Dissertations / Theses on the topic 'Saline water conversion'

Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2018.<br>The present study was centred on the design of a thermal multistage solar still desalination system. The design is a multistage with new configurations such as direct vapour input into each stage using vapour make-up tubes and the integration of a multistage with a basin type solar still. The incorporation of float a valve in the secondary seawater tank to regulate the seawater in the assembly eliminated the need of pumps to the system. The circulation of seawater between the evaporator and the evacuated tube solar collector (ETC) was through the pressure difference and the flow back was controlled through the incorporation of oneway flow valve. The ETC was used as a heat source to supply the thermal energy into the multistage system. The system had no electrical connections and therefore, no forced circulation as no pumps or any electrical components were used. The system consisted of six stages in total, the evaporator supplied the vapour to five of the six stages of the system. The system was tested on the roof of Mechanical Engineering Department and this location was chosen because of less sun’s intensity obstructions. The system was tested for nine (9) days but the distillate collection was not performed for the whole each day. This was due to the controlled access to the roof and the minor repairs that had to occur before the tests were conducted. The duration on which the tests were conducted varied in each day. The data was supposed to be logged from 08h00 am to 18h00 pm but this was not so due to the controlled access to where the tests were conducted. This data logging period was chosen based on the assumptions that the sun’s intensity would be at maximum within this period. The longest period of test was approximately 7 hours and the system managed to produce about 1500 ml and the maximum temperature for the day was 28oC. The system produced a minimum of 225 ml in the space of 3 hours and the temperature of the day was 26oC. The total amount of distillate produced was about 7600 ml and this amount was produced within the period of 49 hours. The 49 hours is equivalent to two days and 1 hour. It is anticipated that the system would have produced more should there be no repairs involved during the tests. The system produced a maximum of 48 ml at night and a minimum of 8ml in some nights. The night tests were not controlled and monitored due to limited access. It was noticed that the system was empty in each morning of the first few days of the tests. This emptiness contributed to the leakage occurred to the evaporator. The leakage of the evaporator was caused by unmonitored heat supplied by the ETC. The evaporator was constructed using unsuitable material and this was another factor which contributed towards the failure of the evaporator.

The distillation of sea water is of importance for the future demands for potable water and other uses in the world. A novel technique, based on electrohydrodynamic (EHD) principles, was used in this realm to desalinate artificial sea water of 3.3% (w/V) concentration. A single point corona electrode was operated at a potential of 5.3 kV (maximum output current 0.3 mA), and was installed one cm over the surface of sea water. The flux of air ions was about 3.0 $ times$ 10$ sp{12}$ cm$ sp{-2}$ s$ sp{-1}$ which produced an average electric wind of 1.72 m s$ sp{-1}$ at the sea water surface. Space charge from a corona electrode generated forces in the media to enhance the evaporation rate by about a factor of three compared with a control freely evaporating sea water. Water vapour was condensed and the condensate's purity was evaluated by chemical and physical analyses. Electrical conductivity and pH of the EHD distillate were found to be 14 $ mu$S cm$ sp{-1}$ and 5.5, respectively. In the absence of Joule heating, the energy required for EHD-distillation was comparable to the latent heat of vaporization of 2.3 $ times$ 10$ sp3$ kJ kg$ sp{-1}$ for water. The steady-state temperature of EHD solution was below that of the corresponding unventilated freely evaporating sea water. Electric wind caused by the ionic drag is considered to be the principal driving force for the enhancement.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, Cape Town, 2007<br>An investigation was performed into a new desalination plant operating on the principles of distillation through the utilisation of solar energy only. The need for such a system is due to the high energy requirements of current large scale desalination systems and that, in the future, more and more desalinated water will be required to sustain life in certain areas. A conceptual design of such a plant was completed and it proved its feasibility by providing an in depth explanation of the principles that govern its operation. A computer model, in the form of a MathCAD program, was developed to simulating this process flow. The accuracy of the program was investigated with the help of a pilot plant. It is shown that such a full scale plant would produce, in the region of Saldanha Bay, a town on the Western Coast of South Africa, 5000m3 ofpotable water a day with a solar absorption/evaporation area of 1,87knlrequiring only 1,75kWh per cubic meter of water produced. Its electrical energy requirements can be provided using solar panels allowing the plant to remain independent of external electrical supplies. This electrical energy requirement is less than 33% of the least energy intensive alternative method, reverse osmosis. Since the production rate is dependent on the absorption/evaporation area the plant can be scaled to fit the specific production rate required.

Thesis (Ph.D.) - University of Glasgow, 1985.<br>BLL : D80152. Ph.D. thesis submitted to the Department of Mechanical Engineering, University of Glasgow, 1985. Includes bibliographical references. Print version also available.

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016.<br>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.

<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 (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018.<br>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.

Thesis (M.S.)--University of Nevada, Reno, 2005.<br>"August, 2005." Includes bibliographical references (leaves 80-84). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

The production of both fresh water and waste streams are progressively increasing over the years due to ongoing population growth coupled with high levels of increase in water consumption. The ongoing growth of human activities, such as industry, recreation, and agriculture, are significantly contributing to the increase in both water demand and severity of degradation of natural water resources. The majority of the industrial wastewaters have a significant impact on the environment; some of which may pose a number of threats to human health and the surrounding environment. Thus, discharge of such waste streams into a surface water and/or groundwater presents a major source of water pollution in many countries. Therefore, these waste streams must be disposed of in an environmentally acceptable manner. The primary concern of the PhD thesis is to seek the most feasible and applicable freezing desalination technologies that are potentially capable to concentrate the dissolved ionic content of the liquid streams, especially for those causing severe pollution problems. Therefore, various forms of melt crystallisation processes, namely; agitated and static crystallisation processes, ice maker machines, a Sulzer falling film crystallisation process, the Sulzer suspension crystallisation process, and the Sulzer static crystallisation process, were experimentally used and investigated. The experimental investigations were carried out on the laboratory bench scale and/or straightforward pilot plant by using aqueous solutions of sodium chloride and/or process brines as feed samples. The study was focused on a number of important parameters influencing the separation performance of the investigated treatment systems. In general, the resulting experimental data for each innovative process were highly encouraging in minimising the volume of the waste stream, and substantially increasing the amount of product water. The obtained product water was ready for immediate use either as drinking water or as a saline water of near brackish water or seawater qualities. Also, relationships between the influences and the separation performance, in terms of salt rejection and water recovery ratios, were explored and determined for the investigated technologies. Based on the experimental results, the Sulzer melt crystallisation processes were scaled up and were combined into a commercial reverse osmosis membrane desalination plant. As a result, three novel treatment option configurations were proposed for minimising the waste stream, whilst increasing the production rate of drinking water and/or preserving a substantial amount of natural water resource from the RO plant's exploitation.

Thesis (M.S.)--University of Nevada, Reno, 2008.<br>"May, 2008." Includes bibliographical references (leaves 35-38). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (MBA)--Stellenbosch University, 2007.<br>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.<br>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.

Nowadays, organic pollutants occurring in surface waters have raised substantial concern in public. Triclosan (TCS) is one of the antimicrobial agents which are utilized in both domestic and industrial application. In this study nanofiltration (NF) of TCS in surface water was investigated. Laboratory scale cross-flow device is operated in total recycle mode and DK-NF and DL-NF membranes were used. Kesikk&ouml<br>pr&uuml<br>Reservoir (Ankara) water was used as raw water. Effect of natural organic matter (NOM) content of raw water on TCS removal is searched through addition of humic acid (HA) into the raw water as to represent for NOM. Steady state permeate fluxes are monitored throughout the experiments to explore the flux behavior of the membranes. During the experiments, performance of the membranes is assessed by monitoring TCS, as well as other water quality parameters, such as UVA254 and total organic carbon (TOC) in the feed and permeates waters. Results obtained put forward that TCS removal by NF membrane is not as same as reported in the literature. In the literature, membrane removal efficiency is reported as above 90%. However, this study proved that this would be true if and only if one does not considers the adsorption of TCS by the system itself, in the absence of membrane. It is now clear that, because of adsorption of the TCS onto the experimental set up (feed tank, pipings etc.)<br>the real TCS removal efficiency of the nanofiltration is around 60-70%.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.<br>Water scarcity in South Africa (SA) and more specifically Cape Town, Western Cape, has escalated to disaster levels in 2018. Agriculture and irrigation account for 62% of SA’s accessible potable water (Thopil & Pouris, 2016), and although the agriculture sector plays a pivotal role in SA’s socio-economic development, the future of the sector is dependent on critical issues such as climate variability and population growth (Besada & Werner, 2015). Wine production in SA is an important agricultural activity, contributing great economic value to the agri-food sector. However, despite this, the wine industry is responsible for vast water consumption and the unsafe disposal of winery wastewater, which are critical issues from an environmental and economic standpoint. The ever-imminent crisis pertaining to the limited supply of fresh water from conventional water resources has necessitated the need to develop alternative water resources to supplement an increased water supply, which include the reuse of wastewater, ground water, brackish water (BW) and seawater (SW) desalination. When fresh water supplies are limited, agricultural irrigation is penalised. The reuse of agricultural wastewater as a substitution for potable water irrigation may prove beneficial in areas where water shortages are severe. Forward osmosis (FO) is a developing desalination technology that has received increased attention as a promising lower-energy desalination technology. FO technology relies on the natural osmotic process, driven by a concentration gradient as opposed to significant hydraulic pressures like reverse osmosis (RO). Water is extracted from a lower concentrated feed solution (FS) to a highly concentrated draw solution (DS). The term “lower energy” is only applicable for applications where the recovery of the DS is not required. FO technology offers several advantages. However, the lack of suitable membrane modules and DSs hinder its practical application. FO offers novelty applications in which specialised DSs are selected to serve as the final product water, most notably concentrated fertilisers for direct fertigation. The aim of this study was to evaluate the performance and compatibility of commercially available cellulose triacetate (CTA) and aquaporin biomimetic FO membranes with commonly used fertilisers for direct fertigation within the SA wine industry, using a fertiliser drawn forward osmosis (FDFO) system.

Deposition of calcium carbonate (CaCO3) and calcium sulfate (CaSO4) causes serious processing problems and limits the productivity of seawater reverse osmosis (RO) desalination. The interactions between CaSO4 and CaCO3 in the dynamic seawater RO systems have been neglected previously because conventional studies mainly focused on individual compounds or mixed compounds in batch systems. The present work evaluates composite fouling behavior of CaSO4 and CaCO3 in a dynamic RO unit. The fouling experiments were performed at constant pressure and velocity by a partial recycling mode which permeate was withdrawn from the system during the recirculation of retentate to simulate the increasing of water recovery level. The fouling phenomena were monitored by the decline of flux. Scanning electron microscopy (SEM) with a combination of elemental dispersive x-ray microanalysis (EDS), and x-ray powder diffraction (XRD) was used to identify the morphological features, chemical compositions and crystalline phases of foulants. The interactions of CaSO4 and CaCO3 were investigated by the comparison between individual CaSO4 or CaCO3 fouling and composite fouling, and by varying SO42-/HCO3- molar ratio of the feed. A recently developed approach, Scaling Potential Index (SPI) incorporated with measured concentration polarization modulus (CP), for assessing the fouling tendency of inorganic salts on the membrane surface was validated in the dynamic tests. In addition, the effectiveness of two generic scale inhibitors, polyacrylic acid (molecular weight =2100, PA) and sodium hexametaphosphate (SHMP) were evaluated. Some of the highlights of the obtained results are as follows: ??????The precipitation kinetics, morphology and adhesive strength of composite scales were different from pure precipitates ??????CaSO4 precipitated as gypsum while CaCO3 precipitated as two crystalline phases: calcite and aragonite ??????The crystalline phases as well as precipitation kinetics were affected by SO42-/HCO3- ratio ??????Scaling Potential Index was able to predict the fouling tendency of CaSO4 and CaCO3 accurately ??????The dosage of PA and SHMP was effective to mitigate fouling Results of this work are significant, not only because they have made contribution to the fundamental understanding of composite inorganic fouling in RO membrane systems which was ignored previously, but also because they may play a key role in the development of scale control.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2018.<br>A membrane distillation crystallization (MDC) experimental setup was designed, constructed and commissioned with rectangular mixing crystallizer tanks. The advantages and disadvantages of a rectangular mixing tank are compared to the traditional cylindrical mixing tank with baffling by means of a computational fluid dynamic (CFD) analysis in Ansys Fluent. The effect of tank configuration and geometry on the hydrodynamic and mixing characteristics for efficient momentum, solid suspension, heat and mass transfer were investigated. The hydrodynamic conditions in a crystallizer-mixing tank determine the quality of fluid mixing essential for optimal crystallization. Forty-five degree pitched blade turbines (PBT) were used to provide the agitation in the stainless steel rectangular jacketed tanks. Clear polycarbonate replicas of the rectangular tanks were manufactured to visually observe the mixing process in the tanks. Silica particles were used to represent the calcium carbonate crystals in the experiment. The data gathered from these experiments showed that the tanks should be operated between 600 to 750 rpm in the CFD simulations to simulate partial to complete suspension. In the numerical simulations a rectangular tank was compared to a cylindrical tank with baffling of the same volume. The partial differential equations solved in the numerical simulation were the conservation of mass (continuity), conservation of momentum and additional turbulence equations. In order to solve the turbulent fluid flow characteristics, the industry standard two-equation model, namely the K-epsilon model was used. This model was refined by the addition of the Wen-Yu drag model, the Simonin turbulent dissipation and the Simonin et al. turbulence interaction models. The RANS based RNG (k-ε), derived from the instantaneous Navier-Stokes equation was selected as the preferred model to analyse the hydrodynamic flow fields in the tanks. The 3D sliding mesh method was used to compute a time accurate solution. The Eulerian-granular multiphase model was used to predict the degree of solids suspension in the tanks. The efficiency of mixing within the tank was measured by the tank’s ability to keep the crystals in suspension and preventing any particle from settling at the bottom for more than 1-2 second(s). The mixing tanks were initially loaded with 5% v/v, which equates to a loaded height of approximately 10 mm. The simulations were done with the use of the volume fraction function to visually observe the cloud height and gauge the homogeneity and distribution of the particulates within the fluid flow fields. The results from the experimental setup were compared to the CFD simulations to qualify the use of CFD simulations for the comparison of the geometrically different tanks. Lastly, the findings from the CFD simulations were used to compare the tanks and determine if the rectangular tank built for the MDC experiment perform satisfactorily to replace a standard cylindrical tank with baffling for this application.

Water scarcity for agriculture is one of the most important challenges to improve food security worldwide. In this thesis we study the potential to develop a low-cost controller for a small scale brackish desalination plant that consists of proven water treatment technologies, reverse osmosis, cation exchange, and nanofiltration to treat groundwater into two final products: drinking water and irrigation water. The plant is powered by a combination of wind and solar power systems. The low-cost controller uses Arduino Mega, and Arduino DUE, which consist of ATmega2560 and Atmel SAM3X8E ARM Cortex-M3 CPU microcontrollers. These are widely used systems characterized for good performance and low cost. However, Arduino also requires drivers and interfaces to allow the control and monitoring of sensors and actuators. The thesis explains the process, as well as the hardware and software implemented.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.<br>ENGLISH ABSTRACT: This investigation focused on the marine components of large direct seawater intake and brine discharge systems for seawater desalination plants, with the main aim to provide an overall design approach for these components. Due to its complexity, an overall and systematic design approach, addressing all the components (feedwater requirements, plant technology, marine structures and environmental issues) is required to ensure an optimum design. A literature review was done on the various desalination technologies, the main components of a seawater desalination plant, as well as the physical, hydraulic, operational and environmental issues regarding seawater extraction facilities, marine pipelines and discharge structures (diffuser). In order to obtain practical input to the development of an overall design approach, information regarding the marine structures of ten of the largest existing seawater desalination plants throughout the world were obtained and compared with each other and the available technologies. By way of example, the recently designed marine components of a new seawater reverse osmosis desalination plant in Namibia were reviewed and, as part of this thesis, alternative conceptual concepts which will include two additional components (sump and brine reservoir) were designed. The alternative design was compared with the actual design in order to determine the feasibility of the alternative in terms of operation and cost and subsequently provide input to the overall design recommendations. Furthermore, from the literature review it seems that there are still significant uncertainties regarding the required performance of a brine (dense) outfall and this required more attention in terms of environmental and hydraulic performance. Based on the Namibian plant, the diffuser configuration was analysed in terms of its hydraulic and environmental performance and subsequently some general guidance with specific respect to a brine diffuser was developed, which in turn formed part of the overall design approach for the marine components. Finally, the design approach for seawater intake structures, brine outfalls and the connecting marine pipelines is provided in the form of flow diagrams.<br>AFRIKAANSE OPSOMMING: Hierdie ondersoek handel oor die mariene komponente van groot en direkte toevoer van seewater en die sout-uitvloeisisteme van ontsoutingsaanlegte van seewater. Die doel is om ‘n oorsigtelike ontwerpbenadering vir hierdie component te verskaf. As gevolg van die kompleksiteit, is ‘n oorsigtelike en sistimatiese benadering, wat al die komponente (vereistes vir toevoerwater, tehnologie by die aanleg, mariene omstandighede en omgewingsfaktore) in ag neem noodsaaklik om die beste ontwerp te verseker. ‘n Literêre oorsig is gedoen ten opsigte van die tegnologie van verskeie ontsoutingsmetodes, die hoofkomponente van ‘n seewater-ontsoutingsaanleg, asook die fisiese, hidrouliese, operasionele en omgewingskwessies rakende die fasiliteite om die seewater te onttrek, die mariene pyplyne en die strukture vir die afvloei. Ten einde die optimum ontwerp te ontwikkel, is inligting oor die tegnologie en strukture van tien van die grootste bestaande onsoutingsaanlegte in die wêreld bekom, bestudeer en vergelyk Hulle is met mekaar vergelyk, asook met beskikbare tegnologie. As ‘n voorbeeld is die nuut ontwerpte mariene komponente van die nuwe ontsoutingsaanleg in Namibië, waar ontsouting d.m.v. omgekeerde osmose gedoen word ondersoek en as deel van hierdie tesis, is ‘n alternatiewe konsep, wat twee bykomende komponente – ‘n opvangput en reservoir vir die afloop – ontwerp. Hierdie alternatiewe ontwerp is met die werklike aanleg vergelyk om die uitvoerbaarheid van die onderneming en die koste daaraan verbonde te toets. Dit is gebruik as aanbeveling vir die oorhoofse ontwerp. Uit die literêre oorsig blyk dit dar daar nog groot onsekerheid is oor die vereistes van die (digte) waterafloop en dat meer aandag aan die omgewings- en hidrouliese aspekte gegee moet word. Met die Namibiese aanleg as voorbeeld, is die struktuur van die spreiers t.o.v. hidrouliese werkverrigting en die omgewing ontleed. Voortspruitend daaruit is algemene riglyne vir ‘n spesifieke spreier vir afloopwater ontwikkel, wat op sy beurt weer deel vorm van die oorhoofse ontwerp vir mariene komponente. Laastens is die ontwerp vir die strukture vir seewater-invloei, die afloopwater en die mariene verbindingspyplyne as vloeidigramme aangetoon.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.<br>Similar to the energy crisis, the critical state of the water supply in South Africa (SA) is a combination of (i) resource exhaustion and pollution; (ii) increasing demand; and (iii) poor infrastructure. Despite its importance, water is the most poorly managed resource in the world. The disposal of industrial effluents contributes greatly to the poor quality of water. The textile industry consumes great quantities of water and produces enormous volumes of wastewater which requires appropriate treatment before being released into the environment. In an attempt to address the water issues, research globally has focused on advanced technologies such as desalination to increase limited pure water resources. The need for alternative desalination methods for the production of clean water from alternative water resources, such as seawater and brackish water, has gained worldwide attention. Reverse osmosis (RO) and Nanofiltration (NF) have been used as unswerving approaches to yield freshwater. Forward osmosis (FO) is a developing membrane technology that has increased substantial attention as a possible lower-energy desalination technology. However, challenges such as suitable FO membranes, membrane fouling, concentration polarisation, and the availability of effective draw solutions (DS), limit FO technology. FO is seeking more importance in novel areas where separation and recovery of the DS is not required. The aims of this study was to: i) identify alternative water resources and evaluate their potential as suitable feed solution (FS); ii) Identify dyes and evaluate their potential as suitable draw solutions (DS) at different concentrations; iii) assess the use of aquaporin biomimetic membrane and iv) assess a FO system for the production of dye solutions. Osmotic pressure (OP) is the pressure exerted by the flow of water through semi-permeable membrane, separating two solutions with different concentrations of solute. The DS should always have OP higher than the FS in order to achieve high water flux. Three basic dyes (i.e. Maxilon Turquoise, Red and Blue) and three reactive dyes (i.e. Carmine, Olive Green and Black) were selected, based on their common use in the SA textile industry. The respective dye samples were prepared at different concentrations and dye-to-salt mass ratios ranging from 1:10 to 1:60 and assessed for OP using a freezing point osmometer. A lab-scale FO unit was used for all the studies. Feed and draw channels were circulated in a counter-current flow at a volumetric flow rate of 600 mL/min. Feed solutions(FS) included deionised water (DI) as a control, brackish water (BW), synthetic seawater (SSW) and textile wastewater (TWW) collected from two textile factories. OP of the FS (DI, BW5, SSW and SW, Factory 1 and Factory 2) was 0, 414, 2761, 2579, 1505 and 3308 kPa, respectively. Basic Blue and Reactive Black generated a higher OP compared to other selected dyes in the study and were therefore selected to be used as DS at a 1:10 dye-to-salt ratio and 0.02 M concentration. An aquaporin biomimetic FO membrane (Aquaporin, Denmark) was used for all the experiments conducted in the FO mode.

Clinoptilolite samples obtained from two deposits in Turkey were tested for their potential in removing cadmium from aqueous solutions. Preliminary experiments in batch mode revealed inferior cadmium uptake at low pH. Particle size was found to have no effect on cadmium removal efficiency suggesting the use of exchangeable cations found in the internal/available sites. Increasing temperature yielded positive, whereas prewashing had no effect on cadmium removal using both clinoptilolite samples. The Langmuir model fitted the equilibrium data for both samples better than the Freundlich model. The capacity reached after conditioning represents about 4 and 3 fold increase for G&ouml<br>rdes and Bigadi&ccedil<br>samples, respectively. The relatively poor performance of Bigadi&ccedil<br>clinoptilolite was due to low clinoptilolite/high impurity contents. Further studies were carried out only with G&ouml<br>rdes clinoptilolite. The performance of the G&ouml<br>rdes samples conditioned with various chemicals were NaCl&gt<br>KCl&gt<br>As-received&gt<br>CaCl2&gt<br>HCl. 20BV of NaCl solution was found to be sufficient with no pH adjustment or water quality requirement during column conditioning. In column experiments, among the tested flowrates 5, 10 and 15 BV/hr, highest flowrate indicated inferior utilization of the removal capacity. No significant difference by decreasing particle size indicated pore diffusion resistance not to be a limiting factor. In five conditioning and regeneration cycles, clinoptilolite exhibited 36% increase in operating capacity. Cadmium removed by clinoptilolite in progressing cycles was concentrated by about 7 times. Overall, this study shows that Manisa-G&ouml<br>rdes clinoptilolite is advantageous for the removal of cadmium ions from aqueous solutions and hold great potential to be used in practical applications.

Renewable power generation from the controlled mixing of sea and fresh water is relatively unexplored when compared to the development for solar, wind, and other sustainable power alternatives. When global river discharge was taken into account, an estimated 2.6 TW of obtainable energy exists in untapped salinity gradients. Reverse electrodialysis is one proposed power-generating mechanism for harnessing energy from brackish environments and relies on the transport of aqueous salt ions through an apparatus of ion-exchange membranes. In this thesis, operational parameters, including flow direction, salinity composition, and membrane selectivity, are investigated. For optimal performance, I have employed counter-current flow mode with monovalent ion selective membranes and pure 0.5 M NaCl saline solution. The results show that a maximum open circuit voltage (OCV) level of 2.01 V is obtained with an active membrane area of 0.0756 m². The presence of multivalent ions in the feed solutions hinders OCV levels, but the effects are reduced with monovalent-selective membranes. Preliminary results are insightful; in order to increase the commercially viability of this technology, future work is needed to enhance the performance properties of the ion exchange membranes.

A membrane based treatment scheme was developed for the recovery of the print dyeing wastewaters (PDWs) and the acid dye bath wastewaters (ADBWs) of carpet manufacturing industry. The treatment schemes were developed by selecting the best pre-treatment and treatment processes among the alternatives of chemical precipitation (CP), microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF). The best process train for PDW was CP+NF, where organic matter, color, turbidity and total hardness were removed at &gt<br>95%. The alternative process train CP+UF also removed color and turbidity almost completely, however organic matter rejection was low, being 25% at highest. The quality of NF permeates were suitable for dyeing of light colors whereas UF permeates were suggested for washing of the printed carpets or dyeing of the dark colors. The best process train for ADBW was MF (1.0 mm)+NF, where organic matter rejection increased from 65% to 97% due to pH neutralization. Alternatively, sequential NF was required up to three stages in order to achieve similarly high rejections at the acidic pH of ADBW. Therefore, pH neutralization was realized to be a very important operational parameter affecting the treatment scheme. Although pH neutralization increased the flux declines by almost 5%, chemical cleaning was very effective to restore the original fluxes. Finally, ADBW was mixed with PDW, which already had a pH around neutral, so that the pH of ADBW would rise towards neutral without chemical consumption. The results suggested that these wastewaters could be treated together as long as they were mixed up to equal volumes at pH around neutral. Therefore, a final treatment scheme, which involved single NF for the mixture of PDW and ADBW, following their individual pre-treatment stages, was proposed as the most efficient process train.

Rapid urbanization and population growth have represented a great challenge to water resources management, since wastewater generated in urban areas forms a non-conventional source, wastewater reuse is being recognized as a sustainable water management approach. This study focuses on with the potential and practibility of implementing wastewater reuse techniques in Izmir region, especially with the aim to use treated wastewater and nutrient for agriculture. To this end, qualititative and quantitative agricultural water demand were considered. This thesis introduces a wastewater reuse planning model and optimization method with an emphasis on the wastewater treatment technology used as well as the agricultural demand in the area of the study. The model was developed with considerations over water quality, wastewater treatment and discharge. The objective of the model is to upgrade existing wastewater treatment plants or to design new treatment plants in regard to reuse wastewater in agriculture. The model is also capable of comparing treatment technologies from the point of design and cost. Three case studies were represented so as to demonstrate the modeling process and optimization studies for agricultural irrigation.

Thesis (DPhil)--Stellenbosch University, 2002.<br>ENGLISH ABSTRACT: Freshwater is the most fundamental of all life-supporting resources that determine our social, economic and political wellbeing. It is, however, only a small percentage of the world's water resources and is also unevenly distributed. Arid regions make-up about forty percent of the world's land area and have a large proportion of the world population, however, they only have a small fraction of the freshwater compared to other areas. Conventional freshwater sources in arid environments such as surface water in rivers, lakes and dams are often seasonal, available mainly during the rainy season. Equally, only a small part of the rain (0 - 5% of rainfall) infiltrates into groundwater reserves, and even this groundwater displays high rates of salinisation such that the end-water is too saline for human consumption. The poor quality of groundwater in arid regions is generally understood, however, it is always assumed that this is mainly a problem in areas where surface water does not occur. The study investigates seasonal groundwater salinisation in ephemeral (seasonal) river sources in some parts of Namibia and aims to derive a better understanding of the nature of this problem and how it affects people in these areas. It also looks at some possible solutions to the problem with the aim of informing water managers and scientists who are responsible for formulating solutions for water supply to areas in arid regions. These solutions are designed to take advantage of available opportunities in the study areas namely; the abundant supply of solar energy, alternative sources of freshwater such as fog and general atmospheric moisture, and adaptations for water collection in animals that inhabit these regions. The results show that groundwater in shallow ephemeral river sources of the Namib Desert and the Cuvelai delta in North central Namibia display high seasonal variation in Total Dissolved Solids (TDS) and chemical composition. The lowest TDS values are recorded during the rainy season, mainly after the first rains in the high rainfall areas and only after flood events in the lower rainfall regions. The groundwater salinity increases during the remainder of the year and in most cases becomes too saline for drinking purposes. The investigations of possible solutions indicate that small-scale photovoltaic reverse osmosis; solar distillation and fog collection could be used to address the seasonal shortage of potable water in these areas. The low-pressure (6 bar) reverse osmosis desalination experiments show that it is possible to operate the unit on a solar-driven pump to produce enough water to cover the typical daily water demand of a village in the Namib Desert. This unit would produce about 4600 litres per day (l/day) of 500- mg/l TDS product water, which exceeds the water production of similar world-leading small-scale RO units in Australia and The Canary Islands. The results also show that the cost of solar distillation units (solar stills) can be reduced sufficiently to make them a viable option for water supply to individual households in these rural areas. The study also found that fog is a feasible alternative source of freshwater in some of the study areas. The fog water is generally of 'A' quality drinking water according to the WHO-derived Namibian Drinking Water Quality Guidelines (NDWQG) and can be used directly or mixed with the saline groundwater to provide potable water. Mixing of the above-mentioned waters is particularly suitable in the Central Namib Desert because the period of high groundwater salinity coincides with that of peak fog deposition. The results also show that fog water can be collected with vanous polymeric greenhouse shade netting that can be easily obtained, and provides guidelines on the correct percentage shade coefficient and weave of possible fog collector mesh to intending users of fog collection technology in areas where the polypropylene mesh that is used in Standard Fog Collectors is not available. The investigations of surface properties of fog-harvesting beetles and experiments with various prototype collectors show that it is possible to increase water production in fog collectors existing today. The hydrophobic surface conditions as were found on the cuticles of fog-basking beetles (Onymaeris unguicularis and Onymacris bieolor) would enhance formation and runoff of large fog droplets on the collector surface. The prototype extractor-fan- and cooling system-based collectors show that it is possible to increase fog collection on polymeric meshes about three times and also that a comparable volume of atmospheric moisture can be collected even when there is no fog, up to a relative humidity of about 40%. In conclusion the study emphasizes that groundwater salinity in arid regions is at times a seasonal problem that should be considered in water supply strategies for these regions. Also that atmospheric moisture is a feasible alternative source of freshwater in some arid regions that often exceeds rainfall several times and should be considered as an important aspect of the strategies to address water problems in these areas. The study strongly recommends that scientists, engineers and water managers in these regions should always investigate the available opportunities such as climatic conditions (e.g. fog deposition) and adaptations for water collection/conservation that are found in the endemic plants and animals in order to develop sustainable solutions to this problem. They should also constantly update themselves on developments/opportunities that arise in the larger water industry that could be of benefit to water supply initiatives for remote areas in developing countries. Lastly, the study serves to better the understanding of the nature of groundwater salinity in arid environments that are dependent on seasonal surface flow for water supply as well as to contribute to the formulation of solutions to this problem in these areas, particularly in west coast hyper arid environments where conventional sources of freshwater are most inadequate. It also emphasises the role of materials science (polymers) and environmental engineering as well as that of UNESCO associated scientific institutions in the formulation of sustainable solutions to some of the current water problems in arid regions. Keywords: Arid lands, hydrochemistry, sources of freshwater, desalination, atmospheric moisture<br>AFRIKAANSE OPSOMMING: Vars water is die mees fundamentele van aIle lewensonderhoudende natuurlike hulpbronne wat ons sosiale, ekonomiese, en politieke welstand bepaal. Dit is egter slegs 'n klein gedeelte van die totale waterbronne van die wereld, en is boonop baie oneweredig versprei. Natuurlike waterarm gebiede (woestyne en halfwoestyne) beslaan ongeveer veertig persent van die landoppervlakte van die aarde en word bewoon deur 'n relatief groot persentasie van die wereldbevolking, maar beskik oor slegs 'n klein gedeelte van die varswater in vergelyking met ander gebiede. Konvensionele bronne van varswater in waterarm gebiede, soos oppervlaktewater in riviere, mere en darnme, is dikwels seisoenaal, en slegs beskikbaar gedurende die reenseisoen. Verder beland slegs 'n klein gedeelte van die reenval (0 - 5%) in die ondergrondse waterreserwes, en selfs hierdie grondwater vertoon 'n hoe mate van versouting, sodat die eindproduk te brak is vir menslike gebruik. Die swak gehalte van grondwater in waterarm gebiede word algemeen verstaan, maar daar is tot nog toe aanvaar dat dit oor die algemeen slegs 'n probleem is in gebiede waar oppervlaktewater me voorkom nie. Hierdie studie ondersoek seisoenale grondwaterverbrakking in seisoenale rivierbronne in sekere dele van Namibie en beoog om 'n beter begrip te formuleer van die aard van die probleem en hoe dit die inwoners van hierdie gebiede raak. Daar word ook ondersoek ingestel na moontlike oplossings vir die probleem, met die doel om 'n inligtingsbron vir waterbestuurders en wetenskaplikes wat verantwoordelik is vir die formuleer van oplossings vir watervoorsiening in waterarm gebiede daar te stel. Hierdie oplossings is ontwerp om voordeel te trek uit die beskikbare geleenthede in die ondersoekgebiede, naamlik; die oorvloedige beskikbaarheid van sonenergie, altematiewe bronne van varswater soos mis (Eng. "fog") en atmosferiese vog in die algemeen en aanpassings (Eng. "adaptations") vir die opvang van water wat voorkom by diere, veral insekte, in hierdie gebiede. Die resultate toon dat grondwater in die vlak seisoenale rivierbronne van die Namibwoestyn en die Cuvelai-delta in noordsentraal Namibie hoe seisoenale variasie in totale opgeloste stowwe (TVS) en chemiese samestelling vertoon. Die laagste TVS-waardes word waargeneem tydens die reenseisoen, hoofsaaklik na die eerste reen in die hoe-reenvalgebiede en eers na vloede in die lae-reenvalgebiede, Die soutgehalte van die grondwater neem toe gedurende die res van die jaar en in die meeste gevalle verbrak die water tot ondrinkbare vlakke. Die ondersoek na moontlike oplossings dui aan dat kleinskaalse fotovoltaiesgedrewe tru-osmose, sondistillasie en die opvang van mis (Eng."fog collection") aangewend kan word om die seisoenale tekort aan drinkwater in hierdie gebiede aan te spreek. Die laedruk (6 bar) tru-osmose-ontsoutingseksperimente wys dat dit moontlik is om die eenheid met behulp van 'n sonkraggedrewe pomp te bedryf en voldoende water te lewer vir die tipiese daaglikse drinkwaterbehoeftes van 'n nedersetting in die Namibwoestyn. Hierdie eenheid sal sowat 4600 liter per dag (l/d) water, met 'n TVSwaarde van 500 mg/I, lewer. Dit is aansienlik meer as die lewering van soortgelyke eenhede in Australie en die Kanariese Eilande. Die resultate wys ook dat die koste van sondistillasie-eenhede genoegsaam verminder kan word om dit 'n lewensvatbare opsie vir watervoorsiening aan enkelhuishoudings in die plattelandse gebiede te maak. Die studie het ook bevind dat die opvang van mis 'n toepaslike alternatiewe bron van varswater is in sekere van die studiegebiede. Die miswater is oor die algemeen 'A' -gehalte drinkwater vol gens die Namibiese gehalteriglyne Vir drinkwater (gebasseer op bepalings van die Wereldgesondheidsorganisasie) en dat dit net so, of vermeng met brak grondwater, gebruik kan word as drinkwater. Vermenging is besonder geskik in die sentrale Namibwoestyn, aangesien die periode van hoe grondwaterverbrakking saamval met die piek van benutbare misneerslag. Die resultate toon ook aan dat miswater opgevang kan word met verskeie tipes polimeriese skadunet, wat maklik verkrygbaar is, en verskaf riglyne vir die optimale skadu-koeffisient en weefpatroon van moontlike misvangsnette vir voomemende gebruikers van misvangstegnologie in gebiede waar die polipropileennet wat in die standaard miskollekteerders gebruik word nie, beskikbaar is nie. Die ondersoek van oppervlakeienskappe van mis-koesterkewers (Eng. "fog harvesting beetles") en eksperimente met verskeie prototipe versamelaars toon dat dit moontlik is om die waterproduksie van bestaande kollekteerders te verhoog. Die hidrofobe oppervlaktetoestande soos gevind op die opperhuid van die mis-koesterkewers (Onymacris unguicularis en Onymacris bicolor) bevorder die vorming en afloop van groot misdruppels op die versameloppervlak. Die prototipe suigwaaier- en verkoelerstelselgebasseerde versamelaars toon dat dit moontlik is om die misvogversameling op polimeriese nette tot drie maal te verhoog en dat 'n vergelykbare volume atmosferiese vog versamel kan word, selfs in die afwesigheid van mis, tot by 'n relatiewe humiditeit van ongeveer 40%. Ten slotte benadruk die studie dat grondwatersoutgehalte in waterann gebiede soms 'n seisoenale probleem is, en dat dit in ag geneem moet word in watervoorsieningstrategiee vir sulke gebiede. Dit benadruk ook dat atmosferiese vog 'n bruikbare alternatiewe bron van varswater kan wees in sekere areas, waar dit dikwels verskeie male meer is as reenval, en gesien behoort te word as 'n belangrike aspek in strategiee om waterprobleme in hierdie gebiede aan te spreek. Die studie beveel sterk aan dat wetenskaplikes, ingenieurs en waterbestuurders in hierdie gebiede altyd die beskikbare geleenthede soos klimaatstoestande (bv. misneerslag) en aanpassings vir vogvangslbewaring wat voorkom by inheemse plante en diere sal navors om sodoende onderhoudbare oplossings vir die probleem te vind. Hulle behoort deurlopend op hoogte te bly met ontwikkelings/geleenthede wat ontstaan in die wyer waterindustrie, wat van waarde kan wees in by waterverskaffmgsinisiatiewe vir afgelee gebiede in ontwikkelende lande. Laastens dien die studie om 'n beter begrip daar te stel van die aard van grondwatersoutvlakke in waterarm gebiede wat afhanklik is van seisoenale oppervlaktevloei vir watervoorsiening sowel as om 'n bydrae te lewer tot die formuleer van oplossings tot die probleem in hierdie gebiede, veral in die hiperdroe omgewings aan die Namibiese weskus, waar konvensionele waterbronne mees onvoldoende is. Dit benadruk ook die rol van materiaalkundige wetenskappe (polimere) en omgewingsingenieurswese sowel as die UNESCO-geassosieerde wetenskaplike instellings in die formulering van volhoubare oplossings vir sommige van die huidige waterprobleme in waterann gebiede. Sleutelwoorde: Waterarm gebiede, hidrochemie, bronne van varswater, ontsouting, atmosferiese vog

Coagulation and flocculation processes are important parts of water and wastewater treatment. Coagulation or destabilization of colloidal suspensions results in aggregation of colloidal particles by physical and chemical processes. Flocculation results in the formation of larger and settleable structures by bridging. Alginate, a polysaccharide obtained from marine brown algae, produces a gel structure when mixed with calcium ions, which is expected to be a potential coagulant in water treatment. This study aims to determine the use of calcium alginate as a potential coagulant during water treatment and determine its capabilities and deficiencies in coagulation processes. The study was conducted on turbid water samples prepared in the laboratory and those taken from the inlet of Ankara ivedik Water Treatment Plant (IWTP) by running typical jar tests. The main experimental variables were initial alginate and calcium doses, initial turbidity of water samples and the order with which the two chemicals are dosed. The main criteria investigated to check the success of the system was the final turbidity values and the turbidity removal capacity of calcium- alginate. Experiments were conducted on three different laboratory &ndash<br>prepared turbid water samples and on the raw water taken from the inlet point of Ankara ivedik Drinking Water Treatment Plant (IWTP). These were prepared as high (150 NTU) medium (80 NTU) and low (10 NTU) turbidity samples. The calcium concentrations tested varied between 30 and 200 mg/L and alginate concentrations tested varied between 0.04 to 40 mg/L. Depending on the initial turbidity and initial calcium concentration of water sample the results depict that calcium alginate could be used as an effective coagulant for high (150 NTU) and medium (80 NTU) turbidity water sample especially at the calcium doses of 120 and 160 mg/L for low alginate concentration doses like 0.4 mg/L. The final turbidity met both the requirements of Drinking Water Standards applied in Turkey and Europe. Generally, the higher the initial turbidity was, the higher the turbidity removal efficiency achieved, even with very low alginic acid concentration. As the initial turbidity decreased, initial concentration of calcium required for the effective coagulation processes decreased. However, for low (10 NTU) turbidity water samples the system did not work properlyHowever, for low turbidity water samples, the turbidity removal efficiency decreased, and it was difficult to meet the limits.

Chromium is a common groundwater pollutant originating from industrial processes such as metal plating, leather tanning and pigment manufacturing. Permeable reactive barriers (PRBs) have proven to be viable and cost-effective systems for remediation of chromium contaminated groundwater at many sites. The purpose of this research presented in this thesis is to focus on two parameters that affect the performance of PRB on chromium removal, namely the concentration of reactive media and groundwater flux by analyzing the data obtained from laboratory column studies. Laboratory scale columns packed with different amounts of iron powder and quartz sand mixtures were fed with 20 mg/l chromium influent solution under different fluxes. When chromium treatment efficiencies of the columns were compared with respect to iron powder/quartz sand ratio, the amount of iron powder was found to be an important parameter for treatment efficiency of PRBs. The formation of H2 gas and the reddish-brown precipitates throughout the column matrix were observed, suggesting the reductive precipitation reactions. SEM-EDX analysis of the iron surface after the breakthrough illustrated chromium precipitation. In addition to chromium<br>calcium and significant amount of iron-oxides or -hydroxides was also detected on the iron surfaces. When the same experiments were conducted at higher fluxes, an increase was observed in the treatment efficiency in the column containing 50% iron. This suggested that the precipitates may not be accumulating at higher fluxes which, in turn, create available surface area for reduction. Extraction experiments were also performed to determine the fraction of chromium that adsorbed to ironhydroxides. The analysis showed that chromium was not removed by adsorption to oxyhydroxides and that reduction is the only removal mechanism in the laboratory experiments. The observed rate of Cr(VI) removal was calculated for each reactive mixture which ranged from 48.86 hour-1 to 3804.13 hour-1. These rate constants and complete removal efficiency values were thought to be important design parameters in the field scale permeable reactive barrier applications.

In the present study, the recovery of the indigo dyeing rinsing wastewater originating from a denim textile mill to the degree of reuse quality, which generally requires nanofiltration (NF), was investigated. In order to control flux decline and hence to maintain an efficient NF<br>coagulation, microfiltration (MF) and sequential MF plus ultrafiltration (UF) pretreatment process alternatives were tested. All pretreatment alternatives were optimized to reduce chemical oxygen demand (COD) and color load to NF. Coagulation process was investigated using the coagulants, aluminum sulfate (Al2(SO4)3.18H2O) and ferric chloride (FeCl3.6H2O) by running a series of jar tests. The results showed that coagulation process did not provide an effective and efficient pretreatment due to high dose of coagulant requirement. MF tests run by using 0.45, 2.5 and, 8 &micro<br>m membranes indicated that MF through 0.45 &micro<br>m pore-sized membrane is the best process providing 64% color and 29% COD removals, leading to a color value of 2493 Pt-Co and COD of 892 mg /L in the permeate. Application of sequential MF+UF filtration provided a significant benefit over single MF in terms of rejections and also permeate flux. UF applied after MF provided additional 62% color and 4% COD removals leading to 960 Pt-Co color and 856 mg/L COD. NF tests conducted using pretreated wastewater via single MF and sequential MF+UF indicated that single MF is the best pretreatment to NF and this treatment scheme provided 99% color, 97% COD and 80 % conductivity removals and satisfied reuse criteria.

Effect of ionic strength on the efficiency of heavy metal removal and recovery from aqueous solutions via continuous mode polymer enhanced ultrafiltration (PEUF) method was examined. Application of PEUF to divalent ions of cadmium, nickel and zinc after their prior linking with polyethylenimine (PEI) results in complete removal of metal ions from single component aqueous solutions at high pHs. Binding ability and hence the extent of metal retention in high ionic strength medium exhibits differences between solutions containing single and multicomponent metal mixtures. In single component metal solutions, extent of retention decreases but binding order of metals remains unaffected both in low and high ionic strength medium. But, in binary component metal mixtures, with increase in ionic strength the binding order of metals changes. Fractional separation of Cd, Ni and Zn ions from equimolar binary and ternary mixtures of these metals and effect of ionic strength on fractional separation efficiency were investigated. Depending on pH and salt concentration and metal pairs present in the solution fractional separation can be achieved.Dynamic and static light scattering experiments were performed in order to gain insight about the conformational changes in PEI structure due to the pH and ionic strength alternations in solution. It was found that, the increase in ionic strength reduces the size of the macromolecules. A chemical equilibrium model was developed in order to estimate the apparent binding constants of metal-PEI complexes. Based on the data obtained from continuous and batch mode PEUF experiments apparent binding constants were estimated and compared to reveal the performance differences between these operational modes.

Thesis (MEng) -- Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: South Africa has historically been reliant on inexpensive surface and groundwater resources; however, as pressure on these resources continues to grow, seawater desalination has begun to emerge as a potential future supply source. One of the towns earmarked as a candidate for large-scale seawater desalination is Cape Town. In order to maximise the benefits and minimise the costs of such a scheme, the desalination plant needs to be considered as an integral part of the current system. Integrated planning has been lacking at the existing seawater desalination plants in South Africa, most of which were constructed as emergency schemes and are financially cumbersome for the municipalities to operate and manage. Recent research related to inter-basin water transfer schemes has shown that a comprehensive approach is required in assessing water supply from a new scheme in which the system as a whole is modelled stochastically and the estimated water transfer extracted. This comprehensive approach was the foundation of the modelling undertaken in this research. Existing models of the Western Cape system were adapted to include a seawater desalination plant, and short-term and long-term analyses were completed for a variety of possible desalination plant operating scenarios and capacities. The increase in system yield and the annual supply from the desalination plant were determined. First-order capital and operating costs were estimated, and these costs were combined with the annual supply values to calculate and compare unit reference values. The maximum increase in yield was found to occur when the seawater desalination plant is used as a base supply, operational all the time. There was little benefit, in terms of system yield, in using the desalination plant as an emergency supply source only. Unit reference values for the desalination plant decrease as the percentage supply from the desalination plant increases, meaning that the lowest possible cost per cubic metre of water supplied is when the desalination plant is used as a base supply. It was also apparent that the unit reference values decrease with an increase in desalination plant capacity, suggesting that, from an economic perspective, the optimal solution would be to have one large desalination plant operational immediately. The lower the reservoir trigger level at which the desalination plant becomes active, the larger the stochastic variation in the supply from the desalination plant and hence the larger the variation in the costs. Hence, using stochastic modelling to calculate unit reference values is particularly important for integrating a desalination plant into an existing conventional supply system when used as a peak or emergency supply source.<br>AFRIKAANSE OPSOMMING: Suid-Afrika maak histories staat op goedkoop oppervlak- en grondwaterhulpbronne. Namate druk op hierdie hulpbronne aanhou toeneem, begin seewaterontsouting egter as ’n moontlike toekomstige waterbron na vore tree. Een van die stede wat as ’n kandidaat vir grootskaalse ontsouting geïdentifiseer is, is Kaapstad. Vir die meeste moontlike voordele teen die laagste moontlike koste, moet so ’n ontsoutingsaanleg as ’n integrale deel van die huidige stelsel beskou word. Geïntegreerde beplanning het tot dusver tekortgeskiet by bestaande ontsoutingsaanlegte in Suid-Afrika, wat merendeels as noodskemas opgerig is en waarvan die bedryf en bestuur ’n finansiële las op munisipaliteite plaas. Onlangse navorsing oor skemas vir tussenbekkenwateroordrag toon dat ’n omvattende benadering vereis word om watervoorsiening uit ’n nuwe skema te beoordeel. Volgens so ’n benadering word die stelsel in die geheel stogasties gemodelleer en die geraamde wateroordrag onttrek. Dié omvattende benadering was dan ook die grondslag vir die modellering wat in hierdie navorsing onderneem is. Bestaande modelle van die Wes-Kaapse stelsel is aangepas om ’n ontsoutingsaanleg in te sluit, en kort- en langtermynontledings is vir verskeie moontlike ontsoutingsaanlegvermoëns en -bedryfscenario’s voltooi. Die toename in stelselopbrengs en die jaarlikse watervoorsiening uit die ontsoutingsaanleg is bepaal. Kapitaal- en bedryfskoste van die eerste orde is geraam, welke koste toe met die jaarlikse voorsieningswaardes gekombineer is om eenheidsverwysingswaardes te bereken en te vergelyk. Die maksimum toename in opbrengs blyk te wees wanneer die ontsoutingsaanleg as ’n basisbron dien wat te alle tye in werking is. Wat stelselopbrengs betref, was daar weinig voordeel in die gebruik van die aanleg as ’n noodwaterbron. Eenheidsverwysingswaardes vir die ontsoutingsaanleg neem af namate die persentasie voorsiening uit die aanleg toeneem, wat beteken dat die laagste moontlike koste per kubieke meter water verkry word wanneer die ontsoutingsaanleg as ’n deurlopende basisbron dien. Dit was ook duidelik dat die eenheidsverwysingswaardes afneem met ’n toename in aanlegvermoë, wat te kenne gee dat die optimale oplossing uit ’n ekonomiese oogpunt sou wees om onmiddellik een groot ontsoutingsaanleg in bedryf te stel. Hoe laer die opgaardamvlak waarop die ontsoutingsaanleg in werking tree, hoe groter die stogastiese variasie in watervoorsiening uit die aanleg, en hoe groter die variasie in koste. Daarom is die gebruik van stogastiese modellering om eenheidsverwysingswaardes te bereken veral belangrik vir ’n ontsoutingsaanleg wat as ’n spits- of noodwaterbron dien.

The rejections of selected N-nitrosamines by commonly used high-pressure nanofiltration (NF) and reverse osmosis (RO) membranes were quantitatively evaluated using a bench-scale cross-flow filtration apparatus. The selected nitrosamines included N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPYR), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA) and N-nitrosodiphenylamine (NDPHA). Nitrosamine rejections were evaluated under steady state at elevated feed concentrations, since NDMA rejections were found to be consistent with feed concentrations over three orders of magnitude. The steady-state nitrosamine rejections by NF membranes varied significantly, from 9 to 75%, depending on nitrosamine compounds and tested membranes. For hydrophilic compounds, rejections increased with increasing molecular weight. The nitrosamine rejections by brackish RO membranes reached as high as 97% for higher molecular weight nitrosamines. However, for low molecular weight nitrosamines such as NDMA, rejections as low as 54% were observed. This low level of rejections was attributed to diffusive solute transport being more effective than convective transport. Physicochemical properties such as molecular weight and aqueous diffusivity showed reasonable correlations with nitrosamine permeability constants.

Thesis (MScEng)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: South Africa is a relatively dry country with an annual average rainfall of 464mm compared to a world average of 860mm (WSA, 2009). Water shortages and droughts are fairly common to the western and high lying of regions South Africa. Due to its population growth and the rapid development, like the rest of the world, there has been an increased demand for water. Due to increasing costs of procuring water and its decreasing availability, the option of using seawater as a source for freshwater or directly in industrial processes has become competitive, especially in the arid parts of the world. The design of seawater intakes forms an integral part of providing a secure source of seawater. The objective of this thesis is to aid in the development of guidelines for the design of small scale seawater abstraction systems on rocky coastlines using the Horizontal Well Method. Recommendations for guidelines will be given.<br>AFRIKAANSE OPSOMMING: Geen opsomming

Nitrogen and phosphorus removal is often required before discharge of treated wastewater to sensitive water bodies. Kayseri Wastewater Treatment Plant (KWWTP) is a biological wastewater treatment plant that includes nitrogen and phosphorus removal along with carbon removal. The KWWTP receives both municipal wastewater and industrial wastewaters. In this study, KWWTP was modeled by using a software called GPS-X, which is developed for modeling municipal and industrial wastewaters. The Activated Sludge Model No.2d (ASM2d) developed by the International Association on Water Quality (IAWQ) was used for the simulation of the treatment plant. In this model, carbon oxidation, nitrification, denitrification and biological phosphorus removal are simulated at the same time. During the calibration of the model, initially, sensitivities of the model parameters were analyzed. After sensitivity analysis, dynamic parameter estimation (DPE) was carried out for the optimization of the sensitive parameters. Real plant data obtained from KWWTP were used for DPE. The calibrated model was validated by using different sets of data taken from various seasons after necessary temperature adjustments made on the model. Considerably good fits were obtained for removal of chemical oxygen demand (COD), total suspended solids (TSS) and nitrogen related compounds. However, the results for phosphorus removal were not satisfactory, probably due to lack of information on volatile fatty acids concentration and alkalinity of the influent wastewater.

Biological nitrogen removal was simulated for a Vacuum Rotating Membrane (VRM) type membrane bioreactor (MBR) operated in METU campus. In order to simulate the biological MBR plant, a dynamic model that describes the process is needed. In this thesis, the Activated Sludge Model No.1 (ASM1), which still is the most widely used model developed by the International Association on Water Quality (IAWQ), has been used to simulate the carbon oxidation, nitrification and denitrification processes occurring in the plant using AQUASIM software package. Once the model was established, sensitivities of the model parameters were analyzed. Then, parameter estimation was carried out for the optimization of the sensitive parameters. As we have several distinct data sets available two parallel modeling study was carried out for the calibration of the model. Finally, the calibrated model by different data sets was validated by using the remaining data sets. The model results were consistent with the measured data especially in terms of MLSS concentration in the system. However model results for the nitrogen removal were not extremely successful<br>the reason for this might be the inadequate available data on nitrification-denitrification process occurring in the system.

The aim of this master thesis study was improvement of the required operational conditions for aerobic granulation in sequencing batch reactors (SBRs). In the first part of the study, membrane bioreactor sludge (MBS) and conventional activated sludge (CAS), were used to investigate the effect of suspended seed sludge type on granulation in SBRs. The MBS granules were found to be advantageous in terms of size, resistance to toxic effects, stability and recovery compared to CAS granules. During non-inhibitory conditions, sCOD removal efficiencies were 70&plusmn<br>13% and 67&plusmn<br>11% for MBS and CAS, and total nitrogen (TN) removal efficiencies were 38&plusmn<br>8% and 26&plusmn<br>8%, respectively. In the second part of the study, the effects of period sequence (anoxic-aerobic and aerobic-anoxic) on aerobic granulation from MBS, and sCOD, N removal efficiencies were investigated. Granules developed in anoxic-aerobic period sequence were more stable and larger (1.8-3.5 mm) than granules developed in aerobic-anoxic sequence. Under steady conditions, almost 95% sCOD, 90% Total Ammonia Nitrogen (TAN) and around 39-47 % of TN removal was achieved. Almost 100% denitrification in anoxic period was achieved in anoxic-aerobic period sequence and it was observed around 40% in aerobic-anoxic period sequence. The effects of influent sulfate (from 35.1 mg/L to 70.2 mg/L) on treatment efficiencies of aerobic granules were also investigated. The influent SO42- concentrations of 52.6 mg/L to 70.2 mg/L promoted sulfate reduction. The produced sulfide (0.24 mg/L to 0.62 mg/L) inhibited the ammonia-oxidizing bacteria (AOB) performance by 10 to 50%.

Thesis (MEng) -- Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: When desalinating brackish water by reverse osmosis (RO) or other techniques, high overall water recoveries are essential to minimize brine production and the associated disposal costs thereof. As the overall water recovery increases, concentrations of sparingly soluble salts (e.g. barium sulphate, calcium sulphate) reach levels above saturation, especially near the membrane surface, drastically increasing the scaling propensity. Antiscalants are typically dosed into the feed water to prevent such scaling during RO desalination. However, the carry-over of antiscalant into the concentrate stream can complicate subsequent salt precipitation processes that may be used to increase overall water recovery. These precipitation techniques are sometimes used to reduce the levels of super-saturation in the RO concentrate prior to a subsequent RO desalination step. The purpose of this study was to assess the feasibility of reducing calcium sulphate scaling on RO membranes, by using periodic permeate flushing when feeding a lab-scale RO unit with a supersaturated calcium sulphate solution in the absence of anti-scalant. The overall water recovery was increased by recycling the concentrate, after an intermediate de-supersaturation step. This simulated a multiple-stage RO system, typical of processes used in high-recovery acid mine drainage (AMD) treatment plants. De-supersaturation of the concentrate intermediate was achieved with direct seeded gypsum precipitation, in the absence of any antiscalant. On the membrane surface inside the membrane unit, calcium sulphate concentrations greatly exceeded saturation levels – a combined consequence of the normal concentration process and the well-known surface-based concentration polarisation phenomenon. Therefore, periodic forward-flushing of the supersaturated solution from the membrane unit was performed with permeate. In theory, the periodic flushing removes the highly concentrated layer at the membrane surface during every flush, before scaling can occur. Various flushing regimes were evaluated to assess the effectiveness of the process. A lab-scale desalination unit with a 0.106 m2 flat sheet polyamide RO membrane was designed and constructed. The unit could operate at a feed rate of 12-14 L/h and at permeate fluxes of 12-24 LMH. Super-saturated feed solutions were prepared by mixing sodium sulphate and calcium chloride dihydrate salts with demineralised water, with an initial salinity of ± 5300 mg/L TDS, corresponding to a gypsum saturation index (SIg) of 1.2 for most experiments. The total production time, net permeate production and flux decline were used to compare the flushing efficiency in different experimental runs. Initial tests showed that scaling could be prevented (when operating the unit in full recycle mode, i.e. where both concentrate and permeate were recycled to feed), at flushing frequencies between 12 and 2.4 h-1, when the membrane feed and concentrate were slightly under-saturated (SIg = 0.9) and slightly super-saturated (SIg = 1.1) respectively. However, when switching the same system to non-flushing mode after 24 hours of operation, membrane scaling occurred within 2-3 hours, as indicated by a strong decline in flux. However, when operating the system in concentrate recycle mode (i.e. permeate is withdrawn) with super-saturated feed solutions (e.g. SIg = 1.2), and thus a notably more super-saturated solution in the membrane concentrate, scaling could not be prevented (albeit delayed for some time) with intermittent permeate flushing. A fractional 25-1 factorial design was used to determine which factors had the most significant effect on total production time and permeate production rate, testing five factors: 1) flushing frequency, 2) flushing volume, 3) permeate soak time, 4) permeate flux and 5) instantaneous recovery. The ANOVA analysis showed that total production times were, not surprisingly, primarily affected by the permeate flux, where operation at 24 LMH resulted in a lower net permeate production between 3.0 - 4.2 L, compared to 7.6 - 9.7 L at 12 LMH. Higher permeate fluxes clearly resulted in higher levels of concentration polarisation at the membrane surface, thus increasing the propensity for membrane scaling. Flushing frequency and instantaneous recovery also affected the net permeate production, where 6 h-1 and 10 % were the optimal values respectively within the range of test conditions. The lowest permeate production rate resulted in the highest net permeate volume production (i.e. also longest total production time), confirmed by a least squares regression. In summary: This study showed that periodic permeate flushing could delay the membrane scaling process. However, it failed to prevent membrane scaling completely when operating the system with supersaturated calcium sulphate solutions in the absence of antiscalants. The flushing technique effectively delayed the onset of precipitation, but scaling eventually occurred if the lab-scale RO system was operated in concentrate recycle mode with oversaturated feed solutions (SIg = 1.2). Additional experiments at different cross-flow velocities during permeate flushing, while using an optimised RO test cell flow channel design, are recommended for future studies.<br>AFRIKAANSE OPSOMMING: Gedurende die ontsouting van brakwater deur tegnieke soos tru-osmose (TO), is ʼn maksimum herwinning van water noodsaaklik om die produksie, en die gepaardgaande kostes van verwydering, van die sout/brak neweproduk te minimeer. Soos die herwinning van water verhoog, so ook verhoog die konsentrasie van moeilik-oplosbare soute (soos bariumsulfaat, kalsiumsulfaat) in die sout konsentraat stroom, totdat die soute uiteindelik superversadiging bereik. Hierdie superversadiging gebeur veral naby die membraanoppervlak, waar dit lei tot ʼn verhoogde kans van presipitasie en skaalvorming. Om dit te voorkom word die voerwater na ʼn TO stelsel tipies gedoseer met antiskaalmiddels. Hierdie antiskaalmiddels verlaat die stelsel saam met die konsentraat, waar hulle gevolglike die presipitasie van soute bemoeilik. Presipitasie van soute uit die konsentraat kan tipies gebruik word om die vlak van superversadiging in die konsentraat te verlaag, waarna verdere TO behandeling gebruik word om selfs ʼn hoër algehele waterherwinning te bewerkstellig. Die doel van hierdie studie was om die vatbaarheid van die vermindering van kalsiumsulfaat (gips) skaalvorming in die afwesigheid van antiskaalmiddels op TO membrane te toets. Dit is bewerkstellig deur ʼn laboratoriumskaal TO eenheid te voer met ʼn superversadigde kalsiumsulfaat oplossing en die membraan periodies met skoon produkwater (permeaat) te was. Die algehele waterherwinning is verhoog deur met ʼn tussenstap die versadigingsvlak van gips in die konsentraat te verlaag, waarna dit hersirkuleer is na die voertenk. Sodoende is ʼn multi-stadium TO stelsel nageboots, soos dit tipies in hoë herwinningsaanlegte, soos met die herwinning van suur mynwater (E: acid mine drainage, AMD), gebruik word. ʼn Verlaging in superversadiging van die konsentraat in die tussenstap is behaal deur die konsentraat direk aan gipskristalle bloot te stel om presipitasie te bewerkstellig in die afwesigheid van enige antiskaalmiddels. Gedurende eksperimente het die soutkonsentrasie op die membraanoppervlak in die TO eenheid superversadigingsvlakke vêr oorskry, as gevolg van die natuurlike konsentrasie proses en die bekende konsentrasie polarisasie oppervlaksverskynsel. Om hierdie superversadiging teen te werk is periodiese saamstroom spoeling van die membraan met skoon produkwater uitgevoer. In teorie het die periodiese spoeling die hoogs gekonsentreerde oplossing van die membraan oppervlak verwyder voor skaalvorming kan plaasvind. Verskillende spoelpatrone is ondersoek om die doeltreffendheid van die spoeling te bepaal. Om die eksperimente uit te voer is ʼn laboratoriumskaal ontsoutingsaanleg met ʼn maklik verwyderbare 0.106 m2 plat-vel poli-amied TO membraan ontwerp en gebou. Die aanleg kan vloeistof voertempo’s tussen 12-24 L/h hanteer en skoon produkwater teen 12-24 LHM lewer. Die superversadigde voer oplossings, soos gebruik in die meerderheid van die eksperimentes is voorberei deur natriumsulfaat en kalsiumchloried-dihidraat soute te meng in gedemineraliseerde water, tot ʼn soutgehalte van ± 5300 mg/L TDS bereik is. Hierdie soutgehalte stem ooreen met ʼn gips versadigingsindeks (E: gypsum saturation index, SIg) van 1.2. Die skoon produkwater totale produksietyd en netto produksie, asook die membraan vloed afname, is gebruik as veranderlikes om die spoel doeltreffendheid tussen eksperimentele lopies te vergelyk. Aanvanklike toetse het getoon dat skalering voorkom is by effens onderversadigde (SIg = 0.9) en effens superversadigde (SIg = 1.1) voer oplossings met die onderskeie spoel frekwensies van 12 en 2.4 h-1, (terwyl die aanleg in algehele hersirkulasie bedryf is, m.a.w. wanneer beide die konsentraat en produkwater gedurig na die voertenk hersirkuleer word). ʼn Effens-superversadigde eksperiment is ook sonder spoeling uitgevoer vir 24 uur. In hierdie geval het skaalvorming binne twee tot drie uur gebeur, soos bevestig deur ʼn skerp afname in die membraan vloed. Skaalvorming kon nie verhoed word terwyl die aanleg bedryf word met superversadigde (SIg = 1.2) voeroplossings en slegs konsentraat hersirkulasie nie (m.a.w. skoon produkwater word opgevang), alhoewel skaalvorming vertraag kon word. Hierdie operasie het tot beduidend meer gekonsentreerde oplossings in die membraan gelei. Om te bepaal watter faktore die grootste invloed op totale produksietyd en netto produksie van skoon produkwater het, is ʼn fraksionele faktoriaalontwerp van 25-1 uitgelê wat vyf faktore toets, naamlik: 1) spoel frekwensie, 2) spoel volume, 3) skoon produkwater weektyd, 4) membraanvloed en 5) oombliklike herwinning. ʼn AVOVA analise het getoon dat totale produksietyd hoofsaaklik deur membraanvloed beïnvloed is, soos verwag kan word. Dit word gestaaf deurdat die aanleg, bedryf teen 24 LMH, slegs 3 - 4.2 L netto produkwater gelewer het, teenoor 7.6 - 9.7 L by 12 LMH. Hoër membraan vloedtempo’s het tot hoër vlakke van konsentrasie polarisasie op die membraanoppervlak gelei, wat ʼn groter neiging tot skaalvorming tot gevolg gehad het. Spoelfrekwensie en oombliklike herwinning het ʼn invloed op die netto produksie van skoon produkwater gehad, met 6 h-1 en 10 % as die onderskeie optimale waardes. ʼn Kleinstekwadraat regressie het aangedui dat die laagste produksietempo van skoon produkwater die hoogste netto produksie van skoon produkwater gelewer het, (asook die langste produksietyd). In opsomming: Hierdie studie het getoon dat gereelde spoeling met skoon produkwater die membraan skaalproses kan vertraag. Gedurende bedryf met superversadigde kalsiumsulfaat oplossings sonder enige antiskaalmiddels is daar gevind dat skaalvorming nie geheel en al vermy kon word nie. Die spoeltegniek, soos gebruik in hierdie studie, het die aanvang van skaalvorming in die laboratorium skaal TO eenheid vertraag, maar bedryf met konsentraat hersirkulasie en superversadigde oplossings (SIg = 1.2) het steeds skaal gevorm. Bykomende eksperimente teen verskeie kruisvloei snelhede gedurende die spoel stap word aanbeveel vir toekomstige studies.

This study aims to investigate the possibility of using calcium-alginate as a coagulant in low turbidity waters. Jar tests were initially performed with synthetically prepared turbid waters to investigate the effect of alginate and calcium concentrations, alginate&rsquo<br>s molecular weight, rapid mixing time and speed (schedule), initial pH and alkalinity of synthetic water on turbidity removal efficiency of calcium-alginate system step by step. Alum as a coagulant was then used in jar tests conducted with synthetic water to compare with calcium-alginate in terms of its turbidity removal efficiency and produced sludge properties. Finally, raw water acquired from water treatment plant was tested for treatability by using calcium-alginate based on previously determined optimum parameters via jar tests. Experiments of calcium-alginate system with synthetic water showed that calcium was a key parameter in coagulation and high molecular weight alginate performed better in turbidity removal. Significant improvements in turbidity removal were observed when mixing schedules were rearranged<br>especially in case of increasing rapid mixing time following calcium dosing. Calcium-alginate system neither was notably affected by pH or alkalinity nor did significantly change the pH or alkalinity of the medium. Alum worked well in turbidity removal with additional adjustments of pH and alkalinity, however<br>alum produced higher quantities of sludge than calcium-alginate system. &ldquo<br>Raw water&ldquo<br>experiments with calcium-alginate did not result in desired level of turbidity removals due to the excessively different characteristics of this water compared to the synthetically prepared turbid water.

Wastewaters from textile industry contain organic dyes, which cannot be easily treated by biological methods. Therefore, pretreatment by an advanced oxidation process (AOP) is needed in order to produce more readily biodegradable compounds and to remove color and chemical oxygen demand (COD) simultaneously. In this research, ozone (O3) is combined with hydrogen peroxide (H2O2) for the advanced oxidation of an azo dye solution, namely aqueous solution of Acid Red 151, which is called as &ldquo<br>Peroxone process&rdquo<br>. The aim of the study is to enhance the ozonation efficiency in treating the waste dye solution. The effects of pH, initial dye and initial ozone concentrations and the concentration ratio of initial H2O2 to initial O3 on color and COD removals were investigated. Also, the kinetics of O3-dye reaction in the presence of H2O2 was approximately determined. As a result of the experimental study, it was seen that an increase in the initial dye concentration at a constant pH and initial ozone concentration did not change the COD % removal significantly, from a statistical analysis of the data. The results obtained at pH values of 2.5 and 7 gave higher oxidation efficiencies in terms of color and COD removals compared to those at pH of 10. The best initial molar ratio of H2O2 to O3 was found to be 0.5, which yielded highest treatment efficiency for each pH value studied. The results of the excess dye experiments suggest that the ozonation of Acid Red 151 follows an average first order reaction with respect to ozone at pH=2.5 and pH=7 whereas it is around 0.56 at pH=10. By Initial Rate Method, the orders with respect to individual reactants of O3 and dye were determined as one, the total order of the reaction being two for all the studied pH. As a conclusion, a further study of the peroxone process at a pH of 10 can be recommended to determine the reaction kinetics and mechanism at this pH, where radicals play an important role.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2012.<br>Recently much research and development has been done into the creation of desalination systems in South Africa, with particular emphasis on the commercialisation of desalination plants that serve local communities. This has been successful - there are currently plants running at Bitlerfontien, Bushmans River Mouth and Robben Island - although membrane fouling and scaling remains a problem associated with membrane desalination, as it does worldwide The aim of this study was to Investigate the performance of different type of antiscalants on artificially scaled membranes which we prepared inside the lab as well as on scaled membranes which were used in pilot plant. We used two type of anti-sealants in our research: Vitec 3000 and Zinc ions. The effects of these anti-sealants on the membrane were determind and the RO performances of the treated and untreated membrane compared. A suitable autopsy procedure was established and was then used to autopsy the XLE 4040 membranes. The autopsied membranes were characterized by scanning electron microscopy (SEM) and optical microscopy (OM). The SEM and OM results clearly showed that scaling had taken place: deposits were observed for both the shell and core samples, which were not present in the images of the untreated membrane, especially when looking at high SEM images magnification. Results also showed that the anti-sealants reduced the fouling and scaling on the membrane surface. As a result, the membrane rejection improved. Rejection and flux results indicated that commercial anti-sealant was more effective in preventing scaling than the Zinc ions. For Vitec anti-sealant case, the flux was in steady state at 36.8 Imh (5% less) after 5 hours compared to around 35 Imh (8% less) for zinc ions case. In addition; SEM images showed that less deposited particles are formed when the membrane was treated with commercial anti-sealant.

Thesis (MEng)--Stellenbosch University, 2000.<br>ENGLISH ABSTRACT: Fouling is readily acknowledged as one of the most critical problems limiting the wider application of membranes in liquid separation processes. A better understanding of fouling layer formation and its monitoring is needed in order to improve on existing cleaning techniques. Plant operation can be optimised if fouling can be monitored by noninvasion means either on the plant itself or on an attached monitoring device. The overall scope of this research was to develop a non-destructive, real-time, in situ visualisation technique or device for concentration polarisation and fouling layer monitoring. Ultrasonic-time-domain-reflectometry (UTDR) was employed as a visualisation technique to provide real-time characterisation of the fouling layer. A 24 cm-long rectangular flat sheet aluminium cell was designed and used as separation device for a desalination system. The experimental results obtained using this module confirmed that there are an excellent correspondence between the flux decline behaviour and the UTDR response from the membrane. The ultrasonic technique could effectively detect fouling layer initiation and growth on the membrane in real-time. In addition to the measurement of fouling, the ultrasonic technique was also successfully employed for monitoring membrane cleaning. Since no real-time permeation data is available during cleaning operations in industrial applications, a UTDR monitoring device may prove to be a very valuable technique in optimising cleaning strategies. The technique was further tested on an 8-inch diameter spiral wrap industrial module and good results were obtained. Stagnant zones, as well as flux flow behaviour inside the module could be determined. However, more research IS needed to fully understand the complex phenomena inside a spiral wrap module. Overall, the UTDR technique and its use in monitoring devices have a major impact in the membrane industry due to its extremely powerful capabilities.<br>AFRIKAANSE OPSOMMING: Membraan-bevuiling of -verstopping is die grootste struikelblok wat die algemene aanwending van membrane vir verskillende watersuiweringsprosesse negatief beinvloed. 'n Beter begrip van membraan-bevuiling, asook beter metingsmetodes daarvan is nodig om op bestaande skoonmaaktegnieke te verbeter. Die hoofdoel van hierdie studie was die ontwikkeling van 'n nie-destruktiewe-in-lyn visuele tegniek vir die meting van konsentrasie polarisasie en membraan-bevuiling. Deur gebruik te maak van ultrasoniese klank golwe, is 'n tegniek ontwikkel wat 'n direkte visuele aanduiding kon gee van die toestand van membraan-bevuiling binnein die module. 'n Reghoekige aluminium-module, 24 cm lank, is ontwerp en gebou waarbinne die membraan geplaas is vir die skeidingsproses. Resultate dui daarop dat daar 'n uitstekende verband bestaan tussen die afname in permeaatvloei en die ultrasoniese eggo vanaf die membraan. Die ultrasoniese tegniek kon die vorming van en toename in membraan-bevuiling doeltreffend karakteriseer. In teenstelling hiermee, is die tegniek ook suksesvol aangewend om die skoonmaak-proses van membrane te ondersoek. Met min of geen data beskikbaar vir die skoonmaak-proses van membrane in die industriële sektor, het die tegniek enorme potensiaal in die optimisering van bestaande skoonmaak-tegnieke. Die tegniek is verder aangewend op 'n industriële 8-duim deursnee spiraal-module en goeie resultate is verkry. Stagnante sones asook vloed-vloei-patrone binne-in die module kon suksesvol bepaal word. Baie navorsing is egter nog nodig om die ingewikkelde data wat gegenereer word tydens die ondersoek van 'n spiraal-module ten volle te verstaan. Die enorme potensiaal en moontlikhede van die ultrasoniese tegniek kan die begin wees van 'n revolusie in die membraan-industrie.

Abstract in English and German<br>The reported PhD research study was conceived from real water problems experienced by a rural community in South Africa (SA). Specifically, water quality in the Nandoni Dam situated in the Vhembe District, Limpopo Province, South Africa was assessed in order to determine its fitness for use, following complaints by community members using this water for drinking and domestic purposes. The dam supplies water to 55 villages with approximately 800 000 residents. At the inception of the study, there was little scientific information relating to the quality of the water in the dam. Water samples from various sites across the Nandoni Dam, a primary source of domestic water supply in the region, were collected through each season of the year over a period of 12 months to ascertain the concentrations of dissolved salts in the dam. Additionally, harmful polycyclic aromatic hydrocarbons (PAHs) and phenols were assessed. The concentrations of the ions contributing to water salinity were generally lower than the brackish water bracket (i.e. 500 – 30 000 mg/L) but too high for potable water. The concentration of the phenols was relatively higher than the threshold limit of drinking water. Therefore, the water sourced from the Nandoni Dam was found not suitable for human consumption and therefore required integrated water resource management, as well as robust and cost-effective water treatment especially since the salinity of the water was high even after treatment by a water treatment plant sourcing water from the dam. In an attempt to develop a suitable energy-efficient technology or system for complete removal of salts (desalination) from the salty water (including brackish water), electrospun polyvinylidene fluoride (PVDF) nanofibre membranes were synthesised and evaluated for removal of salts using the Direct Contact Membrane Distillation (DCMD) process. The nanofibre membranes were synthesised with combined high mechanical stability, porosity, and superhydrophobicity to prevent fouling and wetting while maintaining high salt rejection and water flux. Organically functionalised silica nanoparticles (f-SiO2NPs) were embedded on PVDF nanofibre membranes using an in-situ electrospinning technique for superhydrophobicity enhancement. These modified membranes displayed Young’s modulus of ~43 MPa and showed highly porous properties (~80% porosity, 1.24-1.41 μm pore sizes) with superhydrophobic surfaces (contact angle >150°). Membranes embedded with octadecyltrimethoxysilane (OTMS), and chlorodimethyl-octadecyl silane (Cl-DMOS), octadecyltrimethoxysilane (ODTS)-modified SiO2NPs were the most efficient; rejecting >99.9% of NaCl salt, with a water flux of approximately 30.7-34.2 LMH at 60°C, thus indicating their capacity to produce potable water. The superhydrophobic membranes were coated with a thin layer consisting of carboxylated multiwalled carbon nanotubes (f-MWCNTs) and silver nanoparticles (AgNPs) to reduce membrane fouling. The AgNPs and f-MWCNTs were uniformly distributed with size diameters of 28.24±1.15 nm and 6.7±2.1 nm respectively as evidenced by transmission electron microscopy (TEM) micrographs. The antibacterial AgNPs embedded in the PVDF nanofibre membranes inhibited the growth of Gram-positive Geobacillus stearothermophilus and Staphylococcus aureus as well as Gram-negative Pseudomonas aeruginosa and Klebsiella pneumoniae indicating their potential to prevent biofilm formation. Fouling tests were conducted using bovine serum albumin (BSA), sodium alginate, colloidal silica, and thermophilic bacteria effluent as model organic, inorganic, and bio-foulants, respectively, using DCMD. The uncoated membranes were characterised by a flux decays ranging from 30% to 90% and salt rejection decays ranging from 1.4% to 6.1%. Membrane coating reduced the flux and salt rejection decays to 10–24% and 0.07–0.75%, respectively. Although the initial flux decreased from 42 to  16 LMH when using coated membranes, the resistance of these coated membranes to water flux and salt rejection decays indicated that coating could be a suitable one-step solution for fouling mitigation in DCMD. The major challenge would be to design the MD membranes with architectures that allow a high-water flux to be maintained i.e., a highly porous layer. Furthermore, the volatile compounds bearing hydrophobic groups were pretreated to reduce their fouling capacity on PVDF nanofibre membranes. In this study, polyacrylonitrile (PAN) and polyethylene-imine (PEI) functionalised-PAN nanofibre membranes were synthesised and evaluated as a pretreatment for the removal of chlorophenol and nitrophenol from solutions. Under optimised experimental conditions, adsorption capacities ranging from 27.3 – 38.4 mg/g for PAN and PEI-modified nanofibres, respectively, were recorded. The PEI-functionalised nanofibres showed a high potential as a pretreatment step to be integrated to MD process. Ultimately an integrated water desalination system was developed. This involved a pretreatment filter (pore size ~100 μm) containing PEI-functionalised PAN nanofibre materials to reduce particulates and large molecules of dissolved organic/inorganic compounds from the water to be treated. In this research, it was observed that the pre-treatment step was not sufficient in removing all traces of compounds causing fouling of the superhydrophobic PDVF nanofibre membranes. As such, coating of the membranes with a thin hydrophilic layer and coupled with the filtration pretreatment step was found to provide fouling-resistance properties, high salt rejection, and low flux decays on brackish water collected at an estuary in Belgium and the Nandoni Dam in South Africa, demonstrating the potential of the MD separation process towards potable water recovery from brackish water.<br>Het onderzoek in dit proefschrift was gebaseerd op concrete waterproblemen die een landelijke gemeenschap in Zuid-Afrika (SA) ervaart. In het bijzonder werd de waterkwaliteit in het Nandoni-reservoir in het Vhembe-district in de provincie Limpopo in Zuid-Afrika onderzocht, om te bepalen of dit water geschikt is voor gebruik, na klachten van leden van de gemeenschap die dit water gebruiken als drinkwater en voor huishoudelijk gebruik. Het reservoir levert water aan 55 dorpen met ongeveer 800.000 inwoners. Bij het begin van het onderzoek was er weinig wetenschappelijke informatie over de kwaliteit van het water in het reservoir. Watermonsters van verschillende locaties in het reservoir, dat een primaire bron van drinkwater is in de regio, werden gedurende verschillende seizoenen van het jaar verzameld over een periode van 12 maanden, om de concentraties van de meest voorkomende ionen in het reservoir te bepalen. Bovendien werden de concentraties van schadelijke polycyclische aromatische koolwaterstoffen (PAK's) en fenolen gemeten. De concentraties van de ionen die bijdroegen aan het zoutgehalte van het water waren in het algemeen lager dan de drempel om het water als brak water te bestempelen (dat wil zeggen 500 – 30 000 mg/l), maar waren te hoog voor drinkwater. De concentratie van de fenolen was hoger dan de limiet voor drinkwater. Daarom bleek het water afkomstig van het Nandoni reservoir niet geschikt voor menselijke consumptie. Een beter geïntegreerd waterbeheer is dus nodig om deze bron voor drinkwater te beschermen, naast een robuuste en kosteneffectieve waterbehandeling. Deze waterbehandeling moet vooral het zoutgehalte van het water naar beneden halen, maar ook de concentraties van fenolen. In een poging om een geschikte energie-efficiënte technologie of een systeem voor de volledige verwijdering van zouten (~ontzilting) uit brak water te ontwikkelen, werden elektrisch gesponnen polyvinylideenfluoride (PVDF) nanovezelmembranen gesynthetiseerd en beoordeeld op verwijdering van zouten met behulp van Direct Contact Membraandestillatie (DCMD). De nanovezelmembranen hadden een gecombineerde hoge mechanische stabiliteit, porositeit en superhydrofobiciteit, die hielp om vervuiling (fouling) en vloeistofintrede in de poriën (wetting) te voorkomen, terwijl een hoge zoutverwijdering en hoge waterflux doorheen de membranen gehandhaafd bleven. Organische gefunctionaliseerde silica-nanodeeltjes (f-SiO2NP's) werden nadien geïncorporeerd in de PVDF nanovezelmembranen met behulp van een in-situ elektrospinning techniek om zo een nog grotere superhydrofobiciteit te bekomen. Deze gemodificeerde membranen hadden een degelijke treksterkte (Young's modulus van ~ 43 MPa) en waren zeer poreus (~ 80% porositeit, 1.24-1.41 μm poriegrootte). Het oppervlak van de membranen vertoonde inderdaad superhydrofobe eigenschappen (contacthoek met water > 150 °). De membranen ingebed met octadecyltrimethoxysilaan (ODTS) SiO2NP's waren het meest efficiënt: ze toonden een zoutretentie van> 99.9% voor NaCl, bij een waterflux van ongeveer 30.7-34.2 l/(m².h) bij 60 ° C (ten opzichte van 20°C in het permeaat), wat aangeeft dat ze in staat zijn om drinkbaar water te produceren. De superhydrofobe membranen werden nadien ook gecoat met een dunne laag bestaande uit gecarboxyleerde multiwall-carbon nanotubes (f-MWCNT's) en zilver nanodeeltjes (AgNP's), in een poging om membraanvervuiling te verminderen. De AgNP's en f-MWCNT’s hadden uniforme diameters van respectievelijk 28,24 ± 1,15 nm en 6,7 ± 2,1 nm (zoals bleek uit transmissie-elektronenmicroscopie (TEM)). De antibacteriële AgNP's ingebed in de PVDF-nanovezelmembranen remden de groei van Gram-positieve Geobacillus stearothermophilus en Staphylococcus aureus bacteriën, evenals Gram-negatieve Pseudomonas aeruginosa en Klebsiella pneumoniae bacteriën. Dit toont het potentieel van deze membranen om biofilmvorming te voorkomen. Vervuilingsproeven (in DCMD) werden uitgevoerd met behulp van runderserumalbumine (BSA), natriumalginaat, colloïdaal silica, en thermofiele bacteriën - als respectievelijk organische, anorganische en biologische vervuiling. De niet-gemodificeerde membranen werden gekenmerkt door een fluxverval, met een daling van de flux met 30% tot 90%, naast een daling van de zoutretentie met 1.4% tot 6.1%. Bij de gecoate membranen daalde de flux slechts met 10-24% en de zoutverwijdering slechts met 0.07-0.75% respectievelijk. Hoewel de initiële flux ook afnam (van 42 naar ± 16 l/(m².h)) bij het gebruik van gecoate membranen, toonde de hogere weerstand tegen vervuiling van deze gecoate membranen aan dat deze coating een geschikte oplossing zou kunnen zijn tegen vervuiling in DCMD. Bovendien kan de synthese in één stap verlopen. De grootste uitdaging zal echter zijn om MD-membranen te ontwerpen waarbij de coating de oorspronkelijke waterflux/de porositeit van de membranen niet teveel verlaagt. Daarnaast werden gemodificeerde PVDF nanovezels geproduceerd om de verwijdering van vluchtige, hydrofobe stoffen (zoals fenolen) door adsorptie aan deze vezels te verhogen. Er werden polyacrylonitril (PAN) en polyethyleen-imine (PEI) gefunctionaliseerde PAN nanovezels gesynthetiseerd, waarna deze geëvalueerd werden als adsorbens (en dus voorbehandeling voor de membraanstap) voor chloorfenol en nitrofenol. Onder geoptimaliseerde experimentele omstandigheden werden adsorptiecapaciteiten tussen respectievelijk 27.3 en 38.4 mg / g voor PAN- en PEI-gemodificeerde nanovezels gemeten. De PEI-gefunctionaliseerde nanovezels vertoonden een hoog potentieel als een voorbehandelingsstap voor de hierboven beschreven DCMD. Tenslotte werd ook een geïntegreerd waterontziltingssysteem ontwikkeld. Dit systeem bestond uit een voorbehandelingsstap met PEI-gefunctionaliseerde PAN-nanovezels (in de vorm van een membraan met poriegrootte ~100 μm), gevolgd door een gemodificeerde DCMD stap. De voorbehandeling diende om deeltjes en grote opgeloste organische verbindingen uit het te behandelen water te verwijderen voor de DCMD-stap. In dit onderzoek werd waargenomen dat de voorbehandelingsstap niet voldoende was om alle organische contaminanten te verwijderen die vervuiling veroorzaakten op de superhydrofobe PDVF nanovezelmembranen in de DCMD-stap. Toch bleek coating van de DCMD membranen met een dunne hydrofiele laag (gekoppeld aan de voorbehandelingsstap) een voldoende bescherming tegen vervuiling te bieden zodat de zoutretentie en waterflux van deze membranen hoog bleef. De combinatie van voorbehandeling – gemodificeerde DCMD werd succesvol getest op water uit de Schelde en uit het Nandoni reservoir, waarmee het potentieel van de technologie om drinkwater uit brak water te produceren werd aangetoond.<br>School of Science<br>Ph.D. (Applied Biological Science : Environmental Technology)