Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Desalination, by means of reverse osmosis (RO), in combination with other processes, can produce potable water at high recoveries. Antiscalants are generally used to reduce scaling on equipment surfaces and to improve water recovery during RO by slowing down the precipitation kinetics of sparingly soluble salts in the RO feed, thereby allowing concentration levels in the RO brine at several times the solubility limit of these salts. In addition, a fraction of the concentrate may be recycled back to the feed of the RO-membrane to improve the overall recovery, but only after the super saturated salts in the concentrate have been precipitated. The inhibitory character of the antiscalants (which are rejected into the concentrate stream) complicates the removal of salt from the concentrate and therefore prohibits such recycling. The focus of this study is aimed at properly understanding some of the parameters that influence the functionality or effectiveness of antiscalants used in high sulphate waters, with the purpose to override the effect of the antiscalant in the concentrate stream and force precipitation of the super saturated salts in solution. A batch crystallization technique, which considers the precipitation of calcium sulphate dehydrate (gypsum) from a solution of changing super saturation, was used to perform precipitation tests 1) on synthetically prepared solutions, super saturated with gypsum and 2) industrial concentrate, rich in sulphate (produced by concentrating acid mine drainage (AMD) by means of a lab scale RO unit). During batch crystallization, the precipitation process was observed by means of monitoring the depletion of calcium, using a calcium selective electrode (ISE). Deductions concerning the kinetics of precipitation were made from observing two kinetic variables (response variables) e.g. the induction time and the growth rate (tC80 – inferential variable). Two antiscalants have been evaluated in this study: a phosphonate based antiscalant (HYDREX) and a polyacrylate antiscalant (BULAB), at concentrations of 4 mg/l and 12 mg/l. The objective was to chemically and physically manipulate the antiscalant effectiveness, override its effect and force precipitation of gypsum by means of changing parameters in the system, such as the temperature (15°C- 25°C), pH (4-10), ferric chloride concentration (2-10 mg/l) or seeding the solution with gypsum seed at a concentration of 0-2000 mg/l. In addition, lime and a combination of gypsum and lime were also used for seeding at concentrations of 2000 mg/l. The induction time, prior to precipitation, was found to be most strongly affected by the change in seed concentration and pH at a given antiscalant concentration. Seed at a concentration of 2000 mg/l was sufficient in most cases to immediately override the effect of HYDREX and BULAB (at 4-12 mg/l) and produce ~ 0 minutes induction time. A pH of 10 increased the adsorption capacity of HYDREX and BULAB, leading to longer induction times (exceeding 24 hours in some cases). At a pH of 4 the adsorption capacity was very low for both HYDREX and BULAB (lower) leading to shorter induction times (zero to 100 minutes). It was especially in the ‘no-seed’ cases that the effect of pH on the induction time was prominent. The rate of precipitation (crystal growth rate) was increased at a temperature of 25°C, compared to 15°C (the rate increased two fold for an increase in 10°C). The addition of lime-seed, instead of gypsum, (at 2000 mg/l) produced growth rates, two times higher compared to when gypsum was used at the same conditions. In Addition, seeding with lime produced induction times (150 minutes for HYDREX and 50 minutes for BULAB) prior to precipitation, compared to zero induction time when gypsum was used at the same conditions. It was proven that an induction time could be eliminated by adding a combination of gypsum and lime both at a concentration of 2000 mg/l. with the added benefit of the higher growth rate. An increase in the calcium concentration increased the crystal growth rate in the presence of HYDREX. The presence of a high pH, however caused the effect of calcium on the growth (in the presence of BULAB) to be overshadowed. At a higher pH the growth rate of gypsum slowed down as a result of the increase in adsorption capacity of the polymer onto the crystal surface. The interaction of the antiscalant with FeCl3 seemed to be important with regard to crystal growth. Higher ferric concentrations (10 mg/l) were sufficient to limit the inhibitory effect of 12 mg/l antiscalant (HYDREX and BULAB) on the crystal growth rate. Conversely, low ferric concentration resulted in slower growth rates in the presence of an antiscalant. The best conditions (within the scope of the current study), sufficient 1) to override the inhibitory effect of antiscalants (HYDREX and BULAB) and 2) to produce rapid precipitation of gypsum, lie in the use of seeding with gypsum and lime (2000 mg/l), adding ferric chloride (10 mg/l), lowering the pH to 4 or lower (which can only be obtained when lime is not added) and setting the solution temperature to a moderate value of 25°C or higher. These ‘best’ conditions were subsequently applied to a concentrate, produced from concentrating AMD in a RO unit, and proved to be even more successful in overriding the effect of HYDREX and BULAB than in synthetic aqueous solutions. The induction times of precipitation of AMD in all cases were ~ 0 minutes, whereas the growth rate increased threefold compared to the synthetic tests. The presence of additional foreign precipitates of aluminum, calcium and magnesium as well as an increased [SO4ª-] x [Caª+] product of 3.73 (AMD concentrate) vs. 3.46 (synthetic solutions) is thought to be responsible for the increase in precipitation kinetics when only gypsum seed was used. The addition of lime caused an increase in the precipitation potential of the brine by increasing the calcium concentration. Although the addition of lime caused an increase in the pH to 12.3 (at which point the antiscalant was most effective), the increase in pH is likely to cause an increase in the natural carbonate in the water, which would stimulate CaCO3 precipitation. The CaCO3 precipitate would be responsible for the adsorption of antiscalants, reducing their efficiency. / AFRIKAANSE OPSOMMING: Ontsouting by wyse van tru-osmose (TO), in samewerking met ander prosesse, kan help om drinkwater te lewer teen verhoogte herwinning. Tipies word antiskaalmiddels gebruik om bevuiling op die oppervlak van toerusting te verminder en terselfdetyd herwinning te verhoog deurdat dit die presipitasiekinetika van superversadigde soute in die TO voerwater vertraag. Dit lei daartoe dat water (superversadig met soute) deur die membraansisteem kan beweeg, sonder om bevuiling te veroorsaak. ‘n Breukdeel van die konsentraat kan herwin word na die TO voer om sodoende die algehele waterherwinning te verhoog. Dit kan egter eers gebeur nadat die soute in die konsentraat neergeslaan en verwyder is. Die inhirente ‘vertragingskarakter’ van antiskaalmiddels (wat ook in die konsentraat stroom beland) kompliseer die verwydering van sout vanuit die konsentraat en verhoed so herwinning. Die fokus van hierdie studie is daarop gemik om die parameters wat die funksionaliteit of effektiwiteit van antiskaalmiddels (wat in sulfaatryke waters gebruik word), beter te verstaan. Die doel is daarop gemik om die betrokke antiskaalmiddel se effek te kanselleer asook presipitasie van die superversadigde soute in oplossing aan te help. ‘n Lot (‘batch’) kristallisasietegniek wat die presipitasie van kalsiumsulfaatdehidraat (gips) beskou vanuit ‘n oplossing waar die konsentrasie verander soos presipitasie plaasvind, is gebruik om presipitasietoetse uit te voer 1) op oplossings wat sinteties versadig is met gips en 2) op sulfaatryke AMD (gekonsentreer met behulp van ‘n laboratoriumskaal TO eenheid). Die presipitasie proses is in elke geval waargeneem, deur die vermindering van die kalsium konsentrasie in die oplossing dop te hou, met die gebruik van ‘n kalsiumselektiewe elektrode. Afleidings rakende die kinetika van presipitasie is gemaak deur twee responsveranderlikes dop te hou: die induksietyd en die kristal groeitempo (tC80). Twee antiskaalmiddels by ‘n konsentrasies van 4 dpm (deetjies per miljoen) en 12 dpm is evalueer: ‘n fosfonaat (HYDREX) and poliakrilaat (BULAB). Die doel was om die antiskaalmiddel se werking chemies en fisies te manipuleer, hul werking teen te werk en presipitasie van gips te forseer. Die manipulasie het geskied deur die volgende parameters te verander: temperatuur (15°C-25°C), pH (4-10), FeCl3 (2-10 mg/l) of saad byvoeging (gips: 2000 mg/l). Kalsiumhidroksied (gebuste kalk) en ‘n kombinasie van gips en gebluste kalk is ook gebruik by konsentrasies van 2000 mg/l. Die induksietyd (by ‘n spesifieke antiskaalmiddel konsentrasie) is die sterkste beïnvloed deur ‘n verandering in saad konsentrasie en pH verandering. In die meeste gevalle was ‘n saad konsentrasie van 2000 mg/l voldoende om die induksie effek van beide HYDREX en BULAB te vernietig en nulminute induksietyd is verkry. ‘n pH van 10 het gelei tot die verhoging van die adsorpsiekapasiteit van HYDREX en BULAB wat gelei het tot langer induksietye (in sommige gevalle het dit 24 uur oorskry). By ‘n pH van 4 was die adsorpsie kapasiteit van beide antiskaalmiddels baie laag (laer vir BULAB) en induksie-tye is beperk tot 100 minute. Dit is veral wanneer geen saad toegevoeg is nie wat die effek van pH prominent was. Die tempo van presipitasie was verhoog by ‘n temperatuur van 25°C (2 keer hoër as by 15°C). Die byvoeging van gebluste kalk teen 2000 mg/l het ‘n kristal groeitempo, 2 keer hoër as in die teenwoordigheid van gips gelewer. Gebluste kalk saad byvoeging het egter gelei tot ‘n indukisetyd (150 minute vir HYDREX en 50 minute vir BULAB). Hierdie probleem is oorkom deur ‘n kombinasie van gips en gebluste kalk te gebuik teen ‘n konsentrasie van 2000 mg/l. Geen induksie tyd is waargeneem met die voordeel van ‘n hoër presipitasietempo (kristal groei). ‘n Verhoging van kalsium konsentrasie verhoog die kristal groei tempo in die teenwoordigheid van HYDREX. Nietemin, die invloed van pH oorskadu die invloed van kalsium op die groei tempo (in die teenwoordigheid van BULAB). By ‘n hoë pH word die kristal groei tempo vertraag as gevolg van die verhoging van die adsorpsiekapasiteit van die antiskaalmiddel. Die interaksie van FeCl3 met die antiskaalmiddel blyk van belang te wees. By hoë FeCl3 konsentrasies (10 dpm), is die werking van beide HYDREX en BULAB (12 dpm) beperk. Die ‘beste’ kondisies (verkry binne die konteks van hierdie studie), 1) om die vertragingseffek van HYDREX en BULAB teen te werk en 2) spoedige presipitasie van gips te bewerk, lê in die gebruik van saad (gips en gebluste kalk teen 2000 mg/l), die byvoeging van FeCl3 (10 mg/l), ‘n lae pH (4 of laer, wat natuurlik net tersprake is wanneer slegs gips as saad gebruik word aangesien geluste kalk die pH sal lig) asook ‘n relatiewe hoë temperatuur (25°C). Hierdie ‘beste’ kondisies is toegepas in AMD konsentraat om die effek van HYDREX en BULAB te vernietg en gips te presipiteer en die gevolg was dat dit selfs meer suksesvol was as in sintetiese oplossings. In elke geval is die induksietyd na nul minute toe verminder, terwyl die kristal groei tempo 3 maal verhoog het in vergelyking met die sintetiese toetse. Die teenwoordigheid van onsuiwerhede insluitende aluminium, kalsium, magnesium sowel as ‘n verhoging in die [SO4ª-]x[Caª+] produk (3.73 teenoor 3.46 vir sintetiese toetse), blyk verantwoordelik te wees vir die versnelling van die kinetika. Met die byvoeging van gebluste kalk is dit waarskynlik dat die verhoging van die pH (12.3) lei tot die verhoging van natuurlike karbonate in die water wat weer CaCO3 stimlueer. Die teenwoordigheid van CaCO3 kan verantwoordelik gehou word vir bykomende nukleasie en groei, sowel as die deaktivering van antiskaal effektiwiteit.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The moisture content of road foundations plays an important role in the durability of the pavement and the driving comfort of the road. After a pavement has been completed, gradual moisture changes occur in the foundations until equilibrium conditions can be reached, and this can have negative results if expansive clays, for example, are present in the foundation. Pre-wetting of the foundation material is seen as a method to minimilize moisture changes after construction, but if the pavement was already completed, it would be very difficult to change or alter the moisture content in the foundation, because water could then only be applied to the shoulder areas of the road and horizontal infiltration in the soil is exceptionally slow. The research which is reported in this account was undertaken to determine whether the process of electro-osmosis could be applied to accelerate water infiltration underneath covered areas, as in, for example, road foundation layers. Electro-osmosis, if found to be successful, has various advantages, of which the most important is that it can be applied without stopping the normal operations of the road. This research was carried out on a mixture of G5 material (TRH14 classification) and fine material in the form of clay with a low plasticity. Firstly, tests were performed to determine the percentage of fines required. It was found that, if too little fines were present infiltration did not occur, because moisture could flow freely through the openings between the rough aggregate. Electro-osmosis also had no effect on the rate of flow. The allocated amount of fines required to fill sufficient openings was about 30% (TRH14 classification of mixture is G10). Free flow was stopped and true infiltration occurred. Simultaneously, the rate of infiltration could be accelerated with electro-osmosis. Furthermore, a two-dimensional model of a road was constructed with electrodes placed on both sides, with the aim to determine the infiltration pattern controlled by electro-osmosis and what the effect of the initial moisture content would be on the process. Water was introduced to the one side of the model road and the wetting of the foundation was investigated. If the electric current for electro-osmosis was switched off, the infiltration was mainly vertical, as expected, but with the current switched on, there was an obvious acceleration of infiltration in the horizontal direction. As in the case of the initial tests, it was found that electro-osmosis was not very successful to accelerate horizontal infiltration at low percentages of fines. Furthermore, it was obvious that electroosmosis was also more effective if the initial moisture content of the soil was low. Low amounts of fines and high initial moisture contents had rather the electroosmotic flow of water passing underneath the road as a result instead of infiltration acceleration, with the result that the moisture content did not change much. The research thus showed that electro-osmosis is a possible manner in which moisture could be conducted into the foundation layers of roads to increase the moisture content if the appropriate amount of fines and moisture content were present in the foundation material. Further research could still be carried out and the materials in each case should be practically evaluated before this method could be continued with. / AFRIKAANSE OPSOMMING: Die voginhoud van padfondamente speel ’n belangrike rol in die duursaamheid van die plaveisel en die rygerief van die pad. Nadat ’n plaveisel voltooi is, vind daar geleidelike vogverandering in die fondamente plaas totdat ewewigstoestande bereik is, en dit kan nadelige gevolge inhou indien uitsettende kleie byvoorbeeld in die fundament teenwoordig is. Voorafbenatting van die fondamentmateriaal word gereken as ’n metode om vogveranderinge na konstruksie te minimeer, maar indien die plaveisel reeds voltooi is, is dit baie moeilik om die voginhoud in die fondament te verander of beheer omdat water dan slegs buite die skouerareas van die pad toegedien kan word en horisontale infiltrasie in grond uiters stadig is. Die navorsing waaroor hierin verslag gedoen word, is onderneem om te bepaal of die proses van elektro-osmose aangewend kan word om waterinfiltrasie onder bedekte areas, soos byvoorbeeld padfondamentlae, te versnel. Elektro-osmose, indien dit suksesvol blyk te wees, hou verskeie voordele in, waarvan die belangrikste dat dit aangewend kan word sonder om die normale bedryf van die pad te staak. Die ondersoek is uitgevoer op ’n mengsel van G5 materiaal (TRH14 klassifikasie) en fynstof in die vorm van klei met ’n lae plastisiteit. Eerstens is toetse uitgevoer om die persentasie fynstof wat nodig is, te bepaal. Daar is bevind dat, indien te min fynstof teenwoordig is, infiltrasie nie plaasvind nie aangesien water vryelik deur die openinge tussen die growwe aggregaat kan vloei. Elektro-osmose het ook geen effek op die vloeitempo gehad nie. Die aangewese hoeveelheid fynstof om genoegsame openinge te vul was ongeveer 30% (TRH14 klassifikasie van mengsel is G10). Vrye vloei is dan gestuit en ware infiltrasie het plaasgevind. Terselfdertyd kon die tempo van infiltrasie versnel word met elektro-osmose. Voorts is ’n twee-dimensionele model van ’n pad gebou, met elektrodes aan weerskante geplaas, met die doel om te bepaal of die infiltrasiepatroon deur elektro-osmose beheer kon word en wat die effek van beginvoginhoud op die proses sal wees. Water is aan een kant van die modelpad ingevoer en die benatting van die fondament bestudeer. Indien die elektriese stroom vir elektroosmose afgeskakel was, was die infiltrasie hoofsaaklik vertikaal, soos verwag, maar met die stroom aangeskakel was daar duidelike versnelling van infiltrasie in die horisontale rigting. Net soos in die geval van die aanvanklike toetse is bevind dat elektro-osmose nie baie suksesvol was om horisontale infiltrasie te versnel by lae persentasies fynstof nie. Dit het verder geblyk dat elektro-osmose ook meer effektief was indien die aanvanklike voginhoud van die grond laag was. Lae hoeveelhede fynstof en hoë aanvanklike voginhoude het eerder elektroosmotiese deurvloei van water onderdeur die pad tot gevolg gehad as infiltrasieversnelling, met die gevolg dat die voginhoud nie veel verander het nie. Die navorsing het dus getoon dat elektro-osmose ’n moontlike wyse is waarop water in die fondamentlae van paaie ingevoer kan word om die voginhoud te verhoog indien die geskikte hoeveelheid fynstof en voginhoud in die fondamentmateriaal teenwoordig is. Verdere navorsing kan nog uitgevoer word en die materiale van elke geval sal prakties evalueer moet word voordat met die metode voortgegaan kan word.

Dricksvattnet ombord på Sjöfartshögskolans fartyg Calmare Nyckel har vid tidigare provtagning visat på undermålig kvalitet. Orsaken till detta har inte undersökts innan. I detta arbete undersöks och identifieras orsaken och ett underlag för förbättring av vattenkvaliteten har tagits fram. Underlaget omfattas också av en arbetsbeskrivning för ombyggnation av färskvattensystemet och ett underlag för installation av en färskvattenproducerande anläggning. För att kontrollera vattenkvaliteten ombord genomfördes vattenprover och en undersökning av färskvattensystemet med endoskop. Resultaten analyserades sedan och ett åtgärdsprogram för förbättring av vattenkvaliteten har rekommenderats. Det nuvarande färskvattensystemet undersöktes och outnyttjade anläggningsdelar identifierades. En arbetsbeskrivning för demontering av ovan nämnda anläggningsdelar togs fram. Sjöfartshögskolan hade förvärvat en begagnad färskvattenanläggning vilken undersöktes för att avgöra om den gick att använda ombord på Calmare Nyckel. Undersökningen visade att anläggningen inte gick att använda och arbetet fortsatte med att utveckla en offert på en färskvattenproducerande anläggning som Sjöfartshögskolan beställde 2009. Ett underlag för installation av den färskvattenproducerande anläggningen togs fram och innehåller montageritningar, arbetsbeskrivningar, materialbehov, plan för monteringsarbetet och resursbehov. Metoden och åtgärdsprogrammet kan i framtida undersökningar fungera som hjälpmedel vid behov av att förbättra vattenkvaliteten ombord på liknande fartyg. / Drinking water onboard Kalmar Maritime Academy’s ship Calmare Nyckel has on previous sampling demonstrated insufficient quality. The reason for this has not been investigated before. This study examines and identifies the cause for the substandard water quality and support material for improvement has been developed. The material also contains a job description for rebuilding of the fresh water system and documents regarding installation of a freshwater generator. Water samples and examination of the fresh water system with endoscope was performed to verify the water quality onboard the ship. The results were analysed and a plan for improvement of water quality was recommended. The current fresh water system was investigated and unused components were identified. A description for removing the mentioned components was made. Kalmar Maritime Academy had acquired a used freshwater generator which was examined to determine whether it could be used onboard Calmare Nyckel. The examination revealed that it could not be used and the study proceeded to develop a quotation on a freshwater generator that Kalmar Maritime Academy had ordered in 2009. Material for the installation of the freshwater generator was created and includes assembly drawings, job descriptions, material requirements, plan for the assembly work and resource needs. The method and plan may in future investigations be used as aids to the improvement of water quality onboard similar vessels.

Partially disulfonated poly(arylene ether sulfone) (BPS) membranes have shown great promise as robust, chlorine tolerant alternatives to the current polyamide materials as reverse osmosis desalination membranes for water purification. The random copolymers are synthesized by direct polymerization of a disulfonated monomer (3,3’-disulfonato-4,4’-dichlorodiphenyl sulfone (SDCDPS)) and other monomers (4,4’-dichlorodiphenyl sulfone (DCDPS) and 4,4’-biphenol (BP)). The sulfonation of the materials adds necessary hydrophilic character and adjusting the percent sulfonation of the material changes the water and salt uptake of the material. Additionally, sulfonation causes the membranes to be charged, making them ion exchangers in which anions are partially excluded from the membrane, thus affecting the partitioning of salt in the membrane. The amount of sodium chloride present in the membrane after equilibration with external soaking solutions of varying concentrations of sodium chloride was measured by measuring the amount of individual ions, i.e., the sodium cation and chloride anion, separately. One area in which this work is unique is that it sought to measure the concentrations of the ions independently of one another. The analysis of sodium and chloride has shown the concentration of sodium in the membrane to be significantly greater than that of chloride, where the uptake of chloride is the limiting factor in the uptake of sodium chloride. The trends in the concentrations as well as in the partition coefficients of the ions are consistent with Donnan Exclusion. / text

<p>This master's theses was carried out on assignment from Stockholm Vatten AB as a part of a project developing new waste water treatment techniques. The goal of the theisis has been to evaluate an anaerobic membrane bioreactor for treatment of waste water from Hammarby Sjöstad. The bioreactor has not been heated and the main interest has been to study the gas production, power consumption and the reduction of organic matter and nutrients.</p><p>The system has been completed with a reverse osmosis unit and a total of four batch runs have been made with good results. The use of reverse osmosis allows nutrient in the waste water to be reintroduced into circulation as the reverse osmosis concentrate can be used as crop nutrient.</p><p>The membrane unit is of VSEP ("Vibratory Shear Enhanced Processing") type and an extensive membrane test has been conducted. This so called L-test helped determine the most suitable type of membrane for the system to allow a higher ±ux and thus lower power consumption. The L-test gave good results and a new membrane with a poresize diameter of 0,45 μm was used.</p><p>The organic load on the bioreactor has been more or less constant, around 0,7 kg COD/day, during the seven weeks of testing. The reduction over the entire system including reverse osmosis has been large, around 99 % regarding organic matter and phosporus and 93 % for nitrogen, making the system suitable for waste water treatment except for high power consumption, around 2 kWh/m3. The production of methanegas has worked although it has been quite low, with average values of 0,13 m3 CH4/kg reduced COD.</p> / <p>Examensarbetet är utfört på uppdrag av Stockholm Vatten AB som en del av det pilotprojekt som utvärderar nya tekniker för avloppsvattenrening för Hammarby Sjöstad. Målsättningen med studien har varit att utvärdera ett system bestående av en anaerob membranbioreaktor för behandling av avloppsvatten från Hammarby Sjöstad. Bioreaktorn har inte varit uppvärmd och det som har studerats är reningseffekten, biogasproduktionen samt energiåtgången.</p><p>Systemet har även innefattat en omvänd osmosanläggning och totalt har fyra försök med denna gjorts med goda resultat. Analyser har koncentrerats till att utvärdera reduktion av organiskt material över membranbioreaktorn och av närsalter och metaller över omvänd osmos anläggningen. Bakgrunden till att använda omvänd osmos är att öka återföringen av näringsämnen från avloppsvatten. Resultatet av försöken med omvänd osmos gav ett koncentrat med högt näringsinnehåll och låg halt av tungmetaller vilket ger möjligheten att sprida det på åkermark.</p><p>Membranenheten är av typen VSEP ("Vibratory Shear Enhanced Processing") och ett membrantest har även utfötts för att finna det membran som passar systemet bäst med avseende på flöde och energiförbrukning. Det så kallade L-testet var omfattande och gav en klar bild över vad som skulle vara det bästa membranet. Det membran som visade sig passa systemet bäst var ett membran med en porstorlek på 0,45 μm. Belastningen av organiskt material på reaktorn under försöksperiodens sju veckor har varit mer eller mindre konstant och låg, cirka 0,7 kg COD/dygn. Reduktionen över hela systemet inklusive omvänd osmosanläggningen med avseende på organiskt material och fosfor har varit mycket hög, omkring 99 %. Reduktionen av kväve var som högst 93 %. Gasproduktionen har fungerat och har i genomsnitt varit omkring 0,13 m3 CH4/kg reducerad COD.</p><p>Energiförbrukningen för systemet i motsvarande fullskala blev omkring 2 kwh/m3.</p>

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According to the Department of Water Affairs (DWAF, 2004 p.15), South Africa’s water resources are scarce and extremely limited and much of this precious resource is utilised and consumed in our industries. Treatment and re-use of effluent generated is, in some cases, preferred over use of alternate water resources (Du Plessis, 2008 p.3). The volume of effluent generated in treatment processes like ultra-filtration (UF) and reverse osmosis (RO) units is determined by the feed water quality, with high water loss through effluent generation at poor feed water quality. Current UF and RO applications require an increased UF production capacity due to the use of UF filtrate for periodic backwashing of the UF membrane units. This results in loss of water and decreases overall recovery. The need therefore exists to increase the overall recovery of product water from the raw water stream by reducing the amount of effluent generated. This would be possible to achieve by using RO brine to backwash the UF unit. The study was conducted to provide a modelling tool, assisting management to optimise the use of RO brine as backwash water on the UF system at the Medupi power station. The secondary objective of this study was the development of a modelling tool that can be used for other projects, new or existing, as a measure and indication of the usability of RO brine as backwash water on UF systems. By successfully applying this newly developed model, the viability of utilising the RO brine as backwash water for the UF was investigated. This modification would lead to utilizing smaller UF units than previously envisioned, which in turn leads to reducing capital cost with 11.07% and operating expenditure with 9.98% at the Medupi power station. This also has a positive environmental impact by reducing the amount of raw water used monthly by 10.34% (108 000 m3/month). / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2014

South Africa is on a path of dramatically increasing its energy supplying capabilties. Eskom (the main utility supplying electricity to the national grid) recently announced that future power station technologies will focus on renewable energy and nuclear power. This is done in an effort to reduce South Africa’s dependance on burning fossil-fuels and thereby decreasing CO2 emissions and other harmful gases. This, together with the fact that there are a lot of fresh water scarce areas especially along the Eastern Cape coast of South Africa, is what inspired this study. This study investigates the use of a 200 MWth High Temperature Reactor (HTR) for cogeneration purposes. Heat from the reactor is utilised for electricity generation (Rankine cycle) and process heat (desalination). Two desalination concepts were evaluated thermodynamically and economically, namely Multi-Effect Distillation (MED) and Reverse Osmosis (RO). Computer software, Engineering Equation Solver (EES), was used to simulate different cycle configurations, where the heat available in the condenser was increased successively. The coupling of the two desalination technologies with a HTR was compared and it was found that a RO plant produces nearly twice as much water while sending the same amount of electricity to the grid (compared to coupling with MED). Coupling options were investigated and each simulation model was optimised to deliver maximum output (power and water). The best configuration was found to be the coupling of a HTR with a RO plant producing 86.56 MW generator power. This is equal to 2077 MWh/day. Using 332 MWh/day for desalination through RO, delivers 73 833 m3/day fresh water and results in 1745 MWh/day sent to the grid. This scenario is the best option from a thermodynamic and economic point of view. From an investment point of view, it will produce an Internal Rate of Return (IRR) of 10.9 percent and the Net Present Value (NPV) is calculated to be R 2,486,958,689. The results and analysis for the different cycle configurations are presented in such a way that an easy comparison can be made. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011

Osmotic stress is a potent regulator of the normal function of cells that are exposed to osmotically active environments under physiologic or pathologic conditions. The ability of cells to alter gene expression and metabolic activity in response to changes in the osmotic environment provides an additional regulatory mechanism for a diverse array of tissues and organs in the human body. In addition to the activation of various osmotically- or volume-activated ion channels, osmotic stress may also act on the genome via a direct biophysical pathway. Changes in extracellular osmolality alter cell volume, and therefore, the concentration of intracellular macromolecules. In turn, intracellular macromolecule concentration is a key physical parameter affecting the spatial organization and pressurization of the nucleus. Hyper-osmotic stress shrinks the nucleus and causes it to assume a convoluted shape, whereas hypo-osmotic stress swells the nucleus to a size that is limited by stretch of the nuclear lamina and induces a smooth, round shape of the nucleus. These behaviors are consistent with a model of the nucleus as a charged core/shell structure pressurized by uneven partition of macromolecules between the nucleoplasm and the cytoplasm. These osmotically-induced alterations in the internal structure and arrangement of chromatin, as well as potential changes in the nuclear membrane and pores are hypothesized to influence gene transcription and/or nucleocytoplasmic transport. A further understanding of the biophysical and biochemical mechanisms involved in these processes would have important ramifications for a range of fields including differentiation, migration, mechanotransduction, DNA repair, and tumorigenesis. / Dissertation

Les déchets liés à l'élevage intensif ont un impact environnemental reconnu du fait de leur composition riche en en matière organique et minérale. Il apparait opportun de promouvoir des procédés de traitement permettant de maitriser l'impact environnemental de ce retour au sol, voire d'ouvrir de nouvelles valorisations au travers de la récupération d'énergie ou de l'exportation de co-produits (azotés et phosphatés notamment). Ce travail entre dans cette démarche en proposant de compléter les étapes de digestion anaérobie de ces déchets par des étapes de séparation sur membranes perm-sélectives. Les essais ont été réalisés sur unités pilotes de laboratoire en utilisant des digestats réels de diverses origines prélevés sur sites. Pour l'étape de clarification par ultrafiltration, la conduite d'une séparation en mode tangentiel est obligatoire au regard de la concentration des suspensions à traiter. La viscosité des suspensions, d'autant plus importante que la suspension est concentrée, apparait comme un paramètre déterminant pour le choix du protocole opératoire. Dans tous les cas, l'opération d'ultra-filtration (UF) permet une rétention conséquente (de 80 à 90%) de la fraction organique encore présente dans les digestats, à l'inverse, la rétention de la fraction minérale soluble est restée négligeable comme attendu. Le seuil de coupure de la membrane d'UF n'est pas apparu déterminant sur cette rétention. Malgré le mode tangentiel de séparation, l'opération de filtration induit une accumulation de composés au voisinage de la membrane qui diminue significativement la perméabilité du milieu filtrant. Cette chute de perméabilité apparaît d'autant plus importante que la suspension présente une concentration en demande chimique en oxygène (DCO) élevée. Ce critère apparaît alors comme le facteur limitant pour atteindre un facteur de concentration volumique (FCV) élevé (réduction des volumes). La surface membranaire à développer est directement liée à la perméabilité membranaire, elle-même dépendante de la concentration de la suspension à traiter donc de la nature du digestat et du FCV à atteindre. Le coût opérationnel de l'opération apparaît directement lié à l'énergie nécessaire pour assurer le mode tangentiel de filtration. Pour l'étape de concentration des sels d'intérêts, la rétention des composés minéraux solubles par osmose inverse haute pression dépasse 90% quels que soient les ions ciblés ou l'origine du digestat. A l'inverse, cette rétention est dépendante de l'ion ciblé et de l'origine du digestat pour les opérations de nano-filtration et d'osmose inverse basse pression. Dans tous les cas, la rétention de la fraction organique résiduelle est importante (>90%) permettant une décoloration du perméat très poussée (elle dépend toutefois du seuil de coupure de la membrane et du FCV choisi). La perméabilité membranaire diminue d'autant plus que la conductivité électrique (CE) de la solution à traiter est importante du fait de la pression osmotique et de l'accumulation de composés solubles au voisinage de la barrière membranaire. Cette conductivité, dépendante du digestat initial et du FCV choisi, apparaît alors comme le paramètre déterminant pour le dimensionnement de l'unité. Sur le plan énergétique, l'énergie liée à la mise sous pression des unités NF/OI est dominante par rapport à la circulation tangentielle du rétentat. Ce travail a permis de confirmer l'intérêt des séparations membranaires pour le traitement des digestats, afin d'une part, d'obtenir une eau de qualité permettant sa réutilisation ou son rejet dans le milieu naturel et d'autre part de récupérer et de concentrer des composés d'intérêt dans les différents rétentats. Ce travail a fait l'objet d'un soutien financier de l'ANR dans le cadre du programme BIOENERGIE 2010 (projet DIVA). / Intense spreading of livestock wastes are recognized to be detrimental to the environment due to their content of organic matter and mineral fraction. Then, it would appear to be necessary to promote greens treatments processes. In fact, anaerobic digestion allows the production of biogas (extremely useful source of renewable energy), whilst digestate should be a highly valuable biofertilizer This work enters in this approach by proposing to complete anaerobic digestion steps by the use of perm-selective membrane separation process. The first step is a clarification step by ultrafiltration, following by a soluble mineral concentration step by nanofiltration, low pressure and/or high pressure reverse osmosis (LPRO, HPRO). The tests were performed in a laboratory-scale pilot unit using real digestates. For clarification step, a cross-flow mode separation is obligate in view of suspended solid concentrations and viscosity which appeared as a determining factor for the choice of operative protocol. In any case, the ultra-filtration operation allows a high organic retention rate (of 80 to 90%). Conversely, soluble mineral retention remained at negligible as expected. The cut-off of ultrafiltration membrane is not a determining factor for this retention. Despite the cross-flow mode separation filtration induces a compound accumulation on the membrane which decreases significantly the permeability of filtering media. This permeability drop appears greater when suspension presents a high COD concentration. This criterion appears as a limiting factor to achieve a high volumic concentration factor (VCF). Membrane surface to develop is then directly related to the membrane permeability which depends on the digestate origin and VCF. The operational cost is linked directly to the energy required to ensure cross-flow mode. The retention of soluble mineral compounds by HPRO exceeds 90% whatever the target ions or the origine of digestate are. However, for NF and LPRO steps, this rejection depends on the target ions or the origine of digestate. In any case, organic retention is important (more than 90%) which allows significant discoloration of permeate. The, the more the electronic conductivity (EC) is, the more permeability decreases of suspension is important, due to an osmotic pressure and soluble compound accumulation on the membrane that increases with EC. This conductivity depends on initial digestate and, of course, of the chosen VCF target, which appears as decisive parameter for unit dimensioning. On the efficient energy, energy linked to separation step chosen is dominant in the absence of cross-flow mode of retentate. This work has allowed to confirm the potential interest of membrane separation to (i) obtain a final effluent: named fresh or new water and (ii) and (ii) to allow the production of liquid fertilizers.This work is financially supported by the National French Agency (Bio-Energy Program 2010, DIVA Project) and by TRIMATEC competitiveness cluster.