As amostras ambientais coletadas na área do Ribeirão dos Cristais, região metropolitana de São Paulo, apresentaram atividade mutagênica sistemática durante os últimos anos. De acordo com estudos já publicados em literatura, essa contaminação estava relacionada ao lançamento de efluentes líquidos de uma indústria de tingimento neste corpo d água. Essa indústria tinge principalmente nylon e poliéster, utilizando em seus processos azo corantes dispersos, entre outros. Os corantes de um produto comercial preto (BDCP), muito empregado por essa indústria, foram detectados recentemente em amostras ambientais coletadas nesse local e se mostraram pelo menos parcialmente, responsáveis pela mutagenicidade mencionada. Esses corantes foram identificados como c.I. Disperse Blue 373, C.I. Disperse Violet 93 e C.I. Disperse Orange 37. A água tratada proveniente do Ribeirão dos Cristais também mostrou atividade mutagênica e esta foi relacionada tanto à presença de nitrocompostos aromáticos, incluindo policíclicos, quanto de produtos mutagênicos secundários formados durante a desinfecção. Este trabalho teve como objetivos a caracterizaçãoquímica de amostras de efluente bruto e tratado, provenientes da indústria de tingimento, lançados no Ribeirão dos Cristais; a avaliação da presença dos corantes c.I. Disperse Blue 373, C.I. Disperse Violet 93 e c.I. Disperse Orange 37 em amostras de sedimento antes e após o lançamento; e a verificação da possível formação de compostos mutagênicos incolores, provenientes dos corantes, a partir do processo de cloração, os quais poderiam explicar a mutagenicidade da água tratada. As amostras de efluente bruto e tratado foram analisadas por Cromatografia em Camada Delgada (CCD) e os corantes do produto comercial preto (BDCP) foram detectados, dentre outros. Quando analisadas por Cromatografia em Fase Gasosa! Espectrometria de Massas (CG/EM) foram detectadas, preliminarmente, várias aminas aromáticas mutagênicas, dentre elas alguns produtos de clivagem dos corantes identificados. Os resultados indicaram que o tratamento empregado pela indústria (sistema de lodos ativados) não é eficiente na remoção desses compostos. Nas amostras de sedimento do Ribeirão dos Cristais, coletadas após o lançamento da indústria de tingimento, foram detectados por CCD o corante C.I. Disperse Blue 373 e o c.I. Disperse Orange 37, porém o corante violeta (C.I. Dispersse Violet 93) não foi detectado. A mutagenicidade das mesmas amostras foi avaliada com a linhagem YGI041 de Salmonella, com e sem S9 e a atividade mutagênica detectada pôde ser explicada pela presença dos corantes nas amostras avaliadas. Tendo em vista que nas amostras de água tratada não foram detectados corantes, porém foi observada atividade mutagênica relacionada à presença de nitrocompostos, submeteu-se uma solução do produto comercial BDCP, em concentração compatível com aquela detectada na água bruta, à cloração em condições similares àquelas realizadas pela Estação de Tratamento de Água (ETA). Após a cloração, foi verificada a formação de substâncias incolores, com atividade mutagênica e perfil cromatográfico semelhante ao apresentado por amostras de água tratada coletadas na saída da ETA. Desta forma, especula-se que as substâncias geradas possam estar relacionadas com a mutagenicidade detectada na água tratada. Os resultados obtidos neste trabalho demonstram que corantes azóicos e seus produtos relacionados são uma importante classe de contaminantes ambientais que deveriam ser melhor avaliados toxicologicamente, especialmente quanto a sua atividade genotóxica e carcinogênica tendo em vista o risco direto e indireto de exposição humana à esses compostos quando liberados para o meio ambiente. / Enviromnental samples collected at Cristais river area in the metropolitan region of São Paulo, had showed repeated mutagenic activity during the last years. According to published studies, this contamination was related to the discharge of a dye processing plant. This industry dyes mainly nylon and polyester, using azo disperse dyes, among others. Recently, the dye components of a black dye commercial product (BDCP), widely used by this industry, were detected in enviromnental samples collected in this area and were considered responsible, at least in part, for the cited mutagenicity. These dyes were identified as: C.I. Disperse Blue 373, C.I. Disperse Violet 93 and C.I. Disperse Orange 37. The drinking water from the Cristais river also showed mutagenic activity related to the presence of nitro aromatic compounds, including polycyclic ones, as well as the usual disinfection by products. The objectives of this work were: the chemical characterization of raw and treated effluent samples from the dye processing plant that discharges its effluent in Cristais river; the evaluation of the presence of C.I. Disperse Blue 373, c.I. Disperse Violet 93 and c.I. Disperse Orange 37 in sediment samples before and after the discharge; and the evaluation of the possible generation of non-colored mutagenic compounds, derived from the dyes, during the disinfection step that could explain the mutagenicity of the drinking water. The raw and treated effluent samples were analyzed using Thin Layer Chromatography (TLC) and the dye components of the BDCP were detected, among others. Several mutagenic aromatic amines, including cleavage by-products of the detected dyes, were preliminary detected using gas chromatography/ mass spectrometry (GC/MS). The results demonstrated that the treatment applied by the industry (activated sludge) was not efficient in the removal of theses compounds. In the Cristais river sediment samples collected downstream the dye processing plant discharge, we detected the dyes C.I. Disperse Blue 373 and C.I. Disperse Orange 37 using TLC, however, the violet component (C.I. Disperse Violet 93) was not detected. The mutagenicity of these samples were evaluated using the strain YG1041 of Salmonella, in the presence and absence of S9 and the mutagenic activity observed could be explained by the presence of the dyes in the samples. Taking into account that dyes were not detected in drinking water samples, but the samples showed mutagenicity related to the presence of nitrocompounds, a solution of the commercial product (BDCP), at similar concentration found in raw water, was chlorinated using the Drinking Water Treatment Plant (DWTP) conditions. After the chlorination, the formation of non-colored substances was verified, and these compounds showed mutagenic and chromatographic profiles similar to the drinking water collected at DWTP. In this sense, we suggest that the generated substances could be related to the mutagenic activity previously detected in the drinking water. The results obtained in this study demonstrated that azo dyes and related compounds are an important class of environmental contaminants that should be better evaluated in relation of its toxicity, mainly in relation to their genotoxic and carcinogenic effects, considering the direct and indirect human exposure risk associated to these compounds once in the environrnent.

As amostras ambientais coletadas na área do Ribeirão dos Cristais, região metropolitana de São Paulo, apresentaram atividade mutagênica sistemática durante os últimos anos. De acordo com estudos já publicados em literatura, essa contaminação estava relacionada ao lançamento de efluentes líquidos de uma indústria de tingimento neste corpo d água. Essa indústria tinge principalmente nylon e poliéster, utilizando em seus processos azo corantes dispersos, entre outros. Os corantes de um produto comercial preto (BDCP), muito empregado por essa indústria, foram detectados recentemente em amostras ambientais coletadas nesse local e se mostraram pelo menos parcialmente, responsáveis pela mutagenicidade mencionada. Esses corantes foram identificados como c.I. Disperse Blue 373, C.I. Disperse Violet 93 e C.I. Disperse Orange 37. A água tratada proveniente do Ribeirão dos Cristais também mostrou atividade mutagênica e esta foi relacionada tanto à presença de nitrocompostos aromáticos, incluindo policíclicos, quanto de produtos mutagênicos secundários formados durante a desinfecção. Este trabalho teve como objetivos a caracterizaçãoquímica de amostras de efluente bruto e tratado, provenientes da indústria de tingimento, lançados no Ribeirão dos Cristais; a avaliação da presença dos corantes c.I. Disperse Blue 373, C.I. Disperse Violet 93 e c.I. Disperse Orange 37 em amostras de sedimento antes e após o lançamento; e a verificação da possível formação de compostos mutagênicos incolores, provenientes dos corantes, a partir do processo de cloração, os quais poderiam explicar a mutagenicidade da água tratada. As amostras de efluente bruto e tratado foram analisadas por Cromatografia em Camada Delgada (CCD) e os corantes do produto comercial preto (BDCP) foram detectados, dentre outros. Quando analisadas por Cromatografia em Fase Gasosa! Espectrometria de Massas (CG/EM) foram detectadas, preliminarmente, várias aminas aromáticas mutagênicas, dentre elas alguns produtos de clivagem dos corantes identificados. Os resultados indicaram que o tratamento empregado pela indústria (sistema de lodos ativados) não é eficiente na remoção desses compostos. Nas amostras de sedimento do Ribeirão dos Cristais, coletadas após o lançamento da indústria de tingimento, foram detectados por CCD o corante C.I. Disperse Blue 373 e o c.I. Disperse Orange 37, porém o corante violeta (C.I. Dispersse Violet 93) não foi detectado. A mutagenicidade das mesmas amostras foi avaliada com a linhagem YGI041 de Salmonella, com e sem S9 e a atividade mutagênica detectada pôde ser explicada pela presença dos corantes nas amostras avaliadas. Tendo em vista que nas amostras de água tratada não foram detectados corantes, porém foi observada atividade mutagênica relacionada à presença de nitrocompostos, submeteu-se uma solução do produto comercial BDCP, em concentração compatível com aquela detectada na água bruta, à cloração em condições similares àquelas realizadas pela Estação de Tratamento de Água (ETA). Após a cloração, foi verificada a formação de substâncias incolores, com atividade mutagênica e perfil cromatográfico semelhante ao apresentado por amostras de água tratada coletadas na saída da ETA. Desta forma, especula-se que as substâncias geradas possam estar relacionadas com a mutagenicidade detectada na água tratada. Os resultados obtidos neste trabalho demonstram que corantes azóicos e seus produtos relacionados são uma importante classe de contaminantes ambientais que deveriam ser melhor avaliados toxicologicamente, especialmente quanto a sua atividade genotóxica e carcinogênica tendo em vista o risco direto e indireto de exposição humana à esses compostos quando liberados para o meio ambiente. / Enviromnental samples collected at Cristais river area in the metropolitan region of São Paulo, had showed repeated mutagenic activity during the last years. According to published studies, this contamination was related to the discharge of a dye processing plant. This industry dyes mainly nylon and polyester, using azo disperse dyes, among others. Recently, the dye components of a black dye commercial product (BDCP), widely used by this industry, were detected in enviromnental samples collected in this area and were considered responsible, at least in part, for the cited mutagenicity. These dyes were identified as: C.I. Disperse Blue 373, C.I. Disperse Violet 93 and C.I. Disperse Orange 37. The drinking water from the Cristais river also showed mutagenic activity related to the presence of nitro aromatic compounds, including polycyclic ones, as well as the usual disinfection by products. The objectives of this work were: the chemical characterization of raw and treated effluent samples from the dye processing plant that discharges its effluent in Cristais river; the evaluation of the presence of C.I. Disperse Blue 373, c.I. Disperse Violet 93 and c.I. Disperse Orange 37 in sediment samples before and after the discharge; and the evaluation of the possible generation of non-colored mutagenic compounds, derived from the dyes, during the disinfection step that could explain the mutagenicity of the drinking water. The raw and treated effluent samples were analyzed using Thin Layer Chromatography (TLC) and the dye components of the BDCP were detected, among others. Several mutagenic aromatic amines, including cleavage by-products of the detected dyes, were preliminary detected using gas chromatography/ mass spectrometry (GC/MS). The results demonstrated that the treatment applied by the industry (activated sludge) was not efficient in the removal of theses compounds. In the Cristais river sediment samples collected downstream the dye processing plant discharge, we detected the dyes C.I. Disperse Blue 373 and C.I. Disperse Orange 37 using TLC, however, the violet component (C.I. Disperse Violet 93) was not detected. The mutagenicity of these samples were evaluated using the strain YG1041 of Salmonella, in the presence and absence of S9 and the mutagenic activity observed could be explained by the presence of the dyes in the samples. Taking into account that dyes were not detected in drinking water samples, but the samples showed mutagenicity related to the presence of nitrocompounds, a solution of the commercial product (BDCP), at similar concentration found in raw water, was chlorinated using the Drinking Water Treatment Plant (DWTP) conditions. After the chlorination, the formation of non-colored substances was verified, and these compounds showed mutagenic and chromatographic profiles similar to the drinking water collected at DWTP. In this sense, we suggest that the generated substances could be related to the mutagenic activity previously detected in the drinking water. The results obtained in this study demonstrated that azo dyes and related compounds are an important class of environmental contaminants that should be better evaluated in relation of its toxicity, mainly in relation to their genotoxic and carcinogenic effects, considering the direct and indirect human exposure risk associated to these compounds once in the environrnent.

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L'objectif de ce travail de thèse est la compréhension de l'impact des propriétés acido-basiques des supports oxydes sur l'interaction métal-support ainsi que les effets du milieu réactionnel sur les propriétés structurales, électroniques, thermodynamique et réactives des catalyseurs métalliques hyper-dispersés. Le catalyseur modèle choisi est un agrégat monométallique de platine déposé sur alumine qui est la référence des études fondamentales pour permettre des progrès dans la compréhension de ce système complexe. La mise en œuvre de calculs dans le formalisme de la théorie de la fonctionnelle de la densité, réalisés à partir de modèles moléculaires périodiques, a permis de déterminer l'état de surface du catalyseur pour des conditions de température et de pression représentatifs de l'expérience. L'influence de la taille des particules conjointement à la présence de chlore sur la stabilité thermodynamique des agrégats de Pt supportés sur alumine-γ a démontré une stabilisation significative des agrégats Pt3 lors de la migration d'espèces de surface (H, OH et Cl) sur la particule. La reconstruction d'une morphologie biplanaire (la plus stable en absence d'hydrogène) vers une morphologie cuboctaédrique pour les forts taux de recouvrement en hydrogène sur les particules de Pt supportées a été démontrée et permet d'expliquer plusieurs observations expérimentales encore mal comprises. L'impact du milieu réactionnel sur la rupture C-C et C-H à partir de l'éthane sur l'agrégat Pt13 supporté sur alumine- γ a été démontré. Les résultats obtenus permettent de mieux comprendre l'importance des conditions de température et de pression du milieu réactionnel (notamment du rapport P(H2)/P(C2H6)) sur la stabilité des intermédiaires réactionnels. Ces résultats sont en accord avec les observations expérimentales et permettent de mettre en évidence que l'optimum de pression en hydrogène est relativement élevé dans le cas des réactions de reforming catalysées par du Pt seul. / The aim of this work is the understanding of the impact of acido-basic properties of oxide supports on the metal-support interaction as well as on the effects of reactive conditions on the structural, electronic, thermodynamic and reactive properties of hyper-dispersed metallic catalysts. The chosen model catalyst is a monometallic platinum cluster supported on alumina which is the reference of fundamental studies to improve the understanding of this complex system. DFT calculations were performed from periodic models to determine the surface state of the catalyst under representative experimental temperature and pressure. The influence of nano-clusters' size combined with the presence of chlorine on the thermodynamic stability of supported Pt clusters on γ-alumina demonstrated a significant stabilization of Pt3 clusters with the migration of surface species (H, OH and Cl) on the particle. The morphology reconstruction from biplanar (the most stable in absence of hydrogen) to a cuboctahedral morphology for the high hydrogen coverages on the supported Pt13 cluster is demonstrated and explains several experimental observations still controversial. The impact of the reactive conditions on the C-C and C-H bond scission from ethane on the Pt13 cluster supported on γ-alumina was demonstrated. Results helps to better understand the importance of temperature and pressure conditions in the reactive medium (notably the P(H2)/P(C2H6) ratio) on the stability of reactive intermediates. These results are in agreement with experimental observations and highlight that the optimum of hydrogen pressure is relatively high in the case of catalytic reforming reactions catalyzed by Pt only.

>Magister Scientiae - MSc / To address the urgent need for safe potable water in South Africa’s rural areas, sustainable systems for water disinfection at the village-scale of operation are required.In this thesis, the development of a small-scale water chlorination system that runs on salt and solar panels is described. The system combines a membrane-based hypochlorite generator, or “membrane electrolyser”, with an automated hypochlorite dosing system.The system was designed to (i) coordinate hypochlorite production and dosing automatically in a flow-through system, and (ii) fit inline with low pressure pipelines from overhead storage tanks or raised water sources. Low cost materials were used for construction, and water-powered mechanisms were devised to control both brine supply to the electrolyser and regulation of water flow. The capacity of the system was based on the maximum daily output of the electrolyser at ~20 g of sodium hypochlorite. This was sufficient chlorinate up to 10 kL of water per day using less than 80 g of salt and less than 0.1 kW.h of electricity. The cost of the system was estimated at ~R10 000 and therefore potentially affordable for communities up to 100 people, e.g. small farms and villages.Testing of the system was carried out at a farm site in Worcester (Western Cape) using remote monitoring of current levels in the electrolyser. Operation of the system over a two month test period, dosing at ~4 mg/L, produced consistent chlorination measured as(FAC). Community participation in maintenance of the brine supply was managed and chlorinated water was made available to the community after a brief social survey was conducted. Community awareness of chlorination was minimal. No significant history of diarrhoea was reported. However, the community regularly boiled their tap water in response to turbidity increase in summer.The system was affected by turbidity increase in the local water, which caused a drop in electrolyser current and chlorine production due to particle blockage of the membrane in the electrolyser. However, turbidity at acceptable levels for chlorination was found to have no detrimental effect on the system’s performance. The system showed promise for rural implementation providing low turbidity was maintained. Therefore,groundwater sites, and surface waters with appropriate clarification systems are recommended for the system’s installation. Further testing of the system will be required to establish its long term viability in the hands of a rural community.

No description available.

No description available.

The freshwater dinoflagellate species, Ceratium hirundinella (C. hirundinella) possesses unique characteristics, such as a thecal-plate cell covering of cellulose, spines and flagella. Unlike most other algae and cyanobacteria, C. hirundinella cells are relatively large in size (up to 450 μm in length and 50 μm in width). These unique characteristics (e.g. cell covering and flagella) and adaptations (e.g. spines) give the dinoflagellate cells the ability to reduce their sinking rate from the euphotic zone and to migrate easily through the water column. When source water contains high concentrations of C. hirundinella cells, water treatment problems and poor aesthetic water quality can be expected. These water treatment problems may include 1) the disruption of coagulation and flocculation, 2) clogging of sand filters and 3) taste and odour problems when cells penetrate into the final water. In Chapter 9 of this study, a list of operational guidelines (including alert levels) and recommendations to assist managers and operators of plants when C. hirundinella cells are causing water treatment problems. During events of high C. hirundinella concentrations in source water, managers and operators of conventional water treatment plants need strategies to optimize coagulants and unit processes. Thus when source water contains motile nuisance algae, such as C. hirundinella, in moderate or abundant quantities, it is advisable to conduct jar stirring test experiments using both turbidity and total photosynthetic pigment (or chlorophyll-a) analyses as indicators of appropriate coagulant choice and dosages. The aims of this study are summarized as follows:  To optimize coagulants and conventional water treatment processes by implementing relevant algal removal strategies and indicators during jar stirring test experiments,  To investigate the changes in surface charge (known as zeta potential) on C. hirundinella cells before and after adding coagulants as part of the treatment processes,  To investigate the physical and chemical impacts on the morphology of C. hirundinella cells after coagulation, flocculation and sedimentation,  To identify organic compounds that may be responsible for taste and odour problems associated with C. hirundinella,  To investigate the efficiency of pre-chlorination on the removal C. hirundinella cells when dosing various coagulants, and  Give recommendations and operational guidelines relevant for a conventional water treatment plant to improve C. hirundinella removal A combined water treatment system (Phipps and Bird Model), consisting of a six paddle jar test apparatus and six sand filter columns, was used to simulate conventional processes (coagulation, flocculation, sedimentation and rapid sand filtration). Source water samples containing relatively high C. hirundinella concentrations (> 500 cell/mℓ) were collected from Benoni Lake (26º10’50.40’’S; 28º17’50.11’’ E) in plastic containers and stored as a homogenous sample in a 200 litre container under laboratory conditions (± 22 °C). Samples were collected from the source water as well as after sedimentation (from the supernatant or sludge) to determine turbidity, total photosynthetic pigment analyses (chlorophyll) and for phytoplankton analyses. Flocs (containing C. hirundinella cells) were collected from the sludge or sediment for scanning electron microscopy investigations and to perform zeta potential analyses. Concentrated C. hirundinella samples were frozen at -80 °C according to the proposed sampling protocol for organic compound analyses. Results obtained from this study proved that using the relevant indicators to determine the appropriate coagulant dosages during jar stirring tests may generally improve the removal of problem-causing algae, such as C. hirundinella cells. Improved algal removal efficiencies will subsequently ensure final water with good aesthetic quality. The surface charge (zeta potential) on C. hirundinella cells can be used to evaluate the best coagulation conditions within an operating window of -10 mV to +3 mV when dosing various coagulants. Scanning electron microscopy investigations revealed major damaging effects to C. hirundinella cells when dosing high Ca(OH)2 concentrations. However, when dosing lower Ca(OH)2 concentrations, in combination with organic polymer, better C. hirundinella cell removal efficiencies with less damaging effects to cells was observed. This study also indicated that the pre-chlorination, without causing cell lyses, can be applied to render the highly motile cells immobile which will subsequently assist the coagulation unit process. The aesthetic quality (e.g. tastes and odours) of drinking water may be influenced when C. hirundinella cells release organic material into the water as a result of cell lyses. Organic compounds, such as fatty acids and dicarboxylic acids can lead to taste and odour problems which associate with the presence of C. hirundinella. Organic compounds also serve as precursors for the formation of harmful chlorine by-products formed during chlorination. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The freshwater dinoflagellate species, Ceratium hirundinella (C. hirundinella) possesses unique characteristics, such as a thecal-plate cell covering of cellulose, spines and flagella. Unlike most other algae and cyanobacteria, C. hirundinella cells are relatively large in size (up to 450 μm in length and 50 μm in width). These unique characteristics (e.g. cell covering and flagella) and adaptations (e.g. spines) give the dinoflagellate cells the ability to reduce their sinking rate from the euphotic zone and to migrate easily through the water column. When source water contains high concentrations of C. hirundinella cells, water treatment problems and poor aesthetic water quality can be expected. These water treatment problems may include 1) the disruption of coagulation and flocculation, 2) clogging of sand filters and 3) taste and odour problems when cells penetrate into the final water. In Chapter 9 of this study, a list of operational guidelines (including alert levels) and recommendations to assist managers and operators of plants when C. hirundinella cells are causing water treatment problems. During events of high C. hirundinella concentrations in source water, managers and operators of conventional water treatment plants need strategies to optimize coagulants and unit processes. Thus when source water contains motile nuisance algae, such as C. hirundinella, in moderate or abundant quantities, it is advisable to conduct jar stirring test experiments using both turbidity and total photosynthetic pigment (or chlorophyll-a) analyses as indicators of appropriate coagulant choice and dosages. The aims of this study are summarized as follows:  To optimize coagulants and conventional water treatment processes by implementing relevant algal removal strategies and indicators during jar stirring test experiments,  To investigate the changes in surface charge (known as zeta potential) on C. hirundinella cells before and after adding coagulants as part of the treatment processes,  To investigate the physical and chemical impacts on the morphology of C. hirundinella cells after coagulation, flocculation and sedimentation,  To identify organic compounds that may be responsible for taste and odour problems associated with C. hirundinella,  To investigate the efficiency of pre-chlorination on the removal C. hirundinella cells when dosing various coagulants, and  Give recommendations and operational guidelines relevant for a conventional water treatment plant to improve C. hirundinella removal A combined water treatment system (Phipps and Bird Model), consisting of a six paddle jar test apparatus and six sand filter columns, was used to simulate conventional processes (coagulation, flocculation, sedimentation and rapid sand filtration). Source water samples containing relatively high C. hirundinella concentrations (> 500 cell/mℓ) were collected from Benoni Lake (26º10’50.40’’S; 28º17’50.11’’ E) in plastic containers and stored as a homogenous sample in a 200 litre container under laboratory conditions (± 22 °C). Samples were collected from the source water as well as after sedimentation (from the supernatant or sludge) to determine turbidity, total photosynthetic pigment analyses (chlorophyll) and for phytoplankton analyses. Flocs (containing C. hirundinella cells) were collected from the sludge or sediment for scanning electron microscopy investigations and to perform zeta potential analyses. Concentrated C. hirundinella samples were frozen at -80 °C according to the proposed sampling protocol for organic compound analyses. Results obtained from this study proved that using the relevant indicators to determine the appropriate coagulant dosages during jar stirring tests may generally improve the removal of problem-causing algae, such as C. hirundinella cells. Improved algal removal efficiencies will subsequently ensure final water with good aesthetic quality. The surface charge (zeta potential) on C. hirundinella cells can be used to evaluate the best coagulation conditions within an operating window of -10 mV to +3 mV when dosing various coagulants. Scanning electron microscopy investigations revealed major damaging effects to C. hirundinella cells when dosing high Ca(OH)2 concentrations. However, when dosing lower Ca(OH)2 concentrations, in combination with organic polymer, better C. hirundinella cell removal efficiencies with less damaging effects to cells was observed. This study also indicated that the pre-chlorination, without causing cell lyses, can be applied to render the highly motile cells immobile which will subsequently assist the coagulation unit process. The aesthetic quality (e.g. tastes and odours) of drinking water may be influenced when C. hirundinella cells release organic material into the water as a result of cell lyses. Organic compounds, such as fatty acids and dicarboxylic acids can lead to taste and odour problems which associate with the presence of C. hirundinella. Organic compounds also serve as precursors for the formation of harmful chlorine by-products formed during chlorination. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015