Local Government, Environmental Affairs and Development Planning
Whether his Department is considering the desalination of seawater; if not, why not; if so, what are the (a) relevant details and (b) costs involved to build a processing plant?
Consideration of desalination plants: The Department has no other option than to consider the desalination of seawater in the coastal areas due to the declining sources of natural drinking water (surface and underground water). Desalination of seawater and re-use of wastewater make use of reverse osmosis which is one of the most expensive ways to obtain drinking water and therefore all other avenues should first be explored before a decision is taken to make use of this method.
The main challenges with the implementation of desalination technology in South Africa are the following:
- High operational costs;
- High operational energy demand; and
- Disposal of brine due to highly concentrated salt content of effluent. In most cases this effluent is returned to the sea.
- Skilled workforce required for operation and maintenance of desalination plants
First desalination plants in the Western Cape: The 2008/09 drought in the Southern Cape was the worst drought in 130 years in the Eden District and the area was therefore declared a disaster area. This forced the Municipalities of Knysna and Mossel Bay to build plants to desalinate seawater. Although water conservation and water demand management were strictly applied and additional boreholes drilled during the two drought years, it was not enough to supply in the high demand in drinking water.
Existing desalination plants: Desalination plants have already been built in the following coastal towns in the Western Cape:
Knysna, Sedgefield, Mossel Bay and Lambert’s Bay.
Future desalination plants: Future desalination plants are being planned for the City of Cape Town and West Coast District Municipality (at Saldanha Bay) depending on the water usage in these areas.
Costs of the plants in Mossel Bay: The water usage for the entire Municipality was about 14 megalitres per day during 2010 and the plant was designed (15 Ml/day) to deliver this amount of water. The project was jointly funded by the National Treasury and PetroSA who contributed R92-million and R80-million respectively to the total project cost of R210 million.
