One reason why groundwater, so often constitutes the main source of drinking water in
many cities and towns around the world, is because it is frequently present in sufficient
quantities at the point of demand. However, this seemingly advantage may sometimes be its
greatest disadvantage, especially in situations where the groundwater occurs at shallow
depths and the area overlying the aquifer is populated densely. This problem is particularly
relevant in the present technological age with its vast quantities of waste that is often
disposed in an uncontrolled manner. Such a situation occurs at Douala the economic capital
of Cameroon in central Africa. The city not only host more than 80% of industries in the
country, but also has the largest urban population of approximately 3 000 000 with a
population density of approximately 350 persons per square kilometre, which continue to
increase at a rate of approximately 120 000 migrants per year from the rural areas, while
the groundwater level is very shallow and may sometimes rise above the soil surface,
especially during floods, which occur not too infrequently.
Although the pollution problem is not restricted to groundwater as such, it is aggravated
here, because of the ancient belief that wastes are safely disposed of, if buried below the
earthâs surface. It took disasters like Love Canal and the Price Landfill to discover the
detrimental effects that this practice may have on the population living on or near polluted
aquifers. Extreme care therefore should be exercised to prevent the pollution of any aquifer
that may pose problems to living organisms or to try and restore a polluted aquifer
threatening the natural environment. Groundwater pollution should therefore receive
urgent attention when discovered.
This thesis describes an attempt to develop a set of guidelines for the restoration of the
groundwater resources at Douala, based on the relatively new technique of permeable
reactive barriers for groundwater remediationâa technique that is also increasingly
applied in the restoration of the Superfund sites in the United States of America.
Modern attempts to clean up contaminated aquifers, relies heavily on the use of suitable
computational numerical models. Such models have in the past always been based on the
classical hydrodynamic dispersion equation. However, an analysis of the equation in this
thesis has shown that the equation cannot account for the longâtail contamination plumes
characteristic of fractured rock aquifers. Fortunately, it is not too difficult to develop a more
suitable equation. For, as shown in the thesis, all that one has to do is to replace the ordinary derivatives in the classical equation with fractional derivatives.
Mechanistic modeling of physical systems is often complicated by the presence of
uncertainties, which was in the past usually neglected in the models used in the restoration
of aquifers.While these uncertainties have regularly been neglected in the past, it is
nowadays imperative that any groundwater model be accompanied by estimates of
uncertainties associated with the model. Although a large number of approaches are
available for this purpose, they often require exorbitant computing resources. The present
investigation was consequently limited to the application of the Latin Hypercube Sampling
method applied to an analytical solution of the hydrodynamic dispersion equation.
It has been known for years that the hydrodynamic dispersion equation discussed in
Chapter 5, is not able to account for the longâtail plumes often observed in studies of
contaminated fracturedârock aquifers. An approach frequently used to account for this is to
replace the ordinary spatial and temporal derivatives in the hydrodynamic equation with
fractional derivativesâa procedure confirmed in this thesis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07182013-110844 |
| Date | 18 July 2013 |
| Creators | Atangana, Abdon |
| Contributors | Prof JF Botha |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-07182013-110844/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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