Desalination is a secure water source that doesn’t depend on rain. In 2020-21 water produced by our 2 desalination plants made up 45% of Perth's water supply.

How does desalination work?

Seawater desalination is the removal of salt and impurities from seawater to produce fresh water. Our desalination plants use a reverse osmosis process. Seawater is pumped into the desalination plant from the ocean and passes through pre-treatment filtration to remove most of the large and small particles.

The filtered seawater is then forced under pressure through special membranes whereby the osmosis process that normally occurs in nature is reversed. The pores in the membranes are so tiny that salt, bacteria, viruses and other impurities are separated from the seawater. In essence they act like microscopic strainers. About half of the water that enters the plant from the sea becomes fresh drinking water. The salt and other impurities removed from the sea water is then returned to the ocean via diffusers, which ensures it mixes quickly and prevents impacted the marine environment.

The desalinated water is then subject to further treatment to meet drinking water standards before it reaches our customers.

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Looking to the future

In late 2017 we started to look at the feasibility of new desalination plants north and south of the Swan River, one near Kwinana close to the existing Perth Seawater Desalination Plant and the other in the northern suburb of Alkimos.

In 2022 we advised that Alkimos is the preferred location for a new desalination plant for Perth’s Integrated Water Supply Scheme. The proposed Alkimos Seawater Desalination Plant will begin operating in 2028.

Frequently asked questions

Desalination does use more energy than sourcing water using traditional methods such as gravity feeding water out of a dam.

However, the energy used to provide enough desalinated water for the daily use for a family of 4 is the same amount of energy needed to run an air conditioner for just 1 hour.

Our desalination plants meet stringent environmental protection criteria and are designed to have minimal impact on the surrounding environment.

Our 2 desalination plants are located near the open ocean. Due to the high energy swell, the concentrated seawater discharged during the process mixes very quickly with the surrounding seawater. The offshore discharge and intake pipelines are designed and located to minimise any effects on sensitive marine habitats, such as seagrasses and reef systems.

Our desalination plants

We operate 2 seawater desalination plants. To help reduce our dependence on rainfall and groundwater, we are preparing to deliver a new seawater desalination plant - Alkimos is the preferred site.