Desalination
Desalination is the process of removing salt from water to make it useable for a range of 'fit for use' purposes including drinking. While high energy and process costs make this a relatively expensive option, advancing technologies mean desalination will provide a viable and weather resistant alternative for urban drinking and non-drinking water supplies.
Our rainfall may be highly variable but Australia is surrounded by water - oceans of it. Unfortunately, this water contains too much salt to drink, wash with, or use to irrigate plants. Many of Australia's groundwater and surface waters systems have also become saline and are not fit for a range of consumptive uses.
Desalination of sea water and other slightly salty (brackish) water supplies could provide a reliable source of fresh water that is not dependent on rainfall.
Desalinated water is produced either by:
- distillation
- evapo-transpiration
- electro-dialysis
- processes that use membranes to separate the salt from the water, such as reverse osmosis.
These processes require a significant amount of energy - the saltier the water, the more energy is required to desalinate it. For this reason it is cheaper to desalinate brackish water or wastewater than sea water.
Desalination is used extensively in the Middle East, North America, Europe, North Africa and the Caribbean. In Australia, a reverse osmosis seawater desalination plant supplies 17% of Perth's drinking water supply. A second plant is planned for south west Western Australia. It is due to be completed in 2011 and will alleviate the need to extract large quantities of groundwater from the local aquifer. Desalination is also being implemented as a water supply option in other parts of Australia, including Sydney, Melbourne, Adelaide and the Gold Coast.