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underwater with coral and fish


Turning ocean water into drinking water

Oceans hold 97% of all the water on Earth. They are a source of drinking water for many people around the world by using a treatment process called desalination.

Why are people using desalination?

Unlike rivers and dams, the amount of water in oceans is not affected by drought.

Using a process called desalination , seawater can be turned into drinking water. This means we have a more reliable drinking water supply that doesn't rely on rainfall. Many countries are using desalination to provide drinking water for their people.

Desalination is a way to make sure people have enough water when:

  • countries do not have enough rain or rivers that are easy to get to
  • countries are affected by drought 
  • rainfall is affected by climate change
  • populations grow faster than existing water supplies.

How does desalination work?

The Sydney Desalination Plant is on the coast at Kurnell between Botany Bay and the Tasman Sea. It is one of the largest desalination plants in the world. It is run by Veolia Water for a group of other companies.

The plant provides an extra source of water for Sydney that doesn't rely on rain. It is an important part of the NSW Government's plan to make sure we have enough water for the future.

How does it work?

  1.  Seawater is pumped into the desalination plant using a large pipe lying on the ocean floor.
  2. The seawater goes through a screen to remove large objects like sand or weeds and then it sinks down through filter beds to remove smaller objects.
  3. Salt is removed using a process called reverse osmosis. High pressure is used to force the seawater through thousands of reverse osmosis membranes, which are like very fine sieves. Fresh water is produced and a salty liquid called seawater concentrate is left behind.
  4. The leftover salty liquid is about twice as salty and two degrees warmer than the ocean. This liquid is returned to the sea through another large pipe that lies on the seabed.
  5. The salty liquid is mixed into the ocean and returns to its normal levels of salt and temperature within 50 - 75 metres from the outlet pipe.

The desalination plant needs a lot of electricity to work, so a wind farm with 67 huge turbines was built at Bungendore (near Canberra). The wind farm produces at least the same amount of electricity that the plant uses. This renewable energy goes into NSW's electricity network.

Drinking water from the desalination plant joins Sydney’s existing water supply through an 18 kilometre pipeline under Botany Bay. The Sydney Desalination Plant can supply drinking water to about 1.5 million people.

Take a virtual tour of the Sydney Desalination Plant.