Thesis (DPhil)--Stellenbosch University, 2002. / 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 / 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

Thesis (MEng) -- Stellenbosch University, 2014. / 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. / 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 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 / 13% and 67&plusmn / 11% for MBS and CAS, and total nitrogen (TN) removal efficiencies were 38&plusmn / 8% and 26&plusmn / 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%.

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.

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 / 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 / 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 / alum produced higher quantities of sludge than calcium-alginate system. &ldquo / Raw water&ldquo / 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.

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 / the reason for this might be the inadequate available data on nitrification-denitrification process occurring in the system.

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 / Peroxone process&rdquo / . 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.

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 / 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.

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.