Lake restoration and management strategies focus on reducing the negative impacts of enriched or polluted inflows. These strategies become of paramount importance when lakes are used for recreational and/or drinking water purposes. Long term control of eutrophication and turbidity problems associated with large inflow loads is usually oriented to catchment management. Although it has been suggested that this is the correct long term approach, public concerns usually require a short term solution. In addition, due to political and economic costs related to changes in catchment management, in-lake restoration technologies have been emerging as a viable pretreatment option, complementary to water treatment plants, both reducing the operational costs of the water treatment plant and ameliorating the water residing in the lakes. This research investigates the effects of two in-lake technologies on the dynamics of inflowing rivers, where basin shape plays a significant role. The three lakes in this study suffer from eutrophication combined with a distinctive water quality problem: from turbidity in Silvan Reservoir (Australia), to heavy metal loads in Coeur d'Alene Lake (USA) and industrial wastes in Lake Como (Italy). Firstly, the influence of basin morphology, wind speed, and wind direction on the fate and transport of two rivers flowing into the L-shaped Coeur d'Alene Lake was examined, and it was shown that transport and mixing patterns in a lake can be greatly influenced by the shape of the lake, leading to important consequences for the plankton ecology in the lake. Secondly, in Silvan Reservoir we investigated the potential to modify the basin shape using vertical barriers, increasing the retention time and hence the barrier capacity to microbial pollution. A final in-lake technology was tested for Lake Como, using a downward pointing impeller to remove polluted water from the coastal margin. Lessons from these three examples indicate that there is significant potential for in-lake remediation at relatively low cost, over relatively short timescales.

Natural stream systems contain a variety of flow geometries which contain flow separation, turbulent shear layers, and recirculation zones. This work focuses on streams with dead zones. Characterized by slower flow and recirculation, dead zones are naturally occurring cutouts in stream banks. These dead zones play an important role in stream nutrient retention and solute transport. Previous experimental work has focused on idealized dead zone geometries studied in laboratory flumes. This work explores the capabilities of computational fluid dynamics (CFD) to investigate the scaling relationships between flow parameters of idealized geometries and the time scales of transport. The stream geometry can be split into two main regions, the main stream flow and the dead zone. Geometric parameters of the dead zone as well as the bulk stream velocity were varied to determine a scaling relationship for the transport time scales. These flow geometries are simulated using the RANS turbulence model with the standard k-ω closure. The standard first order dead zone model is expanded to a two region model to accommodate the multiple time scales observed in the simulation results. While this model currently has limited predictive capability, it provides physical insight into the functional dependence of the dead zone time scales. LES is used to evaluate the performance of the Reynolds Averaged Navier-Stokes (RANS) turbulence model and to describe the anisotropic turbulence characteristics. The differences between the time averaged flow field for Large Eddy Simulation (LES) and RANS was determined to have a significant impact on passive scalar transport. / Graduation date: 2012

Conical spouted beds have been commonly used for drying suspensions, solutions and pasty materials. They can also be utilized in many other processes, such as catalytic partial oxidation of methane to synthesis gas, coating of tablets, coal gasification and liquefaction, pyrolysis of sawdust or mixtures of wood residues. The main objectives of this work include both the experimental research and mathematical modelling of the conical spouted bed hydrodynamics. For experimental research, pressure transducers and static pressure probes were applied to investigate the evolution of the internal spout and the local static pressure distribution; optical fibre probes were utilized to measure axial particle velocity profiles and voidage profiles; the step tracer injection technique using helium as the tracer and thermal conductivity cells as detectors was used to investigate the gas mixing behaviour inside a conical spouted bed. It was found that many factors might affect calibration of the effective distance of an optical fibre probe. Therefore, a new calibration setup was designed and assembled, and a comprehensive sensitivity analysis was conducted to calibrate the optical probes used in this study. For mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. By introducing an adjustable parameter, this model is capable of predicting the total pressure drop under different operating conditions, and estimating axial superficial gas velocity profiles and gauge pressure profiles. A mathematical model based on characteristics of conical spouted beds and the commercial software FLUENT was also developed and validated using measured experimental data. The proposed new CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. At stable spouting states, simulation results agree very well with almost all experimental data, such as static pressure profiles, axial particle velocity profiles, voidage profiles etc. A comprehensive sensitivity analysis was also conducted to investigate the effect of all possible factors on simulation results, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term. The proposed new CFD model was also used successfully to simulate gas mixing behaviours inside a conical spouted bed, and simulate cylindrical packed beds as well as cylindrical fluidized beds in one code package.

Conical spouted beds have been commonly used for drying suspensions, solutions and pasty materials. They can also be utilized in many other processes, such as catalytic partial oxidation of methane to synthesis gas, coating of tablets, coal gasification and liquefaction, pyrolysis of sawdust or mixtures of wood residues. The main objectives of this work include both the experimental research and mathematical modelling of the conical spouted bed hydrodynamics. For experimental research, pressure transducers and static pressure probes were applied to investigate the evolution of the internal spout and the local static pressure distribution; optical fibre probes were utilized to measure axial particle velocity profiles and voidage profiles; the step tracer injection technique using helium as the tracer and thermal conductivity cells as detectors was used to investigate the gas mixing behaviour inside a conical spouted bed. It was found that many factors might affect calibration of the effective distance of an optical fibre probe. Therefore, a new calibration setup was designed and assembled, and a comprehensive sensitivity analysis was conducted to calibrate the optical probes used in this study. For mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. By introducing an adjustable parameter, this model is capable of predicting the total pressure drop under different operating conditions, and estimating axial superficial gas velocity profiles and gauge pressure profiles. A mathematical model based on characteristics of conical spouted beds and the commercial software FLUENT was also developed and validated using measured experimental data. The proposed new CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. At stable spouting states, simulation results agree very well with almost all experimental data, such as static pressure profiles, axial particle velocity profiles, voidage profiles etc. A comprehensive sensitivity analysis was also conducted to investigate the effect of all possible factors on simulation results, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term. The proposed new CFD model was also used successfully to simulate gas mixing behaviours inside a conical spouted bed, and simulate cylindrical packed beds as well as cylindrical fluidized beds in one code package.

One of the most important boron minerals, colemanite is reacted with sulfuric acid to produce boric acid. During this reaction, gypsum (calcium sulfate dihydrate) is formed as a byproduct. In this study, the boric acid production was handled both in a batch and four continuously stirred slurry reactors (4-CFSSR&rsquo / s) in series system. In this reaction system there are at least three phases, one liquid and two solid phases (colemanite and gypsum). In a batch reactor all the phases have the same operating time (residence time), whereas in a continuous reactor all the phases may have different residence time distributions. The residence time of both the reactant and the product solids are very important because they affect the dissolution conversion of colemanite and the growth of gypsum crystals. The main aim of this study was to investigate the dynamic behavior of continuous flow stirred slurry reactors. By obtaining the residence time distribution of the solid and liquid components, the non-idealities in the reactors can be found. The experiments performed in the continuous flow stirred slurry reactors showed that the reactors to be used during the boric acid production experiments approached an ideal CSTR in the range of the stirring rate (500-750 rpm) studied. The steady state performance of the continuous flow stirred slurry reactors (CFSSR&rsquo / s) in series was also studied. During the studies, two colemanites having the same origin but different compositions and particle sizes were used. The boric acid production reaction consists of two simultaneous reactions, dissolution of colemanite and crystallization of gypsum. The dissolution of colemanite and the gypsum formation was followed from the boric acid and calcium ion concentrations, respectively. The effect of initial CaO/ SO42- molar ratio (1.00, 1.37 and 2.17) on the boric acid and calcium ion concentrations were searched. Also, at these initial molar ratios the colemanite feed rate was varied (5, 7.5, 10 and 15 g/min) to change the residence time of the slurry. Purity of the boric acid solution was examined in terms of the selected impurities, which were the magnesium and sulfate ion concentrations. The concentrations of them were compared at the initial molar ratios of 1.00 and 1.37 with varying colemanite feed rates. It was seen that at high initial CaO/ SO42- molar ratios the sulfate and magnesium ion concentrations decreased but the calcium ion concentration increased. The gypsum crystals formed in the reaction are in the shape of thin needles. These crystals, mixed with the insolubles coming from the mineral, are removed from the boric acid slurry by filtration. Filtration of gypsum crystals has an important role in boric acid production reaction because it affects the efficiency, purity and crystallization of boric acid. These crystals must grow to an appropriate size in the reactor. The growth process of gypsum crystals should be synchronized with the dissolution reaction. The effect of solid hold-up (0.04&ndash / 0.09), defined as the volume of solid to the total volume, on the residence time of gypsum crystals was investigated and the change of the residence time (17-60 min) on the growth of the gypsum was searched. The residence time at each reactor was kept constant in each experiment as the volumes of the reactors were equal. The growth of gypsum was examined by a laser diffraction particle size analyzer and the volume weighted mean diameters of the gypsum crystals were obtained. The views of the crystals were taken under a light microscope. It was observed that the high residence time had a positive effect on the growth of gypsum crystals. The crystals had volume weighted mean diameters of even 240 &micro / m. The gypsum crystal growth model was obtained by using the second order crystallization reaction rate equation. The residence time of the continuous reactors are used together with the gypsum growth model to simulate the continuous boric acid reactors with macrofluid and microfluid models. The selected residence times (20-240 min) were modeled for different number of CSTR&rsquo / s (1-8) and the PFR. The simulated models were, then verified with the experimental data. The experimentally found calcium ion concentrations checked with the concentrations found from the microfluid model. It was also calculated that the experimental data fitted the microfluid model with a deviation of 4-7%.

Waste stabilisation ponds (WSP) are a popular form of wastewater treatment worldwide, especially for rural-based manufacturing plants and small community sewage treatment. Ponds offer a robust and operationally simple technology, which are inexpensive where land is available, and have the potential to provide a considerable degree of treatment. However the continued use of WSP is being undermined by their inconsistent performance relative to current discharge requirements, particularly with respect to suspended solids, pathogen and nutrient removal. In a climate of increased public awareness of pollution, and the ever more stringent environmental protection regulations, novel pond designs need to be developed, and existing ponds retro-fitted, to improve their performance. This dissertation investigated the hydraulic modelling of non-mechanically mixed ponds, and produced a modelling framework from which improved pond designs could be evaluated. Computational fluid dynamics (CFD) simulations were used to develop models which were able to predict the hydraulics of arbitrarily shaped, non-mechanically mixed ponds under controlled conditions. The models represent an important departure from traditional pond modelling techniques, which are based on either historical experience or simple hydraulic and reaction models. The CFD approach overcomes the main limitation of these models, as it accounts for spatial variations of parameters within a pond such as fluid velocity, or pollutant concentration. This allows for the prediction of pond hydraulics based on the pond geometry (such as inlet configuration, pond shape or baffle placement), pond inlet boundary conditions and the fluid properties. Thus CFD models allow the rapid investigation of the effect of design modifications on pond performance. The WSP models were designed using a two stage process. The first stage, a steady state simulation, calculated the velocity and turbulence fields for the pond; the second stage, a transient numerical tracer, utilised the underlying steady state results to calculate the advection and diffusion of a tracer species. The species concentration at the outlet was then integrated to produce residence time distributions (RTD) and other quantities which were used to characterise the pond hydraulics, and quantitatively compare the models with experimental results to assess the pond¡¦s performance. These techniques could be applied to any numerical pond flow model, and are a discerning test of the model¡¦s consistency. RTD generated from two-dimensional (2-D) CFD simulations were compared to experimental RTD derived by Mangelson and Watters (1972). In one of the three geometries simulated, the 2-D CFD model successfully predicted the experimental RTD. However, the flow patterns in the other two geometries were not well described, due to the difficulty of representing a three dimensional (3-D) inlet in the 2-D CFD model. As no general relationship could be found for approximating a 2-D inlet in 3-D, full 3-D simulations were used to model the unsuccessful cases. The 3 D simulations provided much improved results, predicting all the major features of the RTD over the first residence time, and matching exponential decay of the RTD after this period. Due to the uncertainty in the exact experimental inlet dimensions, a range of inlet depths were simulated. This showed that the CFD model was sensitive to changes in the inlet configuration, and using the appropriate inlet depth, the simulated RTD matched the experimental results well. A sensitivity analysis of the effect of the inlet turbulent boundary conditions and tracer molecular diffusivity for the k-ƒÕ turbulent model, showed the RTD was insensitive to these properties, thereby confirming similar results in related systems (Benelmouffok, 1989; De Vantier and Larock, 1987). This is significant for future pond modelling, as these properties are difficult to measure experimentally or predict reliably. Tracer studies were performed in this dissertation on five full-scale pond systems. In Tasmania three identical sewage ponds with different inlet and baffle configurations were investigated. However wind conditions in this locality masked any effect of these modifications. Tracer studies were also performed on sugar mill ponds near Mackay. While the models predicted qualitative consistent RTD results, they did not match the experimentally measured RTD due to uncontrolled environmental mixing factors and the long residence times of these ponds. A preliminary investigation of the effect of wind mixing was undertaken by imposing a velocity to the top surface of the model. These results confirmed the strong influence of even small wind velocities due to the large surface area of the ponds. Practical experience has indicated that the pond hydraulics are often the limiting factor in pond performance. Both experimental and simulation results have confirmed this through the presence of short circuiting and dead zones within the pond. Three baffle designs were assessed, all of which improved the pond hydraulics by either dispersing the inlet jet, or utilising the jet to generate specific pond mixing. Finally the work in this thesis has highlighted a number of other areas for future investigation. These include reservations over the use of RTD to characterise full-scale pond hydraulics, and considerations regarding the most efficient use of the inlet mixing in ponds. The hydraulic models developed in this dissertation can be extended to include solids, stratification and reaction models, which would enable the direct validation of the model based on physical or chemical parameters. In addition, a coupled flow and reaction model would provide a tool that could be used to truly optimise pond performance. This offers the possibility of tailoring the design of ponds for specific reactions, such as improved biological nutrient removal.

For this dissertation I studied flow and transport in low gradient Florida streams. Chapter 2 is a statewide analysis of long-term variations in stream discharge. The results from Chapter 2 suggest that changes in mean annual stream discharge are controlled by the Atlantic Multi-Decadal Oscillation (AMO). During the warm phase, mean annual discharge decreases in central Florida and increases in north Florida. The opposite is true during the cool phase, with mean annual discharge increasing in central Florida and decreasing in north Florida. This pattern is observed for both components of stream discharge, base flow and runoff. The following two chapters are part of an analysis of particle transport in low gradient mangrove estuaries. Chapter 3 describes the use of a numerical model to simulate the hydrodynamics of a coastal reach of the Shark River, Florida Everglades and the development of a Lagrangian particle tracking model. The particle tracking model uses the output from the hydrodynamic model to simulate the movement of particles released within the model domain. In Chapter 4, the hydrodynamic and particle tracking models are used to estimate the historical particle residence time in the Shark River Slough Estuary (SRSE) and determine the key factors controlling particle residence time and fate in mangrove estuaries. The mean and median residence times in the model domain are 16 and 8 hours, respectively, and 60% of all particles exit the model domain downstream, towards the Gulf of Mexico. Particle residence time varies greatly depending on the particle release location and timing. The residence time is significantly lower for particles released in the middle of the channel and for particles released during the wet season, spring tides or during upstream flows. Additionally, there is a decreasing trend in mean particle residence time from 1997 through 2017, mirroring an increasing trend in mean annual water levels in the SRSE. The combined results of this dissertation show the impact that a variable climate can have on stream flow and particle transport.

WIEGAND, Mario Cesar. Eutrofização de açudes no semiárido: vulnerabilidade e biomanipulação. 2015. 144 f : Tese (doutorado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Programa de Pós-Graduaçao em Engenharia Agrícola, Fortaleza-CE, 2015. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-08-08T12:50:54Z No. of bitstreams: 1 2015_tese_mcwiegand.pdf: 6034718 bytes, checksum: 6cf2d5454be8ed60f64e12de8f40159c (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-08-08T12:51:28Z (GMT) No. of bitstreams: 1 2015_tese_mcwiegand.pdf: 6034718 bytes, checksum: 6cf2d5454be8ed60f64e12de8f40159c (MD5) / Made available in DSpace on 2016-08-08T12:51:28Z (GMT). No. of bitstreams: 1 2015_tese_mcwiegand.pdf: 6034718 bytes, checksum: 6cf2d5454be8ed60f64e12de8f40159c (MD5) Previous issue date: 2015 / With the increasing water demand and the concern that the supply can not meet that consumption, it is increasingly necessary conserving the available water, in quantity and (especially) quality. This conservation is especially important in semi-arid regions such as the Brazilian Northeast (NEB), where water is scarce. The main causes of pollution (water waste) in smal reservoirs (in the semiarid) are: the animal presence on the reservoir margins, where they defecate and urinate; domestic wastewater (e.g. laundry water, water used in the household); removal of riparian vegetation, which protects reservoirs against silting and organic matter input; presence of outdoor trash; and use of agricultural inputs that contribute to the process of eutrophication. In turn, the main feature of eutrophication process is excess nutrients in water bodies, with considerable growth fluctuations and eventual death of algae and weeds. With the continuity of the process, there is the accumulation of dead matter in the deepest region of these environments, causing the increase in bacterial metabolism that causes the death of fish and other organisms by oxygen lack or reduction, plus the toxin production by blue-green algae, which are harmful to human health and to the biota at large. Therefore, studies that estimating the nutrient input become urgent. With such studies, strategies for the restoration of eutrophic reservoirs can be implemented. Among such strategies there is biomanipulation. Biomanipulation is a biological strategy based in the use of aquatic organisms (e.g. fish), to balance the aquatic ecosystem. Hypothesis: "Is it possible to treat an eutrophic reservoir using biomanipulation?” If so, what are the particularities of biomanipulating a reservoir the semiarid region, especially considering its rich ictiological diversity, with predominantly omnivorous fish population and where fish reproduction occurs throughout the year? Therefore, in order to answer these questions, this thesis was divided in two parts, the first comparing the state of eutrophication and its probable causes in two tropical reservoirs, one in wet climate (La Juventud, Cuba) and the other in semiarid climate (Marengo, Brazil). After estimating the trophic state of the two reservoirs in rainy and dry seasons, we evaluated the influence of hydrology and of land use on reservoir trophic level. It was found that the semi-arid tropical reservoir was eutrophic, while the reservoir on humid climate was mesotrophic. Considering that there is similar land use in the two basins and that, in the rainy season, the nutrient input in the wet basin is considerably higher than the nutrient input in the semiarid basin, the higher trophic state of the semi-arid basin is surprising. The variable that best explains this phenomenon is the water residence time, which directly influences the phosphorus residence time in the reservoir. The high water residence time in the semiarid basin reservoir (three times that of the reservoir in humid climate) is due as much to the low runoff coefficient (93 versus 595 mm per year in the reservoir in humid climate) as to the excessive water evaporation in the semiarid reservoir (1.2 times that of the reservoir in humid climate). These results indicate that semiarid reservoirs are more vulnerable to eutrophication than reservoirs in humid climate in summer periods and, therefore, the management of their basins should be more restrictive to nutrient production; as to the second part, it reflects the particularities of the biomanipulation issue. Thus, in experimental 2000L mesocosms, six treatments were outlined to evaluate the effects of two omnivorous species (Nile tilapia – Oreochromis niloticus and piaba – Astyanax bimaculatus) on eutrophic waters. It was also taken into account the sediment influence as a nutrient source for the eutrophication process. The treatments were: 1. Oreochromis niloticus without sediment; 2. Oreochromis niloticus with sediment; 3. Oreochromis niloticus plus Astyanax bimaculatus without sediment; 4. Oreochromis niloticus plus Astyanax bimaculatus with sediment; 5. Astyanax bimaculatus without sediment and; 6. Astyanax bimaculatus with sediment. Each test was conducted for 45 days. Water samples were taken every 15 days. Tests were performed for total phosphorus, orthophosphate, chlorophyll a and total nitrogen (TN being tested only at the beginning and at the end of each treatment). Testing for dissolved oxygen concentration, temperature, pH and Secchi transparency was done in situ. The sediment was tested for pH, ion content, nutrients (such as Ca2+, Mg2+, Al3+, iron and assimilable phosphorous) and particle size. In order to estimate the treatment water trophic level, the trophic state index (TSI) of Toledo Jr. et al. (1983) was applied. Differences between the TSI values were calculated acording to Carlson (1991). Also, the fish were tested for total phosphorus content. The results suggested that systems containing tilapia showed low efficiency in the recovery of eutrophic waters. The average TSI obtained in these tests showed that the water remained eutrophic. Treatments with piabas showed better efficiency in controlling eutrophication. The average TSI obtained in these tests showed that the water went from eutrophic to mesotrophic. However, the results found by TSI differences do not confirm if the piabas (Astyanax bimaculatus) were alone responsible for this. The same results could be also influenced by light and temperature. As to the total phosphorus content of specimens coming from treatments, tilapia showed higher bioaccumulation than that shown by piabas. However, the results were antagonic to those obtained from specimens taken directly from nature. In short, two omnivorous species were tested for their biomanipulation potential; the Oreochromis nilotucus, which, due to its behavior, proved to be an agent of water quality disruption and the Astyanax bimaculatus, which was shown as being potentially viable for future biomanipulation research. / Com o crescente aumento da demanda de água e a preocupação de que a oferta estabelecida não consiga suprir esse consumo, torna-se necessária a conservação da quantidade e, principalmente, da qualidade da água disponível, especialmente em regiões semiáridas como o Nordeste brasileiro (NEB), onde esse recurso é escasso. As principais causas da poluição da pequena açudagem no semiárido são: a presença de animais nas margens dos açudes, onde defecam e urinam; os efluentes domésticos (e.g. lavagem de roupas, águas utilizadas nas atividades domésticas); o desmatamento da mata ciliar, que protegeria os açudes contra o assoreamento e a entrada de matéria orgânica; a presença de lixo ao ar livre; e o uso de insumos agrícolas que contribuem para o processo de eutrofização. Por sua vez, a principal característica do processo de eutrofização é o excesso de nutrientes nos corpos d’água, apresentando grandes oscilações de crescimento e mortandade de algas e macrófitas. Através da continuidade do processo, há o acúmulo de matéria morta na região mais profunda desses ambientes, causando o aumento do metabolismo de bactérias que ocasiona a mortandade de peixes e outros organismos pela falta ou diminuição de oxigênio, acrescentando-se, ainda, o fato da produção de toxinas, por algas cianofíceas, ser prejudicial à biota e à saúde humana. Diante disso, estudos que estimem o aporte de nutrientes tornam-se impostergáveis para que, a partir daí, medidas que auxiliem na recuperação de reservatórios eutrofizados possam ser tomadas. Entre tais medidas há a biomanipulação. Esta é uma ferramenta biológica e o seu preceito basilar consiste na utilização de organismos aquáticos (e.g. peixes), no sentido de melhorar a qualidade do ecossistema aquático. Pergunta de Partida: É possível tratar um açude eutrofizado usando biomanipulação No caso afirmativo, quais as particularidades para um açude no semiárido, principalmente no que tange a sua ictiofauna a qual apresenta maior riqueza de espécies, estoques com dominância de peixes onívoros e onde a reprodução dos peixes ocorre durante todo o ano? Assim sendo, com o escopo de responder as aludidas questões a presente tese foi dividida em duas partes: a primeira compara o estado de eutrofização e suas prováveis causas em dois reservatórios tropicais, um em clima úmido (La Juventud, Cuba) e o outro em clima semiárido (Marengo, Brasil). Após estimar o estado trófico dos dois reservatórios nas estações chuvosa e seca, avaliou-se a influência hidrológica e de uso do solo sobre o grau de trofia dos lagos. Concluiu-se que o lago tropical semiárido encontrava-se eutrófico, enquanto que o lago úmido encontrava-se mesotrófico. Considerando-se que há similitude entre os usos do solo nas duas bacias e que, na estação chuvosa, o aporte de nutrientes na bacia úmida é consideravelmente superior ao da bacia semiárida, o maior estado trófico da bacia seca sur-preende. A variável que melhor explica esse fenômeno é o tempo de residência da água, que influencia diretamente o tempo de residência do fósforo no lago. O elevado tempo de residência da água na bacia semiárida (três vezes superior ao do lago úmido) deve-se tanto ao reduzido coeficiente de escoamento superficial (93 versus 595 mm anuais na bacia úmida) quanto à excessiva evaporação da água armazenada no reservatório seco (1,2 vezes superior à do reservatório úmido). Esses resultados indicam que lagos semiáridos são mais vulneráveis à eutrofização que lagos úmidos nos períodos de estio e que, portanto, o manejo de suas bacias deve ser mais restritivo à produção de nutrientes; consoante a segunda parte, essa retrata em particular a questão da biomanipulação. Nesse sentido, em mesocosmos experimentais de 2.000 L, foram delineados seis tratamentos para avaliar o efeito de duas espécies onívoras (tilápia do Nilo – Oreochromis niloticus e piaba – Astyanax bimaculatus) sobre águas eutróficas. Observou-se, ainda, a influência do sedimento como fonte de nutriente para o processo de eutrofização. Os tratamentos avaliados foram: 1. Oreochromis niloticus sem sedimento; 2. Oreochromis niloticus com sedimento; 3. Oreochromis niloticus + Astyanax bimaculatus sem sedimento; 4. Oreochromis niloticus + Astyanax bimaculatus com sedimento; 5. Astyanax bimaculatus sem sedimento e; 6. Astyanax bimaculatus com sedimento. Cada ensaio foi conduzidos por 45 dias. Coletas d’água foram realizadas a cada 15 dias. Foram feitas análises de fósforo total, ortofosfato, clorofila a e nitrogênio total, sendo este analisado somente no início e final de cada tratamento. As concentrações de oxigênio dissolvido, temperatura, pH e transparência de Secchi foram feitas in situ. No sedimento realizou-se análises de pH, concentração de íons e nutrientes tais como Ca2+, Mg2+, Al3+, ferro, fósforo assimilável e análise granulométrica. Para se estimar o grau de trofia da água dos tratamentos foi aplicado o índice de estado trófico (IET) de Toledo Jr. et al. (1983). Diferenças entre os IETs foram calculadas conforme Carlson (1991). Fez-se, ainda, a análise do teor de fósforo total nos peixes. Os resultados sugeriram que os sistemas que continham tilápias do Nilo apresentaram baixa eficiência na recuperação de águas eutrofizadas. O IET médio obtido nesses ensaios mostrou que a água manteve-se sempre eutrófica. Os tratamentos com piabas mostraram uma melhor eficiência no controle da eutrofização. O IET médio obtido nesses ensaios revelou que a água passou de eutrófica para mesotrófica, ao final dos mesmos. Contudo, os resultados encontrados pelas diferenças dos IETs não confirmam que as piabas foram sozinhas as principais responsáveis por esse fato. O mesmo pode ter sido influenciado, também, pela luz e pela temperatura. Quanto ao teor de fósforo total, para os espécimes advindos dos tratamentos, a tilápia apresentou bioacumulação superior ao encontrado nas piabas. Todavia, os resultados foram antagônicos para os espécimes oriundos diretamente da natureza. Em suma, foram avaliados aspectos da biomanipulação de duas espécies onívoras; o Oreochromis nilotucus que, em função de seu comportamento, revelou-se um agente perturbador da qualidade da água e o Astyanax bimaculatus, a qual se apresentou potencialmente viável para futuras pesquisas de biomanipulação.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Potentially toxic cyanobacterial blooms have been frequent in Brazilian lakes and reservoirs, causing economic issues as well as public health risks. In Rio Grande do Sul, a series of five reservoirs in the high course of the River Jacuí form a cascade system. One of the reservoirs, Passo Real, mainly accumulates water for hydroelectrical power generation and also regulates water flow to downstream reservoirs, amongst other uses. Blooms of cyanobacteria have been frequently recorded in this water body, possibly due to the long water residence time, associated to weather conditions and nutrient runoff from intense agricultural activities in the surrounding area. The study described herein aimed to: a) verify patterns of climatic, hydrological and limnological conditions, as well as their relationship with blooms of cyanobacteria; b) describe the yearly circulation regime, and thermal stratification of the water column; c) define the most favourable environmental conditions for the incidence of both dispersive and surface accumulative blooms, and also which species are adapted to each bloom type. 60 phytoplankton samples were taken from Passo Real reservoir between October 2009 and January 2013. Cyanobacteria species were identified and counted to estimate specific density and specific biovolume. Each bloom was assigned to a class: dispersive or surface accumulative. Measurements of solar radiation availability, solar shine, air temperature, rainfall, direction, and velocity of wind were taken, and also weather conditions for the sampling period were recorded. Hydrological (inflow, outflow, altitude, usable volume and residence time) and limnological (transparency, water temperature, pH, electric conductivity, total dissolved solids and chlorophyll-a) variables were also measured. The most influential variables favouring bloom formation were: intense rainfall (>20mm) up to ten days before sampling; air temperature mainly above 15ºC thirty days before sampling; low wind speed (<2m·s-1); high inflow caused by intense rainfall, coinciding with agricultural off season; long water residence time, 132 days on average on months with blooms; warmer temperatures and thermal stratification of the water between October and March. The reservoir was classified as warm monomictic, with only one complete vertical circulation in the winter and thermal stratification in the summer. Dispersive blooms were found when wind speed was above 7,9m·s-1, and surface accumulative blooms occurred when wind speed was below 5,5m·s-1. Species of the genus Dolichospermum were more adapted to produce dispersive blooms, mainly D. crassum and D. circinalis. On the other hand, species of Microcystis were better adapted to surface accumulative blooms, namely M. aeruginosa and M. panniformis, which were also indicator species for this type of bloom. / A ocorrência de florações de cianobactérias potencialmente tóxicas tem sido frequente em lagos e reservatórios no Brasil, ocasionando problemas econômicos e riscos à saúde pública. No Rio Grande do Sul há uma série de cinco reservatórios formando um sistema em cascata no Alto Curso do Rio Jacuí. O reservatório Passo Real compõe esse sistema e tem como principal função acumular água para a geração de energia elétrica e regular vazões para os reservatórios a jusante, servindo também aos demais usos múltiplos da água. Florações de cianobactérias têm sido registradas com frequência neste reservatório, possivelmente pelo longo tempo de residência da água, associado às condições meteorológicas e ao aporte de nutrientes, decorrente da intensa atividade agrícola sobre sua bacia de drenagem. Diante do exposto, objetivouse, neste trabalho: a) verificar a ocorrência de padrões nas condições meteorológicas, hidrológicas e limnológicas e a relação destes com as florações de cianobactérias; b) caracterizar o regime anual de circulação e estratificação térmica da água; e c) determinar quais as condições ambientais para a ocorrência de florações dispersivas e acumulativas em superfície e quais as espécies adaptadas a cada uma das florações. Para isto foram coletadas 60 amostras de fitoplâncton no reservatório Passo Real, entre outubro de 2009 e janeiro de 2013. As cianobactérias foram identificadas, estimada a densidade e o biovolume de cada espécie e as florações foram classificadas como dispersivas ou acumulativas em superfície. Foram determinadas as disponibilidades de radiação solar, brilho solar, temperatura do ar, precipitação pluviométrica, direção e velocidade do vento, assim como as variáveis meteorológicas do período coletado. Variáveis hidrológicas (vazão afluente e defluente, cota altimétrica, volume útil e tempo de residência) e limnológicas (Transparência, temperatura da água, pH, condutividade elétrica, total de sólidos dissolvidos e clorofila-a) foram caracterizadas. Dentre as variáveis meteorológicas, hidrológicas e limnológicas analisadas no período estudado, aquelas que tiveram uma influência favorável para a ocorrência das florações foram: precipitações pluviométricas elevadas (>20mm), registradas até 10 dias antes das coletas; ocorrência de temperatura média do ar diária acima de 15°C nos trinta dias que antecederam as coletas; baixa velocidade do vento (<2m·s-1) nos dias que antecederam as coletas com florações; elevadas vazões afluentes, decorrentes das precipitações elevadas, coincidentes com os períodos de entressafra dos cultivos agrícolas; longo tempo de residência da água, média de 132 dias durante os meses com florações; temperaturas elevadas e estratificação térmica da água no período de outubro a março. O reservatório Passo Real foi classificado como monomítico quente, com apenas uma circulação vertical completa no inverno e estratificação térmica no verão. Florações dispersivas ocorreram em condições de velocidade do vento acima de 7,9m·s-1. Florações acumulativas de superfície ocorreram em condições de velocidade do vento abaixo de 5,5m·s-1. Espécies do gênero Dolichospermum estão melhores adaptadas a formar florações dispersivas, principalmente as espécies D. crassum e D. circinalis. Já espécies do gênero Microcystis estão melhor adaptadas a formar florações acumulativas em superfície, com destaque para M. aeruginosa e M. panniformis, indicadoras deste tipo de floração.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-13T11:23:42Z No. of bitstreams: 2 Dissertação - Luciano de Oliveira - 2018.pdf: 5027134 bytes, checksum: a0469fdd822b10eda9e451f4b9c889b2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-13T11:51:19Z (GMT) No. of bitstreams: 2 Dissertação - Luciano de Oliveira - 2018.pdf: 5027134 bytes, checksum: a0469fdd822b10eda9e451f4b9c889b2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-13T11:51:19Z (GMT). No. of bitstreams: 2 Dissertação - Luciano de Oliveira - 2018.pdf: 5027134 bytes, checksum: a0469fdd822b10eda9e451f4b9c889b2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-07-13 / The chlorination process is the most used to promote disinfection of water intended for human consumption. During the course of chlorinated water in the supply systems, the concentration of free residual chlorine (FRC), whose reaction rate depends on the characteristics of the natural water, occurs. In this work, we studied the decay of the FRC concentration related to the reactions in the liquid mass in two types of water, of subterranean and superficial origin, with different concentrations of organic matter, with the perspective of the influence of the water travel time, dependent on consumption scenarios in real distribution networks, whose supply modules are characterized by low population density and that operate under the initial demand conditions predicted in the projects. The effect of temperature and total organic carbon on the values of mass decay kinetic constants (k b ), used in mathematical models that simulate water quality, was considered. The results showed that the variation of the kb values is directly proportional to the water temperature and the TOC. For initial concentrations close to 1.00 mg.L -1 , the values of the kinetic constants for waters from surface water sources maintained in the temperature ranges of 20 to 21 °C and 30 to 31 °C were respectively 0.0888 day -1 and 0.1200 day -1 for samples collected at the ETA filter output of the DAIAsystem and TOC value of 0.4798 mg.L -1 and equal to and 0.1680 day -1 and 0.3024 day -1 for the samples collected at the filter outputs of the Piancó and TOC system ETA of 0.8750 mg.L - . In samples of groundwater with TOC of 0.1740 mg.L -1 , maintained at the same temperature 1 ranges, the kinetic coefficients were 0.0264 day -1 and 0.0480 day -1 , respectively. Experiments for temperature between 30 and 31 °C and near test duration showed a significant difference in chlorine decay behavior in filtered water samples collected at conventional treatment plants, which showed a residual chlorine loss percentage of 64.81% in relation to the initial concentration of 1.08 mg.L -1 of disinfectant (ETA DAIA) and 33.65% in relation to the initial concentration of 1.05 mg.L -1 of disinfectant (ETA Piancó). Raw water samples from the underground spring lost 14.33% of the initial concentration of 1.04 mg.L -1 . The travel times for the most critical nodes and the minimum disinfectant concentrations at the entrance of the supply modules to comply with the legislation were 40 hours and 0.27-0.28 mg.L -1 for the distribution networks of the condominium Valley of the Birds and 144 hours and 0.30-0.36 mg.L -1 for the condominium Terras Alphaville. / O processo de cloração é o mais utilizado para promover a desinfecção das águas destinadas ao consumo humano. Durante o percurso da água clorada nos sistemas de abastecimento ocorre o decaimento da concentração do cloro residual livre (CRL), cuja taxa de reação depende das características da água natural. Neste trabalho estudou-se o decaimento da concentração do CRL relacionado às reações na massa líquida em dois tipos de águas, de origem subterrânea e superficial, com diferentes concentrações de matéria orgânica, com aperspectiva da influência do tempo de percurso da água, dependente de cenários de consumo em redes de distribuição reais, cujos módulos de abastecimento são caracterizados pelo baixo adensamento populacional e que operam nas condições iniciais de demanda previstas nos projetos. Considerou-se o efeito da temperatura e do carbono orgânico total sobre os valores das constantes cinéticas de decaimento em massa (k b ), utilizadas nos modelos matemáticos que simulam a qualidade da água. Os resultados mostraram que a variação dos valores de k b é diretamente proporcional à temperatura da água e ao COT. Para concentrações iniciais próximas a 1,00 mg.L -1 os valores das constantes cinéticas, para águas provenientes de mananciais superficiais mantidas nas faixas de temperatura de foram, respectivamente, iguais a 0,0888 20 a 21 °C e 30 a 31 °C, dia -1 e 0,1200 dia -1 para amostras coletas na saída do filtro da ETA do sistema DAIA e valor de COT de 0,4798 mg.L -1 e iguais a e 0,1680 dia -1 e 0,3024 dia -1 para as amostras coletas na saídas do filtro da ETA do sistema Piancó e COT de 0,8750 mg.L -1 . Em amostras de água subterrânea com COT de 0,1740 mg.L -1 , mantidas nas mesmas faixas de temperatura, os coeficientes cinéticos foram iguais a 0,0264 dia -1 e 0,0480 dia -1 , respectivamente. Os experimentos para temperatura entre 30 e 31 °C e tempos próximos de duração dos testes demonstraram diferença significativa no comportamento do decaimento do cloro em amostras de água filtrada coletadas nas estações de tratamento convencional que apresentaram porcentagem de perda de cloro residual de 64,81 % em relação à concentração inicial de 1,08 mg.L -1 de desinfetante (ETA DAIA) e 33,65 % em relação à concentração inicial de 1,05 mg.L -1 de desinfetante (ETA Piancó). Amostras de água bruta do manancial subterrâneo perderam 14,33 % da concentração inicial de 1,04 mg.L -1 . Os tempos de percurso para os nós mais críticos e as concentrações mínimas de desinfetante na entrada dos módulo de abastecimento para atendimento à legislação foram iguais a 40 horas e 0,27-0,28 mg.L -1 para as redes de distribuição do condomínio Vale dos Pássaros e 144 horas e 0,30-0,36 mg.L -1 para o condomínio Terras Alphaville.