M.Sc. / Drinking water treatment plants in South Africa rely almost entirely on surface water sources, which are often compromised due to high return flows and indirect reuse. The typical treatment plants focus on the removal of physical and microbial contaminants which include turbidity, colour, chemical compounds and micro-organisms. A relatively new alarm to this list is natural organic matter (NOM) which has become a major concern in potable water treatment due to its recent regulation. Conventionally, the drive to remove NOM from potable water would be the desire to remove colour from public water supplies. However, more problems in drinking water treatment associated with NOM have been recently identified. These include taste and odour, its tendency to foul membranes, interference with the removal of other contaminants and its potential to contribute to corrosion and slime growth in distribution systems. Moreover, it causes high demands for coagulants and disinfectants. The NOM is also the main precursor for disinfection by-products (DBPs) formed when it interacts with disinfectants such as chlorine during water disinfection. In this study, different raw water samples, of different NOM composition were collected from selected sources across the country and assessed for the removal of dissolved organic carbon (DOC) and UV absorbance at a wavelength of 254 nm (UV 254) using enhanced coagulation (EC). The efficacy of EC, which can be employed as a practical technology in the removal of both turbidity and NOM, was evaluated in these raw water sources. Jar tests were conducted with ferric chloride as the coagulant, and specific pH values were chosen as target values guiding the different coagulant dosages for the jar tests. The pH of the low-alkalinity (<60 mg/ℓ CaCO3) raw waters were adjusted and raised by the addition of sodium carbonate. Algorithms for finding the optimum coagulant dosage for both turbidity and UV 254 removal were developed and consistently applied to all the results in independent v batch tests, in which residual amounts of UV 254, DOC and turbidity were measured. The raw water parameters and results obtained from these tests were used to develop feed-forward multiplicative models predicting the performance of EC using ferric chloride. The results showed that the raw waters chosen were, indeed, representative of the different water types present in South Africa, and that the general water characteristics were affected by seasonal variations. The EC procedure developed was able to reduce turbidity to levels low enough for removal by subsequent treatment steps in the water treatment train. The residual UV 254 values were in all cases lower than 6 m-1, which theoretically corresponds to about 3.5 mg/ℓ DOC. This was confirmed by the residual DOC values which were found to be lower than 4 mg/ℓ. Generally, the waters of South Africa were found to be amenable to coagulation. In almost all cases, the costs for EC were comparable to those for conventional coagulation, hence EC could be employed as a NOM removal strategy in the South African context.

M.Sc.

M.Ing. (Civil Engineering) / Natural organic matter (NOM) is a complex mixture of organic compounds resulting from the decay of plants and animals. When not properly removed, NOM reacts with disinfectants to form disinfection by-products, of which some are known to be carcinogenic. Regulations have become more and more stringent about the maximum level of NOM in drinking water. Different water treatment processes can be applied to remove NOM. However, because each process targets specific fractions of NOM, this results in the existence of recalcitrant NOM fractions that are not removed, for each treatment process. The main objective of the study was thus to investigate NOM removal by using three advanced water treatment processes alone and in combination. The processes used were enhanced coagulation, granular activated carbon adsorption and ion exchange resin processes. Strong and weak base ion exchange resins were used. Although NOM removal methods have been investigated intensively, little attention is given to a so-called “multi-barrier” approach of NOM removal through enhanced coagulation, granular activated carbon adsorption and ion exchange resin that could be applied in practice. In order to take the seasonal and geographical variability of NOM into account, water samples were collected at eight geographical areas over five to seven seasons from 2010 to 2013. Results showed that different treatment processes remove different NOM fractions with different efficiency. Results also confirmed that EC performs better than the adsorptive treatment processes. But the literature shows that NOM removal by EC is difficult for water with high alkalinity and low SUVA values, which is common with SA waters. The adsorptive processes used for NOM removal revealed that they are not viable options, because even low percentage of NOM removal would require high adsorbent dosages, which removes this approach as a practical option.

D.Phil. (Chemistry) / Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water-pollution control. Among the many organic pollutants are dyes and emerging pollutants such as natural organic matter (NOM). Dyes such as Eosin Yellow (EY), an anionic xanthene fluorescent dye, can originate from many sources such as textile industrial processes, paper pulp industries and agricultural processes. Most dyes are problematic because they are resistant to conventional chemical or biological water-treatment methods and therefore persist in the environment. NOM consists of a highly variable mixture of products found in water and soils. NOM is formed as a result of the decomposition of plant and animal material and is a precursor to the formation of disinfection by-products (DBP) during water disinfection. These organic compounds cause undesirable colour, taste and odour in water. NOM affects the capacity of other treatment processes to effectively remove organic micro-pollutants or inorganic species that may be present in the water. Its removal also uses up chemicals and energy and so it is expensive to treat. Titanium dioxide (TiO2) has emerged as one of the most fascinating materials in the modern era due to its semiconducting and catalytic properties. TiO2 is a large band-gap semiconductor that exists mainly in the anatase (band gap 3.2 eV) and rutile (band gap 3.0 eV) phases. Its response to UV light has led to increased interest in its application in the photocatalysis research field. It has been investigated extensively for its super hydrophilicity and use in environmental remediation and solar fuel production. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the ultimate goal of this research was to fabricate highly photoactive catalysts composed of non-metal, platinum-group metal (PGM) co-doped TiO2 and carbon nanotubes (CNTs) and to apply them for water purification using solar radiation...

Ph.D. / This study explored the possible application of a relatively new electrode called exfoliated graphite electrode (EG electrode) in the electroanalysis of organic and inorganic water pollutants. This study also explored the applicability of this electrode in the removal of heavy metal pollutants in water. The EG material was successfully prepared by intercalating bisulphate ions into graphite flakes (>300 μm) followed by thermal shock at 800°C to obtain an exfoliated graphite. After compressing the EG at high pressure, the obtained circular sheets were used to fabricate electrodes. The electrochemical profiles of EG electrode and glassy carbon electrodes (GCE) were recorded and compared using cyclic voltammetryand square wave voltammetry in the presence of various supporting electrolytes and [Fe(CN)6]3-/4-, [Ru(NH3)6]2+/3+, ferrocene redox probes. In the supporting electrolytes (KCl, H2SO4, NaOH, tetrabutylammoniumtetraflouroborate, phosphate buffers), the potential windows of EG were found, in some cases, to be about 300 mV larger than that of GCE. The diffusion coefficients (cm2s-1) of the redox probes were calculated to be 3.638 x 10-6, 1.213 x 10-6 and 4.411 x 10-6 for [Fe(CN)6]3-/4-, [Ru(NH3)6]2+/3+ and ferrocene, respectively. These values are comparable to those obtained from GCE. Furthermore, EG was modified with various nanomaterials such as poly (propylene imine) dendrimer (PPI), gold nanoparticles, silver nanoparticles, dendrimer–gold nanoparticles composite, cobalt oxide and bismuth. The morphologies of the modified electrodes were studied using scanning electron microscopy and their electrochemical reactivities in the three redox probes were investigated. The current and the reversibility of redox probes were enhanced in the presence of modifiers in different degrees with dendrimer and gold nanoparticles having a favourable edge. The electrochemical determination of o-nitrophenol by square wave voltammetry using a nanocomposite of generation 2 poly(propyleneimine) dendrimer and gold nanoparticles modified GCEand EG electrode were compared. A characteristic reduction peak between -600 mV and -700 mV for o-nitrophenol was observed with enhanced current on both GCE and EG modified electrodes.

D.Phil. (Chemistry) / This thesis describes the improvement of sorption capacity and efficiency of synthetic and biological adsorbents towards selected pollutants by introducing functional groups on the sorbents. Functionalization was achieved by chemically modifying the binding sites of the studied adsorbents. The sorbent materials considered were chemical resins (Amberlite XAD 1180) and biomass (maize tassels and seaweed). The adsorbents were modified with ethylenediamine in order to improve their capacity for extraction of heavy metals, namely lead, copper and cadmium from water. For the removal of phenols from water, maize tassels was modified with polydiallyldimethylammonium chloride (polyDADMAC). The main focus of the proposed study was to formulate cheap and sustainable ways of purifying contaminated water by exploiting the pollutants’ affinity towards the adsorbents. Parameters such as contact time, sorbent quantities, analyte concentrations, desorption solution (for stripping adsorbed metals for sorbent reuse) and pH were optimized. Different isotherms were applied on the experimental data to establish sorption mechanisms and energies involved during the sorption process. The Langmuir isotherm was used to test for monolayer sorption while the Freundlich model tested multilayer adsorption on heterogeneous surfaces...

M.Sc. / Pollutants present in minute concentrations in aquatic environments and which possess long residence times may be accumulated by aquatic organism such as fish, resulting in adverse affects. Bioaccumulation and biomarker responses are often used to qualify and quantify pollutant exposure and effect, and for this reason form a major part of many environmental assessments. To interpret bioaccumulation and biomarker responses the physico-chemical parameters of the environment should be known. This study aimed to spatially and temporally assess the environmental partitioning of heavy metals in three South African freshwater systems, namely the Pongolapoort Dam, Olifants and Luvuvhu Rivers, and to relate these concentrations to bioaccumulation and biomarker responses in tigerfish, Hydrocynus vittatus. This is because there is relatively little known about the bioaccumulation potential and stress responses of tigerfish to pollutants and they have recently become listed as a protected species. Result from this study showed that there were few differences between seasons in terms of metal bioaccumulation in the Pongolapoort Dam with the exception of Se, Zn and Fe. Selenium and Fe concentrations were linked to concentrations found in the environment, whereas Zn was attributed to a disruption in homeostasis within the fish. Increases in MT were found during the winter months and were attributed to increased metal concentrations at this time, namely Zn and Se, whereas decreases in CEA and PC were observed at this time and were linked to depleted energy reserves, stress and a reduction in the presence of pesticides as a result of decreased runoff during the winter months. It was found in the Olifants and Luvuvhu Rivers that there were no distinct decreases in metal concentrations as the rivers flowed through the KNP, and processes such as rainfall, remobilization of sediments, distance of the study area from the source and geology played a great role in the distribution of metals. Metal concentrations in the Olifants River water, sediment and fish were, for the most part, found to be lower than previous studies, possibly due to improvement in management strategies or increased buffering of this river. Only Al and As were significantly higher in tigerfish from the Olifants River, and this was reflected in high MT concentrations. It was suggested that tigerfish from the Olifants River have developed effective mechanisms for the excretion and detoxification of heavy metals that they are exposed to as a result of extended exposure. Concentrations of AChE were also significantly inhibited in tigerfish from the Olifants River which is indicative of greater concentrations of organophosphates and carbamate pesticides than the other sites. Tigerfish from the Pongolapoort Dam had signifcantly higher levels of MT and significantly inhibited concentrations of AChE in comparison to tigerfish from the Luvuvhu River. The tigerfish from the Luvuvhu River had significantly higher concentrations of Se in muscle tissue. Tigerfish from the Luvuvhu River, also experienced stress as a result of pollution as was apparent from significantly depleted energy reserves in comparison to the other sites under study, and higher concentrations of PC and CYP1A which are typical biomarkers responding to halogenated and aromatic pesticides, such as deltamethrin and endosulfan. It was recommended that further studies be done to assess the presence of pesticides within these systems to determine the contribution of these pollutants to the state of tigerfish

Ph.D. / An investigation was made into the physical, chemical and biological conditions of the Elsburgspruit to establish the extent and quality of pollution over a period of two and a half years from January 1987 June 1989. The results obtained during the investigation can be summarised as follows. Serious faecal pollution as reflected by faecal coliforms, faecal streptococci and coliphage organisms occurs over a large stretch of the river, posing a health risk to the people using the recreational area at' Vosloosrust, downstream from the Elsburgspruit near Kathlehong. The occurrence and large numbers of coliphage organisms occurring at certain sampling localities suggest the possible presence of the pathogenic viruses Salmonella, Pseudomonas and Candida. Effluent and seepage waters from mining areas, discharged into the Elsburgspruit were found to be low in pH and high in concentrations of certain metals such as zinc, manganese and iron. Due to the large volume of this particular effluent, the effects thereof on the water quality and fauna of the streams are felt over a distance of more than seven kilometres. As a result, the recovery of the stream from pollution is severely retarded. A number of species of the numerically dominant aquatic and semi-aquatic macrophytes which occurred within the flood-plain of the Elsburgspruit, were found to be able to absorb and to accumulate substantial concentrations of the various heavy metals, directly from the water, or from adjacent moist soils. It was also found that the Spanish reed, Arundo donax, which covers a large area of the wetland region of the Elsburgspruit in its lower section, absorbed and accumulated substantial quantities of the different heavy metals from the water of the stream. A comparison was made of the extent to which metals are deposited into the sediment under both acidic and alkaline conditions...

No description available.

[EN] The contamination of water resources with many industrial, agricultural and other chemicals is one of the key environmental problems that humanity is facing nowadays. Despite the fact that they are usually present at very low concentration, they possess a significant risk to aquatic and human life. To address this issue many national and international institutions set different regulations to monitor and control the water quality. Currently, the monitoring of compounds included in official watch lists is conducted by chromatographic and mass spectroscopic methods. These techniques are approved as "gold standards" for analytical quantitation of organic residues in water. Although they are sensitive and reproducible, cannot be used on-site. The need of sampling and centralized laboratory measurements makes not only the overall cost high but lowering the efficiency of the analysis. Therefore, there is an urgent need to develop suitable field methods to facilitate the in situ measurements at a low cost. Biosensors are therefore an alternative technology that can provide sensitive results in a fast and affordable way. This thesis has focused on the development of a biosensor based on immunoassays and compact disk technology, for the multiplex detection of priority water contaminants. As the methods based on the immunorecognition events are challenging in terms of the selectivity and sensitivity, the major part of the thesis was the selection of the immunoreagents, assay form and procedure. For the detection part, gold nanostructures were selected as sensitive tags for signal enhancement. Therefore, different nanoparticles were studied in order to select the optimal size in terms of the signal enhancement, sensitivity and antibody amount used. Also, the assays performances with signal enhancement and without any amplification were evaluated. The best immunoassay was selected for developing the multiplexed assay. Furthermore, an approach to improve the readout sensitivity of microimmunoassays based on used of gold nanoparticles as both capture and detection species was demonstrated. The method is based on the performance of the immunorecognition event in a homogeneous mode and detection part in the heterogeneous format. Finally, representative water samples were analysed to confirm the applicability of the multi-residue assay. The analytical properties have been established for each methodology and the obtained results have been validated by comparison with reference techniques. The investigations carried out in this work, have resulted in new insights in immunoassay technique that could be useful for screening applications. / [ES] La contaminación de aguas superficiales causada por plaguicidas y productos industriales es actualmente, uno de los grandes problemas medioambientales. Aunque estas sustancias están presentes a niveles muy bajos, tienen efectos perjudiciales en el medio en general y especialmente en humanos. Por este motivo, diferentes instituciones han regulado los niveles de contaminantes en áreas de controlar de la calidad de las aguas, creando listas prioritarias de sustancias peligrosas y tóxicas para el medio ambiente. Actualmente, la monitorización de los contaminantes incluidos en las listas oficiales se realiza mediante técnicas cromatográficas y espectrometría. Estos métodos analíticos están aprobados como técnicas de referencia para la determinación de residuos orgánicos presentes en aguas naturales. A pesar de ser técnicas fiables, reproducibles y sensibles, los métodos cromatográficos no están exentos de inconvenientes. Este tipo de metodologías requiere una instrumentación costosa y una laboriosa preparación de muestra, que hacen que el análisis sea en general complejo. Por ello, el desarrollo de métodos analíticos alternativos que faciliten hacer medidas in-situ a bajo coste y con gran capacidad de trabajo es de gran utilidad. En este sentido, las técnicas inmunoquímicas tienen un gran potencial analítico ya que son en general sensibles y selectivas, se pueden utilizar en el lugar de la toma de muestra y tienen capacidad multianalito. Esta tesis se ha centrado en el desarrollo de un sistema biosensor, basado en la tecnología de disco compacto, para la detección multianalito de diversos contaminantes prioritarios en aguas naturales. Las limitaciones más críticas para el desarrollo de un biosensor multianalito mediante métodos inmunoquímicos son los relacionados con su sensibilidad y selectividad. Por lo tanto, una parte importante de la tesis se ha centrado en la selección de inmunoreactivos, formato y optimización de diferentes parámetros claves del ensayo. Una estrategia utilizada para aumentar la sensibilidad de los ensayos ha consistido en marcar la inmunoreacción con nanopartículas de oro. Para ello, se ha estudiado diferentes tipos (esféricas y cilíndricas) de distinto tamaño y se han comparado sus prestaciones analíticas (relación señal ruido, sensibilidad etc.) También, se han desarrollado inmunoensayos cuantitativos sin necesidad de amplificación de la señal. Por otro lado, se ha desarrollado una aproximación que hemos denominado "inmunocaptura" basada en el uso de nanopartículas de oro como especie de captura de analitos en disolución y que actúa como marcador de la inmunointeracción que tiene lugar en la fase sólida. Finalmente, se han analizado muestras de agua naturales dopadas con distintos niveles de los analitos objeto de estudio para evaluar la utilidad de las metodologías desarrolladas como herramienta de screening masivo en el área medioambiental. Los resultados obtenidos han sido comparados con los obtenidos mediante las técnicas de referencia. Las investigaciones realizadas han permitido desarrollar nuevos formatos de ensayo y conocimientos inmunoquímicos aplicados a la tecnología de disco compacto, aportando nuevas herramientas de screening que permiten la determinación simultánea de contaminantes en aguas naturales por debajo de las concentraciones establecidas en la normativa europea de calidad de agua. / [CA] La contaminació d'aigües superficials causada principalment per plaguicides i altres productes industrials és un dels grans problemes mediambientals actuals. Malgrat que aquestes substàncies estan presents en nivells molt baixos, tenen efectes perjudicials en humans i animals. Per aquest motiu, diferents institucions estatals han regulat els nivells de contaminants en àrees de control de la qualitat de l'aigua, creant llistes prioritàries de substàncies perilloses i tòxiques per al medi ambient. Actualment, la monitorització dels contaminants inclosos en les llistes oficials es realitza mitjançant tècniques cromatogràfiques i d'espectroscòpia de masses. Aquests mètodes analítics estan aprovats com a tècniques de referència per a la determinació de residus orgànics presents en aigües naturals. Malgrat ser tècniques fiables, reproduïbles i sensibles, els mètodes cromatogràfics no estan exempts d'inconvenients. Aquest tipus de metodologies requereix una instrumentació costosa i una laboriosa preparació de mostres que fan que l'anàlisi sigui, en general, complex. Per això, el desenvolupament de mètodes analítics alternatius que facilitin la possibilitat de fer mesures in-situ a baix cost i amb gran capacitat analítica és de gran utilitat. En aquest sentit, les tècniques inmunoquímiques tenen un gran potencial analític ja que són, en general, sensibles i selectives, es poden utilitzar en el lloc de presa de la mostra i tenen capacitat multianalit. Aquesta tesi s'ha centrat en el desenvolupament d'un sistema biosensor, basat en la tecnologia de disc compacte, per a la detecció multianalit de diversos contaminants prioritaris en aigües naturals. Les limitacions més crítiques per al desenvolupament d'un biosensor multianalit mitjançant mètodes inmunoquímics són sensibilitat i selectivitat. Per tant, una part important de la tesi es va centrar en la selecció de inmunoreactius, format i optimització de diferents paràmetres clau de l'assaig. La detecció es va dur a terme mitjançant l'ús de nanopartícules d'or com a marcadors de la inmunointeracció i amplificació de la senyal analítica. S'han estudiat diferents estructures d'or (esferes i cilindres) de diferents tamanys, i s'han comparat les seves prestacions analítiques (relació senyal-soroll, sensibilitat, etc.). També s'han desenvolupat immunoassaigs quantitatius sense necessitat d'amplificació del senyal. Per altra banda, s'ha desenvolupat una aproximació que hem denominat "inmunocaptura", basada en l'ús de nanopartícules d'or com a espècie de captura d'analits en dissolució i que actua com a marcador de la inmunointeracció que té lloc en la fase sòlida. Finalment, s'han analitzat mostres d'aigües naturals dopades amb diferents nivells dels analits objecte d'estudi per avaluar la utilitat de les metodologies desenvolupades com a eina de "screening" massiu en l'àrea mediambiental. Els resultats obtinguts han sigut avaluats per comparació amb els obtinguts mitjançant tècniques de referència. Les investigacions realitzades han permès desenvolupar nous formats d'assaig i coneixements inmunoquímics aplicats a la tecnologia de disc compacte, aportant noves eines de "screening" que permetin la determinació de contaminants en aigües naturals per sota dels límits de concentració establerts per les normes internacionals de la qualitat de l'aigua. / Dobosz, PD. (2017). Screening methodologies for the determination of water contaminant residues by compact disk technology [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/79548 / TESIS