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The management of hypersaline brines is a topic of growing environmental concern. While desalination is an increasingly attractive treatment option, conventional desalination technologies face technical limitations in high-salinity environments. This dissertation guides scientific development in the field of hypersaline desalination and advances our fundamental understanding of the novel technology Temperature Swing Solvent Extraction (TSSE). Chapter 1 motivates the environmental, regulatory, economic, and water scarcity drivers for hypersaline desalination and briefly outlines the objectives and contributions of the thesis. In Chapter 2, the sources and characteristics of hypersaline streams are introduced, and a primer on the energy requirements of high-salinity desalination is presented. The prospects and challenges of emerging technologies for hypersaline desalination are critically reviewed along the dimensions of energy consumption, fit- for-purpose compatibility, and ability to precipitate salts in the bulk solution. TSSE, which utilizes a switchable solvent with thermally responsive polarity to extract and subsequently release water from hypersaline feeds, shows particular promise in this field. Chapter 3 of this dissertation investigates the influence of temperature on the equilibrium partitioning of water, salt, and solvent in biphasic TSSE mixtures. Analysis reveals that TSSE hypersaline desalination performance is inherently constrained by a productivity-selectivity tradeoff: as the operating temperature is tuned to improve water extraction, salt rejection worsens. In Chapter 4, a novel configuration of TSSE with intermediate-step release (TSSE-IR) is introduced, and its desalination performance is assessed. The intermediate temperature step is demonstrated to dramatically improve salt rejection compared to the conventional single-step operation while minimizing sacrifices in water recovery yields. Chapter 5 of the dissertation advances a physical chemistry framework for the a priori prediction of activity coefficients in TSSE biphasic systems. Water partitioning behavior is shown to be enthalpically driven, and salt partitioning behavior is determined to be primarily influenced by the anion. In Chapter 6, the distribution behaviors of organic contaminants, which are present in real hypersaline brines, are measured in TSSE biphasic mixtures. The fate of these compounds can be reliably predicted from the physicochemical properties of octanol-water partition coefficients and acid-base dissociation constants. Finally, Chapter 7 details the contributions and implications of the dissertation, offering suggestions for targeted areas of future research. Overall, this work helps to advance the development of cost-effective and energy-efficient desalination of high-salinity streams to enable a circular water economy.

Thesis (MBA)--Stellenbosch University, 2007. / ENGLISH ABSTRACT: Desalination has been hailed by some as the answer to global freshwater supply shortages, but there is rigorous debate over the appropriateness of utilising desalination technology in regions that are not faced with severe water shortages. The aim of this research report is to provide a strategic overview of the South African desalination equipment market, a region where little research on this topic has been conducted. Secondary and thorough primary research in the form of interviews with desalination equipment suppliers and end users of desalination equipment in South Africa were conducted. The research findings revealed that the South African desalination equipment market, with a total annual revenue figure of R169.80 million in 2006 is very small when compared with the annual revenue figures of other global markets such as Saudi Arabia, which reached R6.61 billion in 2006. The industrial sector is the most active end user in South Africa followed by the commercial and lastly the municipal sector. It is anticipated however that the municipal sector, driven by coastal municipalities, will experience high growth in the medium to long term. Competition levels within the market were found to be high between desalination equipment suppliers, an attribute common in growth markets. Distinct market drivers, restraints and market trends were identified by research participants each of which have a varying influence on the desalination equipment market. South Africa has a fairly active desalination equipment market, which is small by global standards, and it is unlikely that desalination will solve South Africa’s water supply issues. Impoverished citizens, the high cost of desalination and the low cost of current fresh water sources all add to the complexity of the desalination debate in South Africa. / AFRIKAANSE OPOMMING: Ontsouting word deur sommige partye gesien as die antwoord op die wêreldwye vars water voorsieningstekorte, maar daar is breedvoerige debat oor die geskiktheid van ontsouting tegnologie in streke waar daar nie ernstige waterterkort is nie. Die doel van hierdie navorsingsverslag is om ’n strategies oorsig te lewer van die Suid Afrikaanse ontsoutingsmark, ’n streek waarin daar tot dusver min navorsing oor hierdie veld gedoen is. Sekondêre en primêre navorsing in die vorm van onderhoude met ontsoutings-toerusting en eindgebruikers van hierdie toerusting in Suid Afrika is gedoen. Die bevindinge toon dat die Suid Afrikaanse ontsoutings-toerusting mark, met ’n omset van R169.8 miljoen in 2006, baie klein is wanneer dit vergelyk word met ’n mark soos Saudi Arabië, met ’n omset van R6.6 miljard in 2006. Die industriële sektor is die mees aktiewe eidgebruiker in Suid Afrika, gevolg deur die kommersiële en laastens die munisipale sektor. Dit word egter geantisipeer dat die munisipale sektor, gedryf deur kus-munisipaliteite, die grootste groei in die medium tot lang termyn gaan toon. Dei bevindeninge wys verder op hoë vlakke van kompetisie tussen ontsoutings-toerusting voorsieners, ’n algemene verskynsel in groei-markte. Verskeie mark-drywers, beperkings en tendense is deur deelnemers in die navorsing geïdentifiseer, met elk wat ’n wisselende invlied op die ontsoutings-toerusting mark het. Suid Afrika het ’n redelike klein aktiewe ontsoutings-toerusting mark in wêreld-terme en dit is onwaarskynlik dat ontsouting Suid Afrika se water-probleme sal oplos. Arm inwoners, die hoë koste van ontsouting en die huidige lae koste van vars water dra alles by tot die kompleksiteit van die ontsoutingsdebat in Suid Afrika.

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Globally, water is considered an essential resource as it sustains human, animal and plant life. Water is not only essential for all forms of life but imperative for economic growth. The world’s population is increasing at a disquieting rate, which will result in an increased demand for fresh water and food security. The agricultural industry is the main consumer of global freshwater and utilises fertilisers in order to meet food demands. The demand for water in South Africa (SA) has increased considerably due to the rapid expansion of the agricultural industry, and of the municipal and industrial sectors. Agricultural developments in SA are affected greatly as the country is facing a current drought crisis as a result of low rainfall and large water demands. With an abundance of saline water globally, desalinisation will be a major contributor to solving the global freshwater crisis. With limited fresh water resources accompanied by the agricultural industry as a major consumer, alternative measures are required to desalinate water specifically for agricultural use. Forward osmosis (FO) is a membrane technology that gained interest over the past decade because it has several advantages over pressure-driven membrane processes such as reverse osmosis (RO). FO technology is based on the natural osmotic process which is driven by a concentration gradient between two solutions separated by a semi-permeable membrane. Naturally, water will permeate through the membrane from a solution of low solute concentration or low osmotic pressure (OP) known as a feed solution (FS) to a solution of a higher concentration or higher OP also known as a draw solution (DS). Whilst various research studies have contributed to several advances in FO, several process limitations such as reverse solute flux (RSF), concentration polarisation (CP) and membrane fouling remain problematic, hindering FO for large-scale applications. Further investigation is therefore warranted and crucial in order to understand how to mitigate these limitations to develop/improve future processes. The aim of this study was to evaluate a fertiliser-drawn forward osmosis (FDFO) system by investigating the effects of membrane orientation, system flow rate, DS concentration, and membrane fouling on an FDFO systems performance and energy consumption. The FS used was synthetic brackish water with a sodium chloride (NaCl) content of 5 g/L whereas a potassium chloride (KCl) synthetic fertiliser was used as a DS. The membrane utilised was a cellulose triacetate (CTA) membrane and was tested in forward osmosis mode (FO mode) and pressure retarded osmosis mode (PRO mode) whilst the system flow rate was adjusted between 100, 200 and 400 mL/min. Additionally, the DS concentration was altered from 0.5, 1 and 2 M KCl, respectively. Experiments were performed using a bench scale FO setup which comprised of an i) FO membrane cell, ii) a double head variable peristaltic pump for transporting FS and DS’s respectively, iii) a digital scale to measure the mass of the DS, iv) a magnetic stirrer to agitate the FS, v) two reservoirs for the FS and DS, respectively, vi) a digital multiparameter meter to determine FS electrical conductivity (EC) and vii) a digital electrical multimeter to measure system energy consumption. Each experiment comprised of seven steps i) pre-FDFO membrane control, ii) membrane cleaning, iii) FDFO experiment, iv) post-FDFO membrane control, v) membrane cleaning, vi) membrane damage dye identification and vii) membrane cleaning. Pre- and post-FDFO membrane control experiments operated for 5 h whilst each membrane cleaning procedure operated for 30 min. The FDFO experiment operated for 24 h whilst the membrane damage dye identification operated until a minimum of 10 mL water was recovered. The process parameter which largely contributed to a beneficial system performance and specific energy consumption (SEC) was the increase in DS concentration. Water fluxes increased approximately threefold from a DS concentration increase from 0.5 to 1 M, followed by an additional 30 to 50 % rise in water flux at a DS concentration increase 1 to 2 M. SEC decreased by 58 and 53 % for FO and PRO modes, respectively, with a DS concentration increase from 0.5 to 1 M. An additional 35 and 37 % SEC reduction for FO and PRO modes was obtained for a DS concentration increase from 1 to 2 M. Altering the membrane from FO to PRO did not contribute to a beneficial system performance nor did it improve SEC. However, at a DS concentration of 0,5 M, the PRO mode obtained a 5.3 % greater water recovery compared to the FO mode. Conversely, at a DS concentration of 1 and 2 M, the FO mode achieved 5.4 and 7.0 % greater water recoveries compared to the PRO mode. The increase in flow rate also did not increase system performance significantly, however, a fluctuation in system SEC was observed. Throughout the study, no membrane fouling was observed, however, possible minute traces of membrane fouling could be observed from the membrane surface electron microscope (SEM) images. Additionally, minor changes in post- FDFO membrane control water recovery results were noticed which support the possible occurrence of membrane fouling during the FDFO experiment.

<p>The study shows conclusively that brine composition and concentration is highly variable at these South African power utilities and processes such as RO, contact with ash and CO2 ingress can have an impact upon the overall brine quality. Aq.QA was found to be a more accurate tool for classifying waters according to dominant ions than Stiff diagrams but Stiff diagrams still have the superior advantage of being a mapping tool to easily identify samples of similar composition as well as quickly identify what has been added or what has been removed from a water stream. Chemical speciation could identify effluent streams where CO2 dissolution had taken place.</p>

Thesis (M. Phil.)--University of Hong Kong, 1982.

<p>The study shows conclusively that brine composition and concentration is highly variable at these South African power utilities and processes such as RO, contact with ash and CO2 ingress can have an impact upon the overall brine quality. Aq.QA was found to be a more accurate tool for classifying waters according to dominant ions than Stiff diagrams but Stiff diagrams still have the superior advantage of being a mapping tool to easily identify samples of similar composition as well as quickly identify what has been added or what has been removed from a water stream. Chemical speciation could identify effluent streams where CO2 dissolution had taken place.</p>

Graduation date: 1988

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016. / The water desalination process needs large quantities of energy, either directly from fossil fuel or electricity from the national grid. However, these sources of energy significantly contribute to problems such as global warming in addition to creating a drain on the economy, due to their high cost. This dissertation is a description of the research undertaken with the aim of producing a water desalination prototype; a novel approach that was designed using state-of-the-art solar water heating equipment, incorporating the technologies of evacuated tubes and heat pipes. During the execution of the project, various modifications to the original commercially-available solar water heating system were attempted, each aimed at increasing the production of pure water. Finally, the system proved capable of producing a reasonable amount of pure water after twelve lengthy indoor experiments conducted in a laboratory in the department of Mechanical Engineering at the Cape Peninsula University of Technology, Bellville Campus, Cape Town, South Africa. Each experiment lasted five days on the basis of seven hours of exposure to an average amount of simulated solar radiation, followed by seventeen hours daily of inactivity and partial cooling down of the system.

Magister Scientiae - MSc / The study shows conclusively that brine composition and concentration is highly variable at these South African power utilities and processes such as RO, contact with ash and CO2 ingress can have an impact upon the overall brine quality. Aq.QA was found to be a more accurate tool for classifying waters according to dominant ions than Stiff diagrams but Stiff diagrams still have the superior advantage of being a mapping tool to easily identify samples of similar composition as well as quickly identify what has been added or what has been removed from a water stream. Chemical speciation could identify effluent streams where CO2 dissolution had taken place. / South Africa