Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2018. / A membrane distillation crystallization (MDC) experimental setup was designed, constructed and commissioned with rectangular mixing crystallizer tanks. The advantages and disadvantages of a rectangular mixing tank are compared to the traditional cylindrical mixing tank with baffling by means of a computational fluid dynamic (CFD) analysis in Ansys Fluent. The effect of tank configuration and geometry on the hydrodynamic and mixing characteristics for efficient momentum, solid suspension, heat and mass transfer were investigated. The hydrodynamic conditions in a crystallizer-mixing tank determine the quality of fluid mixing essential for optimal crystallization. Forty-five degree pitched blade turbines (PBT) were used to provide the agitation in the stainless steel rectangular jacketed tanks. Clear polycarbonate replicas of the rectangular tanks were manufactured to visually observe the mixing process in the tanks. Silica particles were used to represent the calcium carbonate crystals in the experiment. The data gathered from these experiments showed that the tanks should be operated between 600 to 750 rpm in the CFD simulations to simulate partial to complete suspension. In the numerical simulations a rectangular tank was compared to a cylindrical tank with baffling of the same volume. The partial differential equations solved in the numerical simulation were the conservation of mass (continuity), conservation of momentum and additional turbulence equations. In order to solve the turbulent fluid flow characteristics, the industry standard two-equation model, namely the K-epsilon model was used. This model was refined by the addition of the Wen-Yu drag model, the Simonin turbulent dissipation and the Simonin et al. turbulence interaction models. The RANS based RNG (k-ε), derived from the instantaneous Navier-Stokes equation was selected as the preferred model to analyse the hydrodynamic flow fields in the tanks. The 3D sliding mesh method was used to compute a time accurate solution. The Eulerian-granular multiphase model was used to predict the degree of solids suspension in the tanks. The efficiency of mixing within the tank was measured by the tank’s ability to keep the crystals in suspension and preventing any particle from settling at the bottom for more than 1-2 second(s). The mixing tanks were initially loaded with 5% v/v, which equates to a loaded height of approximately 10 mm. The simulations were done with the use of the volume fraction function to visually observe the cloud height and gauge the homogeneity and distribution of the particulates within the fluid flow fields. The results from the experimental setup were compared to the CFD simulations to qualify the use of CFD simulations for the comparison of the geometrically different tanks. Lastly, the findings from the CFD simulations were used to compare the tanks and determine if the rectangular tank built for the MDC experiment perform satisfactorily to replace a standard cylindrical tank with baffling for this application.

Saline water evaporation from porous media with the associated salt precipitation patterns is frequently observed in a number of industrial and environmental applications and it is important in a variety of topics including, but not limited to, water balance and land-atmosphere interaction, terrestrial ecosystem functioning, geological carbon storage, and preservation of historical monuments. The excess accumulation of salt in soil is a global problem and is one of the most widespread soil degradation processes. Thus, it is important to understand the dominant mechanisms controlling saline water evaporation from porous media. This process is controlled by the transport properties of the porous medium, the external conditions, and the properties of the evaporating fluid. During saline water evaporation from porous media, the capillary induced liquid flow transports the solute towards the evaporation surface while diffusive transport tends to spread the salt homogeneously thorough the porous medium. Therefore, the solute distribution is influenced by the competition between the diffusive and convective transport. As water evaporates, salt concentration in the pore space increases continually until it precipitates. The formation of precipitated salt adds to the complexity of the description of saline water evaporation from porous media. In this dissertation, the effects of salt concentration, type of salt, and the presence of precipitated salt, on the evaporation dynamics have been investigated. The obtained results show that the precipitated salt has a porous structure and it evolves as the drying progresses. The presence of porous precipitated salt at the surface causes top-supplied creeping of the evaporating solution, feeding the growth of subsequent crystals. This could be visualized by thermal imaging in the form of appearance and disappearance of cold-spots on the surface of the porous medium, brought about by preferential water evaporation through the salt crust. My results show that such a phenomenon influences the dynamics of saline water evaporation from porous media. Moreover, a simple but effective tool was developed in this dissertation capable of describing the effects of ambient temperature, relative humidity, type of salt and its concentration, on the evaporative fluxes. Additionally, pore-scale data obtained by synchrotron x-ray tomography was used to study ion transport during saline water evaporation from porous media in 4D (3D space + time). Using iodine K-edge dual energy imaging, the ion concentration at pore scale with a high temporal and spatial resolution could be quantified. This enabled us to reveal the mechanisms controlling solute transport during saline water evaporation from porous media and extend the corresponding physical understanding of this process. Within this context, the effects of particle size distribution on the dispersion coefficient were investigated together with the evolution of the dispersion coefficient as the evaporation process progresses. The results reported in this dissertation shed new insight on the physics of saline water evaporation from porous media and its complex dynamics. The results of this dissertation have been published in 3 peer-reviewed journal papers together with one additional manuscript which is currently under review.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

O feijÃo-de-corda à uma cultura muito importante na dieta das camadas sociais inferiores. O baixo rendimento dessa cultura faz com que cada vez mais a irrigaÃÃo venha como ferramenta para auxiliar no aumento da produtividade. PorÃm, com o advento da irrigaÃÃo o problema da salinidade aumentou bastante. Neste trabalho, avaliou-se o acÃmulo de sais no solo e a produtividade do feijÃo-de-corda [Vigna unguiculata (L.) Walp.], cv. Epace 10, em funÃÃo da fraÃÃo de lixiviaÃÃo e da salinidade da Ãgua de irrigaÃÃo. O experimento foi realizado durante a estaÃÃo seca na Ãrea experimental do LaboratÃrio de HidrÃulica e IrrigaÃÃo/UFC, seguindo um delineamento em blocos ao acaso, com quatro tratamentos e cinco repetiÃÃes, sendo que cada parcela consistiu de 4 linhas de plantio com o comprimento de 5,0m. No tratamento 1 as plantas foram irrigadas com Ãgua do poÃo (CEa = 0,8 dS m-1), sem fraÃÃo de lixiviaÃÃo; os tratamentos 2, 3 e 4, consistiram de Ãgua salina com CEa de 5,0 dS m-1, sem fraÃÃo de lixiviaÃÃo, com fraÃÃo de lixiviaÃÃo de 0,14 e 0,28, respectivamente. Durante as fases de floraÃÃo e frutificaÃÃo foram feitas quatro avaliaÃÃes de trocas gasosas foliares e trÃs determinaÃÃes dos teores de Na+, Ca+2, K+ e Cl-. Ao final do ciclo foram determinadas parÃmetros de crescimento vegetativo e reprodutivo, bem como o acumulo de sais no solo. A aplicaÃÃo de Ãgua salina provocou acÃmulo de sais no solo, porÃm esses efeitos foram parcialmente revertidos pelo aumento da fraÃÃo de lixiviaÃÃo; a salinidade reduziu a produtividade de grÃo, porÃm nÃo afetou sua qualidade e provocou um aumento de 10% no Ãndice de colheita; a reduÃÃo na produtividade ocasionada pela salinidade da Ãgua deveu-se, em parte, à reduÃÃo na assimilaÃÃo lÃquida de carbono durante as fases de floraÃÃo e frutificaÃÃo, associada aos efeitos osmÃticos e ao acÃmulo de Ãons potencialmente tÃxicos nos tecidos foliares; as fraÃÃes de lixiviaÃÃo nÃo tiveram muita influÃncia na superaÃÃo dos danos provocados pela salinidade sobre a produtividade das plantas. / The cowpea is a very important crop in the diet of the inferior social classes, but its productivity is very low, especially is non-irrigated areas. However, the irrigation in semi-arid areas has been associated to soil salinization. The study had the objective to evaluate the effect of water salinity and the leaching fraction on the growth and the productivity of grains of cowpea plants (Vigna unguiculata), cv, Epace 10. The experiment was set up in the experimental area of the LaboratÃrio de HidrÃulica e IrrigaÃÃo/UFC, during the dry season. A completely randomized block design, with five repetitions, was adopted. Each experimental unit consisted of 4 lines of plantation of 5.0 m. The treatments studied were:: 1. Well water with ECw of 0.8 dS m-1 (without leaching fraction); 2. saline water with ECw of 5.0 dS m-1 (without leaching fraction); 3. saline water with ECw of 5.0 dS m-1 with leaching fraction of 0.14; and 4. saline water with ECw of 5.0 dS m-1 with leaching fraction of 0.28. During the flowering and fruit development four measurements of gas exchange and three determinations ion concentrations (Na+, Ca+2, K+, and Cl-) were performed. At the end of the crop cycle, some parameters of vegetative growth and plant yield, and salt accumulation in the soil were observed. The saline water application provoked salt accumulation in the soil profile, but this effect was partially reverted by the increase of the leaching fraction. Salinity reduced plant yield, but it did not affect its quality and caused a 10% increase in the harvest index. The reduction in plant yield was related, at least in part, to decrease in net assimilation of carbon during flowering and fruit development due to osmotic effects and to accumulation of potentially toxic ions. In general, the increase in leaching fraction did not reduce the effect of the salinity on plant development.

nÃo hà / Neste trabalho foi avaliada tolerÃncia de dois genÃtipos de sorgo forrageiro (Sorghum bicolor (L) Moench), considerados sensÃvel (CSF 18) tolerante (CSF 20) ao estresse salino. Sementes selecionadas foram germinadas em vasos contendo 12 kg de solo arenoso em condiÃÃes casa de vegetaÃÃo. Dez dias apÃs a semeadura as plantas passaram a ser irrigadas com Ãgua de diferentes concentraÃÃes de sais. Para o preparo das soluÃÃes salinas, foram utilizados os sais de NaCl, CaCl2.2H2O e MgCl2.6H2O dissolvidos em Ãgua destilada, na proporÃÃo de 7:2:1. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2 x 5, composto por dois genÃtipos, cinco tratamentos em doses crescentes de Ãgua salina (0.5, 2.0 , 4.0, 6.0 e 8.0 dS.m-1) e cinco repetiÃÃes. Durante a fase de crescimento vegetativo foram realizadas mediÃÃes de fotossÃntese e trocas gasosas nas plantas. A coleta das plantas teve inÃcio quarenta e quatro disa apÃs o inÃcio dos tratamentos. Foram realizadas mediÃÃes de caracterÃsticas morfolÃgicas, massas seca e fresca das partes aÃreas das plantas (limbos, bainhas e colmos) e potencial hÃdrico. As raÃzes foram coletadas, juntamente com amostras de solo em trÃs profundidades (0.10, 0.20 e 0.30 m). Foram determinados os teores de Ãons das partes aÃreas e das amostras de solo. O genÃtipo CSF 20 apresentou maiores valores de nÃmero de entrenÃs, altura da planta, diÃmetro do colmo. As reduÃÃes dos padrÃes de crescimento foram maiores para o genÃtipo CSF 18, quando as plantas foram expostas aos maiores nÃveis de salinidade da Ãgua de irrigaÃÃo. A relaÃÃo entre os teores de K+ nos colmos e nos limbos foliares foram bem menores no genÃtipo CSF 20, sugerindo que esse genÃtipo apresenta maior capacidade de distribuiÃÃo de K+ para as folhas. Os maiores valores na relaÃÃo Na+/K+ foram observados no genÃtipo CSF 18 em funÃÃo de sua menor capacidade de acumular K+ nas folhas. O genÃtipo CSF 20 acumulou maior quantidade de carboidratos solÃveis nas folhas. Os resultado mostraram que o genÃtipo CSF 18 mostrou-se sensÃvel à salinidade, enquanto que o genÃtipo CSF 20 mostrou-se tolerante à salinidade. / This work studied the tolerance of two genotypes of forrage sorghum (Sorghum bicolor (L) Moench), one salt sensitive (CSF 18) and another salt tolerant (CSF 20). Selected seeds were germinated in vases containing 12 Kg of sandy soil under greenhouse conditions. Ten days after seeding, plants were irrigated with different salt concentration water. For prepairing saline solutions, NaCl, CaCl2.2H2O e MgCl2.6H2O salts were used solved in destyled water, on proportion 7:2:1. the randomized completely design was used, and the treatments were outlined according to a 2 x 5 factorial arrangment, composed with two genotypes and five tratments of increasing salinity (0.5, 2.0 , 4.0, 6.0 e 8.0 dS.m-1), with five replicates. During vegetative growth measures of photosyntesis and gas exchanges were made. Fourty four days after germination, plants were harvested. The contents measured were morpholocial characteristics, shoot fresh and dry matter production (leaves, blades and colms) and water potential. Roots were colected with soil samples in three deaphts (10, 20 e 30 cm). Solute contents of shoot and soil samples were determinated. The genotype CSF 20 showed higher values of internode number, plant height and colm diameter. The reductions of growth were higher for CSF 18 genotype, when plants were exposed to the higher salt levels irrigation water. The relation of K+ in colms and leaves were lower in genotype CSF 20, sugesting that this genotype shows a higher capacity of distribution of K+ in leaves. The genotype CSF 20 showed higher accumulation of soluble carbohydrates in leaves. Results showed that CSf 18 genotype was most sensible to water salinity and CSF 20 was most tolerant to water salinity.

Bibliography: leaves 118-127.

Most common inorganic foulants in RO processes operating on brackish water are calcium carbonate, calcium sulphate and silica. However, silica fouling is the recovery limiting factor in RO system. Silica chemistry is complex and its degree of fouling strongly depends on the silica solubility and its polymerization under different operating conditions of RO process. In several studies carried out in batch and dynamic tests, the presence of polyvalent cations and supersaturation of silica in solutions were found to be the important factors (apart from pH and temperature) that affected the rate of silica polymerization and its induction period. Agitation did increased silica solubility; however, its effect was negligible in presence of polyvalent cations. Alkalization of water solution by coagulants particularly sodium hydroxide was found suitable for silica removal during pretreatment. The presence of magnesium in solution played a key role in silica removal mostly by the mechanism of adsorption to the metal hydroxide. The options of inline mixing (high agitation) for 5 to 10 minutes and microfiltration before RO were found suitable for silica pretreatment. During dynamic tests, the most dominant mechanism for salt deposition (mostly CaSO4) was particulate type in high concentration water solution; while crystallization fouling was the prevailing mechanism of deposition (mostly CaCO3 and silica) in low concentration solution. Silica showed significant effect on size and shape of inorganic salt crystals during coprecipitation. Moreover, the presence of common antiscalants promoted silica fouling. This important finding recommends an extra caution while using antiscalants in case feed water contains silica to a level that can attain saturation near membrane during RO process. A model was developed to predict the silica fouling index (SFI) based on the experimental data for induction period of silica polymerization. The model takes into account the effect of polyvalent cations and concentration polarization near membrane during RO process. It provides a conservative basis for predicting the maximum silica deposition in RO process at the normal operating conditions. A generalised correlation, which was developed for determination of the mass transfer coefficient in RO process, incorporated the effect of temperature change that is usually not considered in previous correlations. A correlation for reduction of silica content in feed water, down to a safe limit of 15 ppm for RO process, was also formulated and validated by the experimental results.

Nowadays, organic pollutants occurring in surface waters have raised substantial concern in public. Triclosan (TCS) is one of the antimicrobial agents which are utilized in both domestic and industrial application. In this study nanofiltration (NF) of TCS in surface water was investigated. Laboratory scale cross-flow device is operated in total recycle mode and DK-NF and DL-NF membranes were used. Kesikk&ouml / pr&uuml / Reservoir (Ankara) water was used as raw water. Effect of natural organic matter (NOM) content of raw water on TCS removal is searched through addition of humic acid (HA) into the raw water as to represent for NOM. Steady state permeate fluxes are monitored throughout the experiments to explore the flux behavior of the membranes. During the experiments, performance of the membranes is assessed by monitoring TCS, as well as other water quality parameters, such as UVA254 and total organic carbon (TOC) in the feed and permeates waters. Results obtained put forward that TCS removal by NF membrane is not as same as reported in the literature. In the literature, membrane removal efficiency is reported as above 90%. However, this study proved that this would be true if and only if one does not considers the adsorption of TCS by the system itself, in the absence of membrane. It is now clear that, because of adsorption of the TCS onto the experimental set up (feed tank, pipings etc.) / the real TCS removal efficiency of the nanofiltration is around 60-70%.

The rejections of selected N-nitrosamines by commonly used high-pressure nanofiltration (NF) and reverse osmosis (RO) membranes were quantitatively evaluated using a bench-scale cross-flow filtration apparatus. The selected nitrosamines included N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPYR), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA) and N-nitrosodiphenylamine (NDPHA). Nitrosamine rejections were evaluated under steady state at elevated feed concentrations, since NDMA rejections were found to be consistent with feed concentrations over three orders of magnitude. The steady-state nitrosamine rejections by NF membranes varied significantly, from 9 to 75%, depending on nitrosamine compounds and tested membranes. For hydrophilic compounds, rejections increased with increasing molecular weight. The nitrosamine rejections by brackish RO membranes reached as high as 97% for higher molecular weight nitrosamines. However, for low molecular weight nitrosamines such as NDMA, rejections as low as 54% were observed. This low level of rejections was attributed to diffusive solute transport being more effective than convective transport. Physicochemical properties such as molecular weight and aqueous diffusivity showed reasonable correlations with nitrosamine permeability constants.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第18966号 / 工博第4008号 / 新制||工||1617 / 31917 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小池 克明, 教授 石田 毅, 准教授 水戸 義忠 / 学位規則第4条第1項該当