Techno economic viability of desalination processes in South Africa
Laubscher, Louis Jacobus
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The provision of fresh water to sustain current economic development and the ever increasing population is one of the world?s greatest challenges and will become increasingly acute in the immediate future. South Africa is currently utilizing 98% of its available fresh water and with the current growth in population and economy fresh water will rapidly become a limited resource. Cape Town, Port Elizabeth and Durban have been identified by the Department of Water Affairs and Forestry as coastal cities that will be under immense fresh water availability pressure around 2025. Desalination was identified as a viable method to increase coastal freshwater supply. Desalination costs are greatly improved by co–locating the desalination plant at a viable energy/power source. Costs are primarily improved by sharing existing seawater inlet and outfall infrastructure as well as utilizing waste heat produced by the energy source. Generally power plants are the best candidates for desalination co–location. As a large part of the industrial developments are located in the coastal regions, the co–location of seawater desalination plants becomes a viable option. Koeberg nuclear power station at Cape Town, the Thyspunt site proposed for the nuclear power plant fleet and the Coega site proposed for the combined cycle gas turbine power plant at Port Elizabeth and the Shakaskraal site proposed for the combined cycle gas turbine power plant at Durban were identified as possible co–location options. This dissertation presents a techno–economic viability study of different desalination processes in South Africa. The evaluated processes included reverse osmosis, multi stage flash and multi effect distillation as well as a hybrid combination of multi stage flash–reverse osmosis and multi effect distillation–reverse osmosis. The main factors affecting desalination economics such as the selection of the desalination technology, energy source, plant size, plant configuration and certain site specific factors including seawater temperature and quality were assessed and taken into account during the costing evaluations. The independent desalination economic costing programs DEEP 4.0 and WTCost II© were used for the cost evaluation at each identified site. The results from both costing programs identified reverse osmosis as the most economically viable desalination process to be applied on the South African coast. The water transport cost was identified as a costing factor that had a substantial influence on the total cost of all desalination processes, especially on small–scale desalination plants.
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