Microplastic (MP) pollution is ubiquitous in the aquatic environment. Though their properties are known to vary considerably, these particles are typically 1–5,000 μm in size and irregular in shape. Research suggests that MPs pose a significant hazard to aquatic ecosystems, lead to negative economic consequences, and may cause adverse human health effects. The effluents of municipal wastewater treatment plants (WWTPs) comprise a significant source of MPs, containing < 1 MP/L to > 440 MPs/L. Pursuant to the large volumes of wastewater processed, estimated daily effluxes can exceed one billion MPs/day in some WWTPs. Membrane technologies, like those used in some tertiary wastewater treatment applications, appear well-positioned to mitigate releases of MPs. However, research directly characterizing the performance of membranes in these applications is lacking. The studies in this work address this knowledge gap. To this end, irregularly-shaped MPs were produced in a novel milling/sieving process. Ultrafiltration and microfiltration membranes were challenged to these MPs suspended in secondary effluent wastewater to elucidate their fouling behaviour under realistic solution conditions. Subsequently, MPs milled/sieved from a fluorescently-labelled plastic feedstock were utilized in microfiltration experiments. Bulk MP concentrations in samples were easily measured using a plate reader to quantify MP rejection. Improving upon this technique, a new protocol involving a flow cytometer was developed, enabling the identification of individual fluorescent MPs in filtration samples, even when complex solutions chemistries were used. A culminating investigation was performed to bridge a gap in the literature between studies considering small-scale laboratory filtration phenomena and observations of large-scale WWTPs. Thus, the performance of a hollow fiber crossflow microfiltration module was evaluated in the filtration of wastewater containing MPs. Overall findings suggest that incidences of fouling by MPs can be managed via periodic cleaning processes, and the well-informed selection/operation of membrane technologies can contribute to high MP removal efficiencies (> 99%) in tertiary wastewater applications. / Thesis / Doctor of Philosophy (PhD) / The term "microplastics" (MPs) is used to describe microscopic plastic particles. Recent investigations have reported these MPs in lakes, rivers, and oceans across the globe. These reports are concerning as other studies demonstrate that MP pollution can be hazardous to aquatic life, yet the potential effects of MPs on human health remain largely unknown. Many MPs originate from municipal wastewater treatment plants (WWTPs) which discharge large numbers of these particles into the aquatic environment. Researchers often recommend the use of membranes as a barrier to prevent MPs from leaving in the final treated wastewater. This work seeks to assess that recommendation. Assessments of the effectiveness of membranes at withholding MP particles in wastewater are performed over various conditions. The propensity of MPs to interfere with the desired output of treated wastewater is also measured. Overall, findings indicate that carefully designed and operated membranes processes can be well-suited to this application.

Specific conductivity (SC) and total dissolved solids (TDS) are increasingly being used as a parameter used to judge the aquatic health of streams that are impacted by coal mining operations in the Appalachian region of the United States. Due to this, government environmental regulatory bodies have been considering issuing a regulation on SC for all mining operation outfalls. Sulfate typically has the greatest dissolved ion presence in coal mine waters. In literature examining the treatment of mine waters, SC and TDS analysis is typically not reported. The technologies examined in this study were nanofiltration membrane technology and biological sulfate reducing bioreactors. In the nanofiltration study, three different nanofiltration membranes were evaluated for SC reduction: NF270, DK, and NFX. The DK and NFX nanofilters were able to reduce SC levels by an average of 84 percent for both mine waters tested and were able to reach SC levels below the proposed limit of 500 S/cm. The SC levels achieved by the NF270 nanofilters were observed to have much higher variability. The inclusion of microfiltration and simulated-sand filtration were also introduced as a pre-treatment stage in order to determine whether or not nanofiltration performance would improve in terms of SC reduction. In the biological sulfate reducing bioreactor study, multiple bioreactors were established to identify the optimal organic mixture to foster both SC and sulfate reduction. Sulfate reduction began to occur approximately 20 days after the establishment of each bioreactor. SC levels were greater than 13,000 S/cm in each of the bioreactors sampled by the fortieth day of sampling. The probable cause of the increase SC was identified to be the manure/compost used in the study. Future testing should incorporate more sampling in the early phases of experimentation in order to ensure the ability to monitor changes in water quality. / MS

Quelque soit la zone de culture, l'anacardier (Anacardium occidentale L.) est essentiellement cultivé pour la production de noix de cajou, filière d'une grande importance socio-économique notamment au Brésil. Le jus de cajou est un produit secondaire qui résulte du pressage du pédoncule hypertrophié de la noix appelé pomme de cajou (pseudo-fruit). Le traitement des pommes engendre de grands volumes de déchets solides qui sont soit mis en décharge, soit utilisés pour l'alimentation animale. Dans ce contexte, le travail a pour objectif de proposer et d'évaluer un nouveau procédé permettant d'accroître la valeur ajoutée de ce sous-produit en extrayant les caroténoïdes qu'il contient. Le procédé comporte 3 opérations successives : une extraction par pressage associée à une macération enzymatique, une concentration à froid de l'extrait par microfiltration tangentielle et une purification par diafiltration. La première opération a été optimisée à l'aide de 2 plans d'expériences : un plan de criblage de facteurs de Plackett-Burmam (matrice de Hadamard) pour sélectionner les paramètres opératoires les plus influents suivi d'un plan central composite pour les optimiser. La dose de pectinase utilisée durant la macération et la force appliquée lors du pressage sont les paramètres les plus influents sur le profil caroténoïdique de l'extrait. De fortes doses de pectinase associées à une force de pressage élevée permettent d'obtenir à la fois un extrait plus riche en caroténoïdes et une meilleure densité de flux de perméat en microfiltration. L'utilisation de plusieurs cycles successifs de pressage permet d'augmenter les teneurs en caroténoïdes de l'extrait mais augmente également son pouvoir colmatant en microfiltration. L'étude de la concentration de l'extrait par microfiltration tangentielle a montré qu'il est possible d'atteindre un facteur de réduction volumique (FRV) de 20 en maintenant des densité de flux de perméat supérieures à 100 L.h-1.m-2. Les caroténoïdes sont concentrés à hauteur du FRV choisi (jusqu'à 20 fois). La diafiltration a permis de purifier 5 fois les caroténoïdes par rapport à la matière sèche. Un modèle simple basé sur des bilans matières pour prévoir l'impact du FRV et du diavolume sur la composition de l'extrait a été développé et validé. L'extrait final obtenu présente une teneur en caroténoïdes de 70 mg.kg-1. Parmi les 11 molécules identifiées par HPLC-DAD, les caroténoïdes majoritaires sont les isomères cis et trans de l'auroxanthine, la β-cryptoxanthine et le β-carotène. Les extraits finaux obtenus se présentent sous forme de liquides visqueux de couleur jaune intense, faciles à disperser dans l'eau. Ils possèdent un fort potentiel d'utilisation dans la formulation des aliments comme colorant naturel. / Whatever is the area of plantation, cashew (Anacardium occidentale L.) is grown primarily for the production of nuts, a supply chain that has great socioeconomic importance, especially in Brazil. The cashew juice is a by-product that results from pressing the nut hypertrophied peduncle, known as cashew apple, a juicy pseudo fruit. Peduncle processing generates large volumes of industrial solid waste that are usually discarded or sometimes used as animal feed. In this context, this work aimed to propose and evaluate a new process that provides an added value to this industrial byproduct, extracting carotenoids that were contained therein. The process comprised three successive operations: an extraction by pressing associated to an enzymatic maceration, a cold concentration of the extract by crossflow microfiltration and a purification by diafiltration. The first operation was optimized with the use of two experimental designs: a Plackett-Burmam (Hadamard matrix) plan for factors screening to select the most influential operating parameters, followed by a central composite design for optimization. The dose of pectinase used during maceration and the applied force used during the pressing operation were the most influential parameters on the carotenoid extract profile. High doses of pectinase associated with a high pressing force led to a richer carotenoid extract and enhanced the permeate flux in microfiltration. The use of several successive cycles of compression increased the carotenoid content of the extract but also increased its fouling properties during microfiltration. The extract concentration by crossflow microfiltration study showed that it was possible to reach values of volumetric reduction ratio (VRR) of about 20, maintaining the permeate flux above 100 Lh-1.m-2. The carotenoids were concentrated in the same levels of FRV (up to 20 times). The diafiltration allowed purification of carotenoids 5 times in relation to the dry matter. A simple model, based on a mass balance to predict the impact of VRR and diavolume on the extract composition was developed and validated. The final extract obtained presented a carotenoid content of 70 mg.kg-1. Among the 11 compounds identified by HPLC-DAD, the main carotenoids were cis and trans isomers of auroxanthine, β-cryptoxanthin and β-carotene. The final extracts obtained were in the form of viscous liquids of a yellow intense color, and easily dispersed in water. These concentrates have a strong potential for use in the formulation of foods and beverages as a natural dye.

La pomme de cajou est une matière première qui n'est pas exploitée en Côte d'Ivoire alors qu'elle présente un potentiel nutritionnel important. Dans ce contexte, l'étude réalisée s'intéresse à la valorisation des pommes de cajou en jus de fruit. En partant du jus brut de pommes de cajou, il s'agit d'étudier un procédé qui couple plusieurs techniques membranaires pour la production de jus clarifiés et concentrés. Les températures modérées de traitement doivent permettre une meilleure préservation du potentiel vitaminique et sensoriel de la matière première. Les deux variétés de pommes de cajou étudiées sont riches en acide ascorbique (1,2 g.kg-1) et en composés phénoliques (2,9 g.kg-1). Avec un rendement optimal de 82%, l'extraction du jus par pression ne génère pas de dégradation significative des composés d'intérêt. Toutefois, certains d'entre eux se répartissent différemment dans le jus et les tourteaux de presse. Parmi les 50 composés d'arôme identifiés dans le jus de fruit, les esters sont quantitativement les plus abondants. Le traitement du jus de pomme de cajou par microfiltration tangentielle sur membranes tubulaires minérales (0,2 µm, 35 °C) permet de clarifier le produit sans altérer sa teneur en acide ascorbique. La forte rétention des composés phénoliques en diminue l'astringence. Le prétraitement par liquéfaction enzymatique modifie les caractéristiques du jus et permet d'améliorer les performances de la filtration. Certaines des préparations enzymatiques testées présentent un effet synergique sur les densités de flux de perméat (Jp). Lors de la validation du procédé à l'échelle semi-industrielle, des Jp voisines de 70 L.h-1.m-2 ont été obtenues à FRV 8. Les performances sont toutefois très variables d'un jus à l'autre et ne sont pas liées aux caractéristiques des jus mesurées. Les tests classiques de filtrabilité (résistance spécifique en filtration frontale et temps de succion capillaire) ne permettent pas non plus de prévoir le pouvoir colmatant des jus en microfiltration tangentielle. Une meilleure compréhension des phénomènes qui régissent le colmatage membranaire est indispensable pour développer un outil prévisionnel à ce niveau. La nanofiltration tangentielle et l'osmose inverse ont été ensuite utilisées pour pré-concentrer 2,5 à 3 fois le jus clarifié. L'osmose inverse présente l'avantage de retenir totalement les principaux solutés pour une consommation énergétique comparable à celle de la nanofiltration. Enfin, l'évaporation osmotique a permis de concentrer le jus clarifié environ 6 fois sans en altérer la couleur et en préservant plus de 90 % de l'acide ascorbique. Comparé à des concentrés de référence traités par évaporation sous-vide, le concentré obtenu présente un profil aromatique moins altéré. Au final, l'intérêt du procédé proposé est donc vérifié en terme de qualité nutritionnelle et organoleptique. En vue d'une application industrielle, son évaluation économique reste toutefois indispensable / The cashew apple is a raw material which is not exploited in Côte d'Ivoire though it has an important nutritional potential. In this context, the study dealt with the processing of the cashew apple in fruit juice. Starting from the raw juice of cashew apples, a new process that coupled several membrane technologies was proposed for the production of clarified and concentrated juice. Moderate temperatures of treatment should allow a better preservation of the vitamins and sensory potential of the raw material. Both varieties of cashew apples studied were rich in ascorbic acid (1.2 g.kg-1) and phenolic compounds (2.9 g.kg-1). With an 82 percent optimum yield, juice extraction by pressure did not generate significant degradation of the compounds of interest. However, some of them are distributed differently in the juice and the press cake. Among the 50 aroma compounds identified in the fruit juice, the esters were the most abundant. Treatment of cashew apple juice by cross-flow microfiltration on inorganic tubular membranes (0.2 µm, 35 °C), clarified the product without altering its ascorbic acid content. The high retention of phenolic compounds decreased astringency. Pretreatment with enzymatic liquefaction of juice improved the performance of the filtration. Some of the enzyme preparations tested exhibited a synergistic effect on the permeate flux (Jp). During the validation of the process at semi-industrial scale, Jp of 70 Lh-1.m-2 was obtained using a volumetric reduction ratio of 8. However, performances were highly variable from one juice to another and were not related to the measured characteristics of juice. Classical tests of filterability (specific resistance in dead-end filtration and capillary suction time) did not predict the fouling properties of juices in cross-flow microfiltration. A better understanding of the fouling phenomena is absolutely necessary to develop new predictive tests filtrability. Nanofiltration and reverse osmosis were then used to pre-concentrate 2.5 to 3 times the clarified juice. Reverse osmosis allowed to retain entirely the major solutes with an energy consumption very close to nanofiltration. Finally, the clarified juice was concentrated 6 times using osmotic evaporation without altering the color and preserving more than 90% of ascorbic acid. Compared to standard concentrates treated by vacuum evaporation, the concentrate obtained has a less altered flavor profile. The interest of the suggested process was verified in terms of nutritional and sensorial quality. Its economic assessment remains essential for industrial application.

Les installations nucléaires sont génératrices de déchets liquides radioactifs qui doivent être traités avant leur rejet dans l'environnement. Le cobalt et l'argent radioactifs sont, après le tritium et le carbone 14, les principaux radionucléides rejetés par des réacteurs à eau pressurisée. Les traitements de décontamination d'effluents liquides actuellement mis en œuvre dans les installations nucléaires reposent sur des procédés physico-chimiques d'évaporation, de coagulation/floculation, de séparation de phase, de sorption et d'échange d'ions. Ces procédés conventionnels sont très efficaces mais présentent diverses limitations : ils ne retiennent pas ou peu le carbone 14 et, en situation accidentelle, ils ne sont pas faciles à mettre en œuvre pour traiter de grands volumes. Le développement de procédés innovants palliant à ces inconvénients est donc nécessaire. Les technologies de bio-remédiation pourraient être une alternative intéressante dans le secteur nucléaire mais très peu de procédés ont été proposés. Ce travail vise ainsi à développer une filière de traitement d'effluents nucléaires originale basée sur l'action d'une micro-algue photosynthétique, Coccomyxa actinabiotis, résistant aux rayonnements ionisants et accumulant les radionucléides et métaux toxiques. Les réflexions menées en collaboration avec les différents acteurs du projet ont permis d'établir un cahier des charges pour concevoir la filière de traitement et réaliser un pilote en tenant compte des contraintes associées au milieu nucléaire et à l'utilisation d'une matrice biologique. La filière est organisée en plusieurs opérations incluant d'une part la production et la récolte des micro-algues et d'autre part la décontamination de l'effluent. La faisabilité de chacune de ces opérations est tout d'abord étudiée à l'échelle laboratoire. Ainsi, les conditions opératoires et les outils de suivi, de contrôle, et d'optimisation relatifs aux étapes de (i) production de biomasse algale, (ii) séparation et/ou concentration de la biomasse par microfiltration et (iii) décontamination de l'effluent, en particulier l'élimination de l'argent 110m, du cobalt 60 et du carbone 14, sont recherchés. Le montage de la filière complète est ensuite proposé ; basée sur les résultats obtenus à l'échelle de laboratoire, la faisabilité de la bio-décontamination de radionucléides par la micro-algue à l'échelle pilote est également étudiée et démontrée. Ce travail de recherche permet donc d'envisager le développement d'une filière innovante de traitement des effluents liquides d'industries nucléaires et confirme la potentialité de certaines micro-algues à assurer l'élimination de polluants ciblés. / Nuclear plants produce radioactive liquid wastes which are decontaminated before they are released. Radioactive cobalt and silver are the main radionuclides released by water pressurized reactor, after tritium and carbon 14. Liquid effluents are decontaminated by physic-chemical processes, such as evaporation, coagulation, sorption and ion exchange. These technologies are very efficient but cannot neutralize entirely the carbon-14 and, in the case of emergency situation, they are difficult to implement in order to decontaminate high amount of radioactive liquids. It is necessary to look for alternative decontamination methods. Bio-remediation technologies may constitute interesting alternatives in the nuclear field as well, but only a few bio-based technologies have been proposed. This work aims to develop a treatment unit based on the use of a photosynthetic micro-alga, extremely radio-tolerant and owning high capacity to concentrate radionuclides and toxic metals. The technical specification was draft to design the process and construct the pilot unit taking into account the constraints linked to the use of a biological matrix in a nuclear environment. The pilot-scale treatment unit, based on this micro-alga, includes different tasks to ensure the objectives of the process: algae have first to be produced in a growth medium and harvested before ensuring the treatment of the contaminated effluent. The feasibility of these operations is studied at laboratory scale. Operating conditions and monitoring and optimization tools for each step, (i) biomass production, (ii) biomass separation and concentration by microfiltration, (iii) effluent decontamination of silver-110m, cobalt-60, carbon-14, are sought. Based on the results obtained at laboratory scale, the feasibility of bio-decontamination of radionuclides by the micro-alga at pilot-scale is studied and demonstrated. Through this work, the development of an innovative process has to be considered for the decontamination of liquid effluents from the nuclear industry. This work confirms the high potential of algae to ensure the pollutants elimination.

La microfiltration est largement utilisée pour la clarification, la stabilisation et la concentration de nombreuses suspensions à base de fruits (jus de fruits, agro-déchets, vin, etc.). Malgré ses divers avantages, la microfiltration présente néanmoins un inconvénient majeur qui est le phénomène de colmatage qui s’installe pendant l’opération de filtration et entraîne une diminution de la perméabilité membranaire. Si de nombreux mécanismes de colmatage (adsorption, blocage de pores, etc.) sont observés pendant la filtration de suspensions polydisperses comme les jus de fruits ou certains coproduits liquides, le dépôt de particules sur la membrane est souvent supposé être le mécanisme limitant. La formation de ce dépôt est fortement dépendante de l’équilibre entre forces convectives (imposées par le flux de perméat), qui attirent les particules de la suspension à proximité de la membrane, et forces de rétrotransport, qui éloignent les particules de la surface membranaire. La stratégie la plus employée pour maitriser le colmatage membranaire par dépôt est la filtration tangentielle qui permet d’imposer de forts cisaillements à la surface membranaire qui favorisent les mécanismes de rétrotransport des particules. Si cette stratégie de maîtrise du colmatage est amplement utilisée à l’échelle industrielle pour la microfiltration des suspensions à base de fruits, elle nécessite des coûts d’investissement et de fonctionnement non négligeables qui limitent son implantation aux industries présentant de fortes capacités de production et d’investissement. Au regard de cela, l’utilisation d’une configuration de filtration à membranes immergées pour la microfiltration de suspensions à base de fruits pourrait être une alternative intéressante. Cette configuration repose sur l’immersion de la membrane (modules plans ou fibres creuses) dans la suspension à filtrer, et est associée à un mode de filtration externe-interne, frontal ou quasi-frontale. Si l’absence de conditions hydrodynamiques intenses au voisinage de la membrane est associée à des flux relativement bas, les nombreux avantages de ce mode opératoire (coûts de fonctionnement réduits, simplicité opérationnelle, forte compacité, etc.) pourraient favoriser son emploi par les petits producteurs de jus de fruits et/ou les industries de valorisation des coproduits présentant des capacités limitées d’investissement et enclins à minimiser leurs couts opérationnels. Ce travail a ainsi étudié pour la première fois la possibilité d’utiliser un tel système pour la microfiltration de suspensions à base de fruits variées (jus de fruits et coproduits vinicoles). Ce travail de thèse a ciblé ainsi plusieurs objectifs : (i) caractériser le potentiel et le comportement colmatant de suspensions à base de fruits, en lien avec les caractéristiques physicochimiques propres à chaque suspension et au regard de leur filtration par membranes immergées, (ii) étudier des performances d’un système de microfiltration de suspensions à base de fruits par membranes immergées, performances en termes de productivité et de sélectivité et enfin (iii) dégager des pistes de réflexion qui conduiraient à une choix pertinent de conditions de filtration (mode immergé ou tangentiel) pour un type de suspension ciblé. Ce travail fournit ainsi des résultats d’identification de paramètres physico-chimiques clefs qui pourraient constituer un premier guide pour le choix de la configuration membranaire la plus adaptée au produit, permettant d’assurer une productivité acceptable lors de la microfiltration de suspensions à base de fruits. / Microfiltration is widely used to ensure clarification, stabilization, and concentration of various fruit-based suspensions (e.g. fruit juices, food by-products, wine). However, the performances of membrane filtration remain highly challenged by membrane fouling. During microfiltration of polydisperse suspensions, such as fruit-based suspensions, membrane fouling is generally associated to the deposition of particles on the membrane layer. This type of fouling is mainly governed by the equilibrium between convective forces (permeate flow), leading particles to flow towards the membrane, and back-transport forces, removing particles away from the membrane surface. The filtration performances depend strongly on this equilibrium, which is mostly governed by the hydrodynamic conditions of the filtration process and the particles size distribution of the suspension. In food industries, cross-flow microfiltration is generally used to limit membrane fouling. In this configuration, high cross-flow velocities are applied in order to enhance the back-transport forces limiting the deposition of foulant materials on the membrane surface. However, this working mode is well known to be highly energy consuming and might not always be relevant depending on the suspension characteristics. In the light of this, using immersed membranes configuration for the microfiltration of fruit-based suspensions might be an interesting alternative, especially for small producers with limiting investment capacity. In this configuration, widely used in other fields, the membranes are immersed in the suspension and filtration is performed in operating conditions close to that of dead-end filtration with limited back-transport forces and low operating costs. However, the performances of this filtration configuration remain little studied for the microfiltration of fruit-based suspensions. In this respect, this work investigated for the first time the possibility of using immersed membranes configuration for the microfiltration of various fruit-based suspensions (fruit juices and winery byproducts). Firstly, a characterization of the fouling potential of various suspensions during their microfiltration using immersed membranes filtration was performed in relation with their physicochemical properties (particle size distribution). Then, this work allowed highlighting the promising performances of immersed membranes configuration when used for the microfiltration of fruit-based suspensions, in terms of productivity and in terms of selectivity (clarification, concentration of bioactive compounds). Finally, it allowed drawing preliminary results about the relation between the physicochemical characteristics of a suspension and its fouling behavior while using (i) immersed membranes filtration or (ii) conventional cross-flow filtration. These results might be of great interest for the identification of relevant physicochemical parameters to predict the usefulness of using high cross-flow velocity to prevent membrane fouling during the microfiltration of fruit-based suspensions.

Les thématiques liées à l’eau sont un enjeu majeur pour notre environnement. De nombreux procédés de traitement des eaux sont disponibles. Dans ce travail, nous avons développé une alternative au traitement actuel des eaux, de façon à proposer une technologie moins coûteuse, plus facile à opérer et moins consommatrice en produits chimiques.Dans ce cadre, nous avons développé un procédé hybride associant un procédé membranaire de microfiltration à l’oxydation/ précipitation du fer pour le traitement des eaux avec des teneurs élevées en fer fournies par la SONEDE (Société nationale d’exploitation et de distribution des eaux de Sfax, Tunisie).L’étude concerne la précipitation du fer par bullage d’air dans un réacteur couplé à une microfiltration en utilisant plusieurs membranes (commerciale (Kerasep) ou préparées au Laboratoire de Sciences des Matériaux et de l’Environnement (Sfax) à base d’argile, alumine et charbon actif. Deux types d’eaux ont été étudiés : une eau synthétique préparée au laboratoire ayant une certaine concentration en fer dissous et une eau réelle riche en fer provenant d’un forage de la région de Sfax. L’influence des paramètres suivants a été étudiée : concentration initiale en fer, pH et pression transmembranaire. Le procédé a été également évalué pour le traitement de l’eau de forage de la région de Sfax. Pour mieux comprendre le procédé hybride d’aération/MF, des résultats obtenus avec différentes membranes en filtration frontale sont présentés.Dans un objectif d’intensification des procédés, une autre technique de deferrisation est étudiée en considérant un traitement membranaire seul de nanofiltration en appliquant une membrane organique spirale de type NF 2125A (Applied Membranes ®, USA). Les résultats obtenus sont prometteurs en termes de flux de filtration, de rétention en fer et qualité du perméat, conforme aux recommandations de l’OMS.D’un point de vue efficacité, le procédé hybride d’aération/MF donne un flux de perméat plus important que celui issu de la NF. En conclusion, ces deux procédés peuvent s’avérer être des alternatives avantageuses à un procédé classique d’aération suivi d’une filtration sur sable / Water-related issues are a major challenge for our environment. Many processes of water treatment are available. In this work, we have developed an alternative to the current treatment of water, so as to propose a technology less expensive, easier to operate and less consuming chemicals.In this context, we have developed a hybrid process combining a microfiltration membrane process with the oxidation / precipitation of iron for the treatment of water with high iron contents provided by the SONEDE (National Society of Water Exploitation and Distribution Of Sfax, Tunisia).The study concerns the precipitation of iron by bubbling air in a reactor coupled with microfiltration using several membranes (commercial (Kerasep) or prepared at the Laboratory of Materials and Environment Sciences (Sfax) based on clay , Alumina and activated carbon Two types of water have been studied: a synthetic water prepared in the laboratory with a certain concentration of dissolved iron and a real water rich in iron coming from a drilling of the region of Sfax. Parameters were studied: initial iron concentration, pH and transmembrane pressure The process was also evaluated for the treatment of drilling water in the Sfax region. To better understand the hybrid aeration / MF process, results obtained with different membranes in frontal filtration are presented.In order to intensify the processes, another deferrisation technique is studied by considering a single membrane treatment of nanofiltration by applying an organic spiral membrane of type NF 2125A (Applied Membranes ®, USA).The results obtained are promising in terms of filtration flux, iron retention and permeate quality and conform with WHO recommendations. From an efficiency point of view, the hybrid aeration / MF process gives a permeate flow more important than that of the NF. In conclusion, these two processes can prove to be advantageous alternatives to a conventional aeration process followed by sand filtration

Microfiltration is one of the most important processes in membrane sciences that can be used for separating drops/particles above 1 ??m. Depth microfiltration membranes retain drops/particles inside the surface of the membrane, the process is expensive and membranes quickly become fouled. On the other hand, surface microfiltration membranes stop drops/particles on the surface of the membrane and the process is less fouling. Higher permeate flux and lower trans-membrane pressure is obtained with a shear enhanced microfiltration technique. Production of specific size of drops and stability of the drops are very important in testing the microfiltration of crude oil drops/water emulsions. Oil drops from 1-15 ??m were produced with a food blender, operated at its highest speed for the duration of 12 mins. In addition, vegetable oil drops were stabilised with 1% polyvinyl alcohol (PVA), Tween 20 and gum Arabic, stability was assessed on the basis of consistency in the size distribution and number of drops in each sample analysed at 30 mins interval. A slotted pore Nickel membrane with the slot width and slot length of 4 and 400 ??m respectively has been used in the filtration experiments. The slot width to the slot length ratio (aspect ratio) of the used membrane is 100. Vibrating the membrane at various frequencies created shear rates of different intensities on the surface of the membrane. Membrane with a tubular configuration is preferred over the flat sheet because it is easy to control in-case of membrane oscillations both at lab and industrial scale. Besides this, a tubular membrane configuration provides a smaller footprint as compared to the flat sheet. The influence of applied shear rate on slots/pore blocking has been studied. Applying shear rate to the membrane reduced the blocking of the slots of the membrane; and reduction of slots blocking is a function of the applied shear rate. At higher shear rate, lower blocking of the slots of the membrane was verified by obtaining lower trans-membrane pressure for constant rate filtration. The experiments are in reasonable agreement with the theoretical blocking model. Divergence of the experimental data from the theory may be due to involvement of deforming drops in the process. During microfiltration of oil drops, the drops deform when passing through the slots or pores of the membrane. Different surfactants provided different interfacial tensions between the oil and water interface. The influence of interfacial tension on deformation of drops through the slots was studied. The higher the interfacial tension then the lower would be the deformation of drops through the slots. A mathematical model was developed based on static and drag forces acting on the drops while passing the membrane. The model predicts 100% cut-off of drops through the membrane. Satisfactory agreement of the model with the experiments shows that the concept of static and drag force can be successfully applied to the filtration of deformable drops through the slotted pore membranes. Due to the applied shear rate, inertial lift migration velocities of the drops away from the surface of the membrane were created. Inertial lift velocities are linear functions of the applied shear rate. A mathematical model was modified based on inertial lift migration velocities. The critical radius of the drops is the one above which drops cannot pass through the surface of the membrane into the permeate due to the applied shear rate and back transport. The model is used as a starting point and is an acceptable agreement with the experiment. The model can be used to predict the 100% cut-off value for oil drops filtration and a linear fit between this value and the origin on a graph of grade (or rejection) efficiency and drop size to slot width ratio was used to predict the total concentration of dispersed oil left after filtration. Hence, it is shown how it is possible to predict oil discharge concentrations when using slotted filters.

Highly concentrated micellar casein concentrate (HC-MCC), a potential ingredient for cheese making, containing ~20% casein with ~70% of serum proteins removed by microfiltration, and diafiltration of skim milk, and then further concentrated by vacuum evaporation. The objectives of this research were to investigate solubilization, cold gelation, rennet coagulation properties of recombined HC-MCC and cream for its use in cheese making. In Chapter 3, either mixing thawed HC-MCC in water at high temperature (~50C) or addition of trisodium citrate can achieve complete dispersion and more than 80% solubility of HC-MCC in water (3% protein). Overnight storage helps to fully disperse HC-MCC, but only reaches ~30% of solubility at 20C. Cold-gelation of HCMCC is thermally reversible and reducing protein levels in HC-MCC can decrease its CGT. The HC-MCC with less than 16% of protein does not gel at 5C. We propose that cold-gelation of HC-MCC occurs when the kinetic energy of the casein micelles is sufficiently reduced to inhibit their mobility in relation to adjacent casein micelles. In Chapter 4, the recombined concentrated milk (RCM) by mixing thawed frozen HC-MCC and cream with 12% casein at pH 6.6 does not gel until cooled below 12°C. Addition of either sodium citrate or high levels of calcium increased CGT, although low levels of calcium did not impact CGT. Cold gelation of RCM was thermally reversible, even when citrate was added to partially chelate calcium. We propose that cold gelation of RCM occurs when protein strands that have been partially released from the casein micelles entangle, restrict their mobility and form a fine stranded gel network. The RCM at a casein level of 12% (wt/wt) has potential for use in cheese making. In Chapter 5, reducing rennet level can increase coagulation time of RCM (11% casein) without impact on curd firmness or firming rate. Decreased coagulation temperature helps to increase coagulation time and decrease curd firmness rate, but also increases the initial viscosity of RCM. Pre-acidified RCM has no advantage in increasing coagulation time, decreasing curd firmness or firming rate. Microstructure of RCM and its coagulum indicates that the increased curd firmness probably results from the highly inter-linked and longer protein strands in RCM curd. Reducing rennet level can be applied to slow down rennet coagulation of RCM (11% casein) in cheese making.

<p>Циљ овог истраживања је да се испита примене &bdquo;cross-flow&ldquo; микрофилтрације на oбраду џибре од скробних сировина и утицај оперативних параметара (рН,<br />трансмембрански притисак и проток) на флукс пермеата и ефикасност пречишћавања у систему са и без присуства статичког мешача. Микрофилтрација је изведена у условима потпуне рециркулације флуида. Током експеримента коришћене су једноканалне керамичке мембране, са пречницима пора 200 nm, 450 nm i 800 nm (TAMI). У току филтрације одређиван је флукс пермеата, односно његова промена током времена. Поред тога на мембрани од 200 nm испитана је могућност употребе статичког мешача (тип: Kenics) у циљу повећања флукса пермеата, односно смањења прљања површине мембране. Добијени резултати указују на то да је употребом микрофилтрације загађење отпадне воде смањено у односу на почетну вредност у џибри. Проценат смањења ХПК и БПК у пермеату, у систему без мешача, износиo je око 36% и 45%, редом, док је у систему са статичким мешачем овај проценат био нешто мањи, и износио је за ХПК 32%, а за БПК 42%. Садржај суве материја, укупног азота и фосфата такође је смањен, а суспендоване честице су у потпуности уклоњене из џибре. Међутим, садржај пепела у пермеатима повећан је у односу на вредност у џибри. На основу добијених резултата утврђено је да су нешто бољи резултати, у смислу смањења загађења, постигнути након микрофилтрације без употребе статичког мешача. Такође је утврђено да оперативни параметри немају утицаја на ефикасност<br />пречишћавања џибре. На основу резултата статистичке анализе утврђено је да се применом поступка одзивне површине на адекватан начин може описати утицај одабраних оперативних параметара (проток напојне суспензије, трансмембрански притисак и рН напојне суспензије) на флукс пермеата током<br />микрофилтрације џибре у системима без и са присуством статичког мешача. Уметањем статичког мешача долази до пораста флукса пермеата услед стварања турбулентних услова и карактеристичног начина протицања флуида кроз канал мембране, као последица специфичне конструкције примењеног мешача. Примена статичког мешача оправдана је смањењем специфичне<br />потрошње енергије у поређењу са системом без мешача.<br />Оптимални услови извођења процеса микрофилтрације испитиване џибре указују на то да је процес потребно изводити при максималним вредностима протока и трансмембранског притиска (TMP=0,9 bar, Q=160 l/h) на ниским рН вредностима.<br />&nbsp;</p> / <p>Cilj ovog istraživanja je da se ispita primene &bdquo;cross-flow&ldquo; mikrofiltracije na obradu džibre od skrobnih sirovina i uticaj operativnih parametara (rN,<br />transmembranski pritisak i protok) na fluks permeata i efikasnost prečišćavanja u sistemu sa i bez prisustva statičkog mešača. Mikrofiltracija je izvedena u uslovima potpune recirkulacije fluida. Tokom eksperimenta korišćene su jednokanalne keramičke membrane, sa prečnicima pora 200 nm, 450 nm i 800 nm (TAMI). U toku filtracije određivan je fluks permeata, odnosno njegova promena tokom vremena. Pored toga na membrani od 200 nm ispitana je mogućnost upotrebe statičkog mešača (tip: Kenics) u cilju povećanja fluksa permeata, odnosno smanjenja prljanja površine membrane. Dobijeni rezultati ukazuju na to da je upotrebom mikrofiltracije zagađenje otpadne vode smanjeno u odnosu na početnu vrednost u džibri. Procenat smanjenja HPK i BPK u permeatu, u sistemu bez mešača, iznosio je oko 36% i 45%, redom, dok je u sistemu sa statičkim mešačem ovaj procenat bio nešto manji, i iznosio je za HPK 32%, a za BPK 42%. Sadržaj suve materija, ukupnog azota i fosfata takođe je smanjen, a suspendovane čestice su u potpunosti uklonjene iz džibre. Međutim, sadržaj pepela u permeatima povećan je u odnosu na vrednost u džibri. Na osnovu dobijenih rezultata utvrđeno je da su nešto bolji rezultati, u smislu smanjenja zagađenja, postignuti nakon mikrofiltracije bez upotrebe statičkog mešača. Takođe je utvrđeno da operativni parametri nemaju uticaja na efikasnost<br />prečišćavanja džibre. Na osnovu rezultata statističke analize utvrđeno je da se primenom postupka odzivne površine na adekvatan način može opisati uticaj odabranih operativnih parametara (protok napojne suspenzije, transmembranski pritisak i rN napojne suspenzije) na fluks permeata tokom<br />mikrofiltracije džibre u sistemima bez i sa prisustvom statičkog mešača. Umetanjem statičkog mešača dolazi do porasta fluksa permeata usled stvaranja turbulentnih uslova i karakterističnog načina proticanja fluida kroz kanal membrane, kao posledica specifične konstrukcije primenjenog mešača. Primena statičkog mešača opravdana je smanjenjem specifične<br />potrošnje energije u poređenju sa sistemom bez mešača.<br />Optimalni uslovi izvođenja procesa mikrofiltracije ispitivane džibre ukazuju na to da je proces potrebno izvoditi pri maksimalnim vrednostima protoka i transmembranskog pritiska (TMP=0,9 bar, Q=160 l/h) na niskim rN vrednostima.<br />&nbsp;</p> / <p>The aim of this study was to evaluate the usage of microfiltration for starch-based stillage purification. Also, the influence of operating factors (transmembrane pressure, feed flow rate and pH) on permeate flux and removal efficiency was investigated. The microfiltration experiments were carried out in condition of complete recirculation of the fluid. The single channel ceramic membranes used for experiments had a nominal pore sizes of 200 nm,450 nm and 800 nm (TAMI).<br />Another aim was to investigate the improvement of process using Kenics static<br />mixer as turbulence promoter. The obtained results indicates that COD and BOD values in permeates were decreased compared to initial value in the stillage. Removal efficiency of COD and BOD, in the system without static mixer, was about 36% and 45%, respectively, while in the system with static mixer, this efficiency was slightly lower (about 32% for COD and 42% for BOD). Total nitrogen, phosphate and dry matter content were also decreased. Suspended solids were completely removed from the stillage. The ash content of the permeates obtained after microfiltration was higher compared to initial value in the stillage. On the basis of the presented results, it can be said that better results, in terms of removal efficiency, were achieved under the conditions without static mixer. Also, it was determined that<br />experimental factors not affected on the efficiency of stillage purification. According to the results of statistical analyses it was determined that with Response Surface<br />Methodology the influence of operating factors (transmembrane pressure, feed flow rate and pH) on permeate flux can be described in an adequateway.<br />The increase in flux that occurs by placing a static mixer in the membrane channel was caused by the establishment of turbulent flow conditions and the characteristic flow of fluid along the membrane channel, which is a consequence of the characteristic geometry of Kenics static mixer. Application of static mixer was justified by a reduction in specific energy consuption compared with the system without<br />static mixer. Optimal conditions of the investigated stillage microfiltration indicate that the process should be conducted at the maximum values of transmembrane pressure and feed flow rate (TMP=0,9 bar, Q=160 l/h) on low pH values.</p>