This study investigated the changes in leachate composition and clogging evolution in leachate transmission pipes and the use of methanogenesis as a leachate treatment alternative for Bioreactor landfills, by using pilot-scale and laboratory studies. The pilot-scale study consisted of a research station built at Brady Road Landfill, housing sixteen HDPE pipes of three different diameters, conveying leachate intermittently at eight different Reynolds numbers, under reasonably controlled conditions. The pipes were tested for leachate degradation, clogging evolution and hydraulic impairment over time. The laboratory studies carried out tested (1) the effect of turbulence intensity and temperature on leachate degradation and clogging effects and (2) biological pretreatment of leachate prior to injection into a bioreactor cell. The pilot study results showed that under the conditions tested, pipes developed a significant amount of organic and inorganic clog material in less than a year of operation. Since limited quantities of fresh leachate (approx. 3 m3) were used during each leachate degradation analyses, the anticipated effects of clogging in a full scale injection system are expected to be more pronounced, which can negatively impact the long-term hydraulic performance, operation, and service life of a Bioreactor Landfill. The first laboratory study showed that increasing the turbulent energy dissipation rate caused greater amounts of CO2 evolution from the leachate, and temperature increase had an impact on dissolved Ca2+ under atmospheric conditions, affecting clog development. The second and third laboratory studies showed that performing leachate methanogenesis reduces organic (COD, VFA) and inorganic (Ca2+, ISS) clog constituents within the leachate However, the rate of methanogenesis was influenced by the ratio of acetate and propionate. It is suggested that if leachate undergoes methanogenesis in a separate leachate digester prior to re-injection into a bioreactor waste cell, it may protect the pipes and other engineered landfill systems against clogging and its detrimental effects, while allowing for CH4 recovery. However, blending of leachates from different wells or cells prior to the methanogenic digester may be needed to balance the variable concentrations and ratios of acetate and propionate over time from different landfill wells and cells.

Geossintéticos são materiais cada vez mais aplicados em aterros sanitários, cumprindo diferentes funções como barreiras para líquidos e gases. Na função de filtração, o uso destes materiais não está consagrado, principalmente, em função da possível colmatação total ou parcial dos geotêxteis por ação de microrganismos, a chamada colmatação biológica. Neste contexto, o presente trabalho visa avaliar a colmatação de geotêxteis tecidos e não tecidos submetidos ao fluxo de lixiviado de aterro sanitário. Foram utilizados três geotêxteis não tecidos de gramatura 200 g/m², sendo um de filamento contínuo de poliéster (PET) e dois de fibra curta, porém fabricados com polímeros diferentes poliéster e polipropileno (PET e PP) e um geotêxtil tecido de polipropileno, com gramatura 400 g/m². Para avaliar a colmatação dos geotêxteis montaram-se ensaios de permeabilidade de longa duração em que se mediu a condutividade hidráulica ao longo do tempo. Após os ensaios de permeabilidade, realizou-se microscopia eletrônica de varredura para avaliar o fechamento dos poros dos geotêxteis, além de avaliar o crescimento bacteriano ocorrido no interior do geotêxtil. Os resultados obtidos permitem constatar significativa redução da condutividade hidráulica dos materiais após o período de 30 dias de ensaios, onde notou-se a predominância do processo de cegamento. / Geosynthetics materials have been intensively used in landfills in different functions as liquid and gas barriers. As filters, geosynthetics are not completely accepted in designs, since total or partial geotextile clogging can occur for biotic deposition (or impregnation), usually named biological clogging. This work evaluates the clogging on nonwoven and woven geotextiles under leachate flow for landfill application. For this purpose, nonwoven geotextiles with short and long polyester filaments and mass per unit area of 200 g/m² were used, as well as polypropylene and polyester nonwoven geotextiles with mass per unit area of 400 g/m². Cross-plane permeability tests were periodically conducted in geotextiles samples which were under long term leachate flow. After each permeability test, scanning electron microscopy (SEM) was conducted to evaluate the source of pore geotextile clogging, as well as the bacteria growing into the geotextile matrix. Results have shown a significantly reduction on hydraulic conductivity of geotextile filters after 30 days of leachate flow, which was motivated by blinding process.

Neste trabalho buscou-se avaliar a suscetibilidade dos diferentes modelos de tubos gotejadores ao processo de entupimento quando expostos ao uso de cloreto de potássio (branco e vermelho), aplicados via diferentes qualidades de água. O experimento foi realizado em três fases, por um período de doze meses, analisando o desempenho de 22 modelos de gotejadores (autocompensante e convencionais), com quatro tratamentos e dez repetições, sendo cada repetição representada por um gotejador. Na primeira fase, foram aplicados os seguintes tratamentos: (T1) água com fitoplâncton (lago) e cloreto de potássio branco; (T2) água com fitoplâncton (lago) e cloreto de potássio vermelho; (T3) água potável (laboratório) e cloreto de potássio branco; (T4) água potável (laboratório) e cloreto de potássio vermelho. Na segunda fase foram adicionadas partículas sólidas (solo) às soluções dos tratamentos 1 (T1-Lg/B) e 2 (T2-Lg/V), mantendo a mesma solução do tratamento 3 (T3-Lb/B) e adicionado sulfato de ferro à solução do tratamento 4 (T4-Lb/V). Na terceira fase acrescentou-se hidróxido de ferro às soluções referentes a T1 (T1+So) e T2 (T2+So), mais uma aplicação de uma solução concentrada diretamente nas linhas (tubos gotejadores) sem passar pelo sistema de filtragem, sendo os tratamentos: (T1) Água do lago, cloreto de potássio branco, partículas sólidas e hidróxido de ferro, com o orifício do gotejador posicionado para baixo. (T2) água do lago, cloreto de potássio vermelho, partículas sólidas e hidróxido de ferro, com o orifício do gotejador posicionado para cima. (T3) água do lago , cloreto de potássio branco, partículas sólidas e hidróxido de ferro, com o orifício do gotejador posicionado para cima. (T4) água do lago, cloreto de potássio vermelho, partículas sólidas e hidróxido de ferro, com o orifício do gotejador posicionado para baixo. Os modelos de tubos gotejadores analisados apresentaram desempenhos variáveis, tanto na suscetibilidade ao entupimento quanto no coeficiente de variação de vazão, sugerindo que a arquitetura interna dos gotejadores, foi o fator determinante na caracterização do processo de entupimento. Não foi observada diferença significativa da dinâmica de entupimento com relação à aplicação dos cloretos de potássio branco e vermelho na ausência ou presença de fitoplâncton, mostrando que é possível fazer uso do cloreto de potássio vermelho em fertirrigação, tomando o cuidado de verificar a ausência do elemento ferro no adubo (análise de laboratório). A adição de partículas sólidas e do sulfato de ferro aos tratamentos da primeira fase, passando pelo sistema de filtragem, não potencializou mudanças significativas do cenário de suscetibilidade ao entupimento, nas condições de irrigação da segunda fase. A entrada de partículas sólidas e hidróxido de ferro no sistema sem passar pelo sistema de filtragem (fase 3) e o posicionamento do orifício dos gotejadores para baixo intensificaram o processo de entupimento, onde os modelos convencionais foram os mais sensíveis e alguns modelos autocompensantes foram mais tolerantes a presença destes elementos na água de irrigação. O modelo C3 foi o que apresentou melhor desempenho entre os modelos convencionais nas três fases estudadas, sendo que os modelos A2 e A3 destacaram-se entre os modelos autocompensantes, com uma boa recuperação da vazão ao final dos ensaios. / This work aims to evaluate the susceptibility of several dripline models against clogging process when exposed to potassium chloride (white and red), applied through different water qualities (fertirrigation). The experiment was accomplished in three phases, during a period of twelve months, analyzing the performance of 22 drip models (compensating and conventional), with four treatments and ten repetitions, being each repetition a dripper. In the first phase, it was applied the following treatments: (T1) water with fitoplancton (lake) and white potassium chloride; (T2) water with fitoplancton (lake) and red potassium chloride; (T3) potable water (laboratory) and white potassium chloride; (T4) potable water (laboratory) and red potassium chloride. In the second phase, solid particles were added to the solutions of previous treatments 1 (T1-Lg/B) and 2 (T2-Lg/V), maintaining the same solution for treatment 3 (T3-Lb/B) and added iron sulfate to the solution of treatment 4 (T4-Lb/V). In the third phase iron hydroxide was added to the solutions of T1 (T1+So) and T2 (T2+So) treatments, one more application of a concentrated solution directly in drip lines without passing through the filtration system, resulting the following treatments: (T1) water with fitoplancton, white potassium chloride, solid particles and iron hydroxide, with dripper facing down. (T2) water with fitoplancton, red potassium chloride, solid particles and iron hydroxide, with drippers facing up, (T3) water with fitoplancton , white potassium chloride, solid particles and iron hydroxide, with drippers facing up, (T4) water with fitoplancton, red potassium chloride, solid particles and hydroxide of iron, with drippers facing down. Driplines presented a variable performance, regarding the original flow rate levels and variation coefficient, suggesting that internal architecture of emitters, it is a major factor related to clogging resistance to treatments imposed. Statistical differences were not observed for clogging dynamics under the application of white or red potassium chloride, under different water quality conditions, showing that it is possible to use the red potassium chloride for fertirrigation without problems. It is recommended to certify the absence of iron element in the fertilizer based on laboratory analysis. The addition of solid particles and iron sulfate to first phase treatments, going through the filtration system, did not increase the clogging rate or emitters (second phase). The application of solid particles and iron hydroxide in the system without passing through the filtration system (phase 3) and the positioning of drippers facing down, intensified the clogging process. Conventional models were more sensitive and compensating models were more tolerant of this water quality conditions. Models C3 performance better among the conventional models in all phases studied. Models A2 and A3 stood out among compensating models, presenting a good recovery flow rate at the end of the experiment.

Les bassins d’infiltration sont de plus en plus utilisés en milieux urbains pour la réduction des eaux de ruissellement et la recharge des nappes phréatiques. Toutefois, leur fonctionnement est souvent affecté par des problèmes de colmatage, physiques, chimiques et/ou biologiques, qui conduisent à une diminution des capacités d’infiltration et à une altération potentielle de la qualité des eaux infiltrées. Aussi, la prévention de ce risque devient-elle un enjeu majeur pour garantir la pérennité des ouvrages d’infiltration et la qualité des eaux infiltrées. Si les mécanismes impliqués dans le colmatage sont décrits assez finement dans le cas des processus purement physiques ou géochimiques, les verrous scientifiques sont encore importants pour comprendre la contribution du compartiment biologique (biofilms, végétation, invertébrés). Ce travail de thèse avait ainsi pour objectif de quantifier l’influence du compartiment biologique sur les processus de colmatage et de décolmatage dans des bassins d’infiltration. Pour cela, il était composé de deux grands volets : (i) le premier visait à évaluer la contribution relative du biofilm et de l’accumulation de particules fines sur les paramètres hydrodynamiques du milieu poreux support d’infiltration, ceci dans 2 bassins aux caractéristiques contrastées, (ii) le second avait pour objectif d’évaluer les potentialités de processus écologiques (bioturbation, broutage, allélopathie) à décolmater les bassins par l’introduction de macro-organismes (invertébrés et macrophytes) en mésocosmes ou par encagements in situ. Les résultats ont mis en évidence le rôle déterminant de la composante phototrophe des biofilms sur la dégradation de perméabilité des supports d’infiltration. Un effet seuil de la biomasse phototrophe a été observé sur le rayon moyen des pores hydrauliquement fonctionnels, avec pour conséquences des effets non-linéaires sur la perméabilité. Face à ce colmatage biologique, les résultats obtenus en mésocosmes ont clairement montré que la présence de macrophytes tels que Vallisneria spiralis L. et Chara globularis L. permettait de réduire la biomasse algale par allélopathie. Par la suite, l'introduction par encagement dans un bassin d'infiltration de l’espèce V. spiralis a démontré sa potentialité à réduire le phénomène de colmatage en affectant la physiologie du biofilm algal. De plus, l'introduction du gastéropode aquatique Viviparus viviparus qui se nourrit directement du biofilm permettait de maintenir et même d’améliorer les capacités d’infiltration du bassin. Ces résultats offrent des perspectives intéressantes pour le développement futur de techniques d’ingénierie écologique dans la gestion et l’amélioration de la durée de vie des ouvrages d’infiltration. / Infiltration basins are increasingly used in urban areas for stormwater management or groundwater recharge. However, their functions are often affected by physical, chemical and / or biological clogging, leading to a decrease in infiltration rate and a potential alteration of infiltrated water quality. The prevention of clogging is therefore becoming a major challenge to ensure the sustainability of infiltration devices and the quality of infiltrated water. Although the mechanisms involved in clogging are accurately described for purely physical and geochemical processes, scientific obstacles still prevent from understanding the contribution of biological compartment (i.e. biofilms, vegetation, invertebrates). The aim of this work was to quantify the influence of biological compartment on clogging/unclogging processes in infiltration basins. It was divided in two objectives: (i) To assess the relative contribution of biofilm and fine particle accumulation on the hydrodynamic parameters of the porous media in two basins with contrasting characteristics. (ii) To assess the potential of ecological processes (bioturbation, grazing, allelopathy) to unclog the basins, by the introduction of macro-organisms (invertebrates and macrophytes) in mesocosms or in situ enclosures. Results highlighted the critical role of the phototrophic component of biofilms on the degradation of infiltration media permeability. A threshold effect of algal biomass was observed on the hydraulically functional pore size, with non-linear consequences on the permeability. Faced with this biological clogging, the results obtained with mesocosm experiments clearly showed that the presence of the macrophytes Vallisneria spiralis L. and Chara globularis L. could reduce algal biomass by allelopathy. The introduction of V. spiralis by enclosure in an infiltration basin then demonstrated its potential to reduce the clogging by affecting algal biofilm physiology. In addition, the introduction of the aquatic gastropod Viviparus viviparus, which feeds directly on the biofilm, allowed to maintain, and even improve, the infiltration capacity of the basin. These outcomes offer interesting perspectives for the future development of ecological engineering techniques, to manage and improve the lifetime of infiltration devices.

La formation de bouchon est un problème récurrent et presque inévitable lors de l'écoulement de solutions diluées dans des milieux poreux. Actuellement, on ne sait pas comment, à partir du processus initial de déposition de particules à la paroi, ces dernières s'accumulent dans le pore et finissent par le boucher. L'idée générale de ce travail est d'étudier la dynamique de formation de bouchon lors l'écoulement de particules colloïdales au sein de matériaux poreux modèles (canaux microfluidiques). Nous décrivons dans un premier temps, les différents phénomènes physiques impliqués dans la capture de particules et dans l'agrégation colloïdale. Nous faisons également une brève présentation des différentes techniques d'imagerie utilisées dans ce travail et des méthodes de préparation des solutions colloïdales ainsi que des dispositifs microfluidiques. Le troisième chapitre est consacré à l'étude du processus de colmatage en situation de fort confinement (2d). Nous avons identifié deux régimes de colmatage (régime de ''ligne'' et ''d'invasion''). Nous avons ensuite déterminé les processus de capture de particules à l'origine de ces deux régimes, à l'échelle de la particule. Nous avons montré que le processus de colmatage correspond à un phénomène d'auto-filtration. Alors que les premières particules sont capturées de manière « directe » par les parois du pore, la déposition de toutes les suivantes résulte systématiquement d'une interaction avec ces dernières. Finalement, nous avons abordé le colmatage de pore 3d, dont la hauteur est égale à la largeur du pore. Nous avons fourni une description détaillée de l'ensemble du processus de colmatage, à l'échelle du pore et de la particule. Nous avons déterminé les conditions d'adhésion des premières particules à la paroi du pore, les propriétés de croissance des agrégats, ainsi que la manière dont ils se connectent pour obstruer le pore. Nous avons montré que cette dynamique de formation conduit à une structure finale de bouchon très ténue. / Clog formation is a recurring and almost inevitable issue when dilute solution of particles flows in porous media. Currently, we do not know how, from the initial process of particle deposition on the pore wall, particles accumulate in the pore leading to its blocking. The main idea of this work is to study the dynamics of the clog formation, when colloidal particles flow through a single pore (microfluidics channels). In a first part, we describe the various physical phenomenon involved in the particle capture and the colloidal aggregation. We also describe briefly the imaging techniques used in this work as well as the colloidal solution and micro-fluidics chips preparation. The third chapter is devoted to the study of the clogging process in high confinement (2d). We identified two clogging regimes (“line” and “invasion”). We then studied the underlying capture mechanisms, at the particle scale, related to both clogging regimes. We showed that the blockage process corresponds to a self-filtration process. The first particles are captured “directly” by the pore walls, while the deposition of all the following ones systematically results from hydrodynamic interactions with those first still particles. Finally, we addressed the clogging of a 3d pore, in which the height of the pore is equal to its width. We gave a detailed description of the whole clogging process at the pore and at the particle scale. We provided the conditions for the adhesion of the first particles on the pore walls, the properties of subsequent aggregates growth, and how the aggregates eventually merge in order to block the pore. We showed that this dynamics of formation leads to a very loose clog structure.

Hydropower regulation of rivers exhibits a threat to the riverine ecosystems. Fragmentation of flow, landscape disturbances, and water retention are key features of regulated catchments, resulting in reduced floods and geochemical tr¬ansport, non-natural water level fluctuations, and thus disturbed exchange between the river and the aquifer. Storing of water in reservoirs reduces peak flow and turbidity, which increases particle settling and sometimes favours enhanced primary production and formation of a clogging layer. This in turn alters the interaction between surface water and groundwater, with potential secondary effects on the entire watershed. In Scandinavia, only eight large rivers (16%) remain entirely unregulated. The Lule River, the primary focus of this study, belongs to the most regulated rivers of Eurasia with a degree of regulation (i.e. the volume of water that can be stored in the reservoirs and used for regulation) of 72%, and is exposed to both seasonal and short-time regulation.Using hydrogeochemical analysis of two adjacent boreal rivers (pristine Kalix and regulated Lule River) discharging into the Gulf of Bothnia, the effects of regulation on river geochemistry were investigated. For the Lule River, the average maximum runoff was almost halved while the average minimum runoff was tripled as a result of the regulation. The winter transport fraction of total organic carbon, Fe, Si, suspended Mn and P in the Lule River was at least two to three times higher than in the pristine river. During summer, the suspended C/N ratio in the regulated river was 10-20, compared to <10 for the pristine river, suggesting a presence of predominantly decaying organic material due to longer residence times for the regulated river. This was supported by a virtually constant suspended P/Fe ratio throughout the year in the Lule River, indicating low abundance of phytoplankton. Hence, a pronounced impact on the ecosystem of the river, the hyporheic/riparian zone, and the Gulf of Bothnia is expected.In spite of vast anthropogenic pressure on riverine ecosystems, the knowledge regarding the hyporheic zone (the interface between rivers and aquifers where exchange between surface water and groundwater occurs) is limited for regulated rivers. Therefore, this study was extended to also cover the hyporheic exchange along the Lule River. Temporal changes in hyporheic fluxes across the river channel (rates and directions) were determined using seepage measurements and continuous observations of water stages, temperatures, and electrical conductivity for both the river and the groundwater. While the river water level changed frequently (typically twice a day with up to ± 0.5 m), the river remained gaining 90% of the time, and the largest number of observed changes in flow direction (observed at 5 m orthogonal distance from the river) was six times per week. Flow velocities ≤10-4 m d-1 ( zero flow) constituted 1.5% of the total observation time.Although no changes in water temperature were observed for the hyporheic zone, effects of river level variations were detected up to 5 m inland, where electrical conductivity occasionally decreased to surface water levels indicating infiltration of river water into the aquifer (negative fluxes). River discharge regulation may therefore have severe implications on biogeochemical processes and deteriorate the hydroecological functions of the hyporheic zone.

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