http://repositorio.ufc.br/handle/riufc/501 2026-08-01T16:33:22Z http://repositorio.ufc.br/handle/riufc/87304 Título: Modelagem computacional do fechamento dinâmico de válvulas de retenção em regime de transitório hidráulico Autor(es): Silveira Neto, José Paulo da Abstract: The analysis of dynamic check valve closure constitutes a problem of great relevance, since closure under reverse flow can generate significant pressure surges. The numerical modeling of this phenomenon is complex and requires the definition of a large number of input parameters. The objective of this study was to model the dynamic closure of a check valve during hydraulic transients, incorporating the Cavitation Method with Voids and Wave Damping (CMVWD), and to propose a simplified boundary condition based on dimensionless characteristic curves. Three boundary conditions were implemented: the complete dynamic closure model based on the resolution of the momentum equation; the instantaneous closure condition at the onset of flow reversal; and the simplified boundary condition, based on the general orifice equation with determination of the maximum reverse velocity from characteristic curves. The comparison between the three conditions demonstrated that, under direct flow, the discharge and pressure results were identical. The differences were manifested in the closure instant and in the pressure variation resulting from this phenomenon. The simplified boundary condition proved capable of adequately reproducing the results of the complete dynamic closure model, provided that the characteristic curve used is representative of the operational conditions and type of valve simulated, and was validated against experimental data from Himr et al. (2017). A sensitivity analysis was subsequently performed for the CMVWD parameters, specifically the initial void fraction and the damping coefficient, which demonstrated significant influence on flow deceleration at the check valve, as well as on the maximum reverse velocity and the pressure response associated with check valve closure. A dimensionless correlation approach for characteristic curves from different experimental sources was also proposed for the swing check valve, aiming at generalization for different nominal diameters and operating conditions. The correlation obtained had a preliminary character, with a fit compatible with the intended scope of the methodology. Tipo: Tese 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/87250 Título: Uso combinado de fibras de polipropileno e cinza leve de carvão mineral para controle de retração e fluxo de gás em camadas de cobertura de aterros sanitários Autor(es): Elias, Deyvid de Souza Abstract: The final disposal of municipal solid waste (MSW) in sanitary landfills poses challenges, particularly regarding the control of biogas emissions. Final cover layers act as barriers to water infiltration and gas migration; however, their performance may be compromised by the shrinkage and cracking of compacted soils. This thesis evaluated the hydromechanical and environmental behavior of mixtures composed of cover soil, coal fly ash, and polypropylene fibers for application in sanitary landfills. The experimental program comprised 24 formulations, including reference materials, soil–fiber mixtures with 6 and 12 mm fibers, soil–ash mixtures containing 10%, 20%, and 30% residue, and ternary compositions. Physicochemical, mineralogical, microstructural, environmental, and geotechnical characterizations were performed, along with compaction, consistency, shrinkage, hydraulic conductivity, intrinsic air permeability, unconfined compression, indirect tensile strength by diametral compression, image-monitored drying, and numerical modeling using the Vadose/W software. The ash reduced plasticity and volumetric and linear shrinkage, particularly at higher contents; however, it decreased densification and increased water and air transport. In the environmental tests, the leaching extract did not indicate hazardous characteristics, whereas the solubilized extract classified the ash as a non-inert material, making its use conditional upon control of dosage, confinement, and contact with water. The 12 mm fibers increased strength, deformability, and absorbed energy, but higher contents favored agglomeration, loss of homogeneity, and greater pore connectivity. Among the ternary mixtures, the matrix containing 20% ash showed the most favorable mechanical interaction with the fibers, although it remained less advantageous in terms of transport properties. The multicriteria assessment identified S0.75F12, composed of soil and 0.75% of 12 mm fibers, as the formulation with the best overall performance. The mixture reached 544 kPa in unconfined compression and 56.23 kPa in indirect tension, reduced volumetric shrinkage to 32.9%, and exhibited a hydraulic conductivity of 1.86 × 10⁻⁷ cm/s. The modeling indicated similar responses for the soil, S0.50F12, and S0.75F12. It is concluded that ash and fibers produce complementary, although not necessarily synergistic, effects. S0.75F12 is the main candidate for validation at a larger scale, whereas the ash-containing mixtures show potential for controlled-dosage or multilayer systems. Tipo: Tese 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/87158 Título: Modeling river-aquifer interactions in dryland regions to enhance water management strategies Autor(es): Toné, Arthur Jordan de Azevedo Abstract: Water security relies on accurately representing hydrological processes in river-aquifer dynamics, including aquifer recharge driven by rainfall, hyporheic flow, and lateral tributary inflow. River–aquifer studies and hedging models often overlook these processes. This study proposes a conceptual model of river-aquifer interactions in data scarce regions (Chapter 2). Building on this conceptual model, a parsimonious numerical model was developed, and these processes were accurately calculated in a data-scarce region at scales relevant to water management (Chapter 3). Furthermore, a numerical hedging model for a dryland reservoir, featuring an early rationing system based on the identification of drought events and river-aquifer dynamics, is presented (Chapter 4). Short-term field-measured hydrological data were analyzed along with secondary data on hydrogeology, water use, water participation, and satellite imagery. The results from Chapter 2 indicate that the average transmission losses ranged from 12% to 28% of river inflow, while the transmission gains ranged from 10% to 34%. Transmission losses were prevalent at the beginning of the rainy season (rainfall ≤ 10 mm/day), whereas transmission gains were dominant following intense rainfall events (> 20 mm/day). The results from Chapter 3 indicate that the numerical model’s performance measures (Kling-Gupta efficiency, Nash–Sutcliffe efficiency, and percent bias) effectively estimate river and groundwater flow using a simple modeling approach, requiring only minimal calibration (three parameters). Notably, the data required for the model are often available in regions with scarce data. Sensitivity analysis of the simplified model parameters showed that riverbed hydraulic conductivity and aquifer width significantly affected outflow in data-scarce environments. Hyporheic flow is crucial for the water balance in dryland rivers. In contrast, subcatchment runoff demonstrated minimal influence compared to inflow and groundwater fluxes, suggesting a greater dependence on river volume and stage than on intraseasonal rainfall. In Chapter 4, the heading model has key advantages, including the optimization of decision variables (trigger volumes and rationing coefficients) using a genetic algorithm (NSGA-II), integration of water user participation, water allocation connected with drought assessments through a simple drought index, streamflow prediction based on river-aquifer dynamics, and the use of short-term field-measured hydrological data. The results show that the proposed hedging rule maintained system vulnerability below 10% using both simulated and measured inflow data, and the objective function (the modified shortage index) was successfully optimized, even when early rationing occurred during the rainy season. The quantitative analysis suggests that for adaptive hedging in data-scarce drylands, the calculation method (the rule itself) is more critical than the availability of on-site inflow measurements. Therefore, operating rules for a dryland reservoir optimized using simulated data may be effective in satisfying water demands and stakeholder requirements, even when integrated with a simple drought index and in the presence of data uncertainties. This study contributes to a more accurate water balance of key hydrological processes in data-scarce regions and provides valuable tools for similar areas that require viable management solutions. Tipo: Tese 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86649 Título: Enhancement of anaerobic azo dye decolorization under saline and sulfate-rich conditions through electron transfer-based strategies Autor(es): Oliveira Júnior, José Kleber Sousa Abstract: Azo dyes are among the most persistent pollutants in textile wastewaters due to the high stability of their aromatic structures and resistance to conventional biological treatment processes. Reactive Black 5 (RB5), one of the most widely used azo dyes, represents a significant environmental challenge when present in industrial effluents. In this context, this doctoral thesis investigated strategies to intensify the anaerobic decolorization of RB5 under conditions representative of real textile wastewaters, with emphasis on modulating extracellular electron transfer through the use of soluble and insoluble redox mediators and iron-based additives. Batch experiments, with 10h of duration, confirmed that RB5 decolorization occurs predominantly via biological reduction, with abiotic controls showing removals below 5%. The addition of the soluble redox mediator anthraquinone-2-sulfonate (AQS) increased decolorization efficiency from approximately 70% to up to 87% and enhanced the first-order kinetic constant from 0.19 to 0.33 h-1 . Sulfate exerted a limited effect on decolorization (~72- 73%), whereas salinity caused moderate kinetic inhibition. The combined presence of chloride and sulfate constituted the most restrictive condition, reducing RB5 removal to approximately 65-68% and the kinetic constant to 0.15-0.17 h-1 ; nevertheless, AQS maintained a positive effect under all tested scenarios. In continuous anaerobic reactors, RB5 decolorization under control conditions typically ranged from 66 to 75% and decreased to approximately 60-68% in the presence of sulfate due to competition for reducing equivalents. Salinity had a more pronounced impact on organic matter removal, decreasing COD removal to approximately 35-40%, while exerting a comparatively smaller effect on dye decolorization. AQS addition consistently improved RB5 removal by about 5-7%, although at the expense of COD removal. Recovery tests demonstrated rapid restoration of dye decolorization, whereas COD removal exhibited partial and slower recovery, indicating greater resilience of dye-reducing pathways compared to methanogenic processes. The evaluation of iron-based materials revealed strong speciation- dependent effects. Zero-valent iron (Fe0 ) emerged as the most effective additive, increasing RB5 removal to approximately 80-82% in continuous reactors and raising the kinetic constant to up to 0.24 h-1 in batch assays, while providing high operational stability even under reduced hydraulic retention time. Magnetite and soluble iron species (Fe2+/Fe3+) produced more moderate improvements (~69-77%), strongly dependent on dosage and bioavailability. In addition, insoluble carbonaceous materials, such as activated carbon and biochar, particularly when functionalized with AQS, enabled RB5 removals above 80% and promoted enrichment of electroactive microbial consortia. Overall, this thesis demonstrates that intensification of anaerobic azo dye decolorization in complex textile wastewaters can be achieved through targeted modulation of extracellular electron transfer, resulting in significant gains in efficiency, kinetics, and operational robustness. These findings provide scientific and technological foundations for the development of more efficient and resilient anaerobic treatment systems applicable to real textile effluents. Tipo: Tese 2026-01-01T00:00:00Z