Thesis (MEng) -- Stellenbosch University, 2014. / 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. / 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.

M. Tech., (Chemical Engineering, Department of Chemical Engineering, Faculty of Engineering and Technology Vaal University of Technology| / The methods used to remove potassium sulphate (K2S04) and other impurities contained within Karbochem finishing plant effluent were investigated. Reverse osmosis was explored for this application. The study was conducted in two steps. The first step focuses mainly on the effluent treatment using BW30 flatsheet as well as BW30-2540 spiral-wound reverse osmosis membranes for the rejection of potassium and sulphate ions. The membranes were supplied by Filmtec. The second step reveals the possible use of potassium sulphate obtained from the brine stream in the fertiliser and fertigation industry by a literature search. Reverse osmosis study was conducted on a laboratory scale unit using flat sheet membranes and also on a pilot plant scale using spiral wound membrane modules. The tests were conducted at a feed pressure of 20 bar(g) with the membrane rejections being 98% and 99.1% on flat sheet membrane, and 96.9% and 99.4% on spiral wound membrane for potassium and sulphates respectively. The results show that both membranes have completely desalinated. Significant reduction in the concentrations of all problematic quality parameters, especially of potassium and the sulphate ions was noted. Granular activated carbon (GAC) bed treatment was recommended for pretreatment of the effluent prior to exposure of the membrane to avoid organic fouling of the membrane. GAC treatment was tested to illustrate its effectiveness to adsorb the COD's. / NRF

No / The water permeability constant, (K-w), is one of the many important parameters that affect optimal design and operation of RO processes. In model based studies, e.g. within the RO process model, estimation of W-w is therefore important There are only two available literature correlations for calculating the dynamic K-w values. However, each of them is only applicable for a given membrane type, given feed salinity over a certain operating pressure range. In this work, we develop a time dependent neural network (NN) based correlation to predict K-w in RO desalination processes under fouling conditions. It is found that the NN based correlation can predict the K-w values very closely to those obtained by the existing correlations for the same membrane type, operating pressure range and feed salinity. However, the novel feature of this correlation is that it is able to predict K-w values for any of the two membrane types and for any operating pressure and any feed salinity within a wide range. In addition, for the first time the effect of feed salinity on Kw values at low pressure operation is reported. Whilst developing the correlation, the effect of numbers of hidden layers and neurons in each layer and the transfer functions is also investigated. (C) 2014 Elsevier B.V. All rights reserved.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2012. / 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.

M. Tech. (Biotechnology, Department of Biosciences, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Reverse osmosis (RO) membranes are widely used in water purification. The presence of biofilms in water and industrial water purification systems is prevalent. As a result, biofouling which is a biofilm problem causes adverse effects on reverse osmosis process, which include flux decline, shorter membrane lifetime and an increase in energy consumption The effect of biofouling on RO membranes was investigated at a water treatment facility at Sasol, Sasolburg by investigating the quality of water purified by the RO system and the extent of fouling that is attributed to biofouling. Chemical and microbiological data was averaged based on the results obtained from water analysis and samples from a fouled membrane. Bacteriological plate counts ranged between log 1.5 to 4 cfu/ml in water samples and log 3.9 to 4.5 cfu/cm2 on biofilm from the membrane surface. Water analysis indicated a high conductivity of 121 µS/cm in the feed and 81 ppm of the TDS, whereas in the permeate conductivity was found to be around 6 µS/cm and 3.8 ppm of the TDS. This indicated that components present in the feed were retained by the membrane. This was supported by membrane autopsy which showed that the bacteria and elements found in the feedwater were also present on the membrane surface, hence contributing to fouling. An average of 33% of cellular ATP was measured on the biofilm from membrane sample, showing that the fouling bacteria are metabolically active in situ. The results clearly indicated that an important biological activity occurred at the membrane surface.

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.

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

No description available.

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