The water-scarce Namibian town of Swakopmund is to benefit from the biggest desalination plant in Southern Africa.
The Trekkopje plant, launched last Friday, will produce 20-million cubic metres of fresh water a year from seawater, shared between the people of the Erongo region and Areva Resources’ new Trekkopje uranium mine, about 50km east of the town.
Africa’s biggest desalination operation, Algeria’s Hammas plant, purifies up to 200 000m3 of seawater a day. Trekkopje is smaller, processing around 550 00m3 daily. But it is significantly larger than South Africa’s biggest plant, built in Sedgefield last year, which produces up to 150 00m3 a day.
Sedgefield cost R16-million to build, compared with the Trekkopje outlay of R2,5-billion. But the Namibian plant used the best technology on offer.
Like Algiers, Swakopmund lies between the desert and the sea. The town was founded on the Swakop River, but fresh water has always been in short supply.
Areva’s Trekkopje mine will use the bulk of the purified water. It needs about 14-million cubic metres of fresh water a year to operate, but this could fall as the mine becomes more water efficient, Areva officials say.
The mine represents the largest direct foreign investment made in the country and will produce an estimated 3 000 tons of uranium a year when it is fully on stream.
The residual water, currently six million cubic metres, will go to the local municipal water supplier. Areva says it will amount to one-and-a-half times Swakopmund’s annual water consumption.
The plant transforms salt water into grade B drinking water of a high standard, requiring a small amount of chemical processing to raise it to grade A. Most of the world’s cities, including Johannesburg, offer citizens grade B water.
Like the Algiers plant, the Trekkopje plant uses a reverse osmosis process — high pressure (about 63 bars), generated by powerful motors, forces the salt out of the water. For every 100m3 that flows into the plant, just more than 40% is converted into fresh water. The rest flows back into the sea.
But the water is not cheap. Apart from the start-up cost of building the plant, energy is needed to power the 750kW motors. But the Trekkopje plant has installed energy-recovery pressure exchangers, which will use the pressure generated by the engines to help power the motors, reducing energy consumption.
Markus Pfaffontaller, the Areva utility manager, says no new technology has been used but the designers combined what was available on the market to assemble a state-of-the-art, energy-efficient plant.
South African company Keyplan, a division of engineering group Aveng, designed the plant for Areva.
At the launch of the plant, Roger Jardine, Aveng’s chief executive, said the group’s water-treatment solutions could play a significant role in tackling water security throughout Southern Africa and in other regions where arid conditions were a humanitarian concern and restricted industrial growth.
Aveng also uses its water-treatment technology to treat acid mine drainage.
Meanwhile, Buyelwa Sonjica, the Environment and Water Affairs Minister, said in her budget vote last week that South Africa would investigate the use of desalination plants to counter growing water scarcity.
Other Eden region towns, including Plettenberg Bay, Knysna, George and Mossel Bay, are also turning to desalination plants for drinking water. The region has been suffering from a crippling drought, and has been trucking in water to supply the holiday towns.
But the scale of the plants is minuscule compared with Trekkopje and Hammas. Even the proposed Knysna plant will produce just 20 000m3 a day.