Predictions of leachate generation from minerals processing waste deposits
| dc.contributor.advisor | Petrie, Jim | en_ZA |
| dc.contributor.author | Davies, Graham Mark | en_ZA |
| dc.date.accessioned | 2014-10-17T07:30:27Z | |
| dc.date.available | 2014-10-17T07:30:27Z | |
| dc.date.issued | 1995 | en_ZA |
| dc.description | Includes bibliography. | en_ZA |
| dc.description.abstract | The minerals processing industry in South Africa produces significant tonnages of waste material which are disposed of commonly in dedicated waste depositories. These deposits pose a potential to pollute the environment if leachate is generated within the deposit and released to the surroundings. Leachate generation is generally investigated using laboratory columnar experiments which attempt to mimic the physical and chemical processes which occur in the deposit. These experiments, termed lysimeter experiments, are time consuming in that they typically last for at least a few months and can last for up to three years. Lysimeter experiments are also costly to conduct. Because of restrictions such as these, relatively few deposits have been characterised to determine the leachate which they generate and thus the risk which they pose to the environment. There is an urgent need to be able to estimate the environmental risks associated with existing waste deposits. The first step towards assessing this risk would be an ability to predict leachate generation within a specific deposit. Such an ability could be used to identify which of the existing deposits produce significant leachate and thus pose a potential hazard to the environment. Equally, if leachate generation from new deposits could be estimated as a function of waste material and characteristics of the waste deposit, this information could be used to improve the engineering design of waste deposits. The work presented in this thesis involved identifying suitable modelling strategies which could be used to determine leachate generation within waste deposits which contain waste material typical of that produced by the minerals processing industry. Two modelling strategies have been investigated. The first modelling strategy involved a macroscopic model in which all effects such as intrinsic chemical kinetics, intra-particle diffusion, external mass transfer and hydrodynamic considerations are lumped into a single parameter. The result of this approach is an effective reaction rate for the release of hazardous constituents from a volume element of the waste deposit. The effective reaction rate is determined by fitting the model to experimental data based on lysimeter tests. The main advantage of this model is that it eliminates the need for a detailed understanding of the individual factors which contribute to leachate generation. This model was investigated both for its inherent simplicity and for use in cases where insufficient information with respect to the intrinsic chemical reaction rates, intra-particle diffusion, external mass transfer or hydrodynamic aspects exist. The main disadvantage of this model is that it has a limited predictive ability in that the individual significance of any one factor which contributes to leachate generation cannot be determined. For this reason a second, more detailed model, termed the heterogenous columnar model, has also been investigated. | en_ZA |
| dc.identifier.apacitation | Davies, G. M. (1995). <i>Predictions of leachate generation from minerals processing waste deposits</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/8475 | en_ZA |
| dc.identifier.chicagocitation | Davies, Graham Mark. <i>"Predictions of leachate generation from minerals processing waste deposits."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1995. http://hdl.handle.net/11427/8475 | en_ZA |
| dc.identifier.citation | Davies, G. 1995. Predictions of leachate generation from minerals processing waste deposits. University of Cape Town. | en_ZA |
| dc.identifier.ris | TY - Thesis / Dissertation AU - Davies, Graham Mark AB - The minerals processing industry in South Africa produces significant tonnages of waste material which are disposed of commonly in dedicated waste depositories. These deposits pose a potential to pollute the environment if leachate is generated within the deposit and released to the surroundings. Leachate generation is generally investigated using laboratory columnar experiments which attempt to mimic the physical and chemical processes which occur in the deposit. These experiments, termed lysimeter experiments, are time consuming in that they typically last for at least a few months and can last for up to three years. Lysimeter experiments are also costly to conduct. Because of restrictions such as these, relatively few deposits have been characterised to determine the leachate which they generate and thus the risk which they pose to the environment. There is an urgent need to be able to estimate the environmental risks associated with existing waste deposits. The first step towards assessing this risk would be an ability to predict leachate generation within a specific deposit. Such an ability could be used to identify which of the existing deposits produce significant leachate and thus pose a potential hazard to the environment. Equally, if leachate generation from new deposits could be estimated as a function of waste material and characteristics of the waste deposit, this information could be used to improve the engineering design of waste deposits. The work presented in this thesis involved identifying suitable modelling strategies which could be used to determine leachate generation within waste deposits which contain waste material typical of that produced by the minerals processing industry. Two modelling strategies have been investigated. The first modelling strategy involved a macroscopic model in which all effects such as intrinsic chemical kinetics, intra-particle diffusion, external mass transfer and hydrodynamic considerations are lumped into a single parameter. The result of this approach is an effective reaction rate for the release of hazardous constituents from a volume element of the waste deposit. The effective reaction rate is determined by fitting the model to experimental data based on lysimeter tests. The main advantage of this model is that it eliminates the need for a detailed understanding of the individual factors which contribute to leachate generation. This model was investigated both for its inherent simplicity and for use in cases where insufficient information with respect to the intrinsic chemical reaction rates, intra-particle diffusion, external mass transfer or hydrodynamic aspects exist. The main disadvantage of this model is that it has a limited predictive ability in that the individual significance of any one factor which contributes to leachate generation cannot be determined. For this reason a second, more detailed model, termed the heterogenous columnar model, has also been investigated. DA - 1995 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1995 T1 - Predictions of leachate generation from minerals processing waste deposits TI - Predictions of leachate generation from minerals processing waste deposits UR - http://hdl.handle.net/11427/8475 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/8475 | |
| dc.identifier.vancouvercitation | Davies GM. Predictions of leachate generation from minerals processing waste deposits. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1995 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/8475 | en_ZA |
| dc.language.iso | eng | |
| dc.publisher.department | Department of Chemical Engineering | en_ZA |
| dc.publisher.faculty | Faculty of Engineering and the Built Environment | |
| dc.publisher.institution | University of Cape Town | |
| dc.subject.other | Chemical Engineering | en_ZA |
| dc.title | Predictions of leachate generation from minerals processing waste deposits | en_ZA |
| dc.type | Master Thesis | |
| dc.type.qualificationlevel | Masters | |
| dc.type.qualificationname | MSc | en_ZA |
| uct.type.filetype | Text | |
| uct.type.filetype | Image | |
| uct.type.publication | Research | en_ZA |
| uct.type.resource | Thesis | en_ZA |
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