Doctoral Degrees (Civil Engineering)

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Browsing Doctoral Degrees (Civil Engineering) by Author "Brink, Isobel Christine"

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    Design of stormwater ponds towards the reduction of metal toxins in surface waters that are utilised for South African primary food production
    (Stellenbosch : Stellenbosch University, 2016-03) Brink, Isobel Christine; Kamish, W.; Basson, G. R.; Stellenbosch University. Faculty of Engineering. Dept of Civil Engineering.
    ENGLISH ABSTRACT: This research originated from a need for civil engineering practice to address metal pollution in stormwater runoff. Specific emphasis was placed on metals that could affect the quality of crops, livestock and fish in South Africa. Detention and retention ponds are commonly used for surface water quality control, and these types of structures were therefore investigated. No prominent pond design methods were found, however, that directly incorporate consideration of metal pollution in the context of food security. In addition, there was a lack of information on how methods could be adapted to address metal pollution specifically. It was argued that focussing on relationships between pond efficiency and design could generate information towards augmenting design philosophies and methodologies. This became the project thesis. The methodology used for the investigation into relationships between pond efficiency and design was constrained by the available data. Statistics and probability theory were the main tools used. Data was obtained from an international database and therefore little was known about possible sources of error. Although a large variety of data on a number of metal toxins and solids was found, individual data sets were often small. These factors meant that data trends (rather than specifics) between ponds were used as the basis for conclusions. Modelling was employed to theoretically test the validity of trends indicated by statistical analysis. These included identification of pond efficiency predictors with logistic regression, curve fitting of a time polynomial to outflow mass data to indicate the class of particulate settling, and hypothetical sedimentation modelling with MIKE 11 software. Results indicated certain pond parameters that were influential in removal processes, but many of these were not explicitly included in prominent design methods. These methods were therefore found to be inadequate for efficient pond design. Data trends indicated a number of processes of importance in metals removals. This information was used to create conceptual models of pond functioning, which were used to augment established engineering theory for application in pond metals removal. The project thesis was therefore accepted. A design philosophy of high levels of control on pond hydraulics and metal loads was recommended. Detention and retention pond functioning for metals removal was illustrated to be highly complex, making detailed modelling enterprises difficult, time consuming and costly. Control over hydraulics and in/out boundaries can simplify pond design.