Ensuring electricity availability and acquiring access of potable water during emergencies in remote areas are becoming a global challenge around the world. Utilizing solar energy electricity generation by photovoltaics and clean water production by solar distillation have shown its great potential to meet the world’s future energy and water demands. In this work, we fabricated a photovoltaic-membrane distillation-evaporative crystallizer device (PV-MD-EC), in which high electricity generation efficiency (~15%), clean water production rate (~2.66 kg/m2 h) and salt crystallization from seawater can be achieved in such an integrated system under one sun illumination. In addition, the solar cell operates in a much lower temperature at around 48 oC, which is much lower than previous work. The advanced performance is attributed to the utilization of a highly porous and thinner hydrophobic membrane. This design provides a new strategy to address the challenge of water-energy nexus.

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The rising use of mineral-based fertilizer and water for agricultural operations to feed a growing population has polluted water bodies and depleted resources. In addition, nutrient contamination has caused eutrophication and wastewater concerns that conventional wastewater treatment cannot solve. Thus, meeting new water treatment regulations and procuring more value-added products from these procedures is crucial. Conductive ultrafiltration membranes precipitate and extract struvite, an ecologically good fertilizer, from synthetic livestock effluent. This technique produces solid fertilizer and irrigation-quality water. Since the recovery process relies on electrochemical hydrolysis and local pH modulation along the membrane surface, pH correction does not need chemical additions. The system was tested using cow effluent with up to 1,000 mg/L of nitrogen and phosphorus. Analytical tests showed that the precipitates were struvite and that up to 65% of the phosphorus and nitrogen were removed in the first 30 minutes of electrochemical filtration. Low membrane fouling and flux drop made the recovery technique successful. A mathematical model of N, P, and Mg ions in an external electric field explained the fouling and precipitation tests. Thus, precipitation happens near the membrane but not on it. This reduces surface fouling. Forward osmosis was used to make struvite with less energy. A voltage near the FO membrane enabled magnesium to migrate opposite into the feed chamber, where it reacted with ammonium and phosphate in the feed solution to form struvite. Electrical charging increased struvite recovery by 77% and water recovery by 39%. Ion migration may have reduced dilutive and concentrative polarization on the draw and feed sides of the FO membrane, causing the rise. High external voltage, draw concentration, and draw pH made water recovery and struvite precipitation simpler. This study suggests that reverse salt flow might improve FO systems' nutrition and water recovery. These devices were combined with microbial electrolytic cells to generate electricity and prevent biofouling. FO treatment was investigated using vacuum membrane distillation for sustainability and zero discharge. Constant draw solution reconcentration yields more steady flux values than the typical lowering flux. The research will increase knowledge of treatment system synergy in water reclamation and nutrient recovery. It also identifies possible obstacles to development. / Environmental Engineering

Water stress is an ongoing problem in many places in the world, while the demand for clean and safe freshwater is growing due to the increasing population. In many developing countries, water supplies often are contaminated with arsenic, fluoride, etc. Therefore, it is important to realize that water scarcity and contamination issues concern only one sector but many. HVR Water Purification AB is developing a water purification prototype – ELIXIR 500 - using the air gap membrane technology and is implemented in Odisha, India, aiming to supply with 200 litre water daily. This thesis aims to estimate future energy sources to supply this prototype and explore the possibilities of using only renewable energy resources from technical, economic, and environmental perspectives. These are achieved by firstly identifying the energy possibilities in Odisha, India, and then calculating the feasibility of each solution chosen and finally analyzing the results. Among the energy sources, which are power grid, wind and solar power, diesel generator and solar-diesel hybrid system. It is found that the energy source to the prototype supplied by the power grid is 0.057 USD per litre water, which is the cheapest option. However, it is not feasible due to the lack of electrification from the local network. Meanwhile, the solar-diesel hybridized energy system is the most economical option if renewable energy sources are integrated with 0.11 USD per litre water. / Vattenstress ett pågående problem på många ställen i världen medan efterfrågan på rent och säkert dricksvatten växer på grund av den ökande befolkningen. I många utvecklingsländer är vattenförsörjningen ofta förorenade med arsenik, fluor osv. Det är därför viktigt att inse att vattenbrist och föroreningar inte bara rör en sektor utan många. HVR Water Purification AB utvecklade en prototyp för vattenrening - ELIXIR 500 - med hjälp av luftspaltmembrantekniken (eng: air gap membrane distillation och implementeras redan i Odisha, Indien, med målet att förse 200 liter rent vatten dagligt. Denna avhandling syftar till att uppskatta de framtida energikällorna för att tillhandahålla denna prototyp och utforska möjligheterna att endast använda förnybara energikällor ur tekniska, ekonomiska och miljömässiga perspektiv. Dessa uppnås genom att först identifiera de olika energimöjligheter i Odisha, Indien, följt av beräkningar om utförbarhet för varje vald lösning och slutligen en analys av resultaten. Bland energikällorna elnät, vind, sol, diesel generator och sol-diesel hybrid system har visat sig att energikällan till prototypen som levereras av elnätet som kostar 0.057 USD per liter vatten som det billigaste alternativet, men det är inte möjligt på grund av bristen på elektrifiering från det lokala elnätet. Å andra sidan är det hybridiserade energiskombinationen med solkrafts och diesel det billigaste alternativet om förnybara energikällor ska integreras, resultatet visade att vara 0.11 USD per liter vatten.

Landfill leachate is considered as a complex wastewater with various organic and inorganic species which must meet strict discharge standards before its release. Due to such high concentration of diverse pollutants, leachate is low in biodegradation; therefore, a proper usage of physicochemical treatments is required. In this study, membrane distillation (MD) has been used along with Fenton treatment process for pre-coagulation to achieve an effective removal of contaminants. MD is a technology derived with vapor pressure difference across the hydrophobic membrane which traps the feed-wastewater vapor at the entrance of the hydrophobic side before permeation. In order to modify and assist in membrane technology's common drawback, which is dealing with foulants, Fenton oxidation is coupled in the leachate treatment process. Fenton is reserved to be the most effective for leachate treatment and is widely used due to its simple operation and low costs. Fenton oxidation was able to lessen the chemical oxygen demand (COD) concentration of leachate up to 55% while increasing the conductivity and reducing the concentration of NH4-N. The membrane flux and volume had a significant increase with a use of lower COD leachate after Fenton treatment coupled with MD. / Master of Science / Landfilling has been recognized as a principal disposal process of municipal solid wastes globally over the past decades, and this disposal method has been one of the leading concerns for a continuous production of landfill leachate. Leachate is considered as a complex wastewater with a variety of organic and inorganic species which must meet strict discharge standards before its release. Due to such high concentration of diverse pollutants, leachate is low in biodegradation; therefore, a proper usage of physicochemical treatments is required. In this study, membrane distillation (MD) has been used along with Fenton treatment process for pre-coagulation to achieve an effective removal of contaminants. MD is a technology derived with vapor pressure difference across the hydrophobic membrane which traps the feed-wastewater vapor at the entrance of the hydrophobic side before permeation. MD has several advantages which include reduced operating temperature compared to conventional distillation processes, fewer requirements of membrane cleaning, and lower operating hydraulic pressure than other conventional pressure-driven membrane processes such as reverse osmosis (RO). This technology has a common drawback along with other membrane-required technologies which is dealing with foulants. For a reduction in membrane fouling, Fenton oxidation is coupled in the leachate treatment process. Fenton is reserved to be the most effective for leachate treatment and is widely used due to its simple operation and low costs.

Une thermofrigopompe (TFP) est une machine frigorifique qui produit du froid et de la chaleur utiles. L’objectif de ces travaux est de développer le concept de thermofrigopompe pour la production de froid et le dessalement. Le dessalement est réalisé en utilisant la chaleur rejetée au condenseur de la TFP. La technique de dessalement retenue après étude bibliographique est l’AGMD (air gap membrane distillation) pour ses températures de fonctionnement compatibles avec la température de condensation des machines frigorifiques classiques. Ce procédé de distillation a été caractérisé grâce à une installation pilote pour diverses conditions de températures, de débits, d’épaisseurs d’air gap et de compositions de solutions. Une étude de longue durée associée à une observation au MEB a permis évaluer le niveau colmatage des membranes. Un modèle numérique a ensuite été développé à partir des premiers résultats expérimentaux. Des simulations ont permis de dégager des tendances de comportement d’une machine couplée TFPMD. Enfin, un prototype a été construit à partir d’un petit réfrigérateur et d’une cellule d’AGMD fabriquée par impression 3D. Les mesures expérimentales ont permis de valider le concept de TFPMD et d’obtenir de premiers résultats de performance prometteurs. La valorisation de l’énergie thermique perdue par les équipements frigorifiques pour effectuer du dessalement semble donc une solution intéressante au manque d'eau douce qui peut survenir dans de nombreuses régions de la planète. / A heat pump or a refrigerating device produces simultaneously cooling and heating energies. The objective of this research is to develop the concept of heat pump for simultaneous cooling and desalination. Desalination is carried out by recovering the heat rejected by the condenser of the machine. The desalination technique, chosen thanks to the literature review, is AGMD (air gap membrane distillation) because of the compatibility of operating temperatures with the condensing temperature of standard heat pumps. AGMD was characterized using a pilot for different conditions of temperature, flow rate, air gap thickness and solution compositions. A long term study associated to scanning electron microscope images enabled to evaluate the fouling level of the membrane. A numerical model was then developed using the first experimental results. Simulations have revealed patterns of behaviour for a coupled heat pump and AGMD machine. Finally, a prototype was built with a small refrigerator and an AGMD cell manufactured by 3D printing. Experimental measurements were used to validate the concept of heat pump for simultaneous cooling and desalination and to obtain promising performance results. The valorization of the heat lost by refrigeration equipment for desalination seems therefore an interesting solution to overcome the lack of fresh water that can occur in many regions of the planet.

<div>Thermal desalination of high salinity water resources is crucial for increasing freshwater supply, but efficiency enhancements are badly needed. Nanomaterial enhancements and novel condensation regimes offer enormous potential for improving promising technologies like membrane distillation (MD). In this work, we first examined nanofluids for MD, including the role of nanoscale physics, and model system-level energy efficiency enhancements. Our model included the dominant micro-mixing from Brownian motion in fine particle nanofluids (copper oxide) and the unusually high axial conduction from phonon resonance through Van der Waals interaction in carbon nanotube nanofluids. Carbon nanotubes resulted in a consistent, wide range of improvements; while copper oxide particles showcased diminishing returns after a concentration of 0.7%, where Brownian motion effects reduced. However, the enhancements at higher concentrations from liquid layering around nanoparticles were impractical in MD, since the related high surfactant levels compromised the membrane hydrophobicity and promoted fouling. Dilute solutions of metallic nanofluids can be actively integrated to enhance the performance of MD, whereas stronger nanofluid solutions should be limited to heat exchangers that supply thermal energy to MD systems. We then investigated slippery liquid infused porous surfaces (SLIPS) for enhanced condensation rates in MD. Dropwise condensation heat transfer was modelled considering the effects of the departing, minimum droplet radii and the interfacial thermal resistances. Effective droplet shedding from these surfaces led to an experimental thermal efficiency of 95%. Alternatively, porous condensers with superior wicking properties and conductive heat transfer offered a robust solution to high salinity desalination. We modelled the onset of flooding in porous condensers using Darcy’s law for porous media, including the effects of the condenser permeability and determined the optimal condenser thickness at varying system length scales. The increased active area of condensation resulted in a significant enhancement (96.5%) in permeate production and 31.7% improvement in experimental thermal efficiency. However, porous condensers were only compatible with flat plate module designs limiting their practicality.</div>

<p>The water crisis is increasing with every passing day due to climate change and increase in demand. Different desalination methods have been developed over the years to overcome this shortage of water. Reverse Osmosis is the most widely used desalination technology, but cannot treat many fouling-prone and high salinity water sources. A new desalination technology, Membrane distillation (MD), has the potential to purify wastewater as well as highly saline water up to a very high purity. It is a thermal energy-driven desalination method, which can operate on low temperature waste heat sources from industries, powerplants and renewable sources like solar power. Among the different configurations of MD, Air Gap Membrane Distillation (AGMD) is the most versatile and flexible. However, the issue that all MD technology, including AGMD face, is the low energy efficiency. Different sections of AGMD system have been modified and improved over the years through consistent research to improve its energy efficiency, but one section that is still new and unexplored, and has a very high potential to improve the energy efficiency of AGMD, is the ‘air gap’.</p><p> </p><p> </p><p>The aim of this research is to tap into the potential of the air gap and increase the energy efficiency of the AGMD system. It is known that decreasing the air gap thickness improves the energy efficiency parameter called Gained output ratio (GOR) to a great extent, especially at very small air gap thickness. The minimum gap thickness that maximizes the performance is smaller than the current gap thicknesses used. But it is difficult to attain such smaller air gap thickness (< 2mm) without the constant risk of flooding. Flooding can be prevented, and smaller air gap thickness can be achieved if instead of film wise condensation on the condensing surface, a different condensation flow regime is formed. This study tests different novel condensing surfaces like Slippery liquid infused porous surfaces (SLIPS) and Superhydrophobic surfaces (fabricated with different methods) inside the AGMD system with a goal of attaining smaller air gap thickness and improve the performance of AGMD system for the first time. The performance of these surfaces is compared with plain copper surface as well as with each other. Finally, numerical models are developed using the experimental data for these surfaces.</p><div><div><div> </div> </div> </div>

Domestic and industrial water demands are growing globally due to population growth and rapid economic development, placing increasing strains on water resources. Wastewater effluents generated from these and other activities impact the environment and are thus subject to tightening regulation. The focus of research and development in water treatment processes aims at both pollutant removal efficiency and cost of purification. Membrane distillation (MD) is a developing thermally driven technology capable of achieving extremely high environmental performance utilizing renewable energy sources to a high degree. District heating networks, and in particular those driven by biomass, represent an ideal heat supply for MD systems. This thesis presents a technoeconomic assessment of district heating driven MD for water purification in selected industrial applications. The study covers analysis of MD separation performance and the related costs from different district heating integration scenarios. The analyses are based on three types of semi-commercial MD modules, with experiments conducted at laboratory and pilot scales. The case studies include pharmaceutical residue removal from effluents of municipal wastewater treatment plant, wastewater purification in pharmaceutical industry, and ethanol concentration in bioethanol production plant. Full-scale simulation studies were carried out for the identified case studies based on the experimental data obtained from MD module along with process information gathered from the industries. Results from the pharmaceutical residue removal pilot trials showed very good to excellent separation efficiency for 37 compounds at feed concentrations ranging from ng/L to mg/L. From alcohol-water feeds, ethanol concentrations were increased from 5% to nearly 90%. Simulation studies revealed that district heating integration of MD systems is feasible. Costs per unit volume of purified water are higher than competing technologies, however the configurations enable enhanced environmental performance that would be difficult to achieve otherwise. / Kommunala och industriella vattenkrav växer globalt på grund av befolkningstillväxt och snabb ekonomisk utveckling, vilket ökar belastningen på vattenresurserna. Avloppsvatten från alla verk-samheter påverkar miljön och är därmed föremål för tilltagande reglering. Fokus i forskning och utveckling av vattenreningsprocesser syftar till att både öka effektiviteten i avlägsnandet av föroreningarna och att minska kostnaderna för detta. Membrandestillation (MD) är en ny termiskt driven teknik som kan uppnå extremt hög miljö-prestanda genom att den är effektiv och i hög grad kan drivas av förnybara energikällor. Fjärrvärmesystem, särskilt de som drivs av biomassa, utgör en idealisk värmeförsörjning för ett MD-system. Avhandlingen presenterar en teknoekonomisk bedömning av fjärrvärmedriven MD för vattenrening i utvalda industriella applikationer. Studien analyserar MD-systemets separations-prestanda och kostnader i olika fjärrvärmeintegrationsscenarier. Analyserna baseras på tre typer av semi-kommersiella MD-moduler, med experiment utförda på laboratorie- och pilotskala. Fallstudierna innefattar: borttagning av läkemedelsrester från avloppsvatten från kommunalt avloppsreningsverk; avloppsvattenrening i läkemedels-industrin; och uppkoncentrering i bioetanolproduktionsanläggning. Fullskaliga simuleringsstudier har utförts för fallstudierna baserat på experimentella data erhållna från MD-modulen och med processinformation som samlats in från industrin. Resultaten från försöken med läkemedelsrester visade mycket god till utmärkt separationseffektivitet för 37 föreningar vid förorenings-koncentrationer som sträckte sig från ng/liter till mg/liter. Vid uppkoncentrering av alkohol ökades etanolhalten från 5 % till nära 90 %. Simuleringsstudier visade att fjärrvärmeintegration av MD-system är möjlig. Kostnader per volym renat vatten är högre än konkurrerande teknik, men konfigurationerna möjliggör förbättrad miljöprestanda som skulle vara svår att uppnå på annat sätt. / <p>This doctoral research has been carried out in the context of an agreement on joint doctoral research supervision between KTH Royal Institute of Technology, (Stockholm, Sweden), and Politecnico di Torino − PoliTo, (Turin, Italy). Erasmus Mundus Joint Doctorate, SELECT+ (Environomical pathways for sustainable energy services) program. QC 20170523</p> / SLECT+ Erasmus Mundus Joint Doctoral Program

No presente trabalho foram avaliados processos alternativos de dessalinização visando a recuperação e reuso da água contida em salmouras concentradas, sendo o processo de cristalização assistida por destilação por membranas (MDC) investigado com profundidade. Foi desenvolvido um modelo diferencial para o processo de destilação por membranas por contato direto (DCMD), contemplando métodos termodinâmicos rigorosos para sistemas aquosos de eletrólitos fortes, bem como mecanismos de transferência de calor e massa e efeitos de polarização de temperatura e concentração característicos deste processo de separação. Com base em simulações realizadas a partir do modelo matemático assim desenvolvido, foram investigados os principais parâmetros que influenciam o projeto de um módulo de membranas para DCMD. O modelo foi posteriormente estendido com equações de balanço de massa e energia adicionais para incluir a operação de cristalização e desta forma representar o processo de MDC. De posse dos resultados das simulações e do modelo estendido, foi desenvolvido um método hierárquico para o projeto de processos de MDC, com o objetivo de conferir características de rastreabilidade e repetibilidade a esta atividade. Ainda a partir do modelo MDC foram discutidos aspectos importantes em MDC como a possibilidade de nucleação e crescimento de cristais sobre a superfície das membranas, bem como o comportamento do processo com sais com diferentes características de solubilidade e largura da zona metaestável. Verificou-se que para sais cuja solubilidade varia muito pouco com a temperatura e que possuem zona metaestável com pequena largura, caso do NaCl, a operação com resfriamento no cristalizador não é viável pois aumenta excessivamente o consumo energético do processo, sendo nesses casos preferível a operação \"isotérmica\" - sem resfriamento no cristalizador - e o convívio com a possibilidade de nucleação no interior do módulo. No extremo oposto, observou-se que para sais com grande variabilidade da solubilidade com a temperatura, um pequeno resfriamento no cristalizador é suficiente para garantir condições de subsaturação no interior do módulo, sem grande ônus energético para o processo. No caso de sais com pequena variabilidade da solubilidade com a temperatura, mas com largura da zona metaestável elevada, existe certo ônus energético para a operação com resfriamento do cristalizador, porém não tão acentuado como no caso de sais com zona metaestável estreita. Foi proposto um fluxograma alternativo para o processo de MDC, onde foi introduzido um circuito de pré-concentração da alimentação antes do circuito de cristalização, para o caso de alimentação com soluções muito diluídas. Este esquema proporcionou um aumento do fluxo permeado global do processo e consequentemente uma redução na área total de membrana requerida. Verificou-se que através do processo com préconcentração da alimentação de 5% até 10% em massa - no caso de dessalinização de uma solução de NaCl - foi possível reduzir-se a área total da membrana em 27,1% e o consumo energético específico do processo em 10,6%, quando comparado ao processo sem pré-concentração. Foram desenvolvidas ferramentas úteis para o projeto de processos de dessalinização por MDC em escala industrial. / Alternative desalination processes aiming at the recovery and reuse of the water contained in concentrated brines were evaluated, being the membrane distillation crystallization (MDC) process investigated in depth. A differential model for the direct contact membrane distillation (DCMD) process was developed for that matter, comprising rigorous thermodynamic methods for strong electrolytes, heat and mass transfer mechanisms and temperature and concentration polarization effects. Based on simulations from the mathematical model thus developed, the main parameters that influence the design of DCMD membrane modules were investigated. The model was further extended with mass and energy balance equations in order to consider the crystallization unit operation and thus suitably represent the MDC process. Based on the simulations results and the extended model, a hierarchical method was developed for the MDC process design, adding traceability and repeatability characteristics to the design activity. Important aspects of the MDC process such as the possibility of nucleation and crystal growth on the membrane surface, as well as the behavior of the process with salts presenting different solubility characteristics and metastable zone widths were further discussed. It was observed that salts presenting negligible temperature dependence regarding their solubility and small metastable zone widths (i.e. NaCl) do not favor the operation with cooling in the crystallizer due to excessive increase in energy consumption, being the isothermal operation more indicated in such cases even at the risk of nucleation inside the membrane module. On the other hand, it was noticed that for salts whose solubility is highly temperature dependent a slight cooling in the crystallizer is enough to assure subsaturated conditions inside the membrane module with minimal energy consumption increase. In the case of salts with low temperature dependence regarding solubility but with large metastable zone widths, the operating strategy of applying cooling in the crystallizer may increase energy consumption but not as significantly as in the case of salts with small metastable zone widths. An alternative flowsheet for the MDC process was proposed, where a pre-concentration loop was introduced before the crystallization loop, showing good results for dilute feeds since it takes advantage of the higher water activity and consequently higher transmembrane fluxes due to the lower concentration. It was perceived a 27.1% reduction in the required membrane surface and a 10.6% energy consumption reduction for the modified flowsheet with the pre-concentration loop, for a feed comprised of 5% of NaCl. Useful tools aimed for the design of industrial scale processes based on MDC were developed.