Yes / Multistage Flash (MSF) desalination process is still a dominant process, especially in the Gulf region, to produce high quality freshwater. Although there has been energy price surge in recent years, MSF process will continue to operate in that region for some foreseeable future. The key challenge is how to make such processes still profitable. Understanding the dynamics of any processes under uncertainty and disturbances is very important to make a process operationally feasible and profitable. The main aim of this work is to understand the dynamics of industrial scale MSF process using high fidelity and reliable process model. For this purpose, a detailed dynamic model for the MSF process incorporating key and new features is developed and validated against the actual data of a large-scale seawater desalination plant. The model is then used to study the behaviour of large scale MSF processes for disturbances in steam temperature, feed temperature and the recycle brine flow rate. The simulation results show that the last stage requires a longer time to settle compared to the preceding stages. In addition, steam temperature shows insignificant influence on the performance ratio compared to the inlet seawater temperature and recycle brine flow rate. Furthermore, it is found that the productivity of plant can increase in the winter compared to that in the summer. However, this benefit comes at the expense of increased steam consumption in the winter, resulting in a low performance ratio.

Liquid waste discharged from industrial outfalls is categorized into two major classes based on their density. One type is the effluent that has a higher density than that of the ambient water body. In this case, the discharged effluent has a tendency to sink as a negatively buoyant jet. The second type is the effluent that has a lower density than that of the ambient water body and is hence defined as a (positively) buoyant jet that causes the effluent to rise. Negatively/Positively buoyant jets are found in various civil and environmental engineering projects: discharges of desalination plants, discharges of cooling water from nuclear power plants turbines, mixing chambers, etc. This thesis investigated the mixing and dispersion characteristics of such jets numerically. In this thesis, mixing behavior of these jets is studied using a finite volume model (OpenFOAM). Various turbulence models have been applied in the numerical model to assess the accuracy of turbulence models in predicting the effluent discharges in submerged outfalls. Four Linear Eddy Viscosity Models (LEVMs) are used in the positively buoyant wall jet model for discharging of heated waste including: standard k-ε, RNG k-ε, realizable k-ε and SST k-ω turbulence models. It was found that RNG k-ε, and realizable k-ε turbulence models performed better among the four models chosen. Then, in the next step, numerical simulations of 30˚ and 45˚ inclined dense turbulent jets in stationary ambient water have been conducted. These two angles are examined in this study due to lower terminal rise height for 30˚ and 45˚, which is very important for discharges of effluent in shallow waters compared to higher angles. Five Reynolds-Averaged Navier-Stokes (RANS) turbulence models are applied to evaluate the accuracy of CFD predictions. These models include two LEVMs: RNG k-ε, and realizable k-ε; one Nonlinear Eddy Viscosity Model (NLEVM): Nonlinear k-ε; and two Reynolds Stress Models (RSMs): LRR and Launder-Gibson. It has been observed that the LRR turbulence model as well as the realizable k-ε model predict the flow more accurately among the various turbulence models studied herein.

Liquid waste discharged from industrial outfalls is categorized into two major classes based on their density. One type is the effluent that has a higher density than that of the ambient water body. In this case, the discharged effluent has a tendency to sink as a negatively buoyant jet. The second type is the effluent that has a lower density than that of the ambient water body and is hence defined as a (positively) buoyant jet that causes the effluent to rise. Negatively/Positively buoyant jets are found in various civil and environmental engineering projects: discharges of desalination plants, discharges of cooling water from nuclear power plants turbines, mixing chambers, etc. This thesis investigated the mixing and dispersion characteristics of such jets numerically. In this thesis, mixing behavior of these jets is studied using a finite volume model (OpenFOAM). Various turbulence models have been applied in the numerical model to assess the accuracy of turbulence models in predicting the effluent discharges in submerged outfalls. Four Linear Eddy Viscosity Models (LEVMs) are used in the positively buoyant wall jet model for discharging of heated waste including: standard k-ε, RNG k-ε, realizable k-ε and SST k-ω turbulence models. It was found that RNG k-ε, and realizable k-ε turbulence models performed better among the four models chosen. Then, in the next step, numerical simulations of 30˚ and 45˚ inclined dense turbulent jets in stationary ambient water have been conducted. These two angles are examined in this study due to lower terminal rise height for 30˚ and 45˚, which is very important for discharges of effluent in shallow waters compared to higher angles. Five Reynolds-Averaged Navier-Stokes (RANS) turbulence models are applied to evaluate the accuracy of CFD predictions. These models include two LEVMs: RNG k-ε, and realizable k-ε; one Nonlinear Eddy Viscosity Model (NLEVM): Nonlinear k-ε; and two Reynolds Stress Models (RSMs): LRR and Launder-Gibson. It has been observed that the LRR turbulence model as well as the realizable k-ε model predict the flow more accurately among the various turbulence models studied herein.

I takt med att vattenbristen ökar har flera länder börjat använda avsaltning, en innovation som framställer rent men mineralfattigt vatten, för att möta vattenbehoven. Detta kandidatarbete ämnar att bidra med vidare kunskap kring avsaltat dricksvatten med bakgrund till tidigare forksning. Detta görs med hänsyn till tre ämnesområden där frågeställningarna är följande:  Vilka är de fundamentala processerna vid framställning av avsaltat dricksvatten? Vad finns det för hälsorisker med regelbunden konsumtion av avsaltat dricksvatten?  Hur bidrar olika faktorer till att kostnader i samband med avsaltat dricksvatten ökar och/eller minskar?  Denna studie fann att allt avsaltat dricksvatten går igenom tre grundläggande processer; förbehandling, avsaltning och remineralisering. Hälsoriskerna i samband med regelbunden konsumtion av avsaltat dricksvatten var; elektrolytavvikelse som kan leda till t.ex. cancer, 6 % större risk för ischemisk hjärtsjukdom, sköldkörtelproblem och ökad benskörhet. De olika faktorerna som bidrar till att kostnader i samband med avsaltat dricskvatten ökar och/eller minskar är:  Teknologins utveckling (Kostnader har minskat)  Bättre membranfilter (Kostnader har minskat)  Saltlaksavfall miljöpåverkan (Svårt att avgöra kostnder för)  Hälsopåverkan (Kostnader har ökat)  Val av vattenkälla (Påverkar kostnader för avsaltning)  Val av avsaltningsmetod (Påverkar kostnad för avsaltning)  Val av re-mineralisering (Påverkar kostnad för avsaltning)  Anläggningens storlek/kapacitet (Påverkar kostnad för avsaltning)  Val av energikällor (Påverkar kostnad för avsaltning)  Användandet av ERD (Kostnader har minskat)  Eftersom produktionen och konsumtionen av avsaltat dricksvatten förutspås öka bör myndigheter, såsom WHO, införa riktlinjer specifikt för avsaltat dricksvatten och dess mineralinnehåll. Dessutom har denna litteraturstudie kommit fram till slutsatsen att hälso- och miljöaspekter bör sammanvävas på ett bättre sätt med det avsalttade dricksvattnet. / As water scarcity increases, several countries have turned to the use of desalination, an innovation that produces clean but mineral-poor water in order to satisfy the water demands. This bachelor’s thesis aims to provide the reader with further knowledge about desalinated drinking water with background to previous research. This is done with regard to three questions:  What are the fundamental processes in the production of desalinated drinking water?  What are the health risks of regular consumption of desalinated drinking water?  How do various factors contribute to costs increasing and/or decreasing in relation to desalinated drinking water?  This study found that all desalinated drinking water goes throught three fundamental processes; pre-treament, desalination and remineralization. The healthrisks found in realtion to regular consumtion of desalinated drinking water was; electrolyte deviation which can lead to e.g. cancer, a 6% increase of iscehmic heart disease, poor thyroid condition and increased osteoporisis. The different factors that contribute to the costs of desalination increasing and/or decreasing are:  Technology development (costs have decreased) Better membrane filter (costs have decreased) Saline waste environmental impact (difficult to determine costs for) Health impact (costs have increased) Choice of water source (affects cost of desalination) Choice of desalination method (affects cost of desalination Choice of re-mineralization (affects cost of desalination) Plant size / capacity (affects desalination cost) Choice of energy sources (affects cost of desalination) Use of ERD (costs have decreased)  In addition as the production and consumtion of desalinated drinking water is predicted to increase, authorities, such as the WHO, should introduce guidelines specifically for desalinated drinking water and its mineral content. Furthermore, this literature study has come to the conclussion that health and enviorment components should be better interwoven with the production of desalinated drinking water.

Yes / In order to improve the performance of the reverse osmosis (RO) desalination plant powered by photovoltaic (PV), two cooling systems were proposed in this study to cool the PV and preheating the RO feed water as well. In the cooling design (1), the cooling fluid flows in direct contact with the back surface of the PV through channels of half circular cross-sections. While in the design (2), it flows through channels of squar cross-sections fixed on the PV back surface. Two nano-fluids were also tested as cooling fluid: H2O/CuO and H2O/Al2O3, in addition to distilled water for the purpose of comparison. The effect of changing the weight concentration of the nano-fluid (0.05, 0.1, and 0.15%) on the PV performance was also investigated. The results showed that the PV integrated with the cooling design (1) achieves better performance compared to design (2) at all studied cooling fluids. The improvements in the electric efficiency of the PV integrated with design (1) reached 39.5, 34.8 and 27.3 % when CuO and Al2O3 nano-fluids and distilled water were used as cooling fluid, respectively, compared to the uncooled PV. Based on the obtained experimental results, the PV integrated with design (1) was selected to power the RO with H2O/CuO nano-fluid of weight concentration 0.15% and flow rate 0.15 kg/s being used as the coolant. The RO powered by the improved PV was tested at different salinities of brackish water when the preheating technique was implemented. The results showed that the proposed PV-RO desalination system produces 366 l/day when brackish water of salinity 3000 ppm was used.

no / The optimal operation policy of flexible RO systems is studied in this work. The design and operation of RO process is optimized and controlled considering variations in water demands and changing seawater temperature throughout the day. A storage tank is added to the system layout to provide additional operational flexibility and to ensure the availability of freshwater to customer at all times. A steady state model for the RO process is developed and linked with a dynamic model for the storage tank. The membrane modules are divided into a number of groups to add flexibility in operation to RO network. The total operating cost of the RO process is minimized in order to find the optimal layout and operating variables at discreet time intervals for three design scenarios. (C) 2013 Elsevier Ltd. All rights reserved.