The effects of four oxidants upon water treatment process parameters were investigated. The four oxidants under consideration were ozone, chlorine dioxide, potassium permanganate, and chlorine, Experimentation was directed towards the impact of these oxidants upon turbidity, TOC, and color removal, as well as reduced manganese oxidation. Studies were conducted with an experimental water with enhanced TOC levels. Experimentation was accomplished by a series of jar tests in which solution pH, coagulant dose, and oxidant dose were varied. Results show that, in general, oxidant application had either no impact or a negative impact upon TOC, turbidity, and color removal. Further deterioration of finished water quality was observed with increasing oxidant dose. Reduced manganese was oxidized by both potassium permanganate and chlorine dioxide. Ozone effectively oxidized reduced manganese in waters of low TOC, while chlorine was an ineffectual oxidant. Additionally, particle counts were conducted. Results show that the application of an oxidant increased the number of smaller particles present alter settling However, this immense of particles did not significantly alter settled turbidity levels. / Master of Science

In this study, the effects of organics removal efficiency, oxidant dose, and alum dose on aluminum hydroxide sludge characteristics were assessed. In order to maintain control over operating parameters, a continuous-flow laboratory-scale plant was operated in the laboratory with daily monitoring of pH, as well as influent and effluent turbidity, total organic carbon, and color. Sludge thickening and dewatering characteristics were found to worsen when increasing amounts of organic matter were incorporated into the sludge floe matrix. Sludge properties improved with increases in oxidant dose and decreases in alum dose and alum/influent turbidity ratio. Changes in coagulation mechanism from sweep to charge neutralization were hypothesized to be partially responsible for changes in sludge properties caused by changing alum dose. Improvements in thickening and dewatering characteristics were found to be heavily dependent upon increases in sludge floe density, as well as decreases in aggregate water content. / M.S.

The objectives were to evaluate permanganate and chlorine dioxide as preoxidants both when they were dosed individually and when they were dosed together, for their abilities to improve water treatment plant performance. The specific goals were to determine the effect of the preoxidant conditions on coagulant requirements, filter operation, and the removals of organic carbon, trihalomethane precursors, iron, and manganese. Also, the interaction of the preoxidants with each other when dosed together was investigated. The preoxidant conditions were evaluated on both plant- and laboratory-scale bases. The plant-scale study focused on the ability of the preoxidants to enhance those aspects of plant performance listed above. The laboratory-scale study reinforced the results of the plant-scale study and included investigations to the interactions between the two oxidants when they were dosed simultaneously. The plant-scale study yielded information regarding the extent to which these oxidants helped remove the raw water constituents listed previously. The laboratory-scale study expanded on these results and included information concerning the reasons why these oxidants performed in the manner that they did. During the period of lake stratification, when trihalomethane removal caused the greatest treatment concerns, chlorine dioxide provided the greatest removal efficiency (65 percent), but organic carbon removal suffered (45 percent), While the lake was mixing and reduced manganese posed the greatest treatment concerns, the simultaneous use of chlorine dioxide and permanganate resulted in the greatest removal efficiency (95 percent), however, objectionable tastes-and-odors were formed. In comparison, chlorine dioxide was more apt to oxidize organic compounds (including trihalomethane and taste-and-odor precursors), and permanganate was more apt to oxidize manganese(II). When the two oxidants were dosed simultaneously, chlorine dioxide had the capacity to maintain permanganate for extended periods, possibly beyond the hydraulic retention time of the plant. Methods were developed to measure 1) chlorite concentrations in the presence of oxidized forms of manganese and 2) the relative sizes and shapes of molecular—size distributions of naturally occurring organic matter. / Ph. D.

This critical overview document (COD) presents, discusses and brings together the selected portfolio of publications that the author believes make a significant contribution to the field of wastewater treatment, focusing on the removal of endocrine disrupting chemicals (EDCs) in wastewater treatment applications. The aim of the research within this COD was to investigate the fate, mechanisms and optimisation of EDCs removal in wastewater treatment applications. The key objectives were to: 1. Investigate and understand the mechanisms of removal of EDCs in wastewater and sludge treatment processes. 2. Evaluate novel methods for the removal of EDCs in water and wastewater treatment applications. 3. Establish the kinetic and thermodynamic properties of the removal processes to inform process modelling of full scale design of treatment processes.

M.Ing. / Rietvlei Dam was completed in 1933, and has been utilized as a drinking water source for the City of Pretoria since then. The original process configuration operated for almost 50 years before being upgraded in 1988. This upgrading was mainly due to the eutrophication of the impoundment. The new plant worked excellently under normal conditions but certain serious problems did occur and full production could not be maintained at all times. Activated Carbon and Ozone are two possible solutions to these problems. This study was directed at investigating the possible implementation of Preozonation, Granular Activated Carbon, and Ozone and Granular Activated Carbon in combination (case study), and it was shown that: All these processes are beneficial to the final water quality. Pre-ozonation proved to be the most cost effective process, but the least effective process in improvement of the water quality. Ozone and Granular Activated Carbon in combination proved to be the least cost effective process, but should be the most effective in improvement of the water quality. Granular Activated Carbon proved to be the optimun process with regard to cost and water quality improvement. The final recommendation is the implementation of Granular Activated Carbon with an empty bed contact time of 10 minutes.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / Horizontal subsurface flow constructed wetlands (HSSF CWs) are being considered in South Africa as an alternative waste water treatment technology which is low in capital costs and typically requires less operational infrastructure when compared to conventional treatment technologies. HSSF CWs may thus be a potential solution for solving the challenge of ensuring reliable access to clean water for rural communities whose municipalities may not be able to afford the construction of a waste water treatment plant as well as not being able to supply sufficient technical expertise for the operation thereof. Proper design of HSSF CWs requires a detailed investigation into the hydraulic behaviour as it has a direct effect on the treatment performance in these systems. In this study, three available hydraulic modelling methodologies for HSSF CWs were compared and these are the impulse, step change integral and step change derivative modelling methodologies. Hydraulic data were generated from planted and unplanted pilot scale HSSF CWs using residence time distribution (RTD) studies and the modelling results using each methodology were compared. It was found that each methodology was capable of suggesting a different hydraulic behaviour for the same system being studied and since it is not possible to evaluate an analytical answer to the problem independently it was not possible to determine which modelling methodology was the most accurate. Practical limitations of the experiments used to feed hydraulic data to the respective methodologies were also highlighted. Despite a well-designed sampling regime it was not possible to capture sufficient data surrounding the peak of the impulse response curve and may have impacted negatively on the modelling results. No such difficulties were encountered with the step change tracer experiments. The mathematical techniques which each methodology employs were also critically assessed. It was found that numerical differentiation in the step change derivative modelling approach introduced noise into the RTD curve and may have affected subsequent results. Ultimately each methodology has its own associated strengths and weaknesses and choice of methodology may be dictated by other factors such as cost to set up the hydraulic experiment as well as equipment availability. Tasks two and three of this dissertation dealt with how Biomimicry can be used as a tool to develop more sustainable HSSF CW designs and hydraulic modelling processes. In task two, hydraulic data generated from the first task were used to develop estimates of the velocity profiles inside a planted HSSF CW to identify regions most prone to clogging, a phenomenon which would be a serious concern for rural communities whose sole water treatment system would be the CW. Biomimetic design principles were combined with the modelling results to develop a modular system design allowing for sections of the CW to be removed for cleaning while still allowing for continuous treatment of the waste water. Task three explored the use of heat as a hydraulic tracer. Heat is considered more environmentally friendly when compared to chemicals as tracers as the CW can equilibrate to ambient conditions post study and the effluent does not require dedicated disposal infrastructure. Heat is non-conservative in these systems and processes such as absorption by the subsurface media and loss to the surroundings distort the hydraulic response curve from which the hydraulic behaviour cannot be directly obtained. In this study a mathematical model was developed which maps a heat tracer response curve to one which would be obtained if a conservative chemical tracer were used. It was tested by conducting a combined heat-chemical tracer study on an unplanted laboratory-scale HSSF CW and the predicted chemical response curve was compared with the actual experimental response curve. The model performed satisfactorily indicated by a 5% and 6% relative difference in the Peclet number (Pe) and mean of the RTD respectively. In each of these chapters, an abstract is provided which summarizes the main findings of the study. / MT2017

As estações de tratamento de água são indústrias nas quais a água bruta (matéria prima)deve ser transformada em água potável (produto final) através da aplicação de produtos em operações e processos. Esta indústria é uma das poucas à qual todos os seres humanos fazem uso do seu produto. Nos últimos tempos tem-se constatado aumento na demanda que, aliado a sensível piora da qualidade da água bruta, conduz a necessidade de funcionamento eficiente das estações, tanto do ponto de vista técnico quanto do econômico. Essa eficiência só será atingida através do gerenciamento adequado. Com vistas às necessidades de nosso país nesse setor, levantou-se informações sobre algumas estações de tratamento de água de abastecimento através de visitas técnicas e aplicação de questionário elaborado. Analisou-se formas de gerenciamento para estas estações de modo que o resultado possibilitasse melhoria do produto e do serviço. Cabe salientar que este trabalho não apresenta uma análise quantitativa dos custos. O desenvolvimento do trabalho permitiu algumas sugestões: de maneira geral não tem existido por parte dos sistemas gerenciadores grandes preocupações com a qualidade dos mananciais; a aquisição dos produtos químicos é realizada pelo menor preço; um número pequeno das ETAs visitas adotam critério técnico para fazer a dosagem de produtos químicos; os resíduos gerados nos decantadores e filtros são descartados nos cursos d'água próximos as ETAs; entre outras. A partir dessas conclusões pôde-se propor medidas para o melhor funcionamento destas estações.

A utilização de polímero natural como auxiliar de floculação pode ser alternativa interessante para o aumento da capacidade de estações de tratamento de água para abastecimento. O polímero natural é um produto de baixo custo, de fácil preparo e aplicação. Por ser produzido em larga escala e utilizado nos mais diversos setores da indústria, o polímero natural apresenta-se como alternativa aos polímeros sintéticos que, de maneira geral, são produtos de elevado custo e produzidos com matéria prima geralmente importada. No presente trabalho procurou-se demonstrar a eficiência dos polímeros naturais de fécula de batata e de fécula de mandioca na clarificação da água, mediante a realização de ensaios de laboratório e testes de campo - realizados na estação de tratamento ETA-2 de Valinhos (SP) - para diferentes características da água bruta. A gelatinização dos polímeros foi feita à temperatura ambiente, utilizando-se hidróxido de sódio. Para os testes na ETA-2, foram aproveitadas as instalações existentes e executadas pequenas adaptações para aplicação dos polímeros naturais. Conclui-se que, apesar de alguns ajustes que devem ser feitos, principalmente nos filtros, é possível utilizar os polímeros naturais na ETA-2 com grande probabilidade de êxito, com vistas ao aumento da capacidade de tratamento. Os resultados demonstraram que, tanto o polímero de fécula de batata como o de fécula de mandioca, foram eficientes como auxiliares de floculação na clarificação da água. / Natural polymer utilization as flocculation aid may be an effective alternative for upgrading the capacity of water treatment plants with low cost, easiers to prepare and apply. As natural polymers are large scale produced and applied in many different industrial sectors, it comes as a fesiable alternative for synthetic polymers that are generally high cost and made of imported materials. On this work it was tried to show the efficiency of natural polymers such as potato and manioc starch, for clarifying water by jar-test evaluations and field tests - carried out on water treatment plant WTP-2 of Valinhos (SP - Brazil) - for different characteristics of raw water. The polymer gelatinization was obtained by sodium hydroxide application. For the tests at WTP-2 the existing facilities were utilized and only small adaptations were made to apply natural polymers. The conclusion was, in despite of needing filters adjustments which must be made on water treatment plant for polymer application, it is possible to utilize the product with high successful probability for upgrading the capacity of water treatment plant. The results showed that even potato as well as cassava starchs were efficient on plant clarified water.

N-Nitrosodimethylamine (commonly known as NDMA) is a probable human carcinogen that has been recognized as an emerging drinking water contaminant in recent years. Previous studies have shown that certain N-containing organic compounds may form NDMA in reaction with chlorine or monochloramine and the NDMA yield is affected by the structure of the organic-N compounds, water conditions and treatment parameters. Many amine-based water treatment polymers contain organic-N functional groups and thus have been suspected as potential NDMA precursors in water treatment systems. The purpose of this research was to systematically assess the potential NDMA formation from different structural types of water treatment polymers in reactions with various oxidants and probe the possible factors that influence the NDMA formation. Robust analytical methods for detection of NDMA and the well-known NDMA precursor dimethylamine (DMA) in the reaction samples were established. The cationic polyacrylamide (cationic PAMS), aminomethylated polyacrylamide (Mannich), poly-diallyldimethylammonium chloride (polyDADMAC) and polyamine polymers were evaluated in reactions with nitrite, free chlorine, monochloramine or chlorine dioxide in aqueous solutions at circumneutral pH and room temperature conditions. This study employed high dosages of polymer and oxidant and long reaction time in order to assess the maximum potential to form NDMA. A range of operational parameters that may affect the above reactions were also evaluated.

The objective of this study was to provide a technique, based on the residence time distribution of a process, for modelling, assessing and improving flow in the processes of water and waste water treatment works. The technique should be accessible to the staff managing and operating the works. From a review of the literature, a preference was given for the experimental method used for determination of the tracer response, including choice of tracer and tracer addition and monitoring. Data analysis techniques were reviewed, and the method of time domain fitting was developed into a computer program, IMPULSE. IMPULSE provided a tool for analysis of residence time data, and removed the constraint of numerical complexity. Using the building blocks of IMPULSE, a realistic flow model can be constructed from tracer data and evaluated. IMPULSE allows a quantitative comparison of models proposed for a process, and provides the parameters of the models. These parameters quantify the non-idealities in a process. A knowledge of the non-idealities provides a basis for decision-making when modifying a process. The results of tracer experiments performed on some water and waste water treatment processes were analysed using IMPULSE. The results showed that collection of good experimental data was critical to the success of the analysis. It is proposed that a guide be produced which draws out the main points raised in the study, including collection of tracer data and use of IMPULSE. The guide should be accessible and easily understandable to the staff managing and operating water and waste water treatment works. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 1995.