Thesis advisor: Gail C. Kineke / To determine the role of cohesive suspended particle characteristics on sediment transport patterns in an energetic estuary floc size, density, and settling velocity were investigated in the Connecticut River estuary over three years spanning varying fluvial discharge regimes. Concurrent measurements of in-situ floc size, flow, bed stress, salinity and suspended-sediment concentration (SSC) were used to identify primary influences on floc size variability. Water discharge ranged from 202 to 910 m³/s between the three sampling campaigns, and the timing of major sediment discharge events preceding measurement periods from 23 to 162 days. Two distinct particle populations were observed under high and low sediment discharge regimes. With abundant fluvial sediment input, flocculation occurred resulting in large, loosely-packed flocs dominating the suspended signal (median sizes of 194-209 µm; median excess densities of 13-17 kg/m³). Following an extended period of low sediment discharge, small, dense aggregates resuspended from the bed were observed throughout the water column (median size of 171 µm and excess density of 60 kg/m³). The timing of and partial decoupling of water and sediment discharge led to inter-annual patterns of cohesive particle characteristics controlled by fresh sediment supply. The large, light flocs with lower settling velocities characteristic of high sediment supply regimes likely bypass the estuary. Smaller compact aggregates dominated the low-sediment discharge regimes. However, the similar disaggregated size distribution of the two regimes suggests the same fine source material is reintroduced to the estuary with the intrusion of the salt wedge, which extends farther up-estuary during low discharge regimes and ultimately supplies the off-channel bays and coves. / Thesis (MS) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Master of Science in Engineering - Engineering / Wastewater is generated in the production of water-based paints when vessels and filling lines are washed in between batches. This results in a dilute paint wastewater stream. This dissertation concerns the study of the treatment of wastewater, using flocculation and coagulation processes. Standard jar test were used in screening the flocculants. The inorganic flocculants used were ferric chloride (FeCl3) and aluminium sulphate (Al2(SO4)3) A thermodynamic model is developed for understanding the coagulation and flocculation process for inorganic flocculants. Properties such as the effect of bulk concentration, pH and feed concentration of flocculant on wastewater were investigated. The impact of kinetics and other properties such as the influence of redox potential on flocculation experiments are also evaluated in order to have an understanding of the properties that influence the flocculation of wastewater. It was found that thermodynamics could be used to predict gross flocculation behaviour. However mixing and the rate of the nucleation and growth of flocs are also important and need to be controlled for efficient and reproducible flocculation.

Orientador: Rodrigo B. Moruzzi / Co-orientador: Samuel C. Oliveira / Banca: Marcius Fantozzi Giorgetti / Banca: Marcelo de Julio / Resumo: Neste trabalho foram definidas as combinações escalonadas de gradientes médios de velocidade de floculação em sistemas de câmaras em série e obtidos seus respectivos tempos de floculação total visando atender ao critério do menor tempo de floculação total: nesse sentido foram empregados metologias apresentadas por Argman e Kaufman (1970), Bratby (1981) e Pádua (1994), as quais apresentam modelo de cinética de floculação, metodologia para obtenção dos coeficientes matemáticos por meio de ensaios em escala de laboratório e método para estimativa dos gradientes médios de velocidade de floculação em unidades com escoamento contínuo a partir de ensaios em reatores estáticos. Além disso, foi analisada a sensibilidade do modelo matemático e realizada a aplicação do conjunto obtido pela metodologia concebida por Pádua. Foram obtidos de 15 a 495 combinações de gradiente médio de velocidade de floculação a depender do número de câmaras em série (variando de 2 a 8) resultando em 1.281 combinações distintas, posteriormente foi aplicado a estas combinações 9 diferentes eficiências, resultando em 11.529 valores de floculação total: finalmente aplicou-se uma variação na velocidade de sedimentação (0,5; 2,5 e 5 cm/min) correspondente e diferentes relações entre os coeficientes cinéticos, resultando em 34.587 valores de tempo de floculação total. Foram analisados os percentis desse universo em 5 e 10% para os menores tempos de floculação total, resultando em 1.602 e 3.104 valores respectivamente, com valor mínimo de 2,4 minutos e máximo de 20,1 e 23,8 minutos para percentis de 5 e 10%. Observou-se que o modelo é sensível às variações da razão dos coeficientes cinéticos, quanto maior o valor desta relação menores serão os valores de tempo de floculação. O conjunto de resultados pode ser aplicado à metodologia concebida para obtenção de valores ótimos de tempo de floculação total... / Abstract: In this paper the scaled average velocity gradients flocculation in camera systems in series and obtained respective times total flocculation combinations were set to meet the criterion of shorter total flocculation were accrodingly employed methodologies presented by Argman and Kaufman (1970), Bratby (1981) and Padua (1994), which have kinetic flocculation method for obtaining the mathematical model coefficients by tests on laboratory scale and method for the estimation of average velocity gradients flocculation units with flow continuous from tests in static reactors. Furthermore, we analyzed the sensibility of the mathematical model and realized the application of the methodology devised jointly obtained by Padua. Were obtained from 15-495 combinations average velocity gradient flocculation depending on the serial number of cameras (varying from 2 to 8), resulting in 1281 different combinations subsequently was applied to nine different combinations of these efficiencies, resulting in 11529 values total time of flocculations, and finally applied to a change in sedimentation rate (0,5, 2.5 and 5 cm/min) corresponding to different relationships between the kinetic coefficients, resulting in 34587 values for total time of flocculation. We analyzed the percentiles of this universe in 5 and 10% for the lowest times total flocculation, resulting in 1602 and 3104 values, respectively, with minimum maximum of 20.1 and 23.8 minutes value of 2.4 minutes and for percentiles of 5 and 10%. It was observed that the model is sensitive to variations of the ratio of the kinetic coefficients, the larger value of this ratio will be smalller time values flocculation. The result set can be applied to the methodology designed to obtain optimal values of total flocculation time, cheking different situations from those observed when the isolated application of the methodology, experiencing a reduction in total time of flocculation in the comparative methods / Mestre

The ability to separate a suspension into its respective solid and liquid constituents is an important requirement in the chemical, wastewater and mineral industries. Typically, separation occurs in open, large diameter tanks known variously as thickeners, settlers or clarifiers. The design and operation of these devices have been based, until recently, on kinematic models and macroscopic mass balances. The problem with these approaches is that consolidation in the bed is not described accurately and consequently, the area required for thickening is often grossly overestimated. Recently, Buscall and White [24] proposed a 1−D phenomenological theory of dewatering that encompasses both sedimentation and consolidation, providing a more solid grounding for understanding, simulating and optimising dewatering in a range of devices, including thickeners. This theory identifies two important rheological parameters; a concentration dependent yield stress, Py (φ) and hindered settling function, R(φ). / Despite representing a significant improvement over a kinematical approach, Buscall and White’s dewatering theory involves a number of simplifications so that in practise, simulations often underestimate dewatering in full sized thickeners [97, 153]. One aspect of thickening that is poorly understood is the effect of raking. At the base of the thickener, a rake transports the thickened sediment to the outlet. An additional effect from raking is to increase the average solid concentration in the underflow [33, 46]. Raking introduces normal and shear stresses, which cannot be described within a one-dimensional framework. Therefore, observed differences between predicted and measured thickener underflow concentrations are attributed to the action of the rake. / The aim of this thesis is to develop a better understanding of how shear stresses effect compressional dewatering in both pilot and full scale thickening operations. Before attempting to quantify the effect of shear on dewatering, it was considered necessary to first establish that the 1-D model was capable of predicting dewatering in the absence of shear. Up until now, no known studies have been undertaken to validate the model under controlled conditions. To approximate one-dimensional flow with no shear, a tall narrow column with no moving parts was used. Two solid fluxes and several bed heights were studied, and the outputs from the column were compared with the 1-D model predictions. The results show that under ideal conditions, the model predicted the underflow solid concentration to within 10 %. / The effect of shear on dewatering was investigated using a Couette shear device. Couette geometry was chosen to provide uniform shear. Since in Couette flow, no normal stresses act in the direction of rotation, the mechanism behind dewatering can investigated. These experiments showed that shear caused dewaterability to improve up to a critical shear rate, beyond which dewaterability was adversely affected. The relationship between this critical shear rate and flocculation conditions was investigated by using different flocculant dosages. The shear modified Py (φ,γ) and R(φ,γ) can be input to the 1−D model, thereby incorporating shear indirectly. As a result, the model predicted an order of magnitude increase in solids flux. / The above procedure was used to characterise the dewaterability of a real thickener feed as a function of shear rate. The optimum shear rate was determined by finding the minimum R(φ,γ). Then, Py(φ) and R(φ) were input into the thickener model. The predicted underflow concentration could then be compared against plant data. / Even when shear is taken into account, the model still under predicts the performance of the thickener. To understand this result, the pilot column work was revisited since the control over experimental conditions was far greater. To introduce shear, concentric cylinders were installed in the column and rotated at a fixed speed. Thus, the effect of shear and bed height on underflow density were determined at different rates of shear. This showed that the underflow concentration increased with bed height; a result not expected based on the model prediction. The effects of shear on underflow density were secondary to bed height. / The bed height dependence can only be explained if dewatering is not steady but changes over time. For a four metre bed height the residence time is eight times longer than a one metre bed. Improvements in dewatering could be related to time dependent restructuring of aggregates which would result in an associated change in R(φ). By fluidizing suspensions for times corresponding to the residence times in the tall column, R(φ) and Py(φ) could be determined, as functions of volume fraction and time. Aggregate properties including structure and density were measured before and after fluidization using focussed beam reflectance measurement (FBRM) and floc density analysis (FDA).

Recent progress in algae biotechnology indicates that microalgae have the potential of becoming a significant source for food, feed proteins, nutraceuticals, and lipids for biofuels. Typically low concentrations of microalgae cultures (less than 2 g/L) make harvesting of algae biomass one of the key economic bottlenecks for microalgae production of biofuels and bioproducts. Among the various biomass harvesting options currently under consideration, flocculation appears to be the least expensive and most flexible method for harvesting and initial concentration of dilute algal cultures. In addition to initial biomass concentration, processing factors that could also affect harvesting efficiency include culture pH, flocculant dosage, and media ionic strength (conductivity). This thesis reviews challenges of harvesting and concentration of green microalgae and examines the effect of pH, flocculant dosage, and culture conductivity on charge neutralization and flocculation of Nannochloris oculata by aluminum chloride. N. oculata flocculation was studied by manipulating the culture pH and ionic strength before the addition of aluminum chloride. The removal efficiency, concentration factor, settling rate, and zeta potential of the culture were measured to assess the effect of processing variables and understand mechanisms that govern N. oculata flocculation by aluminum chloride. Flocculation tests conducted with culture concentrations of 10^7 cells/ml revealed that AlCl3 concentration of 0.05 g/L and flocculation pH of 5.3 were optimal conditions for achieving 100% removal efficiency and a twentyfold algae concentration. At flocculant concentrations greater than 0.05 g/L, removal efficiencies were equally good but resulting concentration factors decreased with increasing AlCl3 dosage. Zeta potential measurements were correlated with flocculation dosage, initial cell concentration, medium pH, and aluminum solubility curves to conclude that densely charged multi-valent aluminum hydroxide species were responsible for the efficient flocculation at pH 5.3 with 0.05 g/L AlCl3.

No description available.

Acidified dairy products are one of the oldest types of food products. Unfortunately all of them are low in dietary fibre. Thus, to improve health benefit of these products the idea of fortifying them with dietary fibre seems attractive. However dairy products enriched with Glucagel (a commercial product that is high in barley β-glucan) were found to suffer from textural defects. When the Glucagel concentration exceeded a certain value (5 g/L), dramatic phase separation was observed in set yogurt and yogurt drink with volume fraction of casein micelles greater then 0.108. To investigate interactions of β-glucan polymers and casein micelles in the milk prior to setting of yogurt, mixtures of yogurt milk and Glucagel were systematically studied. Depending on the volume fraction of casein micelles and the Glucagel concentration, a stable phase or a gel or a sedimented material could exist. The driving force for phase separation was depletion flocculation of casein micelles in the presence of β-glucan. The phase separation responsible for textural defects in yogurt systems supplemented with high amounts of Glucagel can be avoided by the reduction of β-glucan molecular weight, a process that limits the range of attraction between micelles. Incubation of Glucagel with lichenase for 90 min resulted in homogeneous (stable) yogurt systems with Glucagel concentrations as high as 10 g/L.

Acidified dairy products are one of the oldest types of food products. Unfortunately all of them are low in dietary fibre. Thus, to improve health benefit of these products the idea of fortifying them with dietary fibre seems attractive. However dairy products enriched with Glucagel (a commercial product that is high in barley β-glucan) were found to suffer from textural defects. When the Glucagel concentration exceeded a certain value (5 g/L), dramatic phase separation was observed in set yogurt and yogurt drink with volume fraction of casein micelles greater then 0.108. To investigate interactions of β-glucan polymers and casein micelles in the milk prior to setting of yogurt, mixtures of yogurt milk and Glucagel were systematically studied. Depending on the volume fraction of casein micelles and the Glucagel concentration, a stable phase or a gel or a sedimented material could exist. The driving force for phase separation was depletion flocculation of casein micelles in the presence of β-glucan. The phase separation responsible for textural defects in yogurt systems supplemented with high amounts of Glucagel can be avoided by the reduction of β-glucan molecular weight, a process that limits the range of attraction between micelles. Incubation of Glucagel with lichenase for 90 min resulted in homogeneous (stable) yogurt systems with Glucagel concentrations as high as 10 g/L.

No description available.

Thesis (PhD)--University of South Australia, 2003.