Thesis (Ph.D.(Civil Engineering))--University of Pretoria, 2001. / Summaries in Afrikaans and English. Includes bibliographical references.

M.Ing. (Civil Engineering) / The dissolved air flotation process can be used for different functions in the drinking waterand sewage treatment fields. The focus for this study was on thickening of activated sludge. At first literature was studied to identify all possible parameters. Then five plants were visited periodically and the physical layout and operating parameters were documented. With the examination of the data the different existing models were evaluated, and new relationships were investigated.

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Please read the abstract in the section 00front of this document / Dissertation (MEng (Geotechnical Engineering))--University of Pretoria, 2006. / Civil Engineering / unrestricted

M.Sc. / Atmospheric emissions of dust and chemicals from gold mine tailings are ongoing environmental management issues on the Witwatersrand, where residential areas have developed in proximity to dumps. Residual amounts of cyanide, used as a chemical in the gold extraction process, are deposited with the mineral tailings. This study deals with the evaluation of population exposure to cyanide vapour emitted from gold mine tailings dams, an issue of environmental impact and public health concern. The first part of this study deals with the determination of the emission factors of cyanide vapour from three selected gold mine tailings dams: one under reclamation; one no longer operational; and one fully operational as a slimes deposition site. These three sites are located in the Boksburg area of the Ekurhuleni Metropolitan Municipality. Twelve samples were collected in all: six from the Cason (2628AAL91) mine dump (under reclamation in 2006); four from the ERPM tailings complex [comprising the dormant deposits 4/L/47, 4/L/48, 4/L/49 and 4/L/50, which are north of the N17 national highway; and the 2628ACL1 deposit, which is south of the N17]; and two from the Rooikraal (active) deposition site. All samples were collected in the year 2006. In the second part of the study, the obtained emission factors were used in an Industrial Source Complex dispersion model to measure the degree of population exposure to cyanide vapour for communities that are in proximity to the operational gold mine tailings dams in the Johannesburg Metropolitan Municipality. In the third part, a health risk assessment was carried out for communities in proximity to the selected gold mine tailings dams. The study revealed the average flux (± std. dev.) of Cason to be (4.7 ± 0.8) x 10-7 g m-2 s-1, the average flux of ERPM (3.9 ± 0.6) x 10-7 g m-2 s-1, the average flux of Rooikraal (1.7 ± 0.2) x 10-5 g m-2 s-1. The concentrations of cyanide vapour emitted from the older tailings deposits (sand) that are under reclamation and the dormant slimes dams are very low (and pose little health risk to occupants of adjacent land). However, HCN emission factors from operational tailings dams, which are receiving continuous depositions, are 3 to 80 times higher than the emission factors from dormant mine tailings. Ambient cyanide concentrations near the active tailings deposits may sometimes exceed selected international health standards. The average hourly, daily and annual dispersion model calculations for the Nasrec tailings deposition sites in Johannesburg revealed that 117 938, 18 722 and 8 130 people respectively were exposed to hydrogen cyanide concentrations that were above international (Ontario, Canada) standards. This raises environmental concerns that require institution of cyanide monitoring and setting of emission limits applicable to South African legal and environmental circumstances. These conclusions are based on a small number of emission factor determinations and hence these findings should be regarded as provisional. Further testing and verification are required for emission factors from a larger number of dormant, reworked and active tailings dams.

Esta dissertação é uma contribuição, através de uma pesquisa bibliográfica, sobre o tema instrumentação e monitoramento em empreendimentos de barragens de rejeitos da mineração. Nesta pesquisa apresentam-se os objetivos básicos da instrumentação de barragens e suas características técnicas, metodologia construtiva das barragens de rejeitos e seu monitoramento através de auscultação da instrumentação. Como limitação do trabalho, devido à variedade de instrumentos que podem ser instalados em uma barragem, buscou-se pesquisar os instrumentos de medição de deslocamentos e controle de fluxo percolante, sendo os mais utilizados em barragens de terra e rejeitos. Justifica-se este tema motivado pelos últimos acidentes ocorridos em barragens de contenção de rejeitos, enfatizando a importância e a necessidade permanente da melhoria das condições de segurança e monitoramento das barragens brasileiras. Estes acidentes causam danos à população do entorno da barragem, econômicos ao empreendedor e ambientais. Como resultado obtido nesta pesquisa pode-se concluir que propiciou conhecimento atualizado ao meio técnico nacional de barragens. / This dissertation is a contribution, through a bibliographical research, on the subject of instrumentation and monitoring in enterprises of tailings dams. This research presents the basic objectives of the instrumentation of dams, their technical characteristics, the construction methodology of tailings dams and their monitoring through auscultation of the instrumentation. Due to the variety of instruments that can be installed in a dam, this work was limited to the analysis of two segments, instruments of measurement displacements and those for controlling percolation flow, which are the most commonly used in earth and tailings dams. This study is justified due to recent accidents occurring in tailings dams, which stress the importance and the permanent necessity of the improvement in security and monitoring conditions of Brazilian dams. These accidents cause social, economic and environmental damages to the enterprise. As a result of this research it can be concluded that it contributed with up-to-date knowledge to the national technical dam sector.

A research report submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the Degree of Master of Science by Coursework and Research Report. Johannesburg, March 2016. / A vegetation survey was carried out in July 2014 on the substrates of 5 tailings dams by selecting 10 sampling sites which were previously used as sampling plots during the 1996/97 survey of Weiersbye et al. (2006). At each sampling site a 100m transect horizontally across the substrate and covering all levels of the tailings dam from the flat top to the toe paddock was established. Each transect was surveyed for the frequency of the species occurring and these were categorized based on their mode of colonization (natural, intentionally introduced and persisting) while tailings were collected by digging approximately 20cm into the ground for soil sample collection per substrate. The recorded species were then divided using Raunkier’s classification categories into growth forms and a comparison was done between the two surveys (2014 versus 1996/7) to identify the species that were lost, those that were still persisting and the new ones that had colonized over time. A total of 51 species (over 15ha) in 36 genera within 14 families were recorded on the tailings dams, compared to 168 species (over 765ha), 98 genera and 59 families found in the previous study. Families with the most species in 2014 were similar to those of the 1996/97 survey, following the dominance order of Poaceae >Asteraceae >Fabaceae >Anacardiaceae, with the percentage frequency of grasses (Poaceae) noted to have almost doubled over this period. Compared to 6 species common across the substrates in the previous study, the later survey recorded 12 common species (6 of the species occurring on all substrates) but overall both studies found vegetation cover to be high (above 65%) on flat tops and berms with species richness being high on the toe paddock>slopes>tops and berms and substrates susceptible to low nutritional (N,P,K,C) value. Indigenous plant species (54.9%) were dominating the tailing dams and were mostly perennials (82.3%) that were naturally colonizing and persisting (72.5%) on the tailings dams (similar to the 1996/97 survey), while alien (45.1%) plant species comprised annuals/biennials (17.7%) that were intentionally introduced (27.5%) prior to the 1996/97 survey by contractors. The ceased ameliorative initiatives since the first survey are believed to have significantly contributed to a decrease in herbaceous species richness, which formed the majority of the introduced species in the former survey (58.8% compared to 29.4%) as they depended on the supplementary additions of fertilizers and lime. Approximately 117 species, 62 genera and 45 families (including Chenopodiaceae, which was dominant) were lost over the 17 years period, the majority of these were introduced prior to the 1996/97 vegetation survey, while only Ficus sp. was the only new species colonizing apart from the increase noted in alien species (some invasive in nature). The decrease in species richness has encouraged woody and semi-woody (35.3%) and grasses (35.3%) to dominate the slimes reaffirming their potential as temporal and long term rehabilitation species that have developed physiological tolerance to acidic conditions, salinity and heavy metal pollution. In conclusion, this study has identified the species that can be used for phytoremediation to provide long terms solutions for dust, air and water pollution and soil erosion suppression for rehabilitation of these contaminated lands (Appendix 8). The survey also helps to identify species that are able to naturally colonize and persist on the tailings dams without supplements, making them ideal economic species to use for rehabilitation. Results also highlight the negative impacts of the lack of ameliorative supplementations, which in turn affects the floristic composition and structure on these tailings dams over time. Keywords: Aerial cover, Macronutrients, Tailings dams, Species richness, Tailings Storage Facilities (TSFs) and Vegetation survey / LG2017

Thesis (PhD(Geotechnical)(Civil and Biosystems Engineering)) --University of Pretoria, 2007. / Includes bibliographical references.

Thesis (M.Eng.)(Geotechnical)--University of Pretoria, 2004. / Includes summary. Includes bibliographical references.

Thesis (M.L.(Prof.))--University of Pretoria, 2004. / Includes summary. Includes bibliographical references.