Seawater Desalination
Background
About the technology
Desalination plants are climate independent and provide significant benefits to supply security, over traditional surface and ground water sources.
Desalination can provide high quality drinking water from the ocean by separating salts and other minerals.
Reverse Osmosis is the process (see below) where saline water is pumped through membranes (filters) at high pressure. This separates high quality drinking water from the salty brine discharge water which is sent back to the ocean. Reverse osmosis was chosen for the Perth Seawater Desalination Plant as it is the most economical and environmentally friendly technology.
.jpg)
Current Situation
Perth Seawater Desalination Plant
The Perth Seawater Desalination Plant, located 40 kilometres south of Perth, started supplying water into the water grid in November 2006. In doing so, it became the first plant in Australia to provide desalinated seawater for large scale public consumption.
At full capacity, it is one of the Water Corporation’s biggest single water sources, providing some 17 per cent of Perth’s water needs in 2007.
On average, the plant produces up to 130 million litres of drinking water per day, or 45 gigalitres per year.
As the biggest plant in the southern and eastern hemispheres, it has been heralded as a landmark in the development of the Australian water industry. The plant obtains its annual power requirements from electricity generated by the Emu Downs Wind Farm near Cervantes.
The existing Perth Seawater Desalination Plant in the Kwinana industrial area fully occupies the site - there is no room for expansion.
WA Premier Alan Carpenter announced on 15 May 2007 that a new desalination plant is to be built near Binningup in the Shire of Harvey as the next major water source for customers of the water grid.
1.jpg)
Southern Seawater Desalination Plant
The plant is planned to produce around 50 gigalitres of drinking water per year, with the potential to increase to 100 gigalitres and with a commitment to be supplied from renewable energy. The project also includes around 30 kilometres of pipelines to connect it to the water grid and new pipes to move the water around the scheme and on to customers. Construction work is expected to commence in 2009, and the plant is scheduled to be operational by 2011.
The Future
Likely need for more plants
Perth’s population and water demand are expected to almost double in the next 50 years, and new water sources will be needed to meet this demand. One option will be for additional seawater desalination plants to build on the growing expertise in this area in Western Australia.
Sustainability considerations
Economic | Social and Cultural | Environmental |
| More expensive than other existing sources. | High quality water supply safeguards public health. | Consumes more energy than traditional groundwater and surface water sources. |
| Location close to the ocean and to customers helps to minimise costs. | Developing a world-class desalination capability in Western Australia. | Produces a brine discharge that is returned to the ocean. |
| Renewable energies can add significantly to operating costs. | Increasingly being adopted in other major cities. | Climate independent – more reliable than dams and groundwater schemes. |
The Water Corporation has sought to address the major sustainability considerations by:
- careful site selection to manage environmental and social impacts;
- engagement with local communities to understand and address issues;
- commitment to supply from renewable energy sources or carbon offsets to mitigate energy use;
- careful plant design to optimise efficiencies and reduce costs; and
- extensive ocean monitoring programs.
Potential source yield
There is an unlimited supply of seawater available throughout Western Australia. The major constraints are securing appropriate sites, energy sources and funding. An investment in four to six new plants by 2060 could yield more than 300 gigalitres of new water. This is enough to supply more than 800,000 new homes.
Possible locations
In general, desalination plants are community friendly and can be located close to demand – reducing the need for energy and transport. Future desalination plant sites would be identified on the basis of the following characteristics:
- be in close vicinity to the ocean;
- allow easy integration into the water grid;
- have easy access to a suitable power source or electricity grid;
- be environmentally compatible with minimal environmentally sensitive areas;
- be at least 20 ha in size to accommodate plant components;
- have adequate and available buffers required for chlorination facilities; and
- be supported by land planning for compatible land uses.
Possible sites to expand desalination in the greater Perth metropolitan area include:
- expansion of the proposed Southern Seawater Desalination Plant to full capacity
(additional 50 gigalitres capacity); and - coastal sites north and south of Perth to service growth for new urban development in these corridors.
More work is being undertaken by the Water Corporation to specifically identify these and other possible sites.
Cost
The cost today of water supplied by the future Southern Seawater Desalination Plant is estimated at $2 to $3 a kilolitre. The cost has two main components:
- the desalination plant; and
- connecting the plant to the water grid and transferring water to customers.
The further away from the water grid a plant is located, the higher the costs to connect and move water to customers. Securing sites close to Perth is increasingly difficult.
More Information
Perth Seawater Desalination Plant
Southern Seawater Desalination Plant
Southern Seawater Desalination Plant (Reports)
Key
1.jpg)
Potential source yield (in 50 year planning horizon)
2.jpg)
Potential cost (2007 $)