Of all the strategies to reduce carbon emissions, carbon dioxide (CO₂) geological sequestration is an immediately available option for removing large amounts of the gas from the atmosphere. However, our understanding of the transition behavior between Forchheimer and Darcy flow through porous media during CO₂ injection is currently very limited. In addition, the kinetic mass transfer of SO₂ and CO₂ from CO₂ stream to the saline and the fully coupling between the changes of porosity and permeability and multiphase flow are two significant dimensions to investigate the brine acidification and the induced porosity and permeability changes due to SO₂ co-injection with CO₂. Therefore, this dissertation develops a multiphase flow, contaminant transport and geochemical model which includes the kinetic mass transfer of SO₂ into deep saline aquifers and obtains the critical Forchheimer number for both water and CO₂ by using the experimental data in the literature. The critical Forchheimer numbers and the multiphase flow model are first applied to analyze the application problem involving the injection of CO₂ into deep saline aquifers. The results show that the Forchheimer effect would result in higher displacement efficiency with a magnitude of more than 50% in the Forchheimer regime than that for Darcy flow, which could increase the storage capacity for the same injection rate and volume of a site. Another merit for the incorporation of Forchheimer effect is that more CO₂ would be accumulated in the lower half of the domain and lower pressure would be imposed on the lower boundary of the cap-rock. However, as a price for the advantages mentioned above, the injection pressure required in Forchheimer flow would be higher than that for Darcy flow. The fluid flow and contaminant transport and geochemical model is then applied to analyze the brine acidification and induced porosity and permeability changes due to SO₂ co-injection. The results show that the co-injection of SO₂ with CO₂ would lead to a substantially acid zone near the injecting well and it is important to include the kinetic dissolution of SO₂ from the CO₂ stream to the water phase into the simulation models, otherwise considerable errors would be introduced for the equilibrium assumption. This study provides a useful tool for future analysis and comprehension of multiphase Darcy-Forchheimer flow and brine acidification of CO₂ injection into deep saline aquifers. Results from this dissertation have practical use for scientists and engineers concerned with the description of flow behavior, and transport and fate of SO₂ during SO₂ co-injection with CO₂ in deep saline aquifers.

[pt] O objetivo deste trabalho é ser uma contribuição ao entendimento dos mecanismos envolvidos na migração por gravidade dos compostos orgânicos chamados de DNAPLs, quando eles são liberados em meios porosos e em meios porosos fraturados, para aportar ao desenvolvimento de tecnologias efetivas orientadas principalmente à localização e à remediação do sistema subterrâneo contaminado. Primeiramente são apresentados os conceitos elementares envolvidos nos modelos matemáticos que descrevem o fluxo bifásico em meios porosos, o processo de modelagem de um problema geral da natureza, os modelos conceituais, os matemáticos e os numéricos, e a aplicabilidade dos modelos conceituais conforme a considerações de escala. Em segundo lugar, são desenvolvidas as equações matemáticas que governam os fenômenos em estudo e são apresentadas as soluções às equações governantes a partir de técnicas computacionais e esquemas de integração numérica. As equações do fluxo bifásico são resolvidas mediante técnicas de elementos finitos mistos hibridizados (EFHM) e elementos finitos descontínuos (GD), e as equações do transporte de contaminantes são resolvidas mediante a técnica dos elementos finitos convencionais (EF). Seguidamente são avaliados numericamente problemas de transporte de contaminantes em 1D e 2D, problemas de transporte de contaminantes com transferência de massa, problemas de fluxo bifásico em 2D, e problemas acoplados envolvendo tanto fluxo bifásico como transporte de contaminantes com transferência de massa. Finalmente, são apresentadas as conclusões do trabalho desenvolvido bem como sugestões para trabalhos futuros. / [en] The objective of this work is to contribute to the understanding of the mechanisms involved in the gravity migration of organic compounds, called DNAPLs, when they are released in a porous media and in a fractured porous media, and to contribute to the development of effective technologies mainly oriented to the location and remediation of contaminated underground system. Firstly, some basic concepts are presented, especially those involved in the mathematical models that describe the two-phase flow in porous media, the conceptual models, the mathematical models, as well as the numerical models. Secondly, the mathematical equations that govern the phenomena under study are developed and the solutions to the governing equations from computational techniques and numerical integration schemes are presented. The biphasic flow equations are solved using mixed and hybridized finite element techniques (EFHM) and discontinuous finite element (GD), and the contaminant transport equations are solved by the conventional technique of finite element (FE). Then, some problems are numerically evaluated in 1D and 2D, such as transport of contaminants with and without mass transfer, two-phase flow problems in 2D, and attached problems involving both biphasic flow and contaminant transport with mass transfer. Finally, the conclusions of this thesis as well as the suggestions for future works are presented.

Poly- och perfluorerade alkylsubstanser (PFAS) är samlingsnamnet för en stor grupp kemikalier som det senaste årtiondet tilldelats världsomfattande uppmärksamhet med anledning av frekventa förekomster i vattenmiljö, djurliv och människor. Samtliga PFAS som uppträder i miljön är antropogena och har blivit industriellt framtagna och tillämpade i över 60 år. På grund av deras fysiska och kemiska stabilitet och ytaktiva egenskaper är PFAS eftertraktade inom en rad olika industriella och kommersiella produkter, från filmbildande brandskum till vatten-, smuts- och fettavvisande ytbeläggningar. De omfattande möjligheterna för användning har resulterat i utsläpp av PFAS i miljön, antingen av direkta källor (~80 %) som tillverkning och tillämpning av PFAS-innehållande produkter, eller indirekta källor (~20 %) som nedbrytning och transport av prekursorer. Åtgärder har därför tagits på nationell, regional och global nivå för att begränsa användningen och spridningen av selekterade PFAS-ämnen. En av de mest uppmärksammade föroreningsproblemen med PFAS i Sverige är utsläppen av filmbildande brandsläckningsskum (AFFF) från brandövningsplatser. Som en konsekvens av flera decenniers användning och okontrollerat utsläpp till miljön har koncentrationerna av PFAS uppmätts att vara som högst i anslutning till övningsplatserna. Ämnenas mobilitet och höga vattenlöslighet gör att risken för transport till kringliggande områden är stor, vilket ökar risken att förorena närliggande grundvattentäkter. Flera exempel på PFAS-haltigt dricksvatten i svenska hushåll har bland annat upptäckts i kommuner såsom Uppsala, Ronneby, Halmstad, Botkyrka. Två före detta brandövningsplatser i Bodens kommun har brukat AFFF i övningssyfte i samband med brandövningar då platserna var aktiva. NIRAS Sweden AB har på uppdrag av Försvarsmaktens miljöprövningsenhet utrett området med avseende på PFAS och konstaterade förhöjda nivåer av ämnena i grundvattenmiljö. Eftersom flera ytvattenförekomster gränsar till brandövningsområdet finns det en oro för ämnenas spridningsbenägenhet och potential att påverka närmsta dricksvattentäkt. Syftet med examensarbetet har av den anledningen varit att kartlägga spridningen av PFAS i grundvatten från de två före detta brandövningsstationerna i Boden. Tillvägagångssättet har gått ut på att upprätta en grundvattenmodell i modelleringsprogrammet Visual MODFLOW Classic. Den hydrogeologiska modellen har tillämpats för att utföra föroreningstransport med hjälp av insticksmodulerna MODPATH och MT3DMS. Transport av det mest framträdande PFAS-ämnet i området, PFOS, modellerades från båda brandövningsplatserna och föroreningsplymens utveckling har visualiserats i flera tidssteg. Resultatet från grundvattenmodelleringen visade att grundvattnet från brandövningsområdena i det övre grundvattenmagasinet rör sig i nordvästlig till nordöstlig riktning, men även mot Luleälven. I det undre grundvattenmagasinet rör sig vattnet i nordvästlig, men har också tendens att röra sig mot Luleälven. Föroreningstransporten visade att PFOS har benägenhet att röra sig mot Luleälven i en sydvästlig riktning. Transporttiden av PFOS från brandövningsplatserna till Luleälven beräknades med MODPATH till sex respektive 7 år för den kalibrerade modellen och område 13/24. Visualisering av PFOS-plymen med MT3DMS visade att det tar cirka 100 år för ämnena att nå Luleälven. / Poly- and perfluoroalkyl substances (PFASs) is the collective name for a large group of organic chemicals which in the past decade have gained global attention due to their frequent occurence within the aquatic environment, wildlife and humans. All PFAS that occur in the environment are man-made and have been industrially created and used for over 60 years. Due to their physical and chemical stability and surface active attributes, PFAS are coveted within an array of industrial and commercial products, such as film-forming fire foam to water, dirt and grease-repellent coatings. The many possibilities to use PFAS have led to environmental emissions, either through direct sources (~80%) like manufacturing and application of PFAS-containing products, or indirect sources (~20%), through decomposition and transport of precursors. Within the PFAS-family, perfluoroctanesulfonat (PFOS) and perfluoroctaneacid (PFOA) are the most well-known and studied chemicals which have gained particular attention due to their persistence and high frequency in the environment, in turn leading them to be easily detected in humans and animals globally. PFOS and PFOA have further shown bioaccumulative and toxic traits and have thus increased the regulatory interest in the chemicals in questions of environmental and human health. Measures have therefore been taken on national, regional and global levels to restrict the use and dispersion of selected PFAS-substances affiliated with negative effects. One of the contamination issues to have gained most attention in Sweden is the emission of film-forming fire foam from fire drill locations. The PFAS-containing foam has been used throughout the country for practicing extinguishing fires related to class B: liquid fires, and has been predominantly used by military, airports and industries. As a consequence from the multi decennial use and uncontrolled emissions, the PFAS concentration, mainly PFOS and PFOA, has been measured to be highest in connection with the exercise sites. The substances mobility and high water solubility has increased the risk for their transportation to nearby areas and they may through rainfall infiltrate the ground to potentially reach the groundwater where they risk contaminating nearby groundwater sources. In Sweden, contaminated PFAS-areas are a particularly debatable issue, as about 50% of Swedish drinking water comes from groundwater-related water sources and for that reason, they have increased the general concern for human exposure. Several examples of PFAS-rich drinking water in Swedish households have been found in municipalities as Botkyrka, Halmstad, Ronneby and Uppsala and have in some cases been so high that related water resources have been withdrawn. Even if the intake of drinking water containing large quantities of PFAS substances is not considered to give rise to acute health effects, awareness of the long-term effects of exposure to PFAS is still very limited. A number of experimental and epidemiological studies focusing on PFOS and PFOA, on the other hand, have documented that both high and low doses of the substances can cause a number of adverse health effects. More recently, regulations on legislation for PFAS have reduced the scope of application, preferably for PFOS, but in accordance with this, products such as PFOS-containing fire foams have been substituted with other PFAS which have continued to be used at fire drill locations in Sweden. Continuous emissions of PFAS at these sites are thus still an up-to-date and forthcoming issue, as the substances - together with already existing pollutants - will remain for a long time to come. There are therefore reasons to limit the use further, but due to the lack of data for most PFAS pollutants, there is currently no benchmark value issued by the EU for PFAS other than PFOS. However, the National Food Agency has issued limit values based on the presence of 11 PFAS substances (PFBS, PFHxS, 6:2 FTSA, PFBA, PFPeA, PFHxA, PFHpA, PFNA, PFDA, PFOA och PFOS) with an action threshold of 90 ng·L-1and a health-based limit value for 900 ng·L-1. The values ​​should give an indication that levels of PFAS which are larger in scope than the recommendation are too high and that measures should be taken to minimize the risk of spreading and unhealthy exposure to humans. For this reason, fire drill locations using fire-containing foam containing PFAS in Sweden are a high priority for mapping PFAS distribution in the country and identifying potential areas that are at risk of being affected by the spread of the pollutants in soil and water. As a result, two closed fire drill locations in Boden municipality - as part of a nationwide survey - have been investigated with regard to the fire extinguishing foam that has historically been used and caused pollution in the area. The PFAS-based fire foam is assumed to have had historical application to two exercise sites that operated between 1940 – 1985 and 1987 – 2005, respectively. In 2016, an environmental technical soil survey was carried out with regard to the presumed PFAS occurrence for the area. The investigation was based on sampling of soil and groundwater at four and eight different points respectively, centered around the two fire drill locations, and the results showed that the current contamination in the area was clearly noticeable and that the levels were higher than the Swedish Food Agency's recommended action threshold. Findings of PFOS that exceeded SGI's preliminary target value in groundwater (45 ng·L-1) and in soil (10 µg/kgTS) were also measured in connection with the two fire drill sites, which increased the interest in broadening the mapping of the current pollution situation with the aim of creating a better understanding of the extent of the pollution and potential spreading potential. Because the knowledge of the groundwater flow direction is limited, a hydrogeological model over the fire drill location can lead to a better understanding of the groundwater flow direction and thus the possible spreading direction of the present PFAS substances. The model can also be used as a tool for calculating the time required for the potential of the pollutants to affect the nearest protection object and thereby estimate and prevent the risks for human exposure in the area at the conceivable start of construction work in the now discontinued area. The results from the groundwater modelling showed that the groundwater from the fire drill areas in the upper groundwater reservoir moves in a northwesterly to northeasterly direction, but also towards the Lule River. In the lower groundwater reservoir, the water moves to the northwest and towards the Lule River. The contamination transport showed that PFOS tends to move toward the Lule River in a southwesterly direction. The transport time of PFOS from the fire training sites to the Lule River was estimated with MODPATH to 6 and 7 years respectively for the calibrated model and area 13/24. Visualization of the PFOS plume with MT3DMS showed that it takes about 100 years for the substances to reach the Lule River.

Inthe mining industry people remove rock from the ground to obtain a metal ore. Afterprocessing , the uneconomic fraction called tailings is deposited as a slurry in large reservoirs .The processing adds water and chemical agents to the tailings so that the original structure ofthe material therefore changes, which make storage of tailings complicated. If a tailingreservoir c ollapse s , it can damage p roperties and life downstream . In addition, tailings maycontain contaminants that disturb living organism s and contaminated groundwater in the localarea even under normal operation s . Therefore, tracing the contaminants and study ing thestability of the tailing reservoir s are important. The aim of the thesis is to investigate seepage,contaminant transport, tailings compaction and slope stability of the Zhaoli ditch tailingsreservoir (China) during its construction and afterwards. Simulations are performed with thecomputer program GeoStudio . According to the simulations and the conditions , contaminanttransport was highly related with total head. Total head boundary conditi ons have also a largeeffect on slope stability. The area that has most vertical displacement is at the middle of thetailing s reservoir , and the greatest change of vertical displacement is located near the slope,w here the vertical displacement can increa se 0.5 meter over a 1 0 30 meter distance. Theslope stability can be different from case to case, but the original designed tailing reservoirhave a good safety factor, indicating that the slope is not going to collapse easily. / Vi människor villutnyttja malm erna i marken för att skapa ett mer effektiv t industrisamhälleF ör att utvinna så myck et användbara metaller som möjligt tillsätts kemika lier och vattenunder anriknings processen, vilket gör att deponering av de vattenmättade restprodukt erna isandmagasin blir en utmaning med avseende på dammstabilitet och föroreningstransport.Eftersomdet är svårt att ändra på en färdig byggd damm för anrikningssand e n använder dettaexamensarbete av Geostudio för att simulera hur olika parameter påverkaföroreningstransport i dammen, vattenläckage från dammen samt da mmens stabilitet ochsäkerhet. Projektet har simulerat förhållanden i Zhaoli ditch damm i Kina .Simulering i GeoStudio visar att förorening sspridning är stark kopplad till den totalahydrauliska potentialen och materialets hydrauliska konduktivitet. Rand villkoren medavseende på den hydrauliska potentialen utanför dammen även har en stor inverkan pådammvallens stabilitet. De största vertikala sättningar sker i mitten av dammen, och denstörste sättningsgradient finns i dammvallens sluttning, där en vertikal sättning på 0.5 meteröver ett avstånd på 10 3 0 meter beräknas. Deformation är störst på första lagret överberggrunden. Simuleringarna visar att dammvallens sluttning är stab il med en tillräcklig högsäkerhetsfaktor.

Les travaux de cette thèse portent sur des méthodes de volumes finis sur maillages quelconque pour la discrétisation de problèmes d'évolution non linéaires modélisant le transport de contaminants en milieu poreux et les écoulements diphasiques.Au Chapitre 1, nous étudions une famille de schémas numériques pour la discrétisation d'une équation parabolique dégénérée de convection-reaction-diffusion modélisant le transport de contaminants dans un milieu poreux qui peut être hétérogène et anisotrope. La discrétisation du terme de diffusion est basée sur une famille de méthodes qui regroupe les schémas de volumes finis hybrides, de différences finies mimétiques et de volumes finis mixtes. Le terme de convection est traité à l'aide d'une famille de méthodes qui s'appuient sur les inconnues hybrides associées aux interfaces du maillage. Cette famille contient à la fois les schémas centré et amont. Les schémas que nous étudions permettent une discrétisation localement conservative des termes d'ordre un et d'ordre deux sur des maillages arbitraires en dimensions d'espace deux et trois. Nous démontrons qu'il existe une solution unique du problème discret qui converge vers la solution du problème continu et nous présentons des résultats numériques en dimensions d'espace deux et trois, en nous appuyant sur des maillages adaptatifs.Au Chapitre 2, nous proposons un schéma de volumes finis hybrides pour la discrétisation d'un problème d'écoulement diphasique incompressible et immiscible en milieu poreux. On suppose que ce problème a la forme d'une équation parabolique dégénérée de convection-diffusion en saturation couplée à une équation uniformément elliptique en pression. On considère un schéma implicite en temps, où les flux diffusifs sont discrétisés par la méthode des volumes finis hybride, ce qui permet de pouvoir traiter le cas d'un tenseur de perméabilité anisotrope et hétérogène sur un maillage très général, et l'on s'appuie sur un schéma de Godunov pour la discrétisation des flux convectifs, qui peuvent être non monotones et discontinus par rapport aux variables spatiales. On démontre l'existence d'une solution discrète, dont une sous-suite converge vers une solution faible du problème continu. On présente finalement des cas test bidimensionnels.Le Chapitre 3 porte sur un problème d'écoulement diphasique, dans lequel la courbe de pression capillaire admet des discontinuité spatiales. Plus précisément on suppose que l'écoulement prend place dans deux régions du sol aux propriétés très différentes, et l'on suppose que la loi de pression capillaire est discontinue en espace à la frontière entre les deux régions, si bien que la saturation de l'huile et la pression globale sont discontinues à travers cette frontière avec des conditions de raccord non linéaires à l'interface. On discrétise le problème à l'aide d'un schéma, qui coïncide avec un schéma de volumes finis standard dans chacune des deux régions, et on démontre la convergence d'une solution approchée vers une solution faible du problème continu. Les test numériques présentés à la fin du chapitre montrent que le schéma permet de reproduire le phénomène de piégeage de la phase huile. / In Chapter 1 we study a family of finite volume schemes for the numerical solution of degenerate parabolic convection-reaction-diffusion equations modeling contaminant transport in porous media. The discretization of possibly anisotropic and heterogeneous diffusion terms is based upon a family of numerical schemes, which include the hybrid finite volume scheme, the mimetic finite difference scheme and the mixed finite volume scheme. One discretizes the convection term by means of a family of schemes which makes use of the discrete unknowns associated to the mesh interfaces, and contains as special cases an upwind scheme and a centered scheme. The numerical schemes which we study are locally conservative and allow computations on general multi-dimensional meshes. We prove that the unique discrete solution converges to the unique weak solution of the continuous problem. We also investigate the solvability of the linearized problem obtained during Newton iterations. Finally we present a number of numerical results in space dimensions two and three using nonconforming adaptive meshes and show experimental orders of convergence for upwind and centered discretizations of the convection term.In Chapter 2 we propose a finite volume method on general meshes for the numerical simulation of an incompressible and immiscible two-phase flow in porous media. We consider the case that it can be written as a coupled system involving a degenerate parabolic convection-diffusion equation for the saturation together with a uniformly elliptic equation for the global pressure. The numerical scheme, which is implicit in time, allows computations in the case of a heterogeneous and anisotropic permeability tensor. The convective fluxes, which are non monotone with respect to the unknown saturation and discontinuous with respect to the space variables, are discretized by means of a special Godunov scheme. We prove the existence of a discrete solution which converges, along a subsequence, to a solution of the continuous problem. We present a number of numerical results in space dimension two, which confirm the efficiency of the numerical method.Chapter 3 is devoted to the study of a two-phase flow problem in the case that the capillary pressure curve is discontinuous with respect to the space variable. More precisely we assume that the porous medium is composed of two different rocks, so that the capillary pressure is discontinuous across the interface between the rocks. As a consequence the oil saturation and the global pressure are discontinuous across the interface with nonlinear transmission conditions. We discretize the problem by means of a numerical scheme which reduces to a standard finite volume scheme in each sub-domain and prove the convergence of a sequence of approximate solutions towards a weak solution of the continuous problem. The numerical tests show that the scheme can reproduce the oil trapping phenomenon.

The disposal of waste from agricultural activities has been recognised as a source of environmental contamination by endocrine disrupting chemicals (EDCs). The New Zealand dairy industry produces a large volume of dairy farm effluent, which contains EDCs in the form of estrogens. Most of this dairy farm effluent is applied onto the land for disposal. Groundwater and soil contamination by estrogens following waste application on the land have been reported overseas, but our understanding of the processes and factors governing the fate of estrogens in the soil is poor. Therefore the main goal of the present study was to better understand the fate and transport of estrogens, in particular 17β-estradiol (E2) and estrone (E1) in soil. In order to quantify E1 and E2 in drainage water and soil samples, chemical analysis by gas-chromatography mass-spectrometry (GC-MS) was carried out. This included sample extraction, sample clean-up through silica gel and gel permeation chromatography, and sample extract derivatisation prior to analysis. In order to develop a reliable method to extract estrogens from soil, research was conducted to optimise E1 and E2 extraction conditions by adjusting the number of sonication and shaking events, as well as the volume and type of solvent. Among five solvents and solvent mixtures tested, the best recovery on spiked and aged soil was obtained using an isopropanol/water (1:1) mix. A microcosm experiment was carried out to determine the dissipation rates of E2 and E1, at 8°C and at field capacity, in the Templeton soil sampled at two different depths (5-10 cm and 30-35 cm). The dissipation rates decreased with time and half-life values of 0.6-0.8 d for E1 and 0.3-0.4 d for E2 were found for the two depths studied. A field transport experiment was also carried out in winter, over three months, by applying dairy farm effluent spiked with estrogens onto undisturbed Templeton soil lysimeters (50 cm in diameter and 70 cm deep). The hormones were applied in dairy farm effluent at 120 mg m⁻² for E2 and 137 mg m⁻² for E1. The results of the transport experiment showed that in the presence of preferential/macropore flow pathways 0.3-0.7% of E2 and 8-13% of E1 was recovered in the leachate at the bottom of the lysimeters after 3 months, and 1-7% of the recovered E2 and 3-54% of the recovered E1 was leached within 2 days of application. These results suggest that leaching of estrogens via preferential/macropore flow pathways is the greatest concern for groundwater contamination. In the absence of preferential/macropore flow pathways, a significant amount (> 99.94%) of both hormones dissipated in the top 70 cm of soil, due to sorption and rapid biodegradation. Surprisingly, in all cases, estrogen breakthrough occurred before that of an inert tracer (bromide). This could not be explained by the advection-dispersion transport of estrogens, nor by their presence as antecedent concentrations in the soil. It was therefore suggested that colloidal enhanced transport of estrogens was responsible for the earlier breakthrough of estrogens and caused the leaching of a fraction of the applied estrogens to a soil depth of 70 cm. A two-phase model, adapted from a state-space mixing cell model, was built to describe the observed estrogen transport processes under transient flow. The model takes into account 3 transport processes namely, advection-dispersion, preferential/macropore flow and colloidal enhanced transport. This model was able to successfully describe the estrogen transport observed from the lysimeters.

Two of the most important environmental challenges in the 21st century are to protect the quality of fresh water resources and to utilize renewable energy sources to lower greenhouse gas emissions. This study contributes to the solution of the first challenge by providing methodologies for optimal design of real-time water quality monitoring systems and interpretation of data supplied by the monitoring system to identify potential pollution sources in river networks. In this study, the optimal river water quality monitoring network design aspect of the overall monitoring program is addressed by a novel methodology for the analysis of this problem. In this analysis, the locations of sampling sites are determined such that the contaminant detection time is minimized for the river network while achieving maximum reliability for the monitoring system performance. The data collected from these monitoring stations can be used to identify contamination source locations. This study suggests a methodology that utilizes a classification routine which associates the observations on a contaminant spill with one or more of the candidate spill locations in the river network. This approach consists of a training step followed by a sequential elimination of the candidate spill locations which lead to the identification of potential spill locations. In order to contribute the solution of the second environmental challenge, this study suggests utilizing available excess energy in water distribution systems by providing a methodology for optimal design of energy recovery systems. The energy recovery in water distribution systems is possible by using micro hydroelectric turbines to harvest available excess energy inevitably produced to satisfy consumer demands and to maintain adequate pressures. In this study, an optimization approach for the design of energy recovery systems in water distribution networks is proposed. This methodology is based on finding the best locations for micro hydroelectric plants in the network to recover the excess energy. Due to the unsteady nature of flow in water distribution networks, the proposed methodology also determines optimum operation schedules for the micro turbines.

O objetivo do trabalho é aplicar um modelo numérico que simule a propagação da pluma de contaminação derivada de chorume, como ferramenta numérica que permita uma análise dos parâmetros envolvidos no sistema, tendo como caso de estudo o lixão de São Pedro da Aldeia, levando em conta: o mecanismo de perda de massa durante o transporte e a variabilidade estatística dos principais parâmetros de entrada (input) no modelo numérico. A perda de massa durante o fluxo pode ocorrer tanto por sorção, como por decaimento microbiológico, será estimada através da interpretação probabilística de dados experimentais obtidos no lixão de São Pedro da Aldeia. Os resultados obtidos pela modelagem numérica serão comparados com os resultados experimentais de concentração do íon cloreto obtidos por medições em campo. Os resultados experimentais foram obtidos considerando distâncias crescentes em relação ao lixão, para oito intervalos de tempo distintos, permitindo, assim, comparar os resultados alcançados pela modelagem numérica com dados experimentais reais, obtidos em função do tempo e da distância ao lixão. Para a modelagem numérica, foi utilizada a equação diferencial do transporte advectivo-dispersivo, levando em conta um termo de perda de massa estimado a partir de interpretações estatísticas dos resultados experimentais obtidos. A solução da equação diferencial do fluxo advectivo dispersivo foi analisada pelo método dos volumes finitos, que se mostra adequado para problemas de avanço de frentes de saturação e/ou de contaminação. Para a modelagem probabilística, foi utilizado o Método de Rosenblueth (ou método das estimativas pontuais), considerando-se, como variáveis aleatórias mais relevantes: a condutividade hidráulica k, a concentração iônica inicial Co e o decaimento da concentração iônica em função da distância (x) ao lixão expresso por um termo bo em (mg/l/m). A interpretação estatística das concentrações medidas experimentalmente mostrou uma faixa de variabilidade muito bem representada pela faixa de variação obtida pela conjugação da solução da equação de transporte de contaminantes (pelo método dos volumes finitos) com análise de variabilidade por formulação FOSM (pelo método das estimativas pontuais de Rosenblueth). Os resultados obtidos indicam que, embora com a contaminação crescente, podemos avaliar com poucos dados a contaminação ao longo do tempo. As simulações indicaram coerência com o resultado obtido experimentalmente, validando assim o modelo utilizado. Entende-se que o trabalho conseguiu demonstrar a aplicabilidade e relativa praticidade no que diz respeito ao estudo do fluxo de contaminantes em meios saturados. Os resultados se mostraram satisfatórios no que tange ao entendimento das questões abordadas. / The objective of this work is to apply a numerical model that simulates the propagation of the contamination plume stemmed from leachate as a numerical tool that allows an analysis of the parameters involved in the system, having the landfill of São Pedro da Aldeia as study case. The model takes into account the loss of contaminant mass mechanism during transport and the statistical variability, in the numerical model, of the main input variables. The loss of mass during the flow, which can occur either in the form of sorption or as a microbiological decay, will be assed by probabilistic interpretation of experimental data. The results obtained by the numerical modeling will be compared to the experimental results of the ionic chloride concentration obtained by field mediations. The experimental results were obtained taking into account the growing distances in relation to the landfill, for eight different time intervals, allowing, this way, the comparison of the results reached by the numerical modeling with the real experimental data results, obtained due to the time and the distance of the landfill. For the numerical modeling, the differential equation of the advective-dispersive transport was used, taking into account a term of loss of mass estimated from statistical interpretations of the experimental results. The differential equation solution of the advective-dispersive flow was obtained by the finite volumes method, which was proved adequate to problems concerning the propagation of contaminating plumes in saturated soils. For the probabilistic modeling, the Rosenblueth Method (or point estimate method) was used, considering, as more relevant aleatory variables, the hydraulic conductivity k, the initial ionic concentration and the rate of concentration decay. The statistical interpretation of the concentrations experimentally measured showed one variability band well represented by the variation band obtained by the conjunction of the contaminant transport equation solution (finite volumes method) with the variability analysis of the FOSM formularization (Rosenblueths point estimate method). The obtained results indicate that even with the increasing contamination it is possible, with little data, to evaluate the contamination throughout time. The simulations indicated coherence with the experimentally obtained results validating, this way, the used model. The work demonstrates the applicability and the relative practicity concerning the study of the contaminant flow in saturated environments. Considering the understanding of the boarded questions, the results seemed satisfactory.

O objetivo do trabalho é aplicar um modelo numérico que simule a propagação da pluma de contaminação derivada de chorume, como ferramenta numérica que permita uma análise dos parâmetros envolvidos no sistema, tendo como caso de estudo o lixão de São Pedro da Aldeia, levando em conta: o mecanismo de perda de massa durante o transporte e a variabilidade estatística dos principais parâmetros de entrada (input) no modelo numérico. A perda de massa durante o fluxo pode ocorrer tanto por sorção, como por decaimento microbiológico, será estimada através da interpretação probabilística de dados experimentais obtidos no lixão de São Pedro da Aldeia. Os resultados obtidos pela modelagem numérica serão comparados com os resultados experimentais de concentração do íon cloreto obtidos por medições em campo. Os resultados experimentais foram obtidos considerando distâncias crescentes em relação ao lixão, para oito intervalos de tempo distintos, permitindo, assim, comparar os resultados alcançados pela modelagem numérica com dados experimentais reais, obtidos em função do tempo e da distância ao lixão. Para a modelagem numérica, foi utilizada a equação diferencial do transporte advectivo-dispersivo, levando em conta um termo de perda de massa estimado a partir de interpretações estatísticas dos resultados experimentais obtidos. A solução da equação diferencial do fluxo advectivo dispersivo foi analisada pelo método dos volumes finitos, que se mostra adequado para problemas de avanço de frentes de saturação e/ou de contaminação. Para a modelagem probabilística, foi utilizado o Método de Rosenblueth (ou método das estimativas pontuais), considerando-se, como variáveis aleatórias mais relevantes: a condutividade hidráulica k, a concentração iônica inicial Co e o decaimento da concentração iônica em função da distância (x) ao lixão expresso por um termo bo em (mg/l/m). A interpretação estatística das concentrações medidas experimentalmente mostrou uma faixa de variabilidade muito bem representada pela faixa de variação obtida pela conjugação da solução da equação de transporte de contaminantes (pelo método dos volumes finitos) com análise de variabilidade por formulação FOSM (pelo método das estimativas pontuais de Rosenblueth). Os resultados obtidos indicam que, embora com a contaminação crescente, podemos avaliar com poucos dados a contaminação ao longo do tempo. As simulações indicaram coerência com o resultado obtido experimentalmente, validando assim o modelo utilizado. Entende-se que o trabalho conseguiu demonstrar a aplicabilidade e relativa praticidade no que diz respeito ao estudo do fluxo de contaminantes em meios saturados. Os resultados se mostraram satisfatórios no que tange ao entendimento das questões abordadas. / The objective of this work is to apply a numerical model that simulates the propagation of the contamination plume stemmed from leachate as a numerical tool that allows an analysis of the parameters involved in the system, having the landfill of São Pedro da Aldeia as study case. The model takes into account the loss of contaminant mass mechanism during transport and the statistical variability, in the numerical model, of the main input variables. The loss of mass during the flow, which can occur either in the form of sorption or as a microbiological decay, will be assed by probabilistic interpretation of experimental data. The results obtained by the numerical modeling will be compared to the experimental results of the ionic chloride concentration obtained by field mediations. The experimental results were obtained taking into account the growing distances in relation to the landfill, for eight different time intervals, allowing, this way, the comparison of the results reached by the numerical modeling with the real experimental data results, obtained due to the time and the distance of the landfill. For the numerical modeling, the differential equation of the advective-dispersive transport was used, taking into account a term of loss of mass estimated from statistical interpretations of the experimental results. The differential equation solution of the advective-dispersive flow was obtained by the finite volumes method, which was proved adequate to problems concerning the propagation of contaminating plumes in saturated soils. For the probabilistic modeling, the Rosenblueth Method (or point estimate method) was used, considering, as more relevant aleatory variables, the hydraulic conductivity k, the initial ionic concentration and the rate of concentration decay. The statistical interpretation of the concentrations experimentally measured showed one variability band well represented by the variation band obtained by the conjunction of the contaminant transport equation solution (finite volumes method) with the variability analysis of the FOSM formularization (Rosenblueths point estimate method). The obtained results indicate that even with the increasing contamination it is possible, with little data, to evaluate the contamination throughout time. The simulations indicated coherence with the experimentally obtained results validating, this way, the used model. The work demonstrates the applicability and the relative practicity concerning the study of the contaminant flow in saturated environments. Considering the understanding of the boarded questions, the results seemed satisfactory.