Desalination
The Perth Seawater Desalination Plant has been operational since October 2006, delivering 45 gigalitres a year of safe, reliable drinking water to Perth. The plant is powered by electricity from a renewable energy source and there have been no adverse impacts on the water quality of Cockburn Sound, strictly monitored as a condition of environmental approval.
Work to design and obtain regulatory approvals for the proposed Southern Seawater Desalination Plant at Binningup, 150 kilometres South of Perth, is progressing. The plant is designed to deliver a further 50 gigalitres of water a year, about 16% of total supply, by 2011. This site could be expanded in the future to accommodate another 50 gigalitres a year.
The major advantage of seawater desalination is that it is rainfall independent. The plants can deliver a continuous stream of safe drinking water, which can be used straight away or banked into dams for later use.
More plants could be constructed in other locations around Perth to meet future water supply needs. The Water Corporation is undertaking a detailed study to determine future options for desalination plant sites.
Another major consideration is energy. A desalination plant uses 6 to 10 times more energy to produce a kilolitre of water than sourcing groundwater.
In 2005, United Utilities Australia (UUA) proposed an alternative drinking water source for the Goldfields and Agricultural regions and the Perth metropolitan area. They proposed that water be sourced from a seawater desalination plant at Esperance and piped 385 kilometres to Kalgoorlie. The water would mainly be used for mining operations in the area and for domestic water supply in Kalgoorlie. It would also provide a drinking water source for Esperance.
The seawater desalination pipeline would result in the existing Goldfields and Agricultural water supply pipeline to Kalgoorlie terminating at Southern Cross. The existing scheme would remain predominantly as a scheme for agricultural towns and farmlands.
The State Government reviewed the project and found that at the time it was not the most economical option.
In general, desalination is a much more expensive source of water than traditional surface and groundwater resources. This is influenced by a number of factors including process design, pumping distance, need for new storage, energy costs, and construction. Final costs need to be informed by specific site considerations.
Other social and environmental issues may need to be considered for each plant, depending on the site location. These are addressed in site selection and detailed infrastructure planning with community engagement.
Consideration has also been given to desalinating saline groundwater from country towns. Saline groundwater has been identified as a problem in 38 rural towns in Western Australia, threatening roads, buildings and other infrastructure.
A proactive approach to address this issue has been a collaborative effort between the Department of Agriculture and Food, Local Governments, CSIRO and other agencies to develop water management plans for some of these towns.
This work has identified that the best option is to use this surplus water, treated to an appropriate standard, to irrigate parks and other non-drinking water uses. Using this water as a substitute for drinking water supply proved to be too costly in most instances. Where it does make sense it will be explored as a scheme option for the local town, to minimise pumping costs.