L'idée de base est de permettre à deux microorganismes de partager le même environnement tout en les maintenant séparées à l'aide d'une membrane perméable les retenant sélectivement. La principale contrainte résulte du transfert des composées d'intérêts limité par l'écoulement dans et autour des fibres ainsi que dans module et par le colmatage. Le double bioréacteur a membrane étudié dans cette thèse, de par son fonctionnement, alterne les cycles de filtration et rétrofiltration (ou rétrolavage), limitant ainsi en partie le colmatage. Ce travail de thèse s'est donc attaché à approfondir la connaissance des mécanismes de limitation au transfert mis en jeu lors de la filtration de fluide biologique complexes et évolutifs en fonction des conditions opératoires et des caractéristiques géométriques du module de filtration à fibres creuses. Dans cet objectif, sur la base des choix de configuration de module membranaire proposés dans cette étude, et afin de tendre vers une optimisation rationnelle de l'utilisation de ce dispositif, l'étude s'appuya sur l'utilisation d'outils de mécanique des fluides numériques, complétée par une approche expérimentale menée dans des conditions modèles. Les simulations réalisées par cette approche ont ainsi mis en évidence de grandes variations des vitesses de filtration le long de la fibre et ceci en lien direct avec une augmentation de la perte de charge à l'extérieur des fibres due au confinement induisant une baisse des performances de filtration. De manière similaire, un modèle numérique de formation de dépôt nous a permis d'évaluer l'effet du confinement de fibres. Il entraine une augmentation de pression dans la partie fluide externe induisant une forte variation de pertes de charges entrainant une répartition du dépôt le long de la fibre beaucoup plus inhomogène. Le retour du numérique à l'expérimental réalisé s'est attaché à décrire l'influence des conditions de mise oeuvre sur les performances de filtration du pilote. L'analyse méthodique de l'influence du sens de filtration et de la compacité dans le cas de fluides modèles (suspension de différents microorganismes / solutions de protéines modèles) et dans le cas de fluides biologiques évolutifs (milieux de fermentation + micro organismes) fut réalisée. L'ensemble de ces résultats nous permettent de donner des recommandations aux futurs utilisateurs du double bioréacteur à membranes. / This work presents a specific bioreactor previously designed to study microbial interactions. In this process, the microbial species in two tanks are physically separated by a microfiltration membrane. In order to give to the microorganisms a molecular environment in each compartment similar to the one that would be obtained if the microbial cells were cultivated in the same reactor, two criteria have to be considered: (i) the flow rates between compartments have to be sufficient with respect to the microbial kinetics and (ii) all the molecular compounds of the medium that have an effect on the microorganism behaviour must pass through the membrane. The main constrain is due to transfer of component limited by the fluid flow in and around the fiber of the filtration module. This thesis has therefore committed to deepening the understanding of the mechanisms limiting the transfer involved during the filtration of biological fluid complex according to operating conditions and geometric characteristics of the hollow fiber module of filtration. For this purpose, based on the choice of membrane module configuration proposed in this study, and to strive for a rational optimization of the use of this device, the study relied on the use of CFD tools, supplemented by an experimental approach conducted under models conditions. The numerical simulations of fluid flow have shown a modification of the axial filtration velocity profile with packing density. Similarly, a numerical model of cake deposit was developed and show difference of cake growth along the fiber with packing density. Two experimental hollow fiber modules with two packing densities were tested with clean water and biological fluid, and showed good agreement with the numerical data. These results underline the variations of filtration velocity along the fiber that will allow some predictions on fouling deposit to be done.

Over the past few decades, a growing interest in the thermal conversion of alternative fuels such as biomass and waste-derived fuels has been observed among the energy-producing companies. Apart from meeting the increasing demand for sustainable heat and power production, other advantages such as reducing global warming and ameliorating landfilling issues have been identified. Among the available thermal conversion technologies, combustion in grate-fired furnaces is by far the most common mode of fuel conversion. In recent years, Fluidized-Bed (FB) technologies have grown to become one of the most suitable technologies for combustion and gasification of biomass and waste-derived fuels.In spite of the benefits, however, some difficulties are attributed to the thermal conversion of the alternative fuels. Ash-related issues could be a potential problem, as low-grade fuels may include considerable concentrations of ash-forming elements such as K, Na, S, Ca, Mg, P, Si and Cl. These elements undergo many undesirable chemical and physical transformations during the thermal conversion, and often cause operational problems such as deposition-related issues, slag formation in furnaces, corrosion of the heat transfer surfaces, and bed agglomeration of the fluidized-beds. Ash-related problems in the utility boilers are a major concern that may result in decreased efficiency, unscheduled outages, equipment failures, increased cleaning and high maintenance costs.This thesis investigated the ash behavior and ash-related problems in two different FB conversion systems: a Bubbling Fluidized-Bed (BFB) boiler combusting solid waste, and a Dual Fluidized-Bed (DFB) gasifier using biomass as feedstock. Full-scale measurements, chemical analysis of fuel and ash, as well as thermodynamic equilibrium modeling have been carried out for the BFB boiler (Papers I-IV), to investigate the impact of reduced-bed temperature (RBT) and also co-combustion of animal waste (AW) on the ash transformation behavior and the extent of ash-related issues in the boiler. For the DFB gasifier (Paper V), a thermodynamic equilibrium model was developed to assess the risk of bed agglomeration when forest residues are used as feedstock.The experimental results showed that the RBT and AW co-combustion could decrease or even resolve the ash-related issues in the BFB boiler, resulting in a lower deposit-growth rate in the superheater region, eliminating agglomerates, and a less corrosive deposit (in RBT case). Thermodynamic equilibrium modeling of the BFB boiler gave a better understanding of the ash transformation behavior, and also proved to be a reliable tool for predicting the risk of bed agglomeration and fouling. The modeling of the DFB gasifier indicated a low risk of bed agglomeration using the forest residues as feedstock and olivine as bed material, which was in good agreement following the observations in a full-scale DFB gasifier.

Les bioréacteurs à membranes (BAM) sont de plus en plus utilisés dans le domaine du traitement des eaux résiduaires urbaines notamment lorsque le terrain est limité ou qu’un traitement épuratoire poussé est requis. Néanmoins, la gestion de ces installations et plus particulièrement du colmatage des membranes reste difficile et constitue toujours une source de problèmes pour les exploitants. La modélisation est un outil efficace et déjà éprouvé sur les procédés conventionnels à boues activées pour l’aide à la conduite et à la compréhension de procédé avec les modèles de boues activées de type ASM. Le traitement biologique donc, et aussi les capacités de filtration des membranes (colmatage) sont deux aspects qui peuvent être modélisés sur les BAM. Au cours de ce travail, trois installations réelles ont été étudiées et l’une d’entre elles a été choisie pour le calage du modèle ASM1. La méthodologie a été adaptée aux spécificités des bioréacteurs à membranes et de l’installation modélisée en particulier (fractionnement des eaux usées, calage de l’aération) et un nouveau jeu de paramètres de l’ASM1 a pu être constitué. L’influence des propriétés des boues activées et des conditions d’opération sur les capacités de filtration des membranes reste encore l’objet de nombreuses recherches, généralement sur installations pilotes, et la modélisation dans ce domaine n’en est qu’à ses débuts. L’objectif de ce travail concernant la filtration membranaire a été de caractériser le système « membrane/boues » à travers l’étude des interactions entre les propriétés des boues, les conditions d’opération et les paramètres de la filtration (perméabilité membranaire et vitesse de colmatage) à comparer avec les résultats de la littérature scientifique. Les deux BAM étudiés ont montré des comportements et relations entre paramètres assez différents confirmant la complexité des interactions entre membrane, boues et conditions opératoires. / Membrane bioreactors (MBRs) are becoming increasingly popular for the treatment of municipal wastewater especially when land is limited or when the treatment requirements are high. Nevertheless, the operation of these plants and in particular the fouling of the membrane are still difficult to manage for the operators. Modelling is an efficient tool, which has already been successfully used on conventional activated sludge processes, for the operation and the understanding of the process using Activated Sludge Models (ASM). Biological treatment and membranes filtration capacity (fouling) are two aspects that can be modeled on MBRs. In this work, three full-scale plants were investigated and one of them was chosen for the ASM1 calibration. The usual methodology was adapted to the MBR specificities and to the modeled wastewater treatment plant in particular (wastewater fractionation, oxygen calibration) and a new set of ASM1 parameters was estimated. The influence of the sludge properties and the operating conditions on the membrane filtration capacity is still the subject of numerous studies, generally on pilot-scale MBRs, and modelling is in its early stages. The objective of this work regarding membrane filtration was to characterize the “membrane/sludge” system by studying the interactions between the sludge properties, the operating conditions and the filtration parameters (membrane permeability and fouling rate) and to compare them with the results from the literature. The two studied MBRs showed quite different behaviors and correlations between parameters, validating the statement that the interactions between membranes, sludge and operating conditions are very complex.

La clarification des vins par procédés membranaires en particulier la microfiltration tangentielle a toujours été limitée par le colmatage, générant des flux de perméation faibles incompatibles avec la rentabilité économique. La compréhension, la maîtrise, ainsi que l'anticipation des phénomènes de colmatage font l'objet de ce travail. Dans un premier temps, la contribution individuelle puis en mélange des composés du vin (tannins, pectines, mannoprotéines et levures) au colmatage d'une membrane céramique multicanaux a été évaluée. Une approche fondamentale a permis de proposer des mécanismes de colmatage : la présence des pectines induit les flux de perméation les plus faibles en formant un gel à la surface de la membrane tandis que les levures semblent au contraire avoir un effet protecteur dans le cas d'un vin brut. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique pour l'irréversibilité est un paramètre clef pour contrôler le colmatage. Dans le cas de la filtration de vin, aucun flux critique n'a pu être déterminé ce qui a conduit à définir un critère identifiant une zone de travail où le degré de colmatage reste acceptable. La dernière partie de cette thèse est consacrée à l'étude de la filtration dynamique (RVF) pour une éventuelle application dans le secteur vinicole. Cette technique est testée en présence de deux membranes organiques différentes: PES (hydrophile) et PTFE (hydrophobe). Les observations ont permis de mettre en évidence l'efficacité du système contre le colmatage des membranes PES induite par l'action de l'agitateur. Le colmatage des membranes PTFE est énormément affecté par les interactions molécules/membrane rendant la filtration dynamique inefficace pour lutter contre le colmatage de ces membranes. / Wine clarification by membrane processes mainly cross-flow microfiltration has been limited by membrane fouling generating low permeate fluxes with economic efficiency. Understanding, controlling and anticipation of fouling are the main goals of this work. In a first time, the individual contribution of wine compounds (tannins, pectins, mannoproteins and yeasts) to a multichannel ceramic membrane fouling was evaluated. The fouling mechanisms were analyzed using a fundamental approach. The presence of pectins induce the lowest fluxes by a gel-type formation at the membrane surface while yeasts presence tends to reduce fouling in the case of crude wine (case of mixed components). Because it represents the flux beyond which irreversible fouling appears on the membrane surface, the critical flux for irreversibility is a key parameter to control fouling. No critical flux for irreversibility could be measured, hence a criterion that identifies a range of operating conditions where the degree of fouling remains acceptable was proposed. The last part of this work was devoted to the study of dynamic filtration (RVF) for further application in wine sector. This technique was tested with two different membranes: hydrophilic PES and hydrophobic PTFE. Results have allowed to demonstrate the efficiency of the system to reduce fouling in the case of PES membrane. Fouling of PTFE membrane is greatly influenced by molecules / membrane interaction making dynamic filtration ineffective in reducing of membrane fouling.

Dans les fours de raffinerie, l'efficacité du transfert énergétique vers le pétrole brut avant sa distillation est altérée par la formation d'un composé carboné dans les tubes, appelé coke. Cela conduit à l'augmentation des coûts de production et de maintenance, et exige une compréhension accrue ainsi qu'un meilleur contrôle de ce phénomène. Cet encrassement est de type chimique et induit par les fortes températures. Dans les fours de cette dimension, le transfert de chaleur s'effectue principalement par rayonnement des produits de combustion. Le flux radiatif net sur les surfaces d'échange des tubes dépend de la température de toutes les surfaces solides et a donc besoin d'être prédit avec une précision suffisante. La température sur les tubes est le résultat d'un équilibre entre le rayonnement thermique et la conduction. Le comportement thermique de l'ensemble du système est un problème de couplage entre le rayonnement et la conduction. Une méthodologie complète de couplage est exposée et validée de la manière suivante. Dans ce problème, la flamme est décrite par un modèle analytique axisymétrique avec chimie complexe. Le couplage avec la conduction dans les tubes est réalisé par l'utilisation d'une méthode aux ordonnées discrètes (DOM) avec un modèle spectral de type bandes étroites pour le rayonnement des gaz de combustion. Un bilan énergétique confirme que les transferts de chaleur sont dominés par le rayonnement thermique. Un bon accord avec les mesures disponibles sur un four réel montre que l'approche proposée est capable de prédire le rayonnement thermique. L'étape suivante consiste à coupler le calcul de la température du tube à une loi d'encrassement. Un modèle chimique simple est utilisé. Il est validé à l'aide d'une expérience de laboratoire. La comparaison entre les températures obtenues avec la simulation et celles mesurées par des sondes thermiques montre que la simulation est capable de capturer l'évolution de la température dans le tube avec précision. Enfin, un modèle d'encrassement pour la configuration réelle est trouvé puis appliqué dans une simulation couplée complète. Cette simulation montre un bon accord entre l'évolution de la température sur site et dans la simulation. Une analyse plus poussée est réalisée sur les profils de température, de flux radiatif et de dépôt de coke et montre l'impact de ce dépôt sur l'installation / In industrial refinery furnaces, the efficiency of the thermal transfer to heat crude oil before distillation is often altered by coke deposition inside the process pipes. This leads to increased production and maintenance costs, and requires better understanding and control. Crude oil fouling is a chemical reaction that is, at first order, thermally controlled. In such large furnaces, the predominant heat transfer process is thermal radiation by the hot combustion products, which directly heats the pipes. As radiation fluxes depend on temperature differences, the pipe surface temperature also plays an important role and needs to be predicted with sufficient accuracy. This temperature results from the energy balance between thermal radiation and conduction in the solid material of the pipe, meaning that the thermal behavior of the whole system is a coupled radiation-conduction problem. In this work, this problem is solved in a cylindrical furnace, using the Discrete Ordinate Method (DOM) with accurate spectral models for the radiation of combustion gases, described by a complex chemistry flame model, and coupled to heat conduction in the pipe to predict its wall temperature. An energy balance confirms that heat transfers are effectively dominated by thermal radiation. Good agreement with available measurements on a real furnace shows that the proposed approach is able to predict the heat transfer to the pipe. The method gives an accurate prediction of the radiative source term and temperature fields in the furnace and on the pipe surface, which are key parameters for liquid fouling inside the pipe. Although reasonably accurate results are obtained with simple models, they still can be easily improved by more sophisticated models for turbulence, combustion and radiation. The next step is to couple the calculation of the pipe temperature to a fouling law. Since exact composition of crude oil is not available, one needs to model coke deposition with simple fouling law. The idea is to model the deposition rate by a thermal resistance added to the heated pipe and allows to coupling the calculation of the pipe temperature to a fouling law. A simple chemical model is used, and validated against a labscale experiment, prior to apply it to a furnace configuration. Comparing the temperature obtained with the simulation to the temperature measured by thermal probes at selected locations shows that the simulation is able to capture the temperature variation at these points. It is shown that coking occurs when the temperature has remained high on both sides of the pipe for a sufficient length. We explain how to extract a fouling law in controlled condition when the deposit is induced by thermal stressing of the crude. Finally, the whole system, including radiation,conduction and deposition, is coupled. Results are compared to the real furnace and show relatively good agreement in terms of external skin pipe temperature prediction. This observation validates the methodology exposed in this script

Une étude comparative des caractéristiques statiques, dynamiques et structurale a été menée sur 8 membranes échangeuses d'ions (MEIs), 4 neuves (MEIN) et les mêmes usagées (MEIU) après 2 ans de fonctionnement en ED dans l'industrie agroalimentaire. L'objectif essentiel était de mieux connaître les mécanismes de vieillissement in situ. Nous avons donc mesuré pour chacune de ces MEIs la capacité d'échange, la teneur en eau, la perméabilité ionique, la conductivité électrique, le nombre de transport, l'angle de contact, le courant limite, le module d'Young et la résistance à la traction. Aussi, nous avons effectué des analyses d'IRTF, de MEB et d'EDX. Cette étude nous a permis de conclure que (i) la MEC2 est restée presque stable après les 2 ans d'ED, alors que la MEA1 s'est très fortement dégradée. D'une manière générale, les MEAs sont plus sensibles au vieillissement que les MECs, (ii) les sites fonctionnels sulfoniques s'éliminent de la MEC. Nous ne pouvons pas affirmer ce mécanisme dans le cas des MEAs, mais nous soupçonnons un phénomène d'empoisonnement des sites fonctionnels, (iii) les MEAs se colmatent en surfaces avec des ampleurs différentes entre la MEA1 et la MEA2 / A comparative study of static characteristics, dynamic and structural was conducted on 8 ion-exchange membranes (MEIS), 4 new (IEMN) and the same used (IEMU) after two years of ED operation in the food industry. The main objective was to better understand the mechanisms of in situ ageing. We therefore measured for each IEMs exchange capacity, water content, ionic permeability, electrical conductivity, transport number, contact angle, current limit, Young's modulus and tensile strength. Therefore, we performed analysis of FTIR, SEM and EDX. This study concluded that (i) CEM2 remained almost stable after 2 years of ED, while AEM1 has sharply deteriorated. In general, the AEMs are more susceptible to ageing than CEMs, (ii) the sulfonic functional sites are eliminated from the CEMs. We cannot confirm this mechanism in the case of AEMs, but we suspect a poisoning phenomenon of functional sites, (iii) the AEMs fouled in surfaces with different degrees between AEM1 and AEM2

Les procédés d'osmose inverse (OI) permettent la production d'eau recyclée de très haute qualité grâce à l'élimination de contaminants organiques et inorganiques et de micro-organismes. Le suivi du bon fonctionnement de ce procédé est nécessaire pour valider la rétention des virus pathogènes afin de protéger la santé des usagers. La présence de minéraux et matières organiques dans les effluents rend inévitable le colmatage des membranes lors de leur fonctionnement et diminue ainsi leur performance. Afin d'éviter et d'éliminer ces colmatages, les stations de traitements des eaux utilisent des produits chimiques. Ces derniers vont modifier les performances globales des membranes en polyamide comme par exemple la diminution de la perméabilité à l'eau, et plus particulièrement les performances de rétention des virus, or l'ensemble de ces perturbations n'est que très peu compris et donc peu maitrisé. L'abattement des virus par l'OI sur des membranes intègres ou modifiées (ex : colmatage) ont donc été déterminés en mesurant la rétention d'un virus modèle de type phage MS2 et de substituts comme les sels (mesurés par conductivité), la rhodamine-WT (R-WT) ou les sulfates. La conductivité est, en effet, la technique de contrôle standard dans les stations de traitement des eaux (échelle industrielle).Le premier objectif de ce travail est d'évaluer l'utilisation d'un autre paramètre, les matières organiques dissoutes (DOM) comme nouveau substitut de virus et de déterminer l'impact du dysfonctionnement des procédés d'OI sur l'abattement des DOM et des sels à l'échelle industrielle. Les DOM peuvent en effet également être utilisées comme indicateur de qualité des eaux en fonction de leurs compositions et de leurs concentrations. L'abattement des DOM est donc testé comme nouvelle technique de surveillance afin de distinguer les fuites des changements de performance des membranes. Il est conclu que les DOM peuvent être utilisées comme nouvelle technique de contrôle. De plus, une variation de l'abattement des DOM peut aider à identifier des fuites de manière plus robuste que par l'abattement des sels. Le deuxième objectif est de déterminer l'effet des défauts membranaires sur les abattements d'un virus modèle (phage MS2) et de quatre substituts (R-WT, DOM, sulfate et sels) à l'échelle de systèmes de laboratoire. Deux systèmes à flux longitudinal est utilisés : une membrane plane et un module à spirale. Dans un premier temps, l'effet du colmatage sur les abattements de ces différents virus et substituts est étudié. Le colmatage organique, créé en utilisant un mélange de matières organiques, a pour effet d'augmenter de plus de 0,1 log les abattements de la R-WT, des sels et des DOM. Cette augmentation générale peut être due au blocage des cavités de la membrane et/ou par la sorption des substituts sur les matières organiques.Le colmatage inorganique, créé en utilisant un mélange de sels, n'a pas d'effet sur le rejet des substituts sauf pour les sels qui montre un comportement différent entre les deux systèmes. Dans le système à membrane plane, la couche inorganique permet d'augmenter le passage des sels à travers la membrane. Par opposition, il n'y a pas d'effet sur leur abattement avec le module à spirale. Cette variation entre les deux systèmes peut être causée par la différence de configuration (module à spirale contre membrane plane). Dans un deuxième temps, l'effet du chlore (modes passif et actif) sur la rétention de ces cinq composés est mesuré. Après un contact de 9000 ppm.h de NaOCl à pH 7, la surface membranaire change chimiquement. La formation de liaison Cl dans la couche en polyamide et la rupture des liaisons NH provoquent l'augmentation de la perméabilité à l'eau et diminuent l'abattement de l'ensemble des substituts. Malgré une forte diminution de 1,2 log de l'abattement en sel, l'abattement minimum du phage MS2 reste de 3 log. / One of the major applications of reverse osmosis (RO) process is the production of high quality recycled water by providing a barrier to remove organic and inorganic contaminants as well as pathogens including viruses. In order to protect public health, validation and monitoring of the RO process integrity are necessary to ensure its correct operation. During operation a certain degree of fouling is inevitable and can reduce RO membrane performance. Thus, chemicals are often used in water treatment plants to prevent or remove the membrane fouling. However, these chemicals can modify the integrity of the polyamide layer on RO membrane overtime. Up-to-date, the impact of membrane's physical change on its virus removal efficiency cause by the chemical use during operation is still not well understood.A minimum virus removal efficiency of intact and impaired (e.g. by fouling) RO membranes can be ascertained by measuring the rejection of MS2 phage and virus surrogates such as salt as measured by conductivity, rhodamine-WT (R-WT) or sulphate. However, conductivity measurement is the only full-scale standard monitoring technique. The removal of dissolved organic matter (DOM), which has been used as an indicator of water quality, can possibly be used for this purpose.The first objective of this work was to assess the suitability of DOM as a virus surrogate and to determine the impact of process failure on salt and DOM rejection in full-scale plants. A change of the conductivity does not necessarily mean that the membrane integrity has been breached. Thus, DOM monitoring has been tested and combined with the conductivity monitoring in order to distinguish between leaks and changes in membrane performances. It was concluded that DOM could be used as new monitoring technique. Moreover, a variation of DOM rejection can help identifying leaks better than just conductivity profiling alone.The second objective was to determine the effect of membrane impairments on the rejection of one model virus (MS2 phage) and four virus surrogates (R-WT, DOM, sulphate and salt) using lab-scale RO set-ups. To this aim, two different cross-flow set-ups were used: a flat-sheet and a single 2.5” spiral-wound module.Firstly, the effects of organic fouling and scaling on the rejection of model virus and virus surrogates were studied separately. Organic fouling was created using a mix of organic foulants. The result of this study showed an increase of the rejection by more than 0.1 log for R-WT, salt and DOM. The general increase of the surrogates' rejection might be due to the blocking of cavities of the polyamide membrane and/or to the sorption of surrogates to the fouling layer, which was observed by different autopsy techniques.Scaling was created using a mix of inorganic salts in order to reconstitute the composition of a RO feed water and avoiding the presence of organic foulants. Scaling was found to have no impact on the rejection of all tested virus surrogates except for salt. Salt rejection showed a change of behaviour between different set-ups: with the 2.5” module set-up the inorganic layer led to a stabilisation of the salt rejection, whereas the salt rejection increased with the flat-sheet set-up. This could be explained by the variations of the systems configuration (i.e. spiral module versus flat-sheet, feed spacer height, etc.).Secondly, the long-term impact of membrane ageing by exposure to chlorine, either active under filtration or passive by soaking, on the rejection of the model virus and four surrogates was studied. After a contact time of 9000 ppm∙h NaOCl at pH 7, the membrane surface chemistry changed. The introduction of chlorine in the membrane chemistry and the breakage of amide bonds caused an increase of the water permeability and a decrease of the model virus and virus surrogates rejection.

Os sistemas que combinam processos biológicos com a tecnologia de separação por membranas, com crescimento biológico em suspensão, Membrane Bioreactor (MBR) e crescimento biológico aderido, Moving Bed Membrane Bioreactor (MB-MBR), se destacam como opções compactas e eficientes para tratamento de esgoto doméstico.Embora esta tecnologia seja muito promissora, ainda apresenta como maior desafio a redução de desempenho das membranas, que é causada por um fenômeno complexo denominado depósito, ou fouling, em inglês. Como forma de melhorar o desempenho e prolongar a vida útil das membranas a adição de nanopartículas de argila durante o processo de síntese tem se mostrado eficiente. O presente estudo teve como objetivo determinar a melhor composição para a síntese de membranas em polietersulfona modificadas pela adição de nanopartículas de argila e avaliar o seu desempenho no tratamento de esgoto sanitário, gerado na moradia estudantil do campus São Paulo da Universidade de São Paulo, em sistemas MBR e MB-MBR. A melhor composição para a síntese das membranas modificadas foi de 4% de nanopartículas de argila e 4% de formador de poros, ambos em relação à massa do polímero utilizado. Essa composição resultou em membranas com permeabilidade média de 293 L.m-2.h-1.bar-1, para água desmineralizada enquanto as membranas sem modificação apresentaram permeabilidade inferior a 50 L.m-2.h-1.bar-1, sendo, portanto, essa composição selecionada para sintetizar as membranas utilizadas durante a operação dos sistemas de tratamento por MBR e MB-MBR. Para efeito de comparação, o estudo foi desenvolvido com membranas modificadas e comerciais, no mesmo reator. Durante a operação do sistema MBR, com membranas modificadas e membranas comerciais, a concentração média de Demanda Bioquímica de Oxigênio (DBO5) na alimentação do sistema foi de 440 mg.L-1 e a eficiência de remoção foi superior a 94%. Quando o sistema MBR passou a operar com concentração de Sólidos Suspensos Totais (SST) superior a 8.000 mg.L-1, condição considerada de equilíbrio, a permeabilidade média das membranas modificadas, normalizada para 20 ºC, foi de 1.166,1 L.m-2.h-1.bar-1, enquanto para as membranas comerciais a permeabilidade foi de 326,7 L.m-2.h-1.bar-1. O fluxo de permeado médio, para o sistema MBR, foi em torno de 6 L.m-2.h-1, tanto para as membranas modificadas quanto para as membranas comerciais avaliadas na etapa de operação em equilíbrio. Com a operação dos sistemas MBR e MB-MBR em paralelo, com as membranas modificadas, concluiu-se que, embora as qualidades dos permeados produzidos tenham sido similares, o sistema MB-MBR apresentou menores pressões de operação e, consequentemente, menor propensão à formação de depósitos. Os ensaios de filtrabilidade demonstram que as membranas modificadas apresentaram menor resistência à filtração que as membranas comerciais para o liquor misto de MBR e MB-MBR, no entanto o liquor misto do sistema MB-MBR apresentou menor resistência a filtração. De modo geral, concluiu-se que a adição de nanopartículas de argila na modificação das membranas resultou em poros mais longos, favorecendo o aumento da permeabilidade das membranas modificadas em relação às membranas comerciais. Quanto a operação dos sistemas MBR e MB-MBR em paralelo, a pressão transmembrana para o sistema MB-MBR foi em torno de 10 vezes menor que a pressão transmembrana no sistema MBR. Maiores concentrações de sólidos em suspensão totais no liquor misto dos sistemas de MBR e MB-MBR, resultaram em maiores fluxos críticos e, consequentemente, maior produção de permeado. / Treatment systems that combine activated sludge processes, with suspended or adhered growth, with membrane technology, Membrane Bioreactor (MBR) and Moving Bed Membrane Bioreactor (MB-MBR) are considered compact and efficient options for domestic wastewater treatment. Although this promising technology still presents the reduction of membrane performance as a relevant issue. This reduction on the membrane performance is caused by a complex phenomenon called fouling. An approach to improve the membrane performance and extend its life span is the addition of nanoclay during the synthesis process. Considering what was exposed, this study aimed the production and evaluation of composite polyethersulfone and clay nanoparticles membranes for domestic wastewater treatment. For this purpose, two pilot plants were constructed using the produced membranes for the treatment of the wastewater from the student housing at the University of São Paulo. The best composition of the modified membranes was 4% of nanoclay and 4% of pore former, both based on the polymer mass. This composition resulted in membranes with an average permeability of 293 L.m-2.h-1.bar-1 for demineralized water while membranes without modification had a permeability of less than 50 L.m-2.h-1.bar-1. For performance comparison, commercial membranes were used in the same pilot reactor. During the operation, the average Biological Oxygen Demand (BOD5) from raw effluent was 440 mg.L-1 and the removal efficiency was higher than 94%, for both treatment systems. When the MBR system started to operate with a Total Suspended Solids (TSS) concentration above 8,000 mg.L-1, it reached a stable condition in which the average permeability of the modified membranes, normalized to 20 ° C, was 1,166.1 L.m-2.h-1.bar-1, while for the commercial membranes the permeability was 326.7 L.m-2.h-1.bar-1. The average permeates flux for the MBR system was 6 L.m-2.h-1 for both the membranes types operating at stable conditions. With MBR and MB-MBR systems operating in parallel, with modified membranes, it was found that the quality of the produced permeates were similar, but the MB-MBR system presented lower operating pressures and, consequently, lower propensity to fouling. The filterability assays demonstrated that the modified membranes presented less resistance to filtration of MBR and MB-MBR mixed liquor than the commercial membranes. However, the MB-MBR mixed liquor presented less resistance to filtration. Overall, the comparison tests allowed to conclude that the nanoclay addition in the modification of the membranes resulted in longer pores, which increased the modified membranes permeability. Regarding the operation of the MBR and MB-MBR systems, the transmembrane pressure for the MB-MBR system was about 10 times lower than the transmembrane pressure in the MBR system. Higher concentrations of total suspended solids in the mixed liquor of the MBR and MB-MBR systems resulted in higher critical fluxes and, consequently, higher permeate production.

A fim de garantir a inocuidade, alguns alimentos industrializados são termicamente tratados por um processo contínuo denominado pasteurização, o qual visa inativar os micro-organismos patogênicos, mantendo, ao mesmo tempo, a sua qualidade sensorial e nutricional. Essa operação é aplicada a produtos como sucos, leite, cervejas, polpas, entre outros. A modelagem matemática deste processo tem como intuito auxiliar no entendimento, controle e posterior otimização desta operação. O principal objetivo deste trabalho foi o desenvolvimento da modelagem do processo contínuo da pasteurização HTST do leite e a validação experimental do modelo empírico da incrustação do produto nas placas do trocador de calor, em malha aberta (sem PID). A modelagem fenomenológica foi composta por balanços diferenciais de energia, para temperatura, e de material, para letalidade, nos canais, nas placas, no tubo de retenção e nas conexões do pasteurizador. Também foi realizada a modelagem empírica da incrustação do leite na seção de aquecimento. Os modelos desenvolvidos representam um conjunto de equações diferenciais ordinárias de primeira e segunda ordem, o qual foi resolvido pelo método das diferenças finitas, pelo uso do software gPROMS. O modelo foi aplicado para representar o comportamento de um pasteurizador a placas de escala laboratorial, com e sem incrustação, com e sem perturbações no sistema e durante a partida do equipamento, através de estudo de caso. Os dados simulados foram apresentados pela distribuição unidimensional e temporal de temperatura e da letalidade do tratamento, ao longo do processo, e do perfil do coeficiente global de troca térmica na seção de aquecimento. Para a validação do modelo de incrustação foi realizado um ensaio experimental da pasteurização de solução proteica (similar ao leite). Inseriu-se termopares em diversos pontos do equipamento e as temperaturas foram registradas ao longo do tempo. As placas do trocador foram pesadas e fotografadas antes e depois do teste para controle da quantidade de material depositado. A partir dos resultados laboratoriais, fez-se o ajuste dos parâmetros do modelo de incrustação, simulando novamente. Esses resultados foram comparados aos experimentais, sendo, então, o modelo validado. / In order to guarantee harmlessness, some processed foods are thermally treated in a continuous process named pasteurization, in which the purpose is to eliminate pathogenic microorganisms, while avoiding sensorial and quality losses. This operation is used in products such as juice, beers, milk and dairy food, pulp, and so on. Mathematical modeling of this process seeks to help its understanding, controlling, and optimization. Thus, the aim of this work was to develop and simulate a model of a continuous process pasteurization, and to conduct the experimental validation of a fouling model in the plates of the heat exchanger plates, without a process controller (PID). The phenomenological modeling was composed by differential energy and material balances, for temperature and lethality, respectively, in the channels, plates, holding tube and its connections of the pasteurizer. It was also developed an empirical fouling model for the product in the heating section. All these models represent a set of first and second order differential equations which were solved by a finite difference method through the gPROMS software. This modeling was used to express the behavior of a laboratory scale plate pasteurizer, with and without fouling, with and without system disturbances and during the equipment startup, in a case study. The simulated data was presented by the unidimensional spatial and temporal distribution of temperature and lethality along the process, and overall heat transfer coefficient profile in the heating section. To validate the fouling model, an experimental test by using a protein solution (similar to cow milk) was conducted. The temperature logging over time was done by various thermocouples inserted in the pasteurizer. All the plates were weighed and photographed before and after the tests to quantify the amount of deposits. From laboratory results, fouling model parameters were adjusted and simulation was performed again. These results were compared to the experiments, being the model validated adequately.

Les poudres laitières sont obtenues par concentration du produit liquide (membranes, évaporation sous vide) puis séchage du concentré. Contrairement au séchage par atomisation, peu de travaux ont été menés sur la concentration par évaporation sous vide. Pourtant, la maîtrise du schéma global de production des poudres gagnerait en une meilleure compréhension de cette opération réalisée dans des évaporateurs à flot tombant. Le présent travail vise à étudier comment améliorer les performances des évaporateurs ; il s’appuie sur deux facteurs limitants de l’opération : l’encrassement des surfaces d’échange et la viscosité maximale en sortie des évaporateurs. La contribution des différents constituants des produits à l’encrassement a été étudiée grâce à une méthodologie développée sur un évaporateur pilote.Les résultats obtenus ont permis d’identifier les éléments minéraux qui contribuent à l’encrassement lors de la concentration de microfiltrat et d’ultrafiltrat de lait, de lactosérums acides chlorhydrique et lactique. Afin de dépasser l’extrait sec maximal en sortie des évaporateurs à flot tombant, deux évaporateurs rotatifs à couche mince, de conceptions différentes, ont été testés à l’échelle pilote. Les études de faisabilité ont été menées jusqu’à la poudre. Le potentiel des équipements a été évalué suivant les propriétés fonctionnelles des poudres et le coût énergétique d’élimination de l’eau. Dans l’un des cas, le remplacement de la tour de séchage par deux évaporateurs rotatifs en série constitue une rupture technologique pour la production de poudres de perméat et dimi / Dairy powders are produced using a two-step process: concentration of the liquid product (membrane, concentration by vacuum evaporation) and drying of the concentrate. Contrary to spray-drying, vacuum concentration has been poorly investigated. However, a better understanding of this unit operation carried out in falling-film evaporators would lead to an improved control of the global process scheme for the production of powders. This PhD project aims to highlight how to enhance the performances of falling-film evaporators; it focuses on two limiting factors of the vacuum concentration: the fouling of the heating surfaces and the maximal viscosity at the outlet of the falling-film evaporators. The contribution of the different product components to the fouling was investigated using a methodology developed at pilot-scale.Our results showed which mineral elements favored the fouling of falling-film evaporators during the concentration of milk microlfiltrate and ultrafiltrate as well as hydrochloric and lactic acid wheys. Besides, two thin-film rotative evaporators of different designs were tested at pilot-scale in order to exceed the maximum dry matter achieved in falling-film evaporators. The feasibility studies were conducted up to the production of powders. The capabilities of the equipment were evaluated according to the functional properties of powders and the specific energy costs relative to the removal of water. In one case, the combination of two rotative evaporators replacing the spray drier constitutes a technological breakthrough in the production of permeate p