da área da seção transversal na velocidade de sedimentação, as provetas de maiores diâmetros proporcionaram as maiores velocidades, indicando que o efeito de parede interfere no processo; o calculo da capacidade do sedimentador pelos métodos de Kynch e Tiller e Chen forneceram um melhor desempenho utilizando-se o processo de floculação, mostrando assim a importância de se utilizar este processo nos casos de sedimentação de partículas muito finas.O estudo da sedimentação com floculação proporcionou a sugestão de um procedimento para a operação contínua do sedimentador convencional operando com suspensões previamente floculadas.<br>Mestre em Engenharia Química

A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.

Les bassins de retenue-décantation ont trois fonctions principales : stocker les eaux pluviales pour éviter les inondations, favoriser la décantation des polluants particulaires, éviter la remise en suspension et la remobilisation des polluants décantés vers l’aval. La conception et la gestion de telles installations nécessitent de connaître les caractéristiques hydrodynamiques, celles des sédiments et de pouvoir prédire les zones où les dépôts sont fortement contaminés. L’objectif principal de la thèse est d’identifier les zones où les teneurs en polluants sont élevées au niveau des sédiments des bassins de retenue-décantation. Le site d’étude est le bassin de rétention des eaux pluviales de Django Reinhardt (BDR), qui est un bassin sec à l’exutoire d’un bassin versant industriel. Ce bassin a fait l’objet de plusieurs études dans le cadre de de l'Observatoire de Terrain en Hydrologie Urbaine (OTHU).Dans un premier temps, les mesures de vitesses de surface par LSPIV (Large-Scale Particle Image Velocimetry) ont permis de mieux comprendre l’hydrodynamique au sein de l’ouvrage. Ces mesures ont été exploitées pour évaluer les modèles CFD (Computational Fluid Dynamics). C’est la première fois que cette technique de mesure est appliquée au cas des ouvrages de gestion des eaux pluviales. Les résultats montrent que les modèles CFD identifient la principale zone de recirculation qui favorise la décantation. Ces modèles évalués ont ensuite été employés pour simuler le transport de polluants particulaires, leur sédimentation et leur remise en suspension. L’exploitation des résultats de ces simulations a permis d’indiquer les points où les sédiments sont remis en suspension et transférés vers le bassin d’infiltration à l’aval et de prédire les zones d’accumulation en métaux. Les résultats obtenus montrent également que les teneurs en fer dans les sédiments sont fortement corrélées aux vitesses de chute. Le fer pourrait être un bon indicateur du niveau de contamination des sédiments en certains métaux lourds. Les résultats de cette thèse contribuent à améliorer les règles de conception des bassins de retenue-décantation des eaux pluviales et les stratégies de gestion des sédiments associés<br>Stormwater detention basins have three main functions: storing rainwater to prevent flooding, promoting settling of particulate pollutants, avoiding resuspension and remobilization of settled pollutants to the downstream. The design and the management of such facilities requires the knowledge of hydrodynamic and sediment characteristics, as well as the ability to predict areas where deposits are highly contaminated.The main objective of this PhD work is to identify the areas where pollutant levels in sediments are high in detention and settling basin. The studied site is the stormwater detention basin (Django Reinhardt basin or DRB), which is an extended and dry basin at the outlet of an industrial watershed. This basin has been the subject of numerous investigations within the framework of the Field Observatory for Urban Water Management (or observatoire de terrain en hydrologie urbaine - OTHU in French).First of all, the measurements of surface velocities by Large-Scale Particle Image Velocimetry (LSPIV) permits to better understand the hydrodynamic behaviour in the basin. These measurements were used to evaluate CFD (Computational Fluid Dynamics) models. This is the first time this measurement technique has been applied in the case of stormwater management facilities. The results show that CFD models identify the main recirculation zone that promotes settling. These evaluated models were then used to simulate the transport of particulate pollutants, including sedimentation and resuspension. The exploitation of these simulations results enables to (i) identify the preferential areas where resuspended contaminated sediments may be conveyed to the downstream infiltration basin and (ii) predict the accumulation zones of some metals. Results also demonstrate that iron contents in sediments are strongly correlated to settling velocities and can be considered as a good indicator of the level of heavy metals contamination of sediments. The results obtained in this thesis contribute to improve the design of stormwater detention and settling basins and the management of contaminated sediments

Die vorliegende Arbeit beschäftigt sich mit der Thematik des hydraulischen Feststofftransports in Druckrohrleitungen zur Bestimmung der hydraulischen Energieverluste des Wasser-Feststoff-Gemisches und der wirtschaftlichen Gemischgeschwindigkeit (der s.g. kritischen Geschwindigkeit) vcrit. Zu diesem Zweck wurde der Transportvorgang in verschiedenen Rohrkonfigurationen (horizontal, schräg und z. T. vertikal) an einem physikalischen Modell im Hubert-Engels-Labor des Instituts für Wasserbau und Technische Hydromechanik der Technischen Universität Dresden untersucht. Dabei kamen drei Sandfraktionen zum Einsatz (0,1 - 0,5 mm; 0,71 - 1,25 mm und 1,4 - 2,2 mm). Die Partikel weisen eine Dichte von ρF=2650 kg/m³ auf. Ziel der Untersuchungen war, mithilfe der Messdaten eine Formel zur Berechnung des Verlustanteils der dispersen Phase an dem gesamten Energieverlust besonders für das heterogene und das quasi-homogene Transportregime in Abhängigkeit von den Einflussgrößen (Dichte, Konzentration, Partikeldurchmesser etc.) abzuleiten. Ein weiterer Schwerpunkt der Arbeit war, die kritische Gemischgeschwindigkeit genauer zu betrachten und einen entsprechenden Rechenansatz aufzustellen. Diese Geschwindigkeit stellt den Übergang von dem Transport mit beweglicher Sohle zum heterogenen Feststofftransport dar. Nach Abschluss der physikalischen Versuche wurde der Feststofftransport mit der Software ANSYS-Fluent numerisch untersucht. Im Fokus der Modellierung stand die Festsetzung der Wandrandbedingung für die disperse Phase, mit Hilfen derer die physikalisch gemessenen Energieverluste erreicht werden konnten. Die Simulationen wurden mit dem Euler-Granular-Modell durchgeführt. Hierbei wird der Feststoff als zweites Kontinuum betrachtet und seine rheologischen Eigenschaften wurden durch die Erweiterung der kinetischen Theorie der Gase auf die disperse Phase (eng. kinetic theory of granular flow KTGF) berechnet. Das angewendete zwei-Fluid-Modell (TFM) eignet sich sehr gut für alle möglichen vorkommenden Feststoffkonzentrationen und liefert gute Übereinstimmung mit den Messergebnissen im Gegensatz zu dem Euler-Lagrange-Modell (DPM), welches lediglich bei niedrigen Feststoffkonzentrationen Anwendung findet.:Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Symbolverzeichnis Indexverzeichnis 1 Einleitung und Zielsetzung 2 Grundlagen des hydraulischen Feststofftransports in Rohrleitungen 2.1 Das Energiegesetz 2.2 Feststofftransport in Rohrleitungen 2.3 Partikeleigenschaften 2.4 Typisierung der Partikelbewegung mit der Strömung 2.5 Einfluss der Turbulenz auf die Partikelbewegung in horizontaler Rohrleitung 2.6 Transportzustände in horizontaler Rohrleitung 2.7 Transportzustände in vertikaler Rohrleitung 2.8 Stopfgrenze 2.9 Kräftebilanz an einem Feststoffpartikel 2.10 Dimensionsanalyse 2.10.1 Auflistung der Einflussgrößen 2.10.2 Anzahl der dimensionslosen π-Parameter 2.10.3 Auswahl der Hauptvariablen 2.10.4 Ermittlung der π-Parameter 2.10.5 Form des funktionellen Zusammenhangs 3 Bemessungsansätze des hydraulischen Transports 3.1 Stand des Wissens 3.1.1 Feststofftransport in horizontaler Rohrleitung 3.1.2 Feststofftransport in geneigter Rohrleitung 3.1.3 Feststofftransport in vertikaler Rohrleitung 3.1.4 Die kritische Gemischgeschwindigkeit in horizontaler Rohrleitung 3.1.5 Die kritische Gemischgeschwindigkeit in geneigter Rohrleitung 3.1.6 Weitere Rechenmodelle 3.2 Erweiterung des Energiegesetzes auf Gemischströmung 3.2.1 In horizontaler Rohrleitung 3.2.2 In geneigter Rohrleitung 3.2.3 In vertikaler Rohrleitung 4 Experimentelle Untersuchungen 4.1 Aufbau der ersten Versuchsanlage 4.2 Messtechnik 4.3 Umbau der Versuchsanlage 4.4 Untersuchungsmaterial 4.5 Experimentelles Verfahren 5 Numerische Simulationen mit ANSYS-Fluent 5.1 Grundlagen der Mehrphasenströmungen 5.2 Auswahl des numerischen Modells 5.3 Das Granular-Euler-Modell 5.3.1 Die Erhaltungsgleichung 5.3.2 Die kinetische Theorie der dispersen Phase 5.4 Modellvalidierung 6 Vorstellung der Untersuchungsergebnisse 6.1 Ergebnisse der experimentellen Untersuchungen in horizontaler Leitung 6.1.1 Experimentelle Untersuchungen zum Energieverlust 6.1.2 Experimentelle Untersuchung zu der kritischen Geschwindigkeit 6.2 Ergebnisse der hydronumerischen Untersuchungen in horizontaler Rohrleitung 6.2.1 Randbedingungen 6.2.2 Numerische Lösung und Konvergenz 6.2.3 Parameteranalyse anhand eigener Versuche 6.2.4 Numerische Untersuchungen zur Wechselwirkung zwischen den hydraulischen Kenngrößen 6.3 Ergebnisse der experimentellen Untersuchungen in vertikaler Leitung 6.4 Ergebnisse der experimentellen Untersuchungen in geneigter Rohrleitung 6.4.1 Experimentelle Untersuchungen zum Energieverlust 6.4.2 Experimentelle Untersuchung zu der kritischen Gemischgeschwindigkeit 6.5 Ergebnisse der numerischen Untersuchungen in geneigter Rohrleitung 7 Fehleranalyse und weitere Betrachtungen 7.1 Degradierung des Feststoffes 7.2 Die Abnutzung der Pumpe 7.3 Abrieb und Durchbruch der Rohrleitungen 7.4 Die Instabilität des Systems bei geringen Geschwindigkeiten 7.5 Messabweichung des Durchflussmessers 7.6 Fehlerquelle bei der Untersuchung der kritischen Gemischgeschwindigkeit 7.7 Fortbewegung der Feststoffe bei Geschwindigkeiten unterhalb vcrit 7.8 Einfluss der Transportkonzentration auf den Arbeitspunkt der Pumpe 8 Zusammenfassung Literaturverzeichnis Anhang<br>The present work deals with the hydraulic transport characteristics of sand-water mixtures in pipelines to determine hydraulic gradients and the deposition-limit velocity (critical velocity). For this purpose, the transport process in various pipe configurations (horizontal, inclined and vertical) was investigated on a physical model at the Hubert Engels Laboratory of the Institute of Hydraulic Engineering and Technical Hydromechanics of the Technical University of Dresden. Three sand fractions were used (0.1 - 0.5 mm, 0.71 - 1.25 mm and 1.4 - 2.2 mm) with particles density of ρF = 2650 kg/m³. The aim of the investigations was to develop a model for calculating the head loss percent-age of the disperse phase in terms of total energy loss, especially for the heterogeneous and quasi-homogeneous transport regime correlating to the influence quantities (density, concentration, particle diameter, etc.). Another important aspect for this work was to consider the critical velocity and to set up a corresponding calculation approach for this parameter. The deposition-limit velocity represents the transition from sliding Bed transport to heterogeneous transport. In the next step, the solids transport process was investigated numerical with ANSYS-Fluent. The focus of the modeling was the determination of the wall boundary condition for the disperse phase, with help of which the physically measured energy losses could be re-stored. The simulations were performed with the Euler Granular model. Here, the solid is considered to be the second continuum, and its rheological properties were calculated by expanding the kinetic theory of gases to disperse phase (KTGF).:Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Symbolverzeichnis Indexverzeichnis 1 Einleitung und Zielsetzung 2 Grundlagen des hydraulischen Feststofftransports in Rohrleitungen 2.1 Das Energiegesetz 2.2 Feststofftransport in Rohrleitungen 2.3 Partikeleigenschaften 2.4 Typisierung der Partikelbewegung mit der Strömung 2.5 Einfluss der Turbulenz auf die Partikelbewegung in horizontaler Rohrleitung 2.6 Transportzustände in horizontaler Rohrleitung 2.7 Transportzustände in vertikaler Rohrleitung 2.8 Stopfgrenze 2.9 Kräftebilanz an einem Feststoffpartikel 2.10 Dimensionsanalyse 2.10.1 Auflistung der Einflussgrößen 2.10.2 Anzahl der dimensionslosen π-Parameter 2.10.3 Auswahl der Hauptvariablen 2.10.4 Ermittlung der π-Parameter 2.10.5 Form des funktionellen Zusammenhangs 3 Bemessungsansätze des hydraulischen Transports 3.1 Stand des Wissens 3.1.1 Feststofftransport in horizontaler Rohrleitung 3.1.2 Feststofftransport in geneigter Rohrleitung 3.1.3 Feststofftransport in vertikaler Rohrleitung 3.1.4 Die kritische Gemischgeschwindigkeit in horizontaler Rohrleitung 3.1.5 Die kritische Gemischgeschwindigkeit in geneigter Rohrleitung 3.1.6 Weitere Rechenmodelle 3.2 Erweiterung des Energiegesetzes auf Gemischströmung 3.2.1 In horizontaler Rohrleitung 3.2.2 In geneigter Rohrleitung 3.2.3 In vertikaler Rohrleitung 4 Experimentelle Untersuchungen 4.1 Aufbau der ersten Versuchsanlage 4.2 Messtechnik 4.3 Umbau der Versuchsanlage 4.4 Untersuchungsmaterial 4.5 Experimentelles Verfahren 5 Numerische Simulationen mit ANSYS-Fluent 5.1 Grundlagen der Mehrphasenströmungen 5.2 Auswahl des numerischen Modells 5.3 Das Granular-Euler-Modell 5.3.1 Die Erhaltungsgleichung 5.3.2 Die kinetische Theorie der dispersen Phase 5.4 Modellvalidierung 6 Vorstellung der Untersuchungsergebnisse 6.1 Ergebnisse der experimentellen Untersuchungen in horizontaler Leitung 6.1.1 Experimentelle Untersuchungen zum Energieverlust 6.1.2 Experimentelle Untersuchung zu der kritischen Geschwindigkeit 6.2 Ergebnisse der hydronumerischen Untersuchungen in horizontaler Rohrleitung 6.2.1 Randbedingungen 6.2.2 Numerische Lösung und Konvergenz 6.2.3 Parameteranalyse anhand eigener Versuche 6.2.4 Numerische Untersuchungen zur Wechselwirkung zwischen den hydraulischen Kenngrößen 6.3 Ergebnisse der experimentellen Untersuchungen in vertikaler Leitung 6.4 Ergebnisse der experimentellen Untersuchungen in geneigter Rohrleitung 6.4.1 Experimentelle Untersuchungen zum Energieverlust 6.4.2 Experimentelle Untersuchung zu der kritischen Gemischgeschwindigkeit 6.5 Ergebnisse der numerischen Untersuchungen in geneigter Rohrleitung 7 Fehleranalyse und weitere Betrachtungen 7.1 Degradierung des Feststoffes 7.2 Die Abnutzung der Pumpe 7.3 Abrieb und Durchbruch der Rohrleitungen 7.4 Die Instabilität des Systems bei geringen Geschwindigkeiten 7.5 Messabweichung des Durchflussmessers 7.6 Fehlerquelle bei der Untersuchung der kritischen Gemischgeschwindigkeit 7.7 Fortbewegung der Feststoffe bei Geschwindigkeiten unterhalb vcrit 7.8 Einfluss der Transportkonzentration auf den Arbeitspunkt der Pumpe 8 Zusammenfassung Literaturverzeichnis Anhang

Os sistemas de esgotos urbanos são classificados em separador absoluto, separador parcial e unitário, conforme o grau de separação que existe no recolhimento dos esgotos sanitários e das águas de drenagem pluviais. Embora a diretriz das cidades brasileiras seja a adoção do sistema separador, na prática ocorre uma importante contribuição das águas de chuvas nas vazões afluentes às estações de tratamento de esgotos como produto das interconexões existentes, clandestinas ou não, entre as redes de esgotos sanitários e pluviais. Esta pesquisa investigou os impactos causados pelos choques de carga orgânica e hidráulica provocados pela contribuição das águas pluviais no desempenho de reatores UASB e seu tempo de recuperação depois de sofrer estes choques. Três reatores de acrílico de 17 litros foram construídos no Laboratório de Saneamento Ambiental do IPH. Os reatores trataram esgoto sintético simulando a concentração de DQO de esgotos domésticos a uma temperatura de 30 ± 2 °C. Um dos reatores serviu de controle enquanto os outros dois receberam choques de carga hidráulica (aumento de vazão) e diluição de matéria orgânica, simultaneamente. A operação dos reatores foi dividida em três fases: 1°) aclimatação, 2°) choques individuais de carga hidráulica e diluição de matéria orgânica 3°) simulação de uma temporada de chuva. Os choques tiveram um efeito deletério na qualidade do efluente, ocasionando quedas na eficiência de remoção de DQO total de até quase 600% e de 200% na eficiência de remoção de DQO dissolvida nos choques mais severos. Também constatou-se perda de parte da biomassa presente nos reatores devido ao aumento excessivo na velocidade ascensional do fluxo. Esta perda tornou-se menor com o tempo devido à pressão de seleção exercida pelos sucessivos choques. O pH dentro dos reatores manteve-se sempre perto da faixa neutra, porém apresentou-se um consumo de alcalinidade que se prolongou por até três vezes o tempo de detenção hidráulica após o início dos choques, devido provavelmente ao aumento na concentração de ácidos graxos voláteis no efluente. A produção de biogás também diminuiu como conseqüência da diluição da carga orgânica afluente. Os efeitos e o tempo de recuperação após os choques dependeram da sua duração e magnitude, sendo que os choques mais severos (menor concentração de matéria orgânica afluente e TDH) causaram maior deterioração na qualidade do efluente e requereram maior tempo de recuperação.Já no que diz respeito às características físico-químicas e biológicas do lodo, verificou-se que os choques causaram diminuição no tamanho médio dos grânulos do lodo e na sua velocidade de sedimentação, provavelmente devido ao aumento das forças abrasivas v provocado pelo incremento na velocidade ascensional do fluxo. De igual modo, a atividade metanogênica específica também apresentou quedas devidas, provavelmente, à diluição da carga orgânica afluente e à diminuição do tamanho das partículas do lodo.<br>Sewerage systems are classified as separate, partially separated, or combined, according to the degree of separation that exists in the collection of municipal wastewater and stormwater runoff. Although the official policy of brazilian cities is for adoption of the separate system, the actual scenario shows that there are significant contributions of stormwater to the flows that are transported to the wastewater treatment plants, partly because of the inappropriate interconnections that exist between the systems. This research investigated the impacts that organic and hydraulic shock loads brought by stormwater contributions have on the efficiency of UASB reactors, as well as the recovery time after the ending of the shocks. Three 17-liters acrylic reactors were built in the Environmental Technology Laboratory at IPH. The reactors were fed with synthetic wastewater prepared to resemble the organic content of wastewater. All reactors were operated at a temperature of 30 ± 2ºC. One of the reactors was used as control while the other two received hydraulic shocks with organic matter dilution, simultaneously. Reactor’s operation was divided in three phases: 1º) star-up, 2º) single organic and hydraulic shocks, and 3º) rain season simulation, with multiple shocks.Shocks have a deleterious effect on the reactor effluent quality. In the most severe cases, drops in removal efficiencies reached up to 200% and 600% for dissolved and total DQO, respectively. Reactor biomass washout occurred due to the increasing upflow velocity. This loss was dampened by the selective pressure exerted by successive shocks. pH in the reactors remained in the neutral range, although alkalinity was consumed for as long as three detention times, probably due to an increase in the concentration of volatile fatty acids in the liquid. Dilution also caused a decrease in biogas production. Recovery time depended on the duration and intensity of the shock, with more severe shocks demanding more time for recovery. The impacts of the shocks on the treatment efficiency depended on duration, organic dilution rate and flowrate increase. Longer shocks, with higher flowrates and dilution rate resulted in the worst conditions for the reactor. Shocks loads caused a decrease in the mean size of the sludge granule, as well as in their sedimentation velocities, probably because of an increase in the abrasive forces acting on the granules brought by the upflow velocity. The specific methanogenic activity also decreased with higher dilution and smaller sized sludge granules.

<p>This thesis presents predictive models for important variables concerning eutrophication effects in lakes. The keystone is a dynamic phosphorus model based on ordinary differential equations. By calculating mass fluxes of phosphorus into, within and out from a lake, the concentrations of different forms of phosphorus in different compartments of the lake are estimated.</p><p>The dynamic phosphorus model is critically tested and several improvements are presented, including two new compartments for colloidal phosphorus, a sub-model for suspended particulate matter (SPM) and new algorithms for lake outflow, water mixing, diffusion, water content and organic content of accumulation sediments are implemented. Predictions with the new version show good agreement against empirical data in five tested lakes.</p><p>The sub-model for SPM uses the same driving variables as the basic phosphorus model, so the inclusion of this model as a sub-model does not require any additional variables. The model for SPM may also be used as a separate model giving monthly predictions of suspended particulate matter in two water compartments and one compartment with SPM available for resuspension in ET-sediments.</p><p>Empirical data from Lake Erken (Sweden) and Lake Balaton (Hungary) are used to evaluate the variability in settling velocity of SPM. It is found that the variability is substantial and may be accounted for by using a dimensionless moderator for SPM concentration. Empirical data from accumulation area sediments in Lake Erken are used to develop a model for the dynamics of phosphorus sedimentation, burial and diffusion in the sediments. The model is shown to provide reasonable monthly predictions of four functional forms of phosphorus at different sediment depths.</p><p>Simulations with the lake phosphorus model using two different climate scenarios indicate that lakes may respond very differently to climate change depending on their physical character. Lake Erken, with a water retention time of 7 years, appears to be much more sensitive than two basins of Lake Mälaren (Sweden) with substantially shorter retention times. The implication would be that in eutrophic lakes with long water retention times, eutrophication problems may become serious if the future becomes warmer. This will be important in contexts of lake management when remedial measures against lake eutrophication have to be taken.</p>

L’objectif de cette thèse est de proposer un modèle d’érosion diffuse qui intègre les principaux processus de ce phénomène (détachement, transport, sédimentation) et qui prend en compte l’interaction des gouttes de pluie avec ces processus. Dans un premier temps, nous avons établi une loi de détachement par la pluie qui inclut l’effet des gouttes et celui de l’épaisseur de la lame d’eau qui couvre la surface du sol. Pour obtenir cette loi, une étude numérique avec le logiciel Gerris a permis de modéliser les cisaillements créés par l’impact des gouttes sur des épaisseurs de lame d’eau variables. Ces cisaillements estiment la quantité de sol détaché par chaque goutte. Nous avons montré, à travers une étude probabiliste, que les gouttes sont quasiment indépendantes lors du détachement. Les détachements de l’ensemble des gouttes sont donc sommés pour établir la loi de détachement pour la pluie. Par ailleurs, l’étude probabiliste a montré la possibilité d’une forte interaction entre les gouttes de pluie et les particules en sédimentation. Par conséquent, pour le processus de transport-sédimentation, nous avons privilégié une approche expérimentale. Cette étude a révélé que l’effet des gouttes de pluie est d’augmenter la vitesse de sédimentation des particules. Enfin, nous avons proposé un nouveau modèle d’érosion qui généralise plusieurs modèles d’érosion de la littérature et décrit l’évolution des concentrations en sédiments avec des effets linéaires et non-linéaires. Selon le choix des paramètres du modèle, celui-ci peut représenter l’érosion diffuse et concentrée à l’échelle du bassin versant, le transport par charriage dans les rivières ou encore le transport chimique. L’intégration du modèle dans le logiciel de ruissellement FullSWOF est aussi réalisée<br>The aim of this work is to formulate an interrill erosion model. This model should take into account the main erosion processes (detachment, transport and sedimentation) and the interaction of raindrops during these processes. First we develop a law for rainfall detachment that includes the effects of the raindrops and the water layer thickness at the soil surface. We use the Gerris software to simulate the shear stresses created by the impacts of raindrops at the soil surface. These shear stresses allow to evaluate the quantity of soil detached by each raindrop. We have shown with a probabilistic approach that raindrops are almost independent during soil detachment. Then by summing all the raindrops detachments we obtain the rainfall detachment law. Futhermore the probabilistic study has revealed the possibility of a strong interaction between raindrops and settling particles. So, we used specific laboratory experiments to investigate the particles transport and sedimentation processes. These experiments show that the effect of raindrops is to increase the particles settling velocity. Finally, we propose a new erosion model which encompasses previous literature erosion models and that can describe the behavior of sediments concentrations with linear and non-linear behaviors. The model is able to simulate interrill and rill erosions at the watershed scale, bedload transport in rivers and chemical transfer. The integration of the model in the FullSWOF runoff software is also carried out

Les contaminants, dissouts ou adsorbés sur les particules, sont principalement délivrés au milieu marin par les fleuves. La dynamique sédimentaire constitue alors un proxy de la dynamique de ces contaminants. Cette thèse s'inscrit dans le projet ANR AMORAD, et se focalise sur la dynamique du matériel particulaire délivré par le Rhône au Golfe du Lion (Méditerranée nord-occidentale), principal contributeur d'apports solides au Golfe (80 % des sédiments). Alors que des études antérieures ont permis de bien représenter les processus au niveau du fond, les processus régissant les comportements des matières en supension (MES), majoritairement rencontrées dans le panache turbide du Rhône, sont encore mal apréhendés. En vue de mieux décrire la dynamique de ces MES et d'améliorer les modèles hydrosédimentaires existants, l'objectif est de mieux caractériser ces particules. À cette fin, un vaste jeu de données issu de capteurs déployés in situ (données collectées pour 12 campagnes en mer, réalisées de 2011 à 2016) a été exploité, permettant d’obtenir une vision 2D verticale mais seulement ponctuelle (spatialement et temporellement). De façon complémentaire, une base de données d'images satellitaires (donnée couleur de l'eau du capteur MERIS-300m acquise entre 2002 et 2012), offrant une vue plus synoptique et long terme mais uniquement en surface, a été exploitée. Le jeu de données d'images satellitaire (plus de 800 images) a été traité de façon innovante par l'application d'un traitement semi-automatique permettant l'extraction de différentes métriques du panache turbide du Rhône (e.g. aire, limites d'extension, forme, centres géométriques, concentrations). La distribution spatiale et les caractéristiques physiques des MES telles que leur concentration dans l'eau, leur diamètre médian ou encore leur vitesse de chute ont été étudiées et estimées en fonction des différents forçages hydrométéorologiques actifs sur la zone d'étude (e.g. débit du Rhône, vents dominants). Un nouveau modèle hydrosédimentaire reposant sur le couplage du modèle hydrodynamique MARS-3D et du module sédimentaire multiclasse MIXSED a été configuré et les données in situ et satellitaires ont pu être mobilisées afin de contraindre la vitesse de chute des sédiments, paramètre clef de la modélisation de la dynamique hydrosédimentaire<br>Contaminants, which can be dissolved in water or adsorbed on particles, are mainly delivered to the coastal environment by rivers. Thus, sediment dynamics reperesent a relevant proxy of contaminants dynamics. ThisPhD thesis is part of the ANR AMORAD project, of which one workpackage focuses on the fate of sediments in the coastal environment. This work focuses on the dynamics of Rhône River sediments in the Gulf of Lions (north-western mediterranean), this river delivering 80 % of the sediments of the Gulf. While previous studies over the area allowed a better understanding of physical processes at the water-sediment interface, processes driving suspended particulate matter (SPM) dynamics are still poorly understood. To better describe this SPM dynamics and improve hydrosedimentary models, the aim is to better characterize these particles. To this end, a large dataset collected from in situ deployed sensors (data collected for 12 field campaigns, conducted from 2011 to 2016) was analyzed to get a 2D vertical but ponctual view (both spatially and temporally). Complementary, a satellite images dataset (MERIS-300m ocean colour archive from 2002 to 2012) was built in order to get a long term and more synoptic view (but limited to surface).This dataset (more than 800 images) was originaly studied, applying a semi-empirical process to extract various Rhône River turbid plume metrics (e.g. area of extension, south-east-westernmost points, shape, centroids, SPM concentrations). Plume metrics and physical properties of SPM such as their concentration in water, their median diameter or their settling velocity were investigated regarding the different hydrometeorological forcings (e.g. Rhône River discharge, prevailing winds). A new hydrosedimentary model, based on the coupling of the 3D hydrodynamical model MARS-3D and the sedimentary module MIXSED, was set and ocean color and in situ data were used to constrain the settling velocity of particles, key parameter of hydrosedimentary modelling

Le procédé à boues activées conventionnel est le plus utilisé pour traiter les eaux usées urbaines. La biomasse (boues activées) croît et forme des flocs biologiques qui doivent être séparés de l'eau traitée. Cette opération s'effectue généralement par gravité dans un clarificateur. Les particules de boues activées sont sujettes à différents comportements de décantation, selon leurs propriétés. La simulation des clarificateurs est probablement le domaine d'application le plus développé de la mécanique des fluides numérique appliquée au traitement des eaux usées. Cependant, l’ensemble des mécanismes de sédimentation ne sont pas toujours représentés de manière complète. Le présent travail a consisté dans un premier temps en l’ajout du mécanisme de compression en tant que terme de second ordre dans l'équation différentielle aux dérivées partielles décrivant la sédimentation de la boue. Les paramètres du modèle ainsi modifié ont fait l’objet d’une identification basée sur des données expérimentales acquises en système fermé. Ensuite, des simulations d’un clarificateur à taille réelle ont permis de valider le modèle sur la base des hauteurs de voiles de boues mesurées et des profils de vitesse des particules. Les petites installations de traitement sont caractérisées par des conditions d’entrée très dynamiques (variations de débits, cycles de marche/arrêt). Ainsi, le modèle validé a été utilisé pour simuler ces conditions particulières de fonctionnement<br>The conventional activated sludge process is the most widely used process for treating urban wastewater. Biomass (activated sludge) grows and forms biological flocs that must be separated from the treated water. This is usually performed by gravity in a clarifier. Activated sludge particles are subject to different settling processes, depending on their properties. Clarifier simulation is probably the most developed field of application for computational fluid dynamics applied to wastewater treatment. However, all sedimentation mechanisms are not always fully represented. This work began by adding the compression mechanism as a second-order term in the partial differential equation describing sludge sedimentation. The parameters of the modified model were identified based on experimental data from a closed system. Then, simulations of a full-scale clarifier allowed the model to be validated based on the measured sludge blanket height and particle velocity profiles. Small treatment plants are characterized by very dynamic inlet conditions (flow variations, on/off cycles). Thus, the validated model was used to simulate these operating conditions<br>El proceso de lodos activados convencional para el tratamiento del agua residual es el más usado para remover los contaminantes del agua residual urbana. La biomasa (lodo activado) crece y forma flocs biológicos que deben ser separados del agua tratada. Normalmente esta acción se realiza por medio de la gravedad en un sedimentador. Las partículas de lodo activado pueden someterse a diferentes comportamientos de sedimentación dependiendo de sus propiedades. La simulación de los clarificadores secundarios es probablemente el área más desarrollada para la aplicación de la mecánica de fluidos computacional en el tratamiento del agua residual. Sin embargo, no todos los mecanismos de sedimentación están siempre representados en un modelo. Este trabajo presenta la adición de la compresión como un término de segundo orden en una ecuación diferencial parcial que describe la sedimentación del lodo. La identificación de los parámetros del modelo se realizó a través de experimentos realizados en un sistema cerrado. Luego, simulaciones en un clarificador a escala real permitieron validar el modelo basándose en la medición de la altura del manto de lodos y los perfiles de velocidad de las partículas. Estaciones depurados de pequeña capacidad se caracterizan por una dinámica discontinua de las condiciones de entrada (variaciones en el caudal, ciclos de encendido/apagado). Así el modelo validado se usó para simular estas condiciones operacionales

碩士<br>國立臺南大學<br>環境生態研究所碩士班<br>99<br>It has been demonstrated that phosphorus is a limiting factor for the growth of phytoplanktons in reservoirs and lakes. High phosphorus concentration can cause algae growth and eutrophication in reservoirs. Since settling characteristic can greatly affect the concentration of phosphorous in a water body, determination of phosphorous settling velocity is critical in assessing the trophic state of a water body. In this study, historical water quality data were analyzed for Tseng-Wen and Nan-Hua Reservoirs, while in-situ determination has also been conducted in Nan-Hua and Hu-Tou Pei Reservoirs to explore phosphorus settling velocity in water bodies of different trophic states. Analysis of historical data indicated that concentrations of total phosphorus, chlorophyll a, and ortho-phosphorous in Nan-Hua and Tseng-Wen Reservoirs followed a trend of reducing concentration from upstream to downstream. In temporal trend, concentrations of both total and ortho- phosphorus were higher in spring and summer, while higher chlorophyll a concentrations were observed in summer and fall. In-situ determination of phosphorous settling velocity was conducted in Nan-Hua and Hu-Tou-Pei Reservoirs, representing moderately eutrophic and a highly eutrophic water bodies. Results showed that average total phosphorus settling flux was 38.95 mg/m2/day for Nan-Hua Reservoir and 90.87 mg/m2/day for the Hu-Tou-Pei Reservoir, which were typical for eutrophic freshwater reservoirs. Average settling velocities were 1.19 m/day and 0.59 m/day respectively. Higher organic phosphorous proportion was also observed in the sediments of the highly eutrophic Hu-Tou-Pei Reservoir than the moderately eutrophic Nan-Hua Reservoir.

碩士<br>國立臺灣大學<br>海洋研究所<br>103<br>We use a 3D hydrodynamic model (ROMS) to investigate the structure and mass distribution of hyperpycnal flows in the Gaoping submarine canyon. We focus on the sensitivity to sediment settling velocity (ws = 0 to 1 mm/s). To simulate hyperpycnal flow events, suspended sediment concentration of 60 g/L and river discharge of 3000 m3/s is specified at the Gaoping river mouth. The numerical model is first validated by comparing model-derived sea-level, vertical profiles of velocity and temperature against observations. Basic flow characteristics is reasonably reproduced by the model. From our numerical experiments with ws of 0, 0.1, and 0.5mm/s, hyperpycnal discharge plunges when entering the coastal ocean. The suspended sediment is concentrated near the bottom (within 1 m) and is transported offshore following the Canyon topography. These features are consistent with hyperpycnal flow. However, when ws exceeds 1 mm/s such that the sediment advective distance (D=U* Ts, U is average outflow speed, Ts is the settling time) becomes shorter than the distance between river mouth and canyon mouth, most of the hyperpcnal discharge deposits on continental shelf before reaching the steep canyon head. We use a simple mass balance model to illustrate the importance of resuspension/erosion processes in maintaining hyperpycnal flow in the canyon. The simple model is based on a balance of mass input from the river and mass removal due to deposition. Without considering resuspendsion processes, the simple model significantly underpredicts the suspended mass in the canyon, suggesting that appreciable amount of sediment is resuspended by the hyperpycnal flow itself to maintain its gravitational force. We also quantify the offshore penetration of the hyperpycnal flow. The bottom-intensified velocity structure (i.e. nose-shaped) obtained from prior laboratory experiments is used as a reference. The penetration distance is defined as the location beyond which the hyperpycnal flow deviates from the nose-shaped structure. The estimated penetration distance is consistent with the center of mass. The positions where hyperpycnal flow loses the nose-shape structure and where divergence of mass flux elevates appear to lock in with topographic features (such as canyon bending, slope changes). These results suggest that the structure and the fate of hyperpycnal flow in the Gaoping cayon is greatly influenced by the canyon topography.

碩士<br>國立臺灣大學<br>土木工程學研究所<br>105<br>The uncertainty of the sediment transport cannot be neglected according to the turbulent bursting. The study adapted two methods to calculated the uncertainty of sediment transport and one method to improved uncertainty analysis method. The first method (first topic) is based on the advection diffusion equation which is in diffusion region. The uncertain of the movement of the sediment particle can be simulated by stochastic particle tracking method(SPTM). By Markov Chain, SPTM can be simplified and calculated the uncertainty of the sediment concentration efficiency. First, the uncertainty of the spatial and temporal sediment concertation caused by the particle size can be calculated. With a similar particle size, the change of temporal sediment concertation is explicit. Secondly the uncertain of the equilibrium sediment concentration caused by fluctuation of turbulence will be estimated. The result of sediment concertation by proposed model is validated against the experiment data and can better describe sediment concentration than the deterministic model (Rouse profile). The first method is more suitable to described the sediment concentration under condition of suspended load. The second method is focus on the trajectory of the sediment particle in non-diffusion region. The particle is force by lifting, gravity, drag, Buoyancy forces. To calculated the foundation force, the more accuracy flow velocity is created by gram charily expansion which considering four order moment of the fluctuation. The bed condition in the study adapt a rebound process. The particle will collide with stochastic particle alignment. In this (second) topic, firstly, the saltation length and height calculated by the proposed model will be validated by experiment. The saltation length and height in the smooth bed is higher than that in rough bed. Secondly the sediment concentration under suspend and bed load condition is compared with Rouse profile and experiment data. Third the supdiffusion and subdiffusion will be discussed. In the first and second topic, the uncertainty of the sediment concentration is calculated by the Monte Carlo Simulation which is extremely time consuming. In the third topic, two new methods are provided. The results simulated by two methods are compared with Simpson method. The first method is derived from the point estimated method(PEM) which only used two or three points. By increasing the accuracy of the simulated result by PEM, the adequative method is used to increase the simulation points. Secondly, Gram Charlier expansion and Hermit Gauss Quadrature is adapted to calculated by uncertainty in the second method. First method is suitable when the simulation points are few and the distribution of the random variable is known. The second method is suitable when the statistical moment of the random variable is only known. The converge of the second method is faster than the other two methods.Key words: Particle tracking method, Markov chain, higher order flow field, Modified Hermite Gauss integral, Adequative Hong’s method.

Yes<br>Sedimentation processes are fundamental to solids/liquid separation in water and wastewater treatment, and therefore a robust understanding of the settlement characteristics of mass fractal aggregates (flocs) formed in the flocculation stage is fundamental to optimized settlement tank design and operation. However, the use of settling as a technique to determine aggregates’ traits is limited by current understanding of permeability. In this paper, we combine experimental and numerical approaches to assess settling velocities of fractal aggregates. Using a non-intrusive in situ digital image-based method, three- and two-dimensional fractal dimensions were calculated for kaolin-based flocs. By considering shape and fractal dimension, the porosity, density and settling velocities of the flocs were calculated individually, and settling velocities compared with those of spheres of the same density using Stokes’ law. Shape analysis shows that the settling velocities for fractal aggregates may be greater or less than those for perfect spheres. For example, fractal aggregates with floc fractal dimension, Df ¼ 2.61, floc size, df > 320 μm and dp ¼ 7.5 μm settle with lower velocities than those predicted by Stokes’ law; whilst, for Df ¼ 2.33, all aggregates of df > 70 μm and dp ¼ 7.5 μm settled below the velocity calculated by Stokes’ law for spheres. Conversely, fractal settling velocities were higher than spheres for all the range of sizes, when Df of 2.83 was simulated. The ratio of fractal aggregate to sphere settling velocity (the former being obtained from fractal porosity and density considerations), varied from 0.16 to 4.11 for aggregates in the range of 10 and 1,000 μm, primary particle size of 7.5 μm and a three-dimensional fractal dimension between 2.33 and 2.83. However, the ratio decreases to the range of 0.04–2.92 when primary particle size changes to 1.0 μm for the same fractal dimensions. Using the floc analysis technique developed here, the results demonstrate the difference in settlement behaviour between the approach developed here and the traditional Stokes’ law approach using solid spheres. The technique and results demonstrate the improvements in understanding, and hence value to be derived, from an analysis based on fractal, rather than Euclidean, geometry when considering flocculation and subsequent clarification performance<br>Rodrigo B. Moruzzi is grateful to São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP) Grant 2017/19195-7 for financial support and to CNPq for the fellowship Grant 301210/2018-7.

The settling velocity of suspended particulate matter (SPM) is a key parameter controlling deposition processes and its accurate determination has been regarded as a top priority in improving numerical models of cohesive sediment transport. Because SPM occurs predominantly as aggregates of organic and inorganic particles in cohesive coastal systems, an in situ quantification of settling velocity is essential. The available techniques to measure the settling velocity of aggregates in the field include: Owen tubes and similar, settling columns equipped with optical sensors, laser systems or video cameras as well as acoustics and holographic systems. None of these techniques is able to directly measure the massconcentration of SPM or its settling velocity mass distribution in situ. In this work, a new instrument (SEDVEL – Sedimentation Velocity) was developed to directly and automatically measure SPM mass of cohesive sediments in situ, from which the mass/concentration distribution of settling velocities can be determined. This instrument consists of an underwater balance (resolution of 0.01 g) placed inside a settling tube, which directly measures the variation in time of the immersed weight of particulate matter (PM) as it settles on a plate located at the tube bottom under quiescent conditions. SEDVEL operates underwater and automatically withdraws water samples ― deployment periods of a few days. The design of SEDVEL and its components are described as well as the procedure adopted in its calibration and data analysis. Results of the assessment of the instrument performance in the laboratory and in the field are analysed. SEDVEL presented consistent and reproducible results when tested in the laboratory. It was able to reproduce the initial particles concentrations ranging from 7 to 200 mg l-1 (r2 = 0.9, p < 0.01) in 13 laboratory experiments. Results also suggested that some particle reflocculation induced by the settling column can take place for concentrations higher than 50 mg l-1. Field trials, carried out in Cleveland Bay at Berth 11 (Townsville Harbour, Australia) and at the Pier (Strand Beach, Townsville, Australia), showed that SEDVEL reproduced the general tendency of the measured SPM concentrations in 42 cycles of measurement (r2 = 0.65, p < 0.01). At the Pier, settling velocities presented a main mode of relatively slow-settling particles/flocs within 0.09 ≤ Ws < 0.5 mm s-1, and usually a second mode of 1.5 ≤ Ws < 3.0 mm s-1. The settling dynamics at this location were mainly determined by erosion and deposition of sediment particles from and to the bottom close to the headland as well as by advection of offshore floc populations during the rising tide. At Berth 11, aggregates were composed mainly of microflocs of low-density and slow settling velocities (0.09 ≤ Ws < 0.12 mm s-1). The estimated mean density of flocs, 40% smaller than the density of inorganic particles, represented better the settling mode measured at this site. SEDVEL constituted a novel idea for measuring settling velocities in situ, and therefore, a considerable amount of development, prototyping and testing was required. Compared with other automated instruments for measuring settling velocities in situ, SEDVEL has a relatively simple working principle, calibration and data analysis procedure. It is also unique in furnishing direct and automated in situ measurements of immersed mass and massconcentration of SPM. The main problems associated with the current SEDVEL version are: zero position drifting among the different cycles of the measurement and from its initial setup, possible floc break-up due to the pumping system used in the water replacement, errors associated with a non-homogeneous distribution of particles on the balance plate and with the definition of the zero position. A general assessment of SEDVEL potential limitations, and improvements to be achieved in future versions of the instrument, are described.

This thesis is part of a project funded by the Minerals Management Service (MMS) (now Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE)) to study the use of epoxy to plug hurricane damaged wells. Some of the wells destroyed by hurricanes are damaged to an extent that vertical intervention from the original wellhead is not possible. These wells have to be plugged to prevent future flows through the well to protect the environment. Cement is usually the preferred plugging material because it is very cheap compared to other materials like epoxy. However, cement can easily get contaminated by sea water or brines present in wells as completion fluids. Therefore, to be able to use cement it has to be placed at the bottom of the well by drilling an offset well all the way to the bottom of the original well. Epoxy, on the other hand, being much more chemically stable can be placed at the very top of the well and let to settle by gravity without fearing contamination. Therefore, in wells described above, epoxy can be much more economical than cement. Placing epoxy at the top of a well and letting it settle by gravity can also be more economical than using cement in other situations such as in a leaking annulus of a well where circulation in that annulus is not possible, or if a well that has been previously plugged starts leaking again after the rig has been removed. Placing epoxy in the manner described can be achieved without using a rig and therefore, would be much more economical than cement. One of the most important factors in this process is to be able to predict the settling velocity of the epoxy to be able to determine the required setting time of the epoxy so that the epoxy does not set prematurely. In addition, it is important to evaluate whether the epoxy can successfully settle to the bottom and how much of it will adhere to the pipe walls while freefalling. This thesis aims to design, build and run an experimental setup that would help study the settling velocity of epoxy. Some experiments were conducted to assess the effect of different parameters that might affect the settling velocity of the epoxy such as the epoxy’s density, the annulus size and the inclination angle. The results show that the settling velocity was proportional to the epoxy’s density. Also the settling speed was almost double in experiments done at an angle compared to experiments done at vertical position. The annulus size did not have any clear effect on the settling speed. The adhesion to the pipe walls was found to be proportional to the epoxy’s viscosity and angle of inclination and was inversely proportional to the annulus size.

The amount and type of cohesive sediment found in gravel river beds can have important implications for the health of aquatic biota, surface/groundwater interactions and water quality. Due to landscape disturbances in the Elbow River watershed, increased sediment fluxes have negatively impacted fish habitat, water quality and water supply to the City of Calgary. However, little is known about the source of cohesive sediment and its interaction with gravel deposits in the Elbow River. This research was designed to: 1) quantify the transport properties (critical shear stress for erosion, deposition, porosity, settling velocity, density) of cohesive sediment and 2) evaluate the potential for coarse gravel to entrap cohesive sediment in the Elbow River. A 5m annular flume was used to conduct erosion and deposition experiments using plane and coarse bed conditions. The critical shear stress for deposition and erosion of the Elbow River cohesive sediments was 0.115Pa and 0.212Pa, respectively. The settling velocity of the cohesive sediment had an inverse relationship between floc size and settling velocity for larger flocs, due to a decrease in floc density with increased size. Cohesive sediment moved from the water column into the gravel bed via the coupling of surface and pore water flow. Once in the gravel bed, cohesive sediments were not mobilized from the bed because the shear produced by the flume was less than the critical shear to mobilize the gravel bed. Using a model developed by Krishnappan and Engel (2006), an entrapment coefficient of 0.2 was determined for the gravel bed. Entrapment coefficients were plotted against substrate size, porosity and hydraulic conductivity, demonstrating a relationship between entrapment coefficient and these variables. It was estimated that 864kg of cohesive sediment is stored in the upper 0.08m of a partially submerged point bar in the Elbow River. Accordingly, when flow conditions are sufficient to mobilize the gravel bed and disturb the amour layer, cohesive materials may be entrained and transported into the Glenmore Reservoir, where it will reduce reservoir capacity and may pose treatment challenges to the drinking water supply.

No<br>Sedimentation of non-homogeneous systems is the typical phenomenon indicating the physical instability as a key measure to the quality control of the preparation products. Currently, the determination methods for the sedimentation of non-homogeneous preparations are based on manual measurement or semi-quantitative observation, lacking of either automation or quantitative dynamic analysis. The purpose of this research was to realize automatic and quantitative monitoring of the sedimentation dynamics for non-homogenous systems as suspension, emulsions at laboratory level. Non-contact measurement method has been established to determine the sedimentation behaviors in a standard quartz tube for sedimentation, with internal diameter and height 23 mm and 215 mm, respectively, with controlled temperature and light intensity. As high performance camera has been equipped, the sedimentation images with high spatial and temporal resolution could be acquired, which can continuously capture sedimentation images with the resolution of 2048 x 2048 pixel at a maximum rate of 60 slides/s. All the pictures were processed to extract the luminance matrix top-down along the fixed vertical midline of each picture, which implied sedimentation characteristics of the system at the moment the picture was taken. Combining all the luminance matrixes along vertical middle lines of the pictures, a time-luminance matrix profile was obtained. Digital image processing techniques were used to eliminate interference and establish a three-dimensional surface model of the sedimentation dynamics. Then, the derivative mutation algorithm has been developed for the intelligent identification of sedimentation interface with threshold optimization so as to quantitatively analyze the sedimentation dynamics with visualization. The sedimentation curve and sedimentation dynamic equation of the non-homogeneous system were finally outputted by numerical fitting. The methodology was validated for great significance in determinations of small volume samples, parallel control multiple batches, and long period of time automatic measurement. (C) 2015 Elsevier B.V. All rights reserved.