Olefin/paraffin separation is a large potential market for membrane applications. Carbon molecular sieve membranes (CMS) are promising for this application due to the intrinsically high separation performance and the viability for practical scale-up. Intrinsically high separation performance of CMS membranes for olefin/paraffin separations was demonstrated. The translation of intrinsic CMS transport properties into the hollow fiber configuration is considered in detail. Substructure collapse of asymmetric hollow fibers was found during Matrimidﾮ CMS hollow fiber formation. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM polyimides with higher rigidity were employed as alternative precursors, and significant improvement has been achieved. Besides the macroscopic morphology control of asymmetric hollow fibers, the micro-structure was tuned by optimizing pyrolysis temperature protocol and pyrolysis atmosphere. In addition, unexpected physical aging was observed in CMS membranes, which is analogous to the aging phenomenon in glassy polymers. For performance evaluation, multiple "proof-of-concept" tests validated the viability of CMS membranes under realistic conditions. The scope of this work was expanded from binary ethylene/ethane and propylene/propane separations for the debottlenecking purpose to mixed carbon number hydrocarbon processing. CMS membranes were found to be olefins-selective over corresponding paraffins; moreover, CMS membranes are able to effectively fractionate the complex cracked gas stream in a preferable way. Reconfiguration of the hydrocarbon processing in ethylene plants is possible based on the unique CMS membranes.

This study was to investigate theory and application of Osmotic Distillation (OD). OD is a new novel membrane separation process used for the concentration of aqueous solutions such as fruit juices without the application of heat. The present work was undertaken to investigate flux limitations focusing on feedside, membrane and stripper side characteristics of OD. Once the limiting areas were identified, further studies were undertaken to determine methods of minimizing those limitations without losing the quality and integrity of the liquid feed. A laboratory scale OD system was used to simulate the industrial process which takes place during the production of grape juice concentrate for the fruit juice industry. Results of a UF pretreatment study showed that the use of UF membranes with pore diameters of 0.1 fÝm or less as a pretreatment for the subsequent OD of grape juice resulted in significant increases in OD flux over that observed for juice not subjected to UF. The study of the physical properties of the feed played an important role in the explanation of the OD process. The increase in OD flux was attributed to a reduction in juice viscosity as the result of the removal of protein and other high molecular weight components. Apart from an increase in OD flux, UF pretreatment of the grape juice proved to be beneficial in other areas of the OD process. HPLC measurements showed that the normal concentration of fermentable sugars in standard 68 oBrix concentrate can be achieved at a lower Brix value in feed subjected to UF pretreatment, further reducing the need to handle highly viscous feeds. UF pretreatment also resulted in an increase in juice surface tension consequently reducing the tendency for membrane wet-out to occur. The study of the deoxygenation of the feed solution shows that the removal of dissolved gases by the pre boiling method and the perstraction with chemical reaction (PCR) method both had a positive affect on OD flux. Pre boiling the brine resulted in an indirect reduction in dissolved oxygen in the feed. Pre boiling both the feed and brine, further increased the flux. Throughout the PCR study, it was evident that stripper side mass transfer of O2 was not limited by flowrate but was limited by higher stripper concentration. However, the latter had an insignificant effect when the sulfite-oxygen reaction was catalysed. The use of a catalyst and increase in temperature gave a significant improvement in overall mass transfer coefficient. Ten types of hydrophobic microporous membranes were tested for their influence on OD flux. While the pore diameter is a considerable factor in mass transport of gases through the membrane, it was also noted that the type of membrane material used had an affect on the overall mass transfer. All top three performing membranes had pore diameters of 0.2 x 10-6 m and were made from polytetrafluoroethylene (PTFE). The choice of brine to use as the stripper was based on criteria that were confirmed by the brine studies performed here. The best performing stripper solutions demonstrating the greatest improvement in OD flux over the most commonly used brines, NaCl, CaCl2 and CH3COOK were aqueous solutions of potassium salts of phosphoric acid, pyrophosphoric acid and blends thereof. These salts agreed with all the required characteristics of a suitable brine, demonstrating high solubility rates, supporting the ability to lower water vapour pressure. The study of the corrosion effects of brine salts confirmed the phosphate salts are superior demonstrating some of the lowest corrosion rates and highest pH.

The present work was undertaken to develop a composite osmotic distillation (OD) membrane consisting of a thin hydrogel coating on a microporous hydrophobic substrate for the concentration of aqueous feeds containing surface-active agents. The range of OD applications using the hydrophobic membrane alone have been severely limited by the propensity for membrane wet-out when contacted by amphiphilic agents such as oils, fats and detergents. Wet-out allows the feed solution to track freely through the membrane pores with a resulting loss of solutes and a decrease in selectivity. The rationale for the approach taken was based on the hypothesis that the high water selectivity of the hydrophilic coating would maintain good water mass transfer to the underlying hydrophobic substrate but exclude other components including surface-active agents. The first stage of this work involved the identification of potential coating materials and the fabrication and structural characterization of films of these materials to determine their suitability. The second stage involved the development of techniques to facilitate adhesion of the hydrophilic coatings to the hydrophobic substrate, and the testing of the resulting composite membranes for OD performance and resistance to wet-out by surface-active agents. Sodium alginate was selected as the major coating component on the basis of its non-toxicity and its potential for stable hydrogel formation. Structural characterization of noncrosslinked films and films crosslinked using a water-soluble carbodiimide (WSC) was carried out using differential scanning calorimetry (DSC), Fourier Transform infrared spectroscopy (FT-IR) and swelling measurements. Maximum crosslinking through esterification of hydroxyl and carboxylic acid groups on adjacent polymer strands using the film immersion method was achieved with a non-solvent (ethanol) concentration of 60 vol % and a WSC concentration of 100 mM at pH 4. These conditions resulted in a hydrogel with an equilibrium water content of 60 wt %. DSC measurements of noncrosslinked and crosslinked alginate films showed an increase in crystallinity and hence rigidity on crosslinking. Therefore, several coatings were prepared as blends of sodium alginate and amorphous highly flexible carrageenan gum in order to meet the flexibility requirements of a membrane subjected to varying operating pressures in an industrial OD plant. Structural characterization with respect to polymer blend ratio was carried out using scanning electron microscopy (SEM), DSC, X-ray diffraction (XRD). The optimisation for crosslinking conditions was undertaken as for sodium alginate alone. Optimum conditions for film preparation were 20 wt % carrageenan content and a crosslinking medium containing 60 vol % non-solvent (ethanol) and 120 mM WSC at pH 4. These conditions produced a hydrogel with an equilibrium water content of 85 wt %. Two different techniques were employed to anchor the coatings on substrate PTFE membranes. For membranes with a nominal diameter of 0.2 µm, the technique involved surface tension adjustment of the coating solution by ethanol addition in order to enhance penetration of the coating solution meniscus into the substrate pores. This was followed by polymer precipitation by the selective removal of water using OD to provide structural interlocking. T-peel strength measurements showed that this technique resulted in a ten-fold increase in adhesion strength when compared with a coating cast without surface tension adjustments. For membranes with a nominal diameter of 0.1µm, an interfacial bonding agent, myristyltrimethylammonium bromide (MTMA), was used. This technique gave a three-fold increase in adhesion strength relative to that of coating cast without the use of MTMA. The composite membranes were tested in extended OD trials using pure water and feeds containing limonene, the major surface-active components of orange oil. The sodium alginate-carrageenan blend membrane, which was the preferred membrane based on flexibility and water sorption considerations, was also tested against full-cream milk and an industrial detergent, sodium dodecylbenzene sulfonate (DBS). The results indicated that the coatings offered little resistance to water transport and were effective in providing protection against membrane wet-out. Durability trials showed that the composite membranes retained their integrity in water for a minimum of 30 days. Overall, this study has expanded the potential applications of OD to include many important industrial concentration steps that are currently being undertaken by conventional processes with unsatisfactory results. These include the concentration of citrus juices, full-cream milk and nuclear power plant liquid waste. These feeds contain limonene, fats and detergents respectively, all of which wet out unprotected hydrophobic membranes.

Cette thèse de doctorat concerne l’étude de la distillation membranaire sous vide pour l’élimination de l’arsenic contenu dans les eaux souterraines. En effet, la contamination des nappes phréatiques par l’arsenic est une problématique majeure dans de nombreux pays, et en particulier au Vietnam. Dans ce pays, choisi comme cas d’étude pour ce travail, environ 13% de la population est empoisonnée par des eaux souterraines contaminées par l’arsenic. De plus, ces eaux souterraines présentent des salinités élevées (5-10 g.L-1) dues à des infiltrations d’eau de mer dans les nappes. Ce travail de thèse a permis de démontrer la faisabilité de la distillation membranaire sous vide (DMV) pour éliminer l’arsenic contenu dans ces eaux et réduire leur salinité afin de les rendre propres à la consommation humaine. Les concentrations en As(III) dans le perméat de DMV sont toujours inférieures aux limites de la norme en eau potable (10 μg.L-1), même pour de très fortes concentrations en As(III) dans l’alimentation (jusqu’à 2000 μg.L-1). La DMV ne nécessite pas de pré-oxydation de l’As(III) en As(V), étape nécessaire dans de nombreux procédés conventionnels de traitement. De plus, un couplage entre l’osmose inverse (OI) et la DMV a été étudié : l’étape d’OI permet une pré-concentration en NaCl et As(III), puis ce rétentat est alors sur-concentré grâce à laDMV. La DMV a montré de très bonnes performances pour traiter un concentrat contenant de très fortes concentrations en As(III) (7000 μg/L). La DMV permet toujours de limiter les teneurs en arsenic dans le perméat à des valeurs en-dessous de la norme. Enfin, unesimulation d’un procédé global, incluant OI et DMV, et fonctionnant à un taux de conversion global de 96%, a été effectuée. Ce couplage ouvre la voie vers un traitement global de l’arsenic permettant de générer de très faibles quantités d’effluents finaux / This PhD work deals with vacuum membrane distillation (VMD) for arsenic removal from groundwaters. Contamination of water resources with arsenic was identified in 105 countries. Approximately 150 million people are being exposed to arsenic contamination, and 147 million of these people live in Asia. In Vietnam, chosen as the case study of this work, 13% of the population is being in risk of arsenic poisoning. Drinking water resources present not only high arsenic concentration (1 – 3050 ppb) but also high salinity (5 – 15 g/L). This work allowed demonstrating the feasibility of VMD to remove arsenic and also salts contained in groundwaters. As(III) concentration in the permeate of VMD was always lower than the standard level for drinking water (10 μg.L-1), even for high As(III) concentrations in the feed (up to 2000 μg.L-1). With VMD, a pre-oxidation step was not necessary to convert As(III) into As(V), as it is the case for other conventional treatment processes. Moreover, a coupling between reverse osmosis (RO) and VMD was studied. RO was considered as a first step to concentrate NaCl and As(III) before this retentate stream was further concentrated by the VMD. VMD could work efficiently with 99.9% of As(III) andNaCl rejections at a very high RO retentate concentrations ([NaCl] = 300 g/L and [As(III)] = 7000 ppb). Arsenic in the permeate was still lower than the required standard for drinking water. Finally, a simulation of the coupling was performed. By coupling of RO and VMD, ahigh global recovery of 96% could be achieved

A cristalização assistida por destilação com membranas (membrane distillation crystallization, MDC) se destaca como uma alternativa aos processos convencionais de cristalização evaporativa com múltiplos estágios e/ou recompressão mecânica de vapor para dessalinização de soluções aquosas concentradas com descarga zero de líquido (zero liquid discharge, ZLD) no meio ambiente. Os principais atrativos da MDC são as condições operacionais mais brandas de temperatura e pressão, o que possibilita o emprego de fontes de calor de baixa entalpia e instalações menos requisitadas mecanicamente. Entretanto, por ser um processo de separação que envolve membranas, a formação de incrustação se destaca como inconveniente. Assim sendo, grande parte dos estudos em MDC têm sido voltados para essa questão, com foco na operação de destilação com membranas (membrane distillation, MD), quando o produto de interesse é a água recuperada. Nesse contexto, esta tese amplia o conhecimento na área, sendo estudados os fundamentos de cristalização e a sua relação com parâmetros selecionados do processo. Dessa forma, estudos teórico-experimentais foram conduzidos investigando os mecanismos de cristalização predominantes nesse, de maneira a ampliar a abrangência das teorias clássicas de cristalização. No primeiro capítulo, realizou-se uma revisão bibliográfica a fim de apresentar os fundamentos tecnológicos, bem como as características, limitações e desafios para consolidação em escala industrial da MDC. No segundo capítulo, foi definido o conhecimento científico produzido através da especificação de objetivos. No terceiro capítulo, a operação MD na configuração DCMD (direct contact membrane distillation) foi caracterizada utilizando equações matemáticas para o cálculo do fluxo de vapor. Os valores calculados foram validados com experimentos em escala de bancada. Foi possível identificar que a difusão ordinária molecular é o mecanismo de transporte de massa dominante nos poros da membrana, e quantificar os fenômenos de polarizações de temperatura e de concentração adjacentes à superfície da membrana. No quarto capítulo, a cristalização foi integrada com a DCMD e explorada em uma unidade de bancada. Os processos elementares e acessórios de cristalização predominantes foram esclarecidos como sendo nucleação primária heterogênea (incrustação por cristalização), nucleação secundária (abrasão de cristais) e crescimento cristalino molecular (aumento de tamanho). O quinto capítulo versou sobre uma estratégia proposta para reduzir a nucleação primária heterogênea, força motriz da incrustação por cristalização na membrana. Com base nos processos elementares e acessórios de cristalização identificados, foi avaliada uma modificação na MDC, a submersão de membranas em cristalizador, a qual foi implementada em escala de bancada. Essa modificação se mostrou mais sensível à formação de incrustação, com possibilidade de se encontrar condições favoráveis, uma vez que foi possível operar o processo durante três horas sem desenvolvimento de incrustação na membrana (tempo máximo investigado), mas precisa ser melhor investigada. Por último, no sexto capítulo abordou-se a nucleação primária heterogênea, relacionando esta com a queda de fluxo de vapor e com a distribuição de sólidos formados. O equacionamento do sistema validado no terceiro capítulo foi aplicado para quantificação da supersaturação local na membrana e respectiva associação com os mecanismos de cristalização. Observou-se que o aumento de fluxo aumenta a supersaturação local, que aumenta a nucleação primária heterogênea, sendo essa responsável pela formação de cristais que permaneceram aderidos na membrana (incrustação por cristalização) e que foram soltos em solução (suspensão). Os cristais soltos em solução são predominantes. A fluidodinâmica de escoamento (geometria dos módulos de membranas) associada à supersaturação local (fluxo de vapor) impactam no desprendimento de cristais na membrana originados por nucleação primária heterogênea. Com o aumento de supersaturação local, o desprendimento de cristais em suspensão é favorecido em módulo de membranas do tipo fibras ocas, enquanto não afeta o módulo do tipo tubular. Em seu conjunto, esta tese contribui para a melhoria do entendimento de aspectos fundamentais selecionados do processo MDC e para o emprego deste conhecimento em situações de interesse prático. / Membrane distillation crystallization (MDC) stand as an alternative to conventional evaporative crystallization processes with multiple-stage evaporator and/or mechanical vapor recompression towards concentrated brine desalination aiming at zero liquid discharge (ZLD) in the environment. The major advantages of MDC are the moderate temperature and pressure conditions, which allow the use of low enthalpy heat sources and facilities less mechanically required. However, as in membrane separation processes, membrane fouling plays an important role in MDC. Therefore, most MDC studies have been focused on that, with emphasis on membrane distillation (MD) operation, when the product of interest is the recovered water. In this context, this thesis extends the knowledge in the field, wherein the crystallization fundamentals and its relation with selected process parameters were studied. Thus, theoretical and experimental approaches were carried out in order to investigate the prevailing crystallization mechanisms in the process, so the range of the current crystallization theories could be extended. In the first chapter, a literature review was carried out in order to introduce selected fundamental concepts, as well as the process characteristics, limitations and challenges for industrial consolidation. In the second chapter, the scientific knowledge produced by this work was defined in its objectives. In the third chapter, the MD operation in direct contact configuration (DCMD) was characterized using mathematical equations for the calculation of vapor flux and validated with experimental data in a bench scale unit. The dominant mechanism of mass transport in porous media was found to be the ordinary molecular diffusion and the temperature and concentration polarization effects were quantified in the vicinity of membrane surface. In the fourth chapter, the crystallization operation was integrated with DCMD and investigated in a bench scale unit. The elementary and accessory crystallization mechanisms were highlighted as heterogeneous primary nucleation (crystallization fouling), secondary nucleation (crystal abrasion) and crystalline molecular growth (increase in size). The fifth chapter describes a strategy proposed in order to reduce heterogeneous primary nucleation, the driving force of membrane crystallization fouling. Based on the featured crystallization mechanisms, a modification in the conventional MDC operation was evaluated, the submersion of membranes into the crystallizer vessel, which was implemented in a bench scale unit. The preliminary results showed that this modification is more sensitive to crystallization fouling, with possibility to find promising conditions, once it was possible to operate during three hours without development of crystallization fouling (maximum period of time investigated), but further investigation is needed. Lastly, in the sixth chapter, the primary heterogeneous nucleation mechanism was explored, associating it to flux decay and solid distribution in the unit. The system equations validated in the third chapter were applied in order to quantify the supersaturation ratio generated in the vicinity of membrane surface and respective association with crystallization mechanisms. It was observed that increasing the vapor flux, the local supersaturation ratio also increase and, as consequence, the primary heterogeneous nucleation as well. This mechanism is responsible for the formation of crystals that remained adhered on membrane surface (crystallization fouling) and released in solution (suspension). The portion of crystals loose in solution was predominantly formed. The fluid dynamic of flow (geometry of membrane module) associated with the local supersaturation ratio (vapor flux) impact in the detachment of crystals in the membrane surface, originated by heterogeneous primary nucleation. With an increase in the local supersaturation ratio, the detachment of crystals is increased in the hollow fiber membrane module, while in the tubular module the detachment of crystals does not change. As a whole, this thesis contributes to a better understanding of MDC selected fundamental aspects and to the use of this knowledge in practical situations.

Abstract Industrial wastewaters are complex waters, which can contain a large variety of compounds such as heavy metals and salts as well as nutrients, e.g. nitrogen compounds and phosphorous. Prevention of wastewater formation is not always possible and therefore new more efficient water treatment techniques are needed. Legislation also supports the use of more efficient water treatment techniques, which can lead to better purification results and the recovery of valuable compounds from wastewaters. One technique, which has been of interest, is membrane technology. Membrane technology can separate heavy metals, salts and nutrients effectively, also at low concentrations, which is not always possible with conventional water treatment methods. The main disadvantage of membrane technologies is membrane fouling, which reduces the membrane permeate flux and separation efficiency. In this thesis membrane techniques were combined into hybrid processes to increase the efficiency of water treatment to reduce fouling and to widen the application areas of membrane technologies, as well as to increase the awareness of the benefits gained when using hybrid membrane processes in wastewater treatment. Three different hybrid membrane processes were applied. Catalytically active nanofiltration membranes were used to purify real mine wastewaters from harmful compounds, including sulphate. A catalytic layer reduced the membrane fouling tendency. Micellar-enhanced ultrafiltration was applied successfully to the separation of heavy metals from phosphorous-rich wastewater of a fertilizer company to achieve selective separation. In addition, reverse osmosis and membrane distillation were applied to the concentration of heavy metals, a metalloid and nitrogen compounds containing synthetic wastewater efficiently. High volume concentration factor was achieved with the RO-MD process. In this thesis high heavy metal, metalloid, and salt removal efficiencies were achieved with all hybrid membrane techniques. Hybrid membrane techniques were also categorized based on their properties. The study provides new knowledge on hybrid membrane techniques in the removal of inorganic compounds from industrial waters. / Tiivistelmä Teollisuuden jätevedet voivat sisältää kohonneita haitta-ainepitoisuuksia, kuten raskasmetalleja ja suoloja. Teollisuuden jätevedet voivat sisältää myös ravinteita, esimerkiksi typen yhdisteitä ja fosforia. Jätevesien syntymistä ei aina voida ennaltaehkäistä, ja siksi uusille entistä tehokkaammille vedenkäsittelymenetelmille on tarvetta. Lisäksi myös lainsäädäntö vaatii entistä tehokkaampaa vesien puhdistusta, mikä osaltaan edistää entistä tehokkaampien puhdistustekniikoiden kehitystä sekä erotettujen aineiden talteenottoa. Yksi aktiivisen tutkimuksen kohteena oleva vesienkäsittelyssä käytetty menetelmä on kalvoerotustekniikka. Kalvoerotustekniikoilla voidaan erottaa tehokkaasti raskasmetalli-ioneja, sulfaattia ja ravinteita, kuten typpiyhdisteitä teollisuuden jätevesistä myös alhaisissa pitoisuuksissa, missä yleisesti käytettävät menetelmät voivat olla tehottomia. Yksi kalvoerotusmenetelmien ongelma on kalvojen likaantuminen, mikä alentaa kalvojen erotustehokkuutta ja vähentää tuottavuutta. Tässä tutkimuksessa kalvojen likaantumistaipumista on vähennetty yhdistämällä kalvoerotustekniikoita muihin erotusmenetelmiin hybriditekniikoiksi. Tässä työssä on tutkittu kolmea eri hybridimenetelmää. Sinkkioksidilla pinnoitettuja nanosuodatuskalvoja tutkittiin ja verrattiin kaupallisiin nanosuodatuskalvoihin kaivosteollisuuden vesien puhdistuksessa mm. sulfaatista. Katalyyttipinnoite muutti kalvoja vähemmän likaantuviksi, ja näin menetelmän tehokkuus parani. Miselliavusteisella ultrasuodatuksella erotettiin fosforipitoisesta lannoitetehtaan jätevedestä raskasmetalleja selektiivisesti, ja näin mahdollistettiin fosforin uudelleenkäyttö. Kolmannessa tutkimuskohteessa konsentroitiin kalvotislauksen ja käänteisosmoosin yhdistelmällä raskasmetalli- ja typpiyhdisteitä sisältävää synteettistä jätevettä pieneen tilavuuteen. Työssä saavutettiin korkeita raskasmetallien ja suolojen erotustehokkuuksia kaikilla käytetyillä tekniikoilla. Työssä arvioitiin myös yhteenvetona erilaisten hybridimembraanitekniikoiden eroja ja ominaisuuksia ja tekniikoita jaoteltiin menetelmien ominaisuuksien mukaan. Työ antoi uutta tietoa hybridimembraanitekniikoista epäorgaanisten aineiden erotuksessa teollisuuden vesistä.

India is experiencing a bitter challenge in terms of water resources, with the lack of access to safe drinking water being attributed to nearly 200 000 deaths per year. The rural population is especially exposed as groundwater make up 85 % of their drinking water, with widespread contamination being reported. One source of contamination is fluoride, which has been identified in concentrations far beyond the recommended limit from the World Health Organization (WHO), causing severe health problems such as skeletal fluorosis. While India has made significant progress in providing households connections to the grid, electricity access remains unreliable, particularly in rural areas. Membrane distillation (MD) is a thermally driven water purification technology which achieves excellent fluoride reduction rates. Several systems with various combinations of technologies integrated with MD has been researched, where the use of photovoltaic thermal hybrid solar collectors (PVT) and heat pumps (HP) has been receiving increased attention as of late. These two technologies have, to the Author’s best knowledge, never been integrated together for MD, which is the basis of this thesis. With the goal of providing an average of 1000 L of potable water a day, three novel off-grid systems are created using the energy modeling software Polysun with weather data from Balasore, India. Two PVT models and three different HPs identified on the market are considered for the systems. The PVTs differ in terms of glazing, and the HPs have various heating capacities and max water supply temperatures, with one being an air source heat pump (ASHP) and two water source heat pumps (WSHP). One configuration of each combination of PVT and HP is created and optimized in terms of MD modules, battery storage capacity, and feed flowrate, evaluated based on the Key Performance Indicators (KPI) production cost, PVT area, and average daily yield. Furthermore, two different controller strategies are evaluated based on their average daily yield, where one prioritize a high coefficient of performance (COP) for the HP, and the other energy recovery from the MD. The final configurations are thereafter compared based on their production cost. Nine out of the ten final configurations achieve a production cost between 60 - 72 $/m3 after being optimized, which is within the reported range for MD but at the higher end. The larger WSHP achieves the lowest production cost at 60.1 $/m3 paired with the glazed PVT, having a gross area of 323 m2. The glazed PVT performs better than the unglazed for all configurations in terms of both production cost and PVT area. However, the cost of the larger WSHP is based on the $/kW of the smaller WSHP while the two PVTs are assigned an identical $/m2, resulting in the price difference between the products being the determining factor for the actual configuration with the lowest production cost. The lowest PVT area for the final configurations is 294 m2. The required PVT area to reach the production goal is heavily dependent on the amount of MD modules, HP heating capacity and max water supply temperature, and battery storage capacity. Only one configuration achieved a higher yield when energy recovery was prioritized, which supplied 20 % of that system’s thermal energy while not utilizing 61 % of the energy recovery potential. / Indien upplever en bitter utmaning med vattenresurser, där bristande tillgänglighet till säkert dricksvatten är attribuerat nära 200 000 dödsfall per år. Befolkningen på landsbygden är särskilt utsatt då grundvattnet representerar 85 % av deras dricksvatten, som till stor del rapporterats som förorenat. En föroreningskälla är fluorid, vilket har identifierats i koncentrationer långt över den rekommenderade gränsen av World Health Organization (WHO), som leder till allvarliga hälsoeffekter som skelettfluoros. Även fast Indien har gjort stora framsteg inom elnätsanslutningar för hushåll, är elektricitetstillgången opålitligt, speciellt på landsbygden. Membrandestillation (MD) är en värmedriven vattenreningsteknik som uppnår utmärkta reduktionsnivåer av fluorid. Det har forskats om flera system med olika kombinationer av tekniker integrerade med MD, där användningen av hybridsolpaneler (PVT) och värmepumpar (HP) har fått ett ökande intresse på sistone. Dessa två tekniker har, till författarens bästa kännedom, aldrig blivit integrerade tillsammans för MD, vilket är grunden för denna uppsats. Med målet att uppnå en genomsnittlig dricksvattenproduktion på 1000 L per dag, har tre egenartade system skapats i energimodelleringsprogrammet Polysun med väderdata baserad på Balasore, Indien. Två PVT modeller samt tre olika värmepumpar är identifierade på marknaden och implementerade i systemen. PVT modellerna skiljer sig i främst i relation till glasering. Värmepumparna har olika värmekapaciteter samt övre gräns på levererad vattentemperatur, varav en är en luftvärmepump (ASHP) och de två resterande vattenvärmepumpar (WSHP). En konfiguration av varje kombination av PVT och HP skapas och optimeras i relation till MD moduler, batterilagring, och flödeshastighet, som utvärderas med prestandaindikatorerna (KPI) produktionskostnad, PVT yta, samt genomsnittlig dricksvattenproduktion. Två olika kontrollstrategier undersöks även baserat på dricksvattenproduktionen, där en strategi prioriterar en hög prestationskoefficient för HP, och den andra energiåtervinning från MD. De slutliga konfigurationerna jämförs sedan baserat på deras produktionskostnader. Nio av de tio slutliga konfigurationerna uppnår en produktionskostnad mellan 60 - 72 $/m3 efter optimeringen, vilket ligger inom det rapporterade intervallet men på den dyrare sidan. Den större WSHP uppnår den lägsta produktionskostnaden på 60.1 $/m3 i kombination med den glaserade PVT, som omfattar en bruttoarea på 323 m2. Den glaserade PVT presterar bättre än den oglaserad för alla konfiguration sett till produktionskostnad samt PVT area. Dock så är kostnad på den större WSHP baserad på $/kW kostnaden för den mindre WSHP, samt att båda PVT är tilldelade en identisk $/m2 kostnad. Detta leder till att den avgörande faktorn för den faktiska konfigurationen med lägst produktionskostnad är prisskillnaden mellan produkterna. Den lägsta PVT arean för de slutgiltiga konfigurationerna är 294 m2. Den nödvändiga PVT arean för att uppnå produktionsmålet är starkt beroende av mängden MD moduler, batterilagringskapacitet, samt värmekapacitet och övre gräns på levererad vattentemperatur för HP. Endast en konfiguration uppnår en större vattenproduktion när energiåtervinningprioriteras, där 20 % av systemets totala värmeenergi kom från energiåtervinning samtidigt som 61 % av den potentiella energiåtervinningen ej utnyttjas.

Water purification systems have made access to drinking water easier by treating water sources which previously could not be used for drinking. Such systems however require energy and materials to build and operate which means they have environmental impacts. This thesis performs a cradle to grave life cycle assessment of a solar driven HVR water purification system used to treat contaminated groundwater in Odisha, India. The system has three subsystems each with different components – a water purification subsystem that uses an air gap membrane distillation (AGMD) process to purify ground water to produce drinking water, a solar photovoltaic subsystem to provide electricity and a solar thermal subsystem with evacuated tube collectors to provide hot water. The timeframe of the study is 15 years and the chosen functional unit is 590 m3 of drinking water produced over 15 years. The environmental impacts of the system are evaluated using the ReCiPe Midpoint (H) impact assessment method and the life cycle is modelled in the software SimaPro using the Ecoinvent database for inventory data. A comparison is then made between the lifecycle impact of a solar driven HVR water purification system and a grid driven HVR system as well as a water purification system with conventional end of life treatment and a system with state of the art end of life treatment. Along with the lifecycle impact, the levelized cost of water of the water purification system has also been calculated. The results show that within the entire system the solar PV subsystem has the highest impact due to the high electricity consumption during silicon purification for manufacturing the solar panels. The solar thermal subsystem has the next highest impact with the biggest contributor being the manufacturing of glass tubes for the solar collectors. The water purification subsystem has the least impact with the highest share due to use of acetic acid during its use phase for maintenance. The modelling results focus on four impact categories and show the following life cycle impacts - global warming potential : 27 180 kg CO2eq, human carcinogenic toxicity : 2 412 kg 1.4-DCB eq, marine ecotoxicity : 2 662 kg 1.4-DCB eq, freshwater ecotoxicity : 1 967 kg 1.4-DCB eq. The grid operated system shows a lifecycle impact 70 to 170 times higher across these four impact categories compared to the solar driven system. This is due to the high share of fossil fuels in the Indian electricity grid. The state-of-the-art end of life treatment shows a 17% and 22% reduction in freshwater as well as marine ecotoxicity impacts of the system compared to conventional end of life treatment with negligible impacts on global warming and human carcinogenic toxicity. The levelized cost of water calculations show that the system with its current runtime of 6 hours when run using solar energy or the grid is not economically competitive compared to bottled water in India. A sensitivity analysis is then performed to evaluate the sensitivity of lifecycle impact to maintenance frequency and the lifetime of components and the sensitivity of the levelized cost of water to discount rate and the production cost of AGMD modules. The analysis shows that only the lifetime of components has a significant influence on the life cycle impactof the system, the maintenance frequency has a significant impact on freshwater and marine ecotoxicitywhile the discount rate and production cost of AGDM modules has no impact on the levelized cost of water. In conclusion the findings of this thesis agree with the major findings of previous studies done on the topic and adds to the limited knowledge in the literature on the life cycle impact of solar powered AGMD systems. / Vattenreningssystem har gjort förenklat tillgången till dricksvatten genom att behandla vattenkällor som tidigare inte gick att komma åt för att dricka. Sådana system kräver dock energi och material för att bygga och fungera, vilket innebär att de kommer med en miljöbelastning. Detta examensarbete utför en livscykelanalys från vagga till grav av ett vattenreningssystem som används för att behandla förorenat grundvatten i Odisha, Indien. Systemet renar grundvatten genom en destillationsprocess för luftgapmembran och möter sitt elbehov med hjälp av ett solcells-PV-delsystem och varmvattenbehov genom ett solvärmedelsystem med evakuerade rörkollektorer. Den valda funktionsenheten är 590 m3 dricksvatten producerat över 15 år. Systemets miljöpåverkan utvärderas med hjälp av konsekvensbedömningsmetoden ReCiPe Midpoint (H) och livscykeln modelleras i programvaran SimaPro med hjälp av Ecoinvents databas. En jämförelse görs sedan mellan miljöpåverkan från ett solcellsdrivet och ett elnätsdrivet vattenreningssystem och en mellan ett vattenreningssystem med konventionell samttoppmodern avfallshantering. Tillsammans med miljöpåverkan har även den utjämnade kostnaden (LCOW) för vatten i vattenreningssystemet beräknats. Resultaten visar att solcellsdelsystemet har störst miljöpåverkan på grund av den höga elförbrukningen under kiselrening för tillverkning av solpanelerna. Solvärmedelsystemet har den näst högsta påverkan med näst högsta andelen på grund av tillverkningen av glasrör för solfångarna. Delsystemet för vattenrening har minst påverkan varav den högsta andelen kommer från användningen för underhåll av systemet under operationella fas. Modelleringsresultaten fokuserar på fyra påverkanskategorier och visar följande potentiell miljöpåverkan - global uppvärmningspotential: 27 180 kg CO2ekv, mänsklig cancerogen toxicitet: 2 412 kg 1,4-DCB ekv, marin ekotoxicitet: 2 662 kg 1,4-DCB ekv, sötvattensekotoxicitet: 1 967 kg 1,4-DCB ekv. Det nätdrivna systemet visar 70 till 170 g[nger högre stor miljöpåverkan jämfört med det solcellsdrivna systemet i de fyra påverkanskategorierna på grund av den höga andelen fossila bränslen i det indiska elnätet. Medtoppmodern avfallshantering minskat systemets akvatiska och marina ekotoxicitetseffekter med en 10 % jämfört med konventionell avfallshantering och med försumbar påverkan på global uppvärmning och mänsklig cancerogen toxicitet. Den utjämnade kostnaden för vatten visar att när systemet med sin nuvarande drifttid på 6 timmar per dag varken kopplad till solenergi eller elnätet är ekonomiskt konkurrenskraftigt jämfört med vatten på flaska i Indien. En känslighetsanalys utförs sedan på fyra parametrar - underhållsfrekvens, komponenters livslängd, diskonteringsränta och kostnaden för destillationsmodulerna för luftgapmembran för att se deras inverkan på systemets miljöpåverkan och utjämnade vattenkostnader. Analysen visar att endast komponenternas livslängd har en betydande inverkan på systemets livscykelpåverkan, underhållsfrekvensen har en betydande inverkan på sötvatten och marin ekotoxicitet medan diskonteringsräntan och produktionskostnaden för AGDM-moduler inte har någon inverkan på den utjämnade kostnaden för vatten. Sammanfattningsvis kommer resultaten av denna studie att lägga till den begränsade kunskapen i litteraturen om livscykelpåverkan av soldrivna luftgapmembrandestillationssystem.

Les petites unités de dessalement au point d’usage sont une alternative pour l’accès à l'eau potable des communautés isolées de zones côtières ou insulaires. Dans cette thèse, la distillation membranaire (MD) est le procédé de choix pour l’application visée. De plus, les lieux d’implantation ciblés souffrent souvent d’un manque d’accès à l’énergie, mais la plupart d’entre eux sont exposés à des niveaux élevés de radiation solaire. Afin de réduire les pertes de chaleur du système et d'intensifier le procédé, un module intégrant des membranes planes de MD sous vide (VMD) et un collecteur solaire à plaque plane (FPC) apparaît comme une technologie possible. Cette étude a pour objectifs d’étudier la faisabilité de ce concept et de déterminer les paramètres de l’équipement et les conditions opératoires les plus favorables pour l’application visée en cherchant à réduire la consommation d’électricité (par des panneaux photovoltaïques PV) et améliorer simultanément l’efficacité énergétique et la production d’eau dans l’ensemble du module VMD-FPC. Les analyses de sensibilité et les optimisations multi-objectifs sont effectuées à partir de séries de simulations. La productivité quotidienne peut atteindre 96 L pour une surface de module de 3 m2. Un coût énergétique quasi-constant d’une puissance PV de 4,2 à 5,0 W L-1 est observé, permettant d’ajuster la capacité du système. Pour une puissance PV limitée à 130 W (installation mobile), plus de 30 L de distillat peuvent être obtenus avec une surface de 0,83 m2 par une belle journée d'été à Toulouse, en tenant compte des paramètres de fonctionnement optimisés et des matériaux réels. / Small-scale desalination at the point of use offers a potential access to drinking water to communities living in remote coastal areas or isolated islands. In this dissertation, Membrane Distillation (MD) is the applied technology for the aforementioned application scenario. Moreover, the target places are also often in the lack of stable and centralized heat and power supply, while most of them benefit from high solar radiations. In order to further reduce the system heat loss and to intensify the process, the integration in the same module of flat-sheet distillation membranes for Vacuum MD (VMD) and direct solar heating by flat-plate collector (FPC) appears as a possible option. This study aims to explore the feasibility of this concept and to determine the more favorable design and operating conditions for the target application. The main task in this regard is to reduce electricity consumption (provided by photovoltaic PV panels) and simultaneously improve the energy efficiency and water production throughout the VMD-FPC module. The sensitivity analyses and multi-objective optimizations are conducted based on series of simulations. Results show that the potential daily productivity of the system can reach up to 96 L for a module surface area of 3 m2. A quasi-constant power cost of PV of 4.2 - 5.0 W L-1 is observed, permitting a flexible adjustment of the system capacity. Under a limitation of an average PV power of 130 W, more than 30 L of distillate can be obtained with a surface area of 0.83 m2 on a sunny summer-day in Toulouse, taking the optimized operating parameters and real-world material properties into account.

Avec une population toujours croissante et la pénurie de plus en plus importante des ressources en eau douce, l’humanité s’est tournée vers les océans pour ses besoins en eau potable. Afin de faire face aux limites des procédés conventionnels de dessalement d’eau de mer, la distillation membranaire (DM) connaît un intérêt croissant. Même si l’intérêt envers la DM pour le dessalement d’eau de mer est apparu au cours des dernières décennies, aujourd’hui le risque de mouillage des membranes est l’un des obstacles majeurs à son développement industriel. Dans le cadre du projet ANR « WETMEM», l’objectif de cette thèse est de développer des outils de compréhension des mécanismes de mouillage en distillation membranaire sous vide. Plusieurs membranes, fabriquées par des partenaires du projet WETMEM, et commerciales ont été étudiées afin de comprendre l’influence des propriétés des membranes sur les indicateurs de mouillabilité. De plus, une définition et une classification des mécanismes de mouillage ont été proposées. Par la suite, deux indicateurs de mouillage ont été développés à l'aide de la microscopie électronique à balayage et de la spectroscopie de dispersion de rayons X selon une méthode appelée « Détection d'intrusion de traceur dissous ». Une preuve de concept a été fournie, dans laquelle différents mécanismes de mouillage ont pu être visualisés et interprétés. Ces indicateurs ex situ ont alors été utilisés avec des indicateurs de mouillabilité (Angle de contact, Pression d’intrusion de liquide) afin de comprendre l’influence de la température (35-50 ° C), de la salinité (22-310 g / L de NaCl sol.) et du débit (400 - 4000 Re) sur le mouillage et la mouillabilité d'une membrane de PVDF en distillation membranaire sous vide. Il a alors été constaté que la salinité a l’impact le plus important sur le mouillage par rapport aux autres paramètres de fonctionnement. En outre, un outil optique in-situ non invasif a été développé. Il permet de visualiser le mouillage in-situ en distillation membranaire. La progression du mouillage in situ a été observée à différentes échelles et pour différentes solutions salines et eaux de mer. / With an ever-increasing population and the growing disparity in potable water resource, humanity has turned its attention to the oceans for its potable water needs. To overcome the current limitations in current desalination technologies, membrane distillation (MD) is actively being developed. The interest of MD for seawater desalination was established in the last decades but today the risk of membrane wetting is one of the major barrier for industrial implementation of MD. Under the framework of the ANR project “WETMEM”, the issue of this thesis was to develop tools for better understanding wetting mechanisms in vacuum membrane distillation. Several fabricated (WETMEM partners) and commercial membranes were studied to understand the influences of membrane properties on wettability. Therefore, a definition and classification on wetting were formulated. After that two wetting indicators were developed using scanning electron microscopy and X-ray dispersion spectroscopy under a method called “Detection of Dissolved Tracer Intrusion”. A proof of concept was provided with various wetting mechanisms visualized and interpreted. These ex-situ indicators were used with wettability tools (Contact Angle, Liquid Entry Pressure) to understand the influence of temperature (35-50°C), salinity (22-310 g/L NaCl sol.) and flow rate (400 – 4000 Re) on wetting and wettability of a PVDF membrane under vacuum membrane distillation. Indeed, it was found that salinity has a greater impact on wetting than the other operating parameters. Additionally, a proof of concept was provided for non-invasive in-situ optical method for visualizing wetting in membrane distillation. Progression of in-situ wetting visualization was validated at different scales for various saline solutions and seawaters.