Kwong Tsz Yan Alex. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 77-84). / Abstracts in English and Chinese. / Abstract --- p.i / Declaration --- p.iii / Acknowledgement --- p.iv / Table of contents --- p.v / List of tables --- p.ix / List of figures --- p.x / Chapter Chapter One : --- Introduction --- p.1 / Chapter 1.1 --- The outbreak of SARS --- p.1 / Chapter 1.2 --- Characteristics of triclosan --- p.2 / Chapter 1.3 --- Environmental fate of triclosan --- p.3 / Chapter 1.4 --- Treatment methods for triclosan --- p.5 / Chapter 1.5 --- Ti02 photocatalysis --- p.6 / Chapter 1.6 --- Addition of hydrogen peroxide to the photocatalytic system --- p.9 / Chapter 1.7 --- Gas chromatography/ ion trap mass spectrometry analysis --- p.10 / Chapter 1.8 --- Scope of work --- p.11 / Chapter Chapter Two : --- Experimental --- p.13 / Chapter 2.1 --- Chemical reagents --- p.13 / Chapter 2.2 --- Photocatalytic experiments --- p.14 / Chapter 2.3 --- "Analysis of 2,8-DCDD and triclosan by GC/ITMS" --- p.15 / Chapter 2.4 --- Optimization of GC/ITMS conditions --- p.17 / Chapter 2.5 --- Analysis of other reaction intermediates by GC/MS (full scan mode) --- p.18 / Chapter 2.6 --- "Analysis of 2,4-dichlorophenol and triclosan by GC/MS (SIM mode)" --- p.20 / Chapter 2.7 --- Effect of hydrogen peroxide concentration on triclosan degradation --- p.20 / Chapter 2.8 --- Determination of total organic carbon (TOC) removal --- p.21 / Chapter 2.9 --- UV-Visible spectrometry --- p.21 / Chapter Chapter Three : --- Results --- p.22 / Chapter 3.1 --- Selection of precursor ions for GC/ITMS analysis --- p.22 / Chapter 3.2 --- Optimization of GC/ITMS conditions --- p.25 / Chapter 3.3 --- "Analysis of 2,8-DCDD and triclosan by GC/ITMS" --- p.27 / Chapter 3.4 --- "Analysis of 2,4-dichlorophenol and triclosan by GC/MS (SIM mode)" --- p.29 / Chapter 3.5 --- "Quantitative measurement of 2,8-DCDD in UV irradiated samples" --- p.31 / Chapter 3.6 --- Photocatalytic oxidation of triclosan by UV at 365nm --- p.33 / Chapter 3.7 --- TOC removal in triclosan degradation --- p.35 / Chapter 3.8 --- Identification of intermediates in photocatalytic oxidation of triclosan --- p.36 / Chapter 3.9 --- Quantitative measurement of the intermediates in photocatalytic oxidation of triclosan --- p.41 / Chapter 3.10 --- Effect of hydrogen peroxide concentration on triclosan degradation --- p.43 / Chapter 3.11 --- Effect of hydrogen peroxide concentration on TOC removal --- p.46 / Chapter 3.12 --- "Effect of hydrogen peroxide concentration on 2,4-dichlorophenol generation during triclosan degradation" --- p.47 / Chapter 3.13 --- "Photocatalytic degradation of 2,4-dichlorophenol" --- p.49 / Chapter 3.14 --- "Identification of intermediates in photocatalytic oxidation of 2,4-dichlorophenol" --- p.50 / Chapter 3.15 --- "Quantitative measurement of the intermediates in photocatalytic oxidation of 2,4-dichlorophenol" --- p.54 / Chapter Chapter Four : --- Discussions --- p.56 / Chapter 4.1 --- "Photochemical conversion of triclosan to 2,8-DCDD" --- p.56 / Chapter 4.2 --- Proposed mechanism of triclosan degradation --- p.57 / Chapter 4.3 --- "Proposed mechanism of 2,4-dichlorophenol degradation" --- p.63 / Chapter 4.4 --- TOC removal in triclosan degradation --- p.65 / Chapter 4.5 --- Effect of hydrogen peroxide concentration on photocatalytic oxidation of triclosan --- p.65 / Chapter 4.6 --- "Adverse environmental and human health effects of 2,8-DCDD" --- p.69 / Chapter 4.7 --- "Adverse environmental and human health effects of 2,4-dichlorophenol" --- p.71 / Chapter 4.8 --- "Discharge limitations for 2,4-dichlorophenol" --- p.73 / Chapter Chapter Five : --- Conclusions --- p.75 / References --- p.77

by chan Cho-Yin. / "November 2005." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 128-142). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Text in English; abstracts in English and Chinese. / by Chan Cho-Yin.

Thesis (Masters of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, [2018]. / Enhancing the efficiency of large scale photocatalytic systems has been a concern for decades. Engineering design and modelling for the successful application of laboratory-scale techniques to large scale is obligatory. Among the many fields of research in heterogeneous photocatalysis, photocatalytic reaction engineering can initiate improvement and application of conservative equations for the design and scale-up of photocatalytic reactors. Various reactor configurations were considered, and the geometry of choice was the annular shape. Theory supports the view that annular geometry, in the presence of constant transport flow properties, monochromatic light, and an incompressible flow, will allow a system to respect the law of conservation of mass. The degradation of a simulated dye, methyl orange (MO), by titanium dioxide (TiO2) with a simulated solar light (halogen lamp) in a continuous recirculating batch photoreactor (CRBPR) was studied. A response surface methodology (RSM) based on central composite design (CCD) was applied to study interaction terms and individual terms and the role they play in the photocatalytic degradation of MO. The studied terms were volume (L), TiO2 (g), 2 (mL), and initial dye concentration (mg/L), to optimize these parameters and to obtain their mutual interaction during a photocatalytic process, a 24 full-factorial CCD and RSM with an alpha set to 1.5 were employed. The polynomial models obtained for the chosen responses (% degradation and reaction rate constant, k) were shown to have a good externally studentized vs normal percentage probability fit with R2 values of 0.69 and 0.77 respectively. The two responses had a common significant interaction term which was the H2O2 initial dye concentration term. The optimum degradation that was obtained in this study was a volume of 20 L, TiO2 of 10 g, H2O2 of 200 mL and the initial dye concentration of 5 mg/L which yielded 64.6% and a reaction rate constant of 0.0020 min-1. The model of percentage degradation was validated on a yield of 50% and 80% over a series of set volumes and the model validation was successful.

Thesis (MSc. (Chemistry)) -- University of Limpopo, 2013 / Drinkable water is water that is safe enough to be consumed by humans or used with low risk of immediate or long term harm. World-wide, insufficient access to portable water and use of sources contaminated with disease vectors, pathogens, and unacceptable levels of toxins is a huge problem. The use of such water for drinking and food preparation leads to the widespread of acute and chronic illnesses. This is a major cause of death and misery in many undeveloped countries. Reduction of waterborne diseases is a major public health goal in developing countries. Nanotechnology offers the possibility of an efficient removal of pollutants and microorganisms from water. Essentially, three classes of nanoscale materials were investigated as functional materials for water purification in this study. Silver nanoparticles, carbon nanotubes and beta ()-cyclodextrin polymers were synthesised and characterised specifically for purification of water samples. β-cyclodextrin is soluble in both water and other aqueous media. In order to render cyclodextrins insoluble, they were converted into highly cross-linked polymers, by polymerisation with a bifunctional linker, hexamethylene diisocyanate. Cyclodextrins were functionalised and synthesised with either the allyl or the benzoyl group. Characterisation with fourier transform infrared (FTIR) spectrophotometer confirmed the functionalisation process. Thereafter the scanning electron microscopy (SEM) analysis confirmed the polymers’ morphology to be spongy, and capable of absorbing contaminants. Multi-walled carbon nanotubes (MWCNTs) were treated with a mixture of sulphuric and nitric acid in order to introduce the carboxyl and hydroxyl groups. These were characterised by SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR spectroscopy to confirm the functionalisation process. Silver nanoparticles were synthesised from sodium citrate and silver nitrate, using sodium dodecyl sulphate as a surfactant. Their characterisation was done by SEM, energy dispersive X ray (EDX) spectroscopy, TEM, UV/Vis spectroscopy and XRD to confirm a face centred cubic structure with an estimated crystallite size ranging from 50 to 100 nm.β-cyclodextrin polymers, functionalised multi-walled carbon nanotubes and silver nanoparticle-doped MWCNTs/cyclodextrin composites were characterised by SEM, TEM, XRD, Brunauer-Emmet-Teller (BET) and EDX. Analysis of the phenolic compound, 4-hydroxynitrobenzene in water, using these nanocomposites, demonstrated good capabilities of removing organic contaminants from water samples as indicated by their high absorption efficiencies of the contaminants. The synthesised metal-organic composites were tested for their effectiveness in removing organic contaminants as well as for eliminating Escherichia coli bacteria from water. The synthesised composites presented up to 97% absorption efficiency of organic contaminants and up to 100% inactivation of the bacteria. There was complete destruction of bacteria from the water analysed at various times and varying concentrations. After a long exposure of the nanocomposites to E. coli, pits were noticeable on the external morphology of the bacteria, thus suggesting that the nanocomposites are bactericidal. The bacterial activity increased with temperature,when studied between 10 oC and 30 oC.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2018. / Trihalomethanes (THMs) are a group of four compounds that are formed, along with other disinfected by-products. This happens when chloride or other disinfectants are used to control microbial contamination in drinking water, which then reacts with natural organic or inorganic substances in water. Trihalomethanes are better known by their common names such as chloroform, bromodichloromethane, chlorodibromomethane and bromoform. These four compounds are known to be classified as cancer group B carcinogens (shown to cause cancer in laboratory animals). Trihalomethane levels tend to increase with pH, temperature, time and the level of “precursors" present. Precursors are known to be organic substances which react with chloride to form THMs. One significant way of reducing the amount of THMs in water is to eliminate or reduce chlorination before filtrations and reduce precursors. There are guideline limits for THMs in the SANS 241:2015 document, but they are not continuously monitored and their levels in natural water are not known. The aim of this study is to develop a rapid, fast and reliable liquid-liquid microextraction technique, to determine the presence of THMs in natural water sources. This study particularly focuses on different water sources e.g. river, underground, borehole and chlorinated water. Chlorinated water is the water that has been presumably treated for bacteria and fungus growth. The results that were obtained for chlorinated water are as follow, 10.120 μg/L − 11.654 μg/L for chloroform, 2.214 μg/L - 2.666 μg/L for bromodichloromethane, 0.819 μg/L − 0.895 μg/L chlorodibromomethane and 0.103 μg/L - 0.135 μg/L for bromoform from validation data. All these THMs concentrations have been found to be below the SANS 241:2015 limits. Natural water shows a very high affinity for chloroform. This is what is expected under normal conditions as chloroform is the most abundant THM of all THMs present in natural water. The liquid-liquid microextraction technique that was optimized and used for the determination of THMs in this study is a rapid, simple and inexpensive technique that provides low limits of detection (LOD) e.g. 0.1999 μg/L chlorodibromomethane and 0.2056 μg/L bromoform and wide dynamic range (LOQ) of 0.6664 μg/L chlorodibromomethane and 0.6854 μg/L bromoform for the determination of THMs.

This study was undertaken to examine the feasibilty of a low-cost aerobic system to treat greywater for reuse.Its purpose was to provide a system that would be easy to maintain, flexible and be affordable for households and small communities in developing countries. This thesis outlines and evaluates the key biological and chemical hazards associated with greywater reuse. It discusses the performance of a variety of wastewater treatment options in use. It presents details of the components of the greywater system,namely, an aerobic grease trap and slow sand filter. Reference is made to the evaporation and treatment bed and ultraviolet disinfection components, but these are not examined. The incorporation of vermitechnology in the preliminary stages of the system for reduction of organics in greywater is reviewed. This study takes the traditional approach to water quality assessment with the measurement of physical, chemical and biological indicators. Assessment of the system involved examining the input characteristics of the greywater, monitoring the vermiculture system and sampling the liquid discharge from the aerobic grease trap and slow sand filter for analysis of the quality indicators. The results obtained under the framework of this study have provided recommendations for further use of the aerobic grease trap and slow sand filter, while propsing an approach for an appropriate long-term monitoring program. / Master of Engineering (Hons)

In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).

The purpose of the study is to find a suitable method for removal of iron and manganese considering local economic and environmental aspects. El Salvador is situated in Central America with a coast line towards the Pacific Ocean. The country borders Guatemala and Honduras. Aguilares is a town situated in the department of San Salvador, with a population of approximately 33,000 people. Currently, the population is provided with water for about two hours per day, since it is the highest capacity of the existing wells. During these two hours many households fill a small tank with water to use for the remainder of the day. The water is not safe to use for oral consumption because of the levels of bacteria and other contamination. One of the wells, situated in the community of Florída is not in use at this date because of the high levels of Iron and Manganese in the ground water which cannot be removed with the present technique.Ground water is naturally pure from bacteria at a depth of 30 m or more, however solved metals may occur and if the levels are too high the water is unsuitable to drink. The recommended maximum levels by WHO (2008) [1] for Iron and Manganese are 2 mg/l and 0.5 mg/l respectively.Literature and field studies led to the following results; Iron and manganese can be removed by precipitation followed by separation. Precipitation is achieved by aeration, oxygenation or chemical oxidation and separation is achieved by filtration or sedimentation.The different methods all have advantages and disadvantages. However the conclusion reached in this report is that aeration and filtration should be used in the case of Florída. What equipment and construction that should be used depends on economic and resource factors as well as water requirements, which is up to the council of Aguilares to deliberate.

Although the kinetics and mechanism of monochloramine decay in organic-free waters are relatively well understood, those in natural waters are not, due to exceedingly complex and poorly defined interactions of monochloramine with natural organic matter (NOM) and particles. Ozonation followed by a biologically activated carbon (BAC) filtration is a commonly practiced process option that affects the characteristics of both dissolved and particulate constituents in the water. However, how these changes in water constituents affect stability of the residual disinfectant, or monochloramine in particular, are currently unknown. Kinetics of monochloramine decay in water samples obtained before and after ozonation and BAC treatments were performed under varying operating conditions were determined by bench-scale batch experiments. Stability of monochloramine in the BAC filter effluent samples obtained at different times after backwashing was determined. It was found that in most cases monochloramine stability was greatly decreased after BAC filtration. Further filtering the BAC effluents with 1.2 and #61549;m polycarbonate membrane resulted in a substantial increase in monochloramine stability. A further increase was observed after filtering the samples using a 0.4 m membrane. This finding suggested that particulate matter generated from the filters could be the major cause of monochloramine instability. The fines from the activated carbon, possible components of the particulate matter eluting from the BAC filters, were found to exert an insignificant monochloramine demand both in the presence and absence of NOM, which is contrary to previous speculation in the literature about their demand for monochloramine. While there appears to exist a relationship between chloramine demand and HPC count of the filter effluent, more research will be needed to determine the effect of nature and type of microorganisms and their byproducts have on chloramine demand. Effect of ozonation on monochloramine stability is also under investigation using both the water sampled from full-scale plant and the synthetic water prepared with Suwannee River NOM.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy