Cape Town - The cost analyses have been made, the tenders were put out and the areas where the plants will be situated have been identified. But do Capetonians know about the process of desalination and how safe the water will be for drinking?
Desalination is a popular solution, but it’s not an overnight one, says Professor Andre Burger, an expert in the field of desalination and water treatment plants at the University of Stellenbosch. Desalination is the process of taking fresh water from the sea and removing the salt in order to make it usable.
Burger said although desalination is one of the best solutions now, it's not the easiest.
“It can be a very difficult task and it needs the best planning. It can never be done in one month. The much more larger ones can take up to three years to complete. The Mossel Bay plant took about six months to build. This is not a quick fix,” he said.
Burger explained that when water is pumped out of the sea only about 45% of the water will be converted to drinking water.
The basic process of desalination. Graphic: Supplied/Stellenbosch University
“The remaining water will be sent back into the sea. The sea salt and whatever else is taken through the pump process. It then goes back into the sea. There is no salt that stays behind. It becomes problematic when we pump water from the harbours as ships leak oil and other chemicals,” he said.
The biggest challenge is to secure a pipeline for the desalinated water to be pumped into the existing water supply network.
“The water that is being pumped out of the sea needs to go into our existing system. The water should also not be too concentrated. Water that is also too corrosive can damage water pipes. The biggest challenge will be the planning. Projects like this need stringent planning,” he said.
There will be a difference in the taste, but it is completely drinkable, Burger said.
“There is nothing to worry about. It is clean water. There is nothing to panic about,” he said.
Typically 4kWh of electricity per kilo-litre of desalinated water is used, Burger added.
Asked if the City has been doing enough, he said: “I think the City of Cape Town is doing what they can. They also have many community challenges. Everyone has to save more water in the long run.”
Cape Town mayor Patricia de Lille said previously that the City will have to budget about R3.3 billion for its water projects. De Lille‚ who visited site for the proposed plant at the weekend said the “modular land-based plant”‚ which will produce 2 million litres per day and will be operational by February, 2018.
The plant will be built on an open air parking lot near Cape Town Harbour’s East Pier and will be one of a network of eight desalination plants spread across the City.
In essence, desalination is expensive, time-consuming, and can be a logistical nightmare.
Yes, desalination is perhaps the most popular solution. But being so expensive, it may well cost Capetonians more in the near future.
Cape Town's planned desalination plants and their expected outputs. Graphic: Lance Witten/Cape Argus
This is where the eight desalinations plants will be based and the amount of fresh water it will produce:
* Hout Bay – 4 million litres per day
* Granger Bay – 8 million litres per day
* Red Hill/Dido Valley – 2 million litres per day
* Strandfontein – 7 million litres per day
* Monwabisi – 7 million litres per day
* Harmony Park – 8 million litres per day
* Cape Town Harbour – 50 million litres per day