*Electronic Theses and Dissertations (ETDs)
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Browsing *Electronic Theses and Dissertations (ETDs) by SDG "SDG-6: Clean water and sanitation"
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Item Benchmarking the technical efficiency of south African municipal water utilities: a double bootstrap DEA approach(University of the Witwatersrand, Johannesburg, 2023) Matutu, Amanda; Dikgang, JohaneEfficiency enhancement in the water sector can help to optimise the use of available resources and mitigate the impact of climate change on water resources, while promoting sustainable water usage. Ultimately, this can lead to cost savings that may be channelled into enhancing service delivery and expanding access to water. Benchmarking is considered a useful method for improving water sector efficiency. The production frontier approach is the most commonly used technique for benchmarking, which can be computed using either non-parametric techniques, including data envelopment analysis (DEA), or parametric methods, including stochastic frontier analysis (SFA). A review of the literature reveals that DEA has become the most frequently used method for efficiency analysis in the water sector. Though a predictable approach, the DEA method may be influenced by measurement errors and anomalies, and it cannot be used to draw statistical conclusions. To address this problem, the double-bootstrap DEA technique was introduced, which permits statistical inference in DEA models. This technique helps the researcher to estimate efficiency scores that have been corrected for bias, and also identifies the factors that influence efficiency. For these reasons, this research employs double-bootstrap DEA to evaluate the efficiency scores of municipal water utilities in the South African water sector. The truncated double-bootstrap regression outcomes show that water consumer debt, consuming units receiving free water, and the effects of climate change (such as temperature variation and altered rainfall patterns) all impact the relative efficiencies of municipal water utilities. The results indicate notable distinctions in rankings and efficiency scores between the double-bootstrap DEA model and the traditional DEA model for both urban and rural municipal water utilities. Using the regression model, this research discovered that water consumer debt and consuming units receiving free water are significant factors influencing the efficiency of urban and rural municipal water utilities. These findings raise concerns about the prospects of South African municipal water utilities, particularly their ability to strike a balance between supporting indigent households and securing revenue for maintenance and future water infrastructure development, as well as efficiently managing water consumer debt and addressing the effects of climate change to deliver desired results consistently and sustainably.Item Trends in reporting on climate change, water and COVID-19 by JSE listed companies(University of the Witwatersrand, Johannesburg, 2022) Seedat, Zakiyyah; Lange, Yvette; Maroun, WarrenEnvironmental, social and governance (ESG) information is increasingly demanded by stakeholders as companies face risks and opportunities due to ESG issues, such as climate change, water and COVID-19. ESG disclosure helps reduce information asymmetry for users of company reports and helps companies maintain their social licence to operate. Disclosure is voluntary and this introduces differences in the information disclosed by companies. This study analysed the annual, integrated and ESG reports of the top 40 Johannesburg Securities Exchange (JSE) listed companies. These reports were analysed following an interpretive approach to determine the extent of disclosure on climate change, water and COVID-19 in 2018, 2019 and 2020. This study also considered the change in disclosure on climate change and water over these three years. A disclosure checklist has been developed using professional literature. Content analysis has been used to codify the disclosed information with disclosures being scored using an ordinal scale. Descriptive statistics have been used to analyse and graphically present the data. Exploratory factor analysis has been used for the identification of major disclosure themes. This study contributes to existing research by considering the current state of ESG disclosure at a time when notable developments in the reporting environment have occurred. The findings indicate that companies have focused on quantitative and strategy-related disclosure, indicating the adoption of similar reporting practices by companies. The study also found that there was no significant change in climate change and water disclosure from 2018 to 2020Item Trimetallic nanoparticles immobilised on polymeric membranes for the degradation of organic pollutants in water(2021) Kgatle, Masako; Moloto, Nosipho; Sikhwivhilu, Keneiloe; Ndlovu, GebhuWater is one of the most essential resources in the world, but its scarcity has become an issue of global concern. The scarcity of water is largely the result of climate change, water pollution and increasing population growth which limits the availability of water resources. Moreover, South Africa has been making headlines since 20 IO due to water shortages experienced. It is, therefore crucial to find cost-effective ways to expand the water supply and address the issue of water pollution. This study seeks to tackle the problem of water pollution emanating from textile industries. Over the last few years, nanotechnology and membrane technology have appeared as some of the most widely used methods for the mitigation of water pollution problems. Particularly, nanoscale zerovalent iron (nZVI) has emerged as one of the most broadly used nanoparticles in wastewater treatment and remediation owing to its low-cost and high effectiveness. However, because of its ease of aggregation and consequent loss of reactivity, nZVI is coupled with one or more transition metals to produce multimetallic systems. Nanoparticles alone quickly agglomerate and form large micro-scale particles owing to the magnetic forces thus losing their mobility and chemical reactivity. To avoid these issues, the nanoparticles are stabilized on polymeric membranes. In this study, two trimetallic nanoparticle systems were synthesized, characterized and tested for catalytic activity. The polyvinylpyrrolidone (PVP)-stabilized Fe/Cu/Ag nanoparticles were synthesized by the sodium borohydride chemical reduction method. These nanoparticles were characterized using XRD, XPS, EDX and TEM. The XRD, EDX and XPS techniques showed the presence of all three metals, including iron oxides due to the oxidation of iron in air. The obtained TEM images showed the characteristic core-shell morphology of the nZVI-based nanoparticles. The evaluation of the catalytic activity of the nanoparticles was conducted using methyl orange (MO) dye as the model pollutant and this showed a remarkable degradation efficiency within few minutes. The effect of parameters such as MO solution pH, initial MO dye concentration and nanoparticle dosage in MO degradation was investigated. The nanoparticles were found to have performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The degradation of MO dye was monitored using UV-Vis analysis and occurred within 1 min. The degradation was found to follow a pseudo first-order kinetic model and was vastly influenced by the studied parameters. The analysis of by-products and reaction pathway were done using LC-MS and this further confirmed that the degradation of MO was indeed rapid. The Fe/Cu/Ag trimetallic nanoparticles were demonstrated as suitable and effectual alternative for the remediation of textile dye wastewater. For the second trimetallic system, three different trimetallic nanoparticles (Fe/(Zn/Ag), Fe/Zn/Ag and Fe/ Ag/Zn) with different metal addition sequences were synthesized. The prepared nanoparticles were characterized using XRD, EDX and TEM analyses. The techniques proved successful synthesis of the nanoparticles and XRD and EDX showed the presence of the three metals together with the oxides. The evaluation of the catalytic reactivity of the nanoparticles was conducted in a series of batch experiments using MO dye as the model pollutant. About 100% of the MO dye was degraded by Fe/ Ag/Zn trimetallic nanoparticles within 1 min and the second-order rate constant obtained was 0.0744 ppm- 1min-\ the rate of reaction was higher than that of the other trimetallic systems. Using Fe/ Ag/Zn trimetallic nanoparticles, parametric tests were conducted at different MO solution pH, initial MO concentration and nanoparticle dosage. The results showed that the reactivity of the Fe/Ag/Zn trimetallic nanoparticles was highly dependent on the aforementioned parameters. Like the Fe/Cu/Ag system, the Fe/Ag/Zn performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The overall kinetic study showed the removal of MO using Fe/Ag/Zn system to follow a second-order kinetic model. The elucidation of the degradation pathway and MO by-products identification were done using LC-MS and the mechanism of degradation displayed the degradation of methyl orange to proceed via azo-bond cleavage. Moreover, the Fe/ Ag/Zn nanoparticles proved to be effective at degrading methyl orange dye and can be used to treat azo-dye wastewater from textile industries. The Fe/Cu/ Ag trimetallic nanoparticle system was immobilized on a polymethacrylic acid grafted polyethersulfone (PMAA-g-PES) membrane to minimize the issue of recoverability and nanoparticle agglomeration. The nanocomposite membranes were prepared by loading different quantities of Fe/Cu/Ag trimetallic nanoparticles onto the PMAA-g-PES membrane for optimization purposes. Characterization was performed using FTIR, NMR, XPS, SEM/EDS and AFM analyses. The PMAA g-PES and nanocomposite membranes were found to have a porous top layer and a rough surface. Moreover, the addition of nanoparticles did not cause any significant changes in the membrane structure, however, further addition of nano particles led to the blockage of pores. The performance of the synthesized membranes was tested using pure water flux and MO (anionic dye) and methylene blue (MB) (cationic dye) dye removal capacity. The negatively charged membranes were found to have more affinity for MB dye than the MO dye and this was ascribed to the charge interaction between the membrane surface and the dyes. The nanocomposite with 5% Fe/Cu/Ag trimetallic nanoparticle loading on PMAA-g-PES membrane (M4-5% membrane) was found to have the best adsorption capacity with about 60% MB dye removal efficiency. Furthermore, the effect of process parameters such as pH, temperature and H2O2 concentration on the removal of MB was studied. The removal efficiency was found to be higher at higher pH and lower temperature. About 100% removal efficiency was obtained when the process was performed at pH 9 in the presence of H2O2 via adsorption and Fenton degradation. This showed that a hybrid of processes was convenient for the removal of MB dye by adsorption (primarily) and degradation using the nanocomposite membrane. Adsorption equilibrium data were assessed using the Langmuir, Freundlich and Temkin models; the Temkin model was the most convenient to explain the adsorption of MB onto M4-5% membrane. Moreover, lcinetic studies were performed on four kinetic models: pseudo first-order, pseudo second order, intraparticle diffusion and elovich models. The pseudo second-order was found to be the best suitable to explain the adsorption of MB onto M4-5% membrane. Thus, the adsorption of MB onto the nanocomposite membrane is an exothermic chemical process that occurs on a heterogeneous surface. Therefore, the nanocomposite membrane has the prospective to be applied in the removal of cationic textile dyes in the presence of an oxidiser.