Ciencias Exactas y Ciencias de la Salud

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Simulation and modeling of three mechanisms of flow through porous media.
(2017-12-05) Romero Flores, Michel; López Salinas, José Luis; García Cuéllar, Alejandro Javier; Rivera Solorio, Carlos Iván
The mathematical modeling of two-phase flow in saturated porous media, as well as the modeling of adsorption/retention behavior of surface active materials in a porous medium composed of a complex network of macro, meso, and micropores in 1-D, 2-D and axisymmetric cases and the displacement of two phases in capillary conducts, were studied. Also, a Comparison of two CFD tools is made (COMSOL and ANSYS Fluent). The results were compared with experimental data from the literature. For the saturated porous media study and mathematical modeling of adsorption/retention behavior, COMSOL software was used, while for the capillary conducts displacement, ANSYS Fluent was chosen. In the saturated porous media analysis, different ways to obtain permeabilities and their effects on the flow in saturated porous media were compared. For the mathematical modeling of adsorption/retention behavior of surface active materials in a porous medium different effects were analyzed: the selection of boundary conditions, the size of the tracer and surfactant signals, effects of reversible and irreversible adsorption, the difference between local equilibrium and the rate-limited process. Also, for 2-D and axisymmetric simulations, heterogeneities, blends of surfactant and dispersion/diffusion effects were studied. The proposed mathematical model compares favorably with experimental data from literature when taking macro and mesoporosity into account. This model should be helpful in guiding the design of dynamic adsorption experiments, and to understand how heterogeneities in the rock may influence the interpretation of experimental results. Finally, capillary displacement was analyzed in an axisymmetric system, and the results were compared against a onedimensional model and experimental results obtained through experimentation. This was done to identify the benefits of simulating this type of phenomena, because, sometimes a simplified model can hide vital information for the experiments. The axisymmetric simulations were superior when showing the complete information of the phenomena but at a much higher computational cost than the one-dimensional model
Mathematical Modelling of a Domestic Wastewater Treatment System Combining a Septic Tank, an Up flow Anaerobic Filter, and a Constructed Wetland
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Fernández del Castillo Barrón, Alberto; SENES GUERRERO, CAROLINA; 253929; Senés Guerrero, Carolina; puelquio, emipsanchez; De Anda Sánchez, José; Díaz Torres, Osiris; Escuela de Ingeniería y Ciencias; Campus Monterrey; Gradilla Hernández, Misael Sebastián
Wastewater treatment is essential for environmental protection, public health, and to ensure water supply for future generations. Conventional treatment technologies, such as activated sludge, are energy-intensive and require constant maintenance as they were designed for large cities. These technologies are not suitable for wastewater treatment in small communities and rural areas. Decentralized treatment approaches combining Anaerobic Reactors (AR) and Constructed Wetlands (CW) have proven more appropriate in these cases. These passive treatment methods require low investment and maintenance. Additionally, they allow for onsite water reuse and energy generation. The combined configuration of an AR sequentially coupled with a CW have proven to be an efficient system by which the limitations of the individual units (AR and CW) are overcome. Chapter one provides the motivation related to global needs of wastewater treatment, problem statement and context, which is the deficit of treatment and current technologies deficiencies. The research question and solution overview provided by the mathematical modeling applied to decentralized treatment technologies. Finally, the main contributions of this work to the state of the art are detailed. In Chapter 2, several systems combining three types of AR (Up-flow Anaerobic Sludge Blanket, Anaerobic Baffled Reactor, and Up-flow Anaerobic Filter) with CW are reviewed as well as their capabilities and drawbacks. An emphasis was made to analyze their performances, characteristics, and the processes involved in pollutant removal (solids, organic matter, nutrients, and sulfate). In Chapter 3, the experimental work of this thesis is presented. Mathematical modeling of the pollutant removal processes occurring in wastewater treatment plants can provide detailed and valuable information. More profound knowledge provided by these models is useful for predicting the future behavior of the treatment systems and can be applied to optimize the operation and facilitate monitoring. Optimal operation procedures and feasible monitoring are essential to ensure the successful implementation of these technologies in rural areas and small communities where investment budgets are limited. The system's efficiency and robustness can also be increased by applying mathematical modeling in design and control. The experimental system evaluated consisted of a Septic Tank (ST), an Up-flow Anaerobic Filter, and a Horizontal Flow Constructed Wetland (HFCW). Sampling was done biweekly for three months. BOD5, COD, TSS, TKN, ON, NH4+, NO2- and NO3- levels were measured. The experimental data was used to develop three different mathematical models: First order kinetics models, Linear Multiple Regression models, and Mass balance models. The first-order kinetic models developed were efficient to predict pollutant removal with significant precision. Multiple linear regression models were found to help reduce the cost and time of monitoring procedures. These models also reflected physical, chemical, and biological processes involved in pollutant removal in a logical manner. Finally, mass balance models indicated that the system is highly tolerant to influent wastewater variations.

Ciencias Exactas y Ciencias de la Salud

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