As a consequence of new coal mining practices, coal preparation plants have been inundated with increased loads of coal and clay particles in their wastewaters. Traditionally, the industry has employed primary sedimentation as the fundamental treatment scheme for these sediment-laden blackwaters. This study was undertaken to determine the effects of a combination of coagulant addition and rapid mixing on the settleability of these particles. After initial testing, aluminum sulfate and two low molecular weight cationic polymers, Cyanamid Magnifloc 513C and Cyanamid 515C, were chosen as primary coagulants for use in this work. An artificial wastewater was prepared from finely powdered (62 to <38 microns) raw coal samples and tap water, after initial tests indicated that typical frothing and/or collector agents had no demonstrable effect on coagulant function. Initially determined optimum coagulant dosages, as well as flocculation and sedimentation times, were kept constant while rapid mix intensities were varied at G values of 330 sec⁻¹, 700 sec⁻¹, 2000 sec⁻¹ and 7000 sec⁻¹ for each sample. Using a combination of residual turbidity and particle size analyses to determine the effectiveness of each rapid mix intensity, it was discovered that only the highest mixing intensities and durations (G(t) values) caused floe disintegration due to overmixing. At the lower G(t) matrices floe formation and settleability was consistently good. When aluminum sulfate was used as a coagulant, the wastewater was tested at a high pH of 8.1 to 8.3 and a low pH of 5.5 to observe floe behavior under different conditions of coagulant mechanism. The test results were similar for both pH values except at the lowest mixing intensities where the high pH samples settled well, resulting in low residual turbidities, but the low pH samples had relatively high turbidities. / Master of Science

Mud makes up a large fraction of sediment transported within rivers to the coasts. Predicting where mud will settle is complicated by the cohesive nature of silts and clays, which can combine to form larger aggregates known as flocs. The size and density, and consequently, the settling velocity, of flocs is highly dynamic and depends on factors such as turbulence levels within the flow and biogeochemical components of the water and sediment. To better predict where mud will deposit, more observations of flocs while in their natural environment is required to better understand the controls on when, where, and to what degree mud is flocculated. However, the need for more field observations is complicated by the dynamic and fragile nature of flocs. This necessitates the need for developing in-situ observation methods to ensure that measured floc sizes are representative of their in-situ size, and not a result of sampling methods. In this thesis, a new instrument for in-situ observation of flocs is presented. In addition, two methods using the data collected from the instrument allow the user to: (1) identify sand within the particle data using a machine learning algorithm, and (2) estimate the mass suspended sediment concentration of the mud and sand fractions of suspended sediment independently. Results from using the instrument in the lowermost Mississippi River reveal differences in floc sizes over the water column, and by season. In addition, a unique observation of flocs in the presence of a salt wedge is presented. Overall, the instrument provided the first known observations of flocs within the Mississippi River, and provides a start to better understanding controls on floc sizes within the fluvial environment. / Master of Science / Flowing water within large rivers carries sediments such as sand and mud to the coasts. Some of the larger sediment carried by rivers can fall to the riverbed if the river does not have enough energy to carry it in the flow. The remaining sediment can be carried to the coasts where it will fall to the bed, providing the material necessary for estuaries or deltas to form and grow. Understanding when and where sediment falls to the bed within rivers, estuaries, and deltas, allows scientists and engineers to predict how these landforms will change over time to better manage them under future climate conditions. Predicting where mud will fall to the bed is particularly difficult because mud has the ability to stick together to form larger aggregates. These aggregates, known as mud flocs, are constantly changing in size depending on the energy in the river and water conditions. As the mud flocs change in size, the speed at which they fall to the bed changes. As such, observing mud flocs while they are in their natural environment is required to understand the conditions under which they form and change in size. This thesis presents a new instrument that can be used to collect images of mud flocs while they are in their natural environment. Results from using the instrument to observe mud flocs in the lowermost Mississippi River are then presented. This new instrument, and observations of mud flocs made with it, provides new insight into mud floc size within the lowermost Mississippi River.

The phenomenon of rapid algal blooms in response to nutrient overloads has been adapted to treat synthetic domestic wastewater. Various algal consortia collected from several eutrophied water bodies were subject to high density algal culture (upto 106-107 cells/mL) and screened for rapid algal growth, pollutant removal, nutrient recovery under mixotrophy and auto-flocculation. When tried in laboratory scale algal ponds, these algal consortia showed growth rates between 0.15 and 1.07 d-1. Results indicate that Chlorella occurred frequently among most consortia although not always the largest in number. While individual algal species varied in growth rates among these consortia, the log phase for most of these algae lasted 4-5 d after which the algal species began to flocculate between day 5-8 at different rates. The flocculation stage lasted between Day 6-8 wherein about 65% cells flocculated during monsoon and over 90% in winter. Although over 90% removal of N and 80% removal of P occurred in this period, the net N and P harvested as flocculated algae ranged from ~30-50% and ~40-70%, respectively. A consortia approach, wherein algal cells auto-flocculate after reaching a high cell density and nutrient removal provides an easy, low energy and sustainable approach to simultaneous wastewater treatment as well as energy and nutrient recovery from domestic wastewaters.

Thesis (PhD (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2009. / In many industrial fermentation processes, Saccharomyces cerevisiae yeast should ideally meet two partially conflicting demands. During fermentation a high suspended yeast count is of paramount importance to maintain a rapid fermentation rate, whilst efficient flocculation should ideally be initiated only on completion of the primary alcoholic fermentation, so as to enhance product clarification and recovery. Most commercial wine yeast strains are non-flocculent, probably because this trait was counter-selected to avoid fermentation problems. In this study, we assessed molecular strategies to optimise the flocculation behaviour of non-flocculent laboratory and wine yeast strains. For this purpose, the chromosomal copies of three dominant flocculation genes, FLO1, FLO5 and FLO11, of a non-flocculent S. cerevisiae laboratory strain (FY23) and two commercial wine yeast strains (BM45 and VIN13) were placed under the transcriptional control of the stationary phase-inducible promoters of the S. cerevisiae ADH2 or HSP30 genes. Under standard laboratory media and culture conditions, all six promoter-gene combinations resulted in specific flocculation behaviours in terms of timing and intensity. The data show that the strategy resulted in the expected and stable expression patterns of these genes in both laboratory and industrial wine yeast strains. Most importantly, the data confirm that inducible expression of the native FLO1 and FLO5 open reading frames, albeit to varying degrees, are responsible for a quantifiable cell-cell adhesion phenotype that can be characterized as a Flo1 flocculation phenotype. On the other hand, we found that inducible expression of the native FLO11 ORF under these conditions resulted in flor/biofilm formation and invasive growth phenotypes. However, the specific impact of the expression of individual dominant FLO genes with regard to characteristics such as flocculation efficiency, cell wall hydrophobicity, biofilm formation and substrate adhesion properties showed significant differences between the commercial strains as well as between commercial and laboratory strains. These adhesion phenotype differences may at least in part be attributed to wine yeast FLO gene open reading frames containing significantly smaller intragenic repeat regions than laboratory strains. The data show that the ADH2 regulatory sequences employed in this study were unsuitable for the purpose of driving FLO gene expression under wine-making conditions. However, HSP30p-based FLO1 and FLO5 wine yeast transformants displayed similar flocculent phenotypes under both synthetic and authentic red wine-making conditions, and the intensities of these phenotypes were closely aligned to those observed under nutrient-rich YEPD conditions. The fermentation activities of HSP30p-based transgenic yeast strains were indistinguishable from that of their parental host wine yeast strains. The chemical composition of wines obtained using transgenic yeast strains were similar to those produced by parental strains. The BM45-derived HSP30p-FLO5 transformant in particular was capable of generating compacted or ‘caked’ lees fractions, thereby providing a distinct separation of the fermented wine product and lees fractions. Furthermore, in this study we report a novel FLO11 induced flocculation phenotype that seems to exclusively develop under authentic red wine-making conditions. This strong FLO11 flocculation phenotype was not wine yeast strain dependant, possessed both Ca2+-dependant and Ca2+-independent flocculation characteristics and was insensitive to inhibition by both glucose and mannose. A distinct advantage of this unique FLO11 phenotype was highlighted in its ability to dramatically promote faster lees settling rates. Moreover, wines produced by HSP30p-FLO11 wine yeast transformants were significantly less turbid than those produced by their wild type parental strains. The benefit of this attractive property is it facilitates simpler and faster recovery of wines and also promotes greater volume recovery of the wine product.

A new continuous one-dimensional sedimentation model incorporating a new continuous flocculation model that considers aggregation and fragmentation processes was derived and tested. Additionally, a new procedure to model sediment particle size distribution (PSD) was derived. Basic to this development were three different parametric models: Jaky, Fredlund and the Gamma probability distribution (GPD) were chosen to fit three different glass micro-spheres PSDs having average particle sizes of 7, 25 and 35 microns. The GPD provided the best fit with the least parameters. The bimodal GPD was used to fit ten sediment samples with excellent results (< 5% average error). A continuous flocculation model was derived using the method of moments for solving the continuous Smoluchowski coagulation equation with fragmentation. The initial sediment PSD was modeled using a bimodal GPD. This new flocculation model resulted in a new general moments’ equation that considers aggregation and fragmentation processes, which is represented by a system of ordinary differential equations. The model was calibrated using a genetic algorithm with initial and flocculated PSDs of four sediment samples and four anionic polyacrylamides flocculants. The results show excellent correlation between predicted and observed values (R2 > 0.9878). A new continuous one-dimensional sedimentation model that resulted in a scalar hyperbolic conservation law was derived from the well-known Kynch kinematic sedimentation model. The model was calibrated using column tests results with glass micro-spheres particles. Two different glass microspheres particle size distributions (PSDs) were used with average diameters of 7 and 37 microns. Excellent values of coefficient of determination (R2 > 0.89, except for one test replicate) were obtained for both the small and large glass micro-spheres PSDs. These results suggest that the proposed sedimentation model can be expanded to model the sedimentation process inside a sediment pond.

Les polymères hydrosolubles sont utilisés dans diverses industries pour permettre la floculation, soit une séparation solide-liquide de particules présentes en suspension colloïdale. Afin de réduire les impacts environnementaux de l’exploitation des sables bitumineux en Alberta, l’industrie est à la recherche de nouveaux moyens et procédés pour traiter les résidus miniers permettant de séparer les matières solides et de récupérer l’eau. L’objectif des travaux présentés est d’améliorer la floculation, la densification et la déshydratation de ces résidus miniers aqueux par de nouveaux polymères synthétiques. Des homopolymères d’acrylamide de différentes masses molaires ont été synthétisés pour étudier l’influence de la masse molaire sur l’efficacité de floculation. Le taux initial de sédimentation (TIS) est le paramètre qui fut utilisé afin de comparer l’efficacité de floculation des différents polymères. Il a été possible de confirmer l’importance de la masse molaire sur l’efficacité de floculation et de déterminer une masse molaire minimale d’environ 6 MDa pour des polyacrylamides, afin d’obtenir l’efficacité de floculation maximale de suspensions colloïdales principalement composées de kaolin. Afin d’étudier l’effet des charges sur l’efficacité de floculation, des polymères anioniques et cationiques ont été synthétisés. Une série de copolymères d’acrylamide et d’acide acrylique ont été synthétisés comme polymères anioniques et deux séries de copolymères ont été synthétisés comme polymères cationiques, soit des copolymères d’acrylamide et de chlorure de diallyldiméthylammonium et des copolymères de 4-vinyl pyridine et de 1-méthyl-4-vinyl pyridinium. Il a été démontré que les charges anioniques des polymères avaient peu d’influence sur l’efficacité de floculation et que leur comportement en présence de sels était différent de ce que prévoyait la littérature. Il a aussi été démontré que les charges cationiques des polymères n’améliorent pas l’efficacité de floculation. Par la suite, des séries de copolymères amphiphiles, avec des monomères d’acrylamide, de N-alkylacrylamides et d’acrylonitrile, ont été synthétisés, pour étudier l’effet du caractère amphiphile sur la déshydratation des résidus miniers. Le pourcentage de déshydratation nette est le paramètre qui fut utilisé afin de comparer l’efficacité de déshydratation des différents polymères. Il a été possible de développer des copolymères amphiphiles qui améliorent l’efficacité de déshydratation par rapport à des homopolymères d’acrylamide. Il ne fut pas possible de déterminer une tendance entre la balance hydrophile/hydrophobe des copolymères amphiphiles et l’efficacité de déshydratation. / Water soluble polymers are extensively used in industry to achieve solid-liquid separations of particles in colloidal suspensions. In a way to reduce the environmental footprint of the mining exploitation, the oil sands industry is searching for new methods to treat tailings resulting from the extraction processes, by separating the solids and recycling the water. The objective of this work is to improve the flocculation and dewatering efficiency of the water-based tailings through the use of new synthetic polymers. Acrylamide homopolymers of different molecular weights were synthetized to study the effect of molecular weight on flocculation efficiency. Initial settling rate (ISR) was the parameter measured to characterize and compare the flocculation efficiencies. The important effect of polymer molecular weight on the flocculation efficiency was confirmed. The minimum molecular weight of polyacrylamide for optimal flocculation efficiency of kaolin colloidal suspensions has been determined to be around 6.8 MDa. To study the effect of charge on flocculation efficiency, anionic and cationic copolymers were synthetized. Copolymers of acrylamide and acrylic acid have been synthetized to study the effect of anionic charge, whereas copolymers of acrylamide and diallyldimethylammonium chloride and copolymers of 4-vinyl pyridine and 1-methyl-4-vinyl pyridinium have been synthetized to study the effect of cationic charge. Anionic copolymers have shown limited effect on the flocculation efficiency and their behaviour in salt solution was revealed to be different than expected from the literature. Cationic copolymers have shown no improvement in the flocculation efficiency. Amphiphilic copolymers were synthetized with acrylamide, N-alkylacrylamides and acrylonitrile monomers to study the effect of amphiphilicity on the dewatering efficiency of tailings. The net water release parameter was measured to compare the dewatering efficiency of the polymers. Amphiphilic copolymers that improve tailings’ dewatering, compared to polyacrylamide, were developed. Thus far, it was not possible to define a trend between hydrophilic/hydrophobic balance and dewatering efficiency of the copolymers.

Une étude de l'impact des mascarets sur le transport des sédiments à l'aide de la simulation numérique a été réalisée dans ce travail. En utilisant le logiciel OpenFOAM CFD, nous avons généré 17 simulations numériques de mascaret avec divers nombres de Froude Fr, allant de 0,99 à 1,66. Deux types de mascarets, ondulant et déferlant, ont été couverts dans ces 17 simulations numériques. Pour les particules sédimentaires non cohésives, nous avons utilisé les équations de Maxey et Riley pour déterminer la trajectoire des particules sédimentaires non cohésives sous l’influence d’un mascaret ondulant. En utilisant le schéma Runge-Kutta du quatrième ordre, une méthode tracker résout les équations de Maxey et Riley qui nécessitent l’information des champs de vitesse au temps t. Pour les particules sédimentaires cohésives, nous avons calculé la distribution des particules sédimentaires cohésives en utilisant un modèle de transport de flocs, présenté par Winterwerp (2001). Dans ce modèle, la concentration volumique solide des sédiments et le diamètre des flocs D sont estimés. Les équations de transport de et D sont résolues en utilisant la méthode des moments présentée par Beaudoin et al. (2002 et 2004). La méthode des moments permet de réduire le temps CPU rendant possible une étude paramétrique. De ce travail, nous avons trouvé une classification du mascaret en fonction du nombre de Froude Fr. Cette classification est également basée sur l’étude menée par Furgerot (2014). Pour un nombre de Froude 1,04 < Fr < 1,43, le mascaret est ondulant. Pour un nombre de Froude 1,43 < Fr < 1,57, le mascaret est partiellement déferlant, similaire à la transition de mascaret définie par Furgerot (2014). Pour un nombre de Froude Fr > 1,57, le mascaret est totalement déferlant. Une analyse de la distribution de la pression a été effectuée par Baddour et Song (1990). Nous avons trouvé que les pressions totales et hydrostatiques d’un mascaret ondulant ont de grandes valeurs sous la crête et le creux. Dans le cas d’un mascaret ondulant, les pressions totales ne sont pas égales à les pressions hydrostatiques. Cela provoque la présence de pressions dynamiques. Dans le cas de mascaret déferlant, les pressions totales deviennent égales aux pressions hydrostatiques. La turbulence réduit les pressions dynamiques. L'impact des mascarets sur le transport de particules sédimentaires non cohésives et cohésives a été étudié dans ce travail. Pour les particules sédimentaires non cohésives, nous avons observé que la trajectoire utilisant l’écoulement généré par OpenFOAM est similaire à la trajectoire de type e proposée par Chen et al. (2010). Des modifications du modèle de Chen ont été faites en incluant les effets de la gravité, l’élévation et l’atténuation pour reproduire des trajectoires de particules non cohésives sous un mascaret ondulant. Nous avons obtenu des relations linéaires entre les paramètres du modèle de Chen modifié (β1 , β2 et β3) et le nombre de Froude Fr. C’est parce que le niveau de la turbulence du mascaret ondulant est faible. L’écoulement induit par mascaret ondulant n’est pas complexe. Ce phénomène physique est quasi linéaire. Le paramètre β1, lié à la célérité avant du mascaret ondulant, diminue lorsque le nombre de Froude Fr augmente. Les paramètres β2 et β3, liés respectivement à l’élévation et à l’atténuation du mascaret déferlant, augmentent lorsque le nombre de Froude Fr augmente. Enfin, pour les particules sédimentaires cohésives, nous avons calculé la distribution de la taille des flocs D sous deux types de mascaret, ondulant et déferlant. Nous avons utilisé le diamètre initial de la particule sédimentaire cohésive d = 4 μm. La taille du floc initial D est égale à 10 μm avec la concentration du floc c = 0,5 kg/m3 . Et nous avons limité la taille maximale du floc à 2000 μm. Nous avons observé que la valeur maximal de la taille des flocs Dmax augmente de façon exponentielle par rapport au nombre de Froude Fr. / A study of the impact of tidal bores on sediment transport by using the numerical simulation has been done in this work. Using OpenFOAM CFD software, we have generated 17 numerical simulations of tidal bores with various values of Froude number Fr, ranging from 0.99 to 1.66. Two types of tidal bores, undular and breaking, have been covered in these 17 numerical simulations. We have studied the behavior of two types of sediment particles, non-cohesive and cohesive sediment particles. For the non-cohesive sediment particles, we have resolved the Maxey and Riley equations to study the influence of undular tidal bores on the trajectory of non cohesive sediment particles. Using the fourth order Runge-Kutta scheme, the method tracker can solve the Maxey and Riley equations that requires the information of velocity fields at time t. For the cohesive sediment particles, we have calculated the distribution of cohesive sediment particles using a floc model that allows to estimate the sediment solid volume concentrationand the diameter of flocs D, presented by Winterwerp (2001). The transport equations of and D are solved using the moment method presented by Beaudoin et al. (2002 and 2004). The moment method has been used because it allows to reduce the CPU time, making feasible a parametric study. From this work, we have found a classification of tidal bores as a function of Froude number Fr. This classification is also based on the study conducted by Furgerot (2014). We have obtained that for a Froude number 1.04 < Fr < 1.43, the tidal bore is undular. For 1.43 < Fr < 1.57, the tidal bore is partially breaking that is similar with the tidal bore transtition defined by Furgerot (2014). For Fr > 1.57, the tidal bore is totally breaking. An analysis of pressure distributions has been performed by Baddour and Song (1990). We found that the total and hydrostatic pressures of undular tidal bores have great values under the crest and the trough wave. In the case of undular tidal bores, the total pressures are not equal to the hydrostatic pressures. In the case of breaking tidal bores, the total pressures become equal to the hydrostatic pressures when the tidal bores are totally breaking. The turbulence reduces the dynamic pressures. The impact of tidal bores on the transport of non-cohesive and cohesive sediment particles have been studied in this work. For the non-cohesive sediment particles, we have observed that the trajectory using the flow generated by OpenFOAM is similar with the type e trajectory proposed by Chen et al. (2010). The modifications of Chen’s model have been done by including the effects of gravity, elevation and attenuation to reproduce non-cohesive particle trajectories under an undular tidal bore. We have obtained that the relationship between the Chen’s parameters (β1 , β2 and β3) and the Froude number Fr are linear. This is because the level of turbulence for undular tidal bores is low. The flow induced by an undular tidal bore is not complex. This physical phenomenon is quasi linear. The parameter β1 , related to the front celerity of tidal bores, decreases when the Froude number Fr increases. The parameters, β2 and β3, related to the elevation and attenuation of tidal bores respectively, increase when the Froude number Fr increases. Finally, for the cohesive sediment particles, we have calculated the distribution of floc size D under two types of tidal bore, undular and breaking. We have used the initial diameter of cohesive sediment particles d = 4 μm. The initial floc size D is equal to 10 μm with the consentration of floc c = 0.5 kg/m3. And we have limited the maximum floc size equal to 2000 μm. We have obtained that the maximum value of floc size Dmax increases exponentially with the Froude number Fr.

A constante exploração dos recursos hídricos para os mais diferentes usos sem um planejamento adequado, tem levado ao comprometimento desses recursos, verificando-se cada vez mais aumento no número de pesquisas e investimentos, visando o estudo de alternativas que viabilizem o tratamento avançado de águas residuárias e sua reutilização. Entre essas alternativas, estão as técnicas de separação dos materiais contaminantes por membranas. Neste trabalho estudou-se a viabilidade da utilização da microfiltração tangencial como alternativa de pós-tratamento de efluente de Reator Anaeróbio de Leito Expandido alimentado com esgoto sanitário, analisando-se a influência da utilização de cloreto férrico como coagulante, bem como, membranas com diferentes tamanhos de poro (0,2 e 1,0 &#956m), no desempenho da microfiltração tangencial. Os ensaios no sistema de microfiltração tangencial foram realizados em batelada, com amostras de efluente do reator anaeróbio de leito expandido (RALEX). Verificou-se que para os ensaios realizados com a membrana de 0,2 &#956m, o aumento das dosagens de cloreto férrico, contribuiu para diminuição nos valores de luxo de permeado. Esta relação não ocorreu de forma direta com a membrana de 1,0 &#956m. Os processos de coagulação e floculação foram essenciais para ambas membranas no aumento na eficiência de remoção da demanda química total de oxigênio (mg/l), fosfato total (mg P/l) e turbidez, no entanto, em relação aos valores de fluxo do permeado,foi prejudicial, pois nos ensaios em que as amostras de efluente do RALEX não foram previamente coaguladas e floculadas, a permeabilidade das membranas foi bem maios. O sistema de microfiltração tangencial operando com a membrana de 0,2 &#956m apresentou melhor desempenho, com valores de fluxo do permeado, em geral superiores a 100 L/m2.h, eficiência de 100% na remoção de coliformes totais e fecais, e a dosagem de 40 mg/l de cloreto férrico, já foi suficiente para uma eficiência média de remoção de DQOt de 95%; P.PO4-3 (89,5%) e Turbidez (96,4%). Portanto, a microfiltração tangencial pode ser considerada uma alternativa eficaz como unidade de pós-tratamento de efluente de reator anaeróbio de leito expandido, produzindo efluente que atende os padrões de reuso na agricultura, para coliforme totais e fecais. / The constant exploration of water resources for the most different uses, without an appropriate planning, has lead to the exhaustion of this resources. This scenery has showed the need of increasing researches and investments on alternative forms of wastewater treatment. This work studied the viability of using crossflow microfiltration as an alternative form of advanced treatment of effluents of Anaerobic Reactor Expanded Bed feed with sewage, examining the effect of the use of ferric chloride as coagulam, as well as of different pore size membranes (0,2 and 1,0 &#956m) on the performance of crossflow microfiltration. The experiments on crossflow microfiltration system were carried out in batch, using effluent samples of anaerobic reactor expanded bed. The results obtained with the 0,2 &#956m membrane showed that the increase of ferric chloride dosages contributed for the reduction on flux values. The 1,0 &#956m membrane did not presented this relation. The flocculation and coagulation processes were essentials for increasing the removal efficiency of Total Chemical Oxygen Demand, Total Phosphorus and Turbidity for both membranes, however, for the flux values the effect was harmful, because when the samples of the Anaerobic Reactor Expanded Bed were not previously coagulated and flocculated, the membranes penneability were higher. The Crossflow Microfiltration System, operating with the 0,2 &#956m membrane, presented better performance, with flux values generally superior than 100 L/m2.h, efficiency around 100% on the removal of Total and Fecal Coliforms. For this membrane (0,2 &#956m) the dosage of 40 mg/l of FeCl3 (first stage) was enough for an average of removal efficiency of Total Chemical Oxygen Demand (95%); Turbidity (96.4%); and P.PO4-3 (89,5%). Therefore, crossflow mocrofiltration can be considered an effective alternative for advanced treatment of effluents of Anaerobic Reactor Expanded Bed, producing a final effluent with large potentiality to be used in agriculture.

A presente pesquisa teve por objetivo a investigação da influência do tamanho de partículas floculadas na eficiência da clarificação de águas para abastecimento por flotação por ar dissolvido (FAD) com o emprego de método e equipamento para a aquisição e análise de imagens especialmente desenvolvidos, tendo em vista à caracterização da distribuição de tamanho de flocos e microbolhas de ar, bem como, o estudo dos aglomerados bolhas-floco (em termos de número de microbolhas de ar aderidas e velocidade ascensional) presentes no processo de flotação e comparação dos dados experimentais àqueles obtidos em simulação com o emprego do modelo matemático proposto por Reali (1991). Os ensaios foram realizados com água sintética (turbidez de 7,5±0,2 NTU; cor aparente de 38±1 uC; alcalinidade de 29,8±0,6 mg\'CA\'CO IND.3\'/L; condutividade de 59,3±0,8 \'mü\'S/cm; UV254nm de 0,128±0,004 \'CM POT.-1\'), a qual foi coagulada com a aplicação de 1,9 mg/L de \'AL POT. 3+\' (pH de 6,6±0,05) e divididos em duas Fases: Fase 1 - ensaios preliminares realizados em escala de laboratório, com o emprego do flotateste; Fase 2 - ensaios realizados em unidade piloto de flotação. Os resultados alcançados demonstraram que: i) a distribuição de tamanho de partículas floculadas influenciou diretamente a clarificação por flotação da água em estudo, sendo que as melhores condições de floculação foram aquelas que conduziram à formação, em sua maioria, de partículas floculadas com diâmetro médio de Feret acima de 300 \'mü\'m; ii) os menores valores residuais dos parâmetros analisados na água em estudo foram alcançados com o emprego do tempo de floculação de 17 min, entretanto a FAD foi capaz de operar também com boa eficiência com a utilização de tempo de floculação de 10 min; iii) o método e equipamento desenvolvidos nesta pesquisa para a aquisição e análise de imagens demonstraram constituir importantes ferramentas para a obtenção das distribuições de tamanho de flocos e microbolhas de ar, bem como, para a determinação do número de microbolhas de ar aderidas às superfícies dos flocos e da velocidade ascensional dos aglomerados bolhas-floco gerados no processo de flotação; iv) mesmo com as diversas simplificações adotadas no desenvolvimento do modelo matemático analisado e considerando as condições experimentais utilizadas nesta pesquisa, foi possível verificar para a água em estudo e para as condições operacionais empregadas nesta pesquisa, que a modelação matemática proposta por Reali (1991) foi capaz de fornecer subsídios para uma adequada estimativa do número de microbolhas de ar aderidas aos flocos, bem como, das velocidades ascensionais dos aglomerados bolhas-floco. / The goal of this research was to investigate the flocculated particles size distribution influence on the dissolved air flotation (DAF) efficiency. Special image acquisition method and equipment were used to characterize the flocculated particles and air microbubbles size distribution, as well as, the clusters (in terms of microbubbles number adhered and rise velocity) in the contact zone outlet of the DAF unit. Besides that, the experimental results were compared with those obtained from the DAF modeling proposed by Reali (1991). The trials were carried out with synthetic water (temperature of 26.0 ± 0.5oC; turbidity of 7.5±0.2 NTU; apparent color of 38±1 CU; alkalinity of 29.8±0.6 mg\'CA\'\'CO IND.3\'/L; conductivity of 59.3±0.8 \'mü\'S/cm; UV254nm of 0.128±0.004 \'CM POT.-1\'), that it was coagulated by applying 1.9 mg/L of \'AL POT.3+\' (22.5 mg/L alum). The trials were divided into two phases: Phase 1 - preliminary tests carried out in laboratory facilities (flotatest); Phase 2 - tests carried out in pilot facilities (DAF pilot unit). The results showed that: i) the flocculation conditions interfered directly on the efficiency of DAF process, and the best flocculation conditions were those that conducted to formation of flocculated particles size with Feret mean diameter above 300 \'mü\'m; ii) the best results were obtained applying flocculation time of 17 min, however, DAF was also capable of operating with a satisfactory efficiency when applying flocculation time of 10 min; iii) the special image acquisition method and equipment developed in this research proved to be a important tool to characterize the flocculated particles and air microbubbles size distribution, as well as, the number of air microbubbles adhered to the flocs surface and the clusters rise velocity; iv) the DAF modeling developed by Reali (1991) provided a reliable prediction of the microbubbles number adhered to the flocs surface, as well as, the clusters rise velocity.

Tendo em vista a potencialidade da remoção de algas utilizando a flotação por ar dissolvido, foi proposto o desenvolvimento de um equipamento de laboratório de fácil operação e manutenção, denominado Floteste, integrando as características geométricas do equipamento Jarteste neste trabalho. Foram realizados ensaios, utilizando água sintética contendo algas da ordem de 108 ind/L e natural proveniente de curso d\'água eutrofizado, possibilitando o aprimoramento do estudo das condições de coagulação, mistura rápida, floculação e flotação. Também, ensaios de flotação seguida de filtração em areia foram feitos visando melhorar a qualidade da água flotada. O jarro do Floteste possui placa de orifícios que proporciona perda de carga suficiente para a distribuição uniforme de água saturada pela seção quadrada do mesmo. Concluiu-se que, principalmente, que a dosagem de coagulante e o respectivo pH de coagulação, tempo e gradiente de velocidade médio de mistura rápida, tempo e gradiente de velocidade médio de floculação, tempo e pressão de saturação e a quantidade de ar fornecido exercem influência significativa na remoção de algas, turbidez, cor verdadeira e do número de partículas nos dois tipos de águas estudadas. / Due to the potentiality of the algae removal by dissolved air flotation, it was proposed the development of an equipment in laboratory scale of easy operation and maintenance, dominated Floteste, integrating the geometric characteristics of the Jarteste equipment in this work. Tests were carried out with synthetic water containing a high concentration of algae (~108 ind/L) and natural water from and eutrophicated source. Besides several improvements in the equipment developed in this study, the rapid mixing can be considered the most important, followed by flocculation and flotation. Also, flotation and sand filtration tests were performed to simulate the floto-filtration technology. The Flotateste vessel have a perforated plate that provides enough loss of load in order to uniform the distribution of saturated water in the bottom. It was concluded, mainly, that the coagulant dose and the pH of coagulation, time and velocity gradient of rapid mixing, time and velocity gradient of flocculation, time and saturation pressure chamber and the amount of air supplied played a significant role in the removal of algae, turbidity, true color and of the number of particles in the two types of water studied.