A large-scale desalination plant. Picture: SUPPLIED
A large-scale desalination plant. Picture: SUPPLIED

The desalination of sea water on an appropriate scale is now both viable and necessary in coastal towns, the Cape Chamber of Commerce says.

The chamber has submitted a letter detailing its views on desalination to the Department of Water and Sanitation, which is developing a water master plan for the future.

"One of the proposals made to the Cape Town City Council was to build a large desalination plant to produce about 250-million litres of water a day, about 30% of Cape Town’s needs in a normal year. When this desalinated water was blended with 70% dam water the result would be an increase in tariffs of just 6.54%," said Janine Myburgh, the president of the Cape chamber.

A large-scale desalination plant is seen as a long-term solution to Cape Town’s water problems. However, there are concerns that the cost of maintaining such a plant would result in residents paying more for water. Desalination removes salt and other minerals from sea water, making it suitable for human consumption.

The technology is also being considered to make acid mine water usable. The government estimates that by 2030 desalination plants could provide up to 10% of SA’s urban water supply.

With the drought in Cape Town showing no signs of abating, city officials have had introduce stringent water restrictions, and also look into various water augmentation schemes including drilling boreholes into the Table Mountain group aquifer, and small-scale desalination plants.

Myburgh said a large-scale desalination plant could be developed in line with the highly successful process used by the Department of Energy to attract independent power producers.

"In terms of this process the desalinating company would design, finance, build, operate and maintain the plant in return for the city’s commitment to purchase the daily water output for an extended period of about 20 years."

Myburgh said the increased cost of desalinated water could also be offset by the lower cost of recycled water, especially for industry.

The use of desalinated water in coastal regions would mean that more water should be available for agriculture and food production, said Myburgh. She pointed out that agriculture had made considerable progress in using water more productively.

Myburgh said agriculture deserved more water to enable more and better food production which would, in turn, create more jobs and export earnings.

On Monday, Cape Town deputy mayor Ian Neilson said that day zero, the day in which most of the taps in the city could run dry, is expected to move out to mid-May from mid-April due to a decline in agricultural usage.

"Many of the agricultural users in the Western Cape Supply System, where the city also draws its water from, have used up the water allocated to them as per agreement with the National Department of Water and Sanitation," said Neilson.

"Agricultural usage is therefore likely to drop significantly over the next weeks. Currently, the agriculture sector is drawing about 30% of the water in the supply scheme. This should fall to about 15% in March and 10% in April. It must be noted that the city does not have any control over agricultural releases, so this is the best estimate we can make with the information at hand."