Water sources: Desalination

Gold Coast Desalination Plant

By Spazio Infinito [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

With National Water Week fast approaching, we thought it apt to launch a series of posts that focus on this year’s thene, “Water sources – there are more than you think.” To kick off the series, let’s take a look at desalination.

What is it?

Desalination plants turn saltwater into freshwater. The desalination process is fairly simple, the most common Australian process is called reverse osmosis, water is pumped under pressure through a membrane that separates most of the water from the salt. The salty water, called brine, is pumped back into the ocean and the freshwater is pumped into our cities.

How is it used?

Check out this video to see how salt water can be converted to drinking quality water.

Where is it being used?

In Australia many of our cities now use desalination plants. Perth has two desalination plants while Sydney, Melbourne, Adelaide and Brisbane have desalination plants ready to use if we need.

While desalinated water makes up part of the mix in some of our major cities, it is also a primary source of water on ships and for many tropical island resorts, like Heron Island, where fresh water isn’t available.

New technology has reduced the cost of desalinated water and how much energy is required, but it is still more expensive than fresh water.

What are some of the benefits of desalination?

People, particularly in large cities, need a lot of fresh water and if it doesn’t rain then large cities can simply use more freshwater than they can store. However saltwater from the ocean is a practically limitless supply of water close to most large cities.

Tugan desal plant at sunset

Tugan Desalination Plant intake during construction.

What are some of the issues with Desalination?

Why is desalinated water more expensive? Firstly, desalination needs more energy to produce, at least 15 times more than water from a big dam. Secondly the desalination plants are quite expensive, Australia was reported to be spending $13.2 billion on desalination plants in 2011 in response to national water shortages. Most of these plants are not being used at the moment, but when the weather turns dry again projected demand means we may need to build even more.

Although desalinated water has been criticised, at the end of a long drought when the dams are nearly dry you might be very happy to be able to drink it. The important thing is to pick the right water source from the available options to provide an environmentally sound and cost effective option.

Have you tried desalinated water?

 

  • VivKay

    Rather than a shortage of water, considering Australia is the driest continent, we are suffering from population overshoot! Diseconomies of scale mean that the public are paying premium prices for a basic human need- water! Nothing grows forever, and instead of the post-Colonial and post-war immigration levels, we need to face the 21st century and become ecological sustainable. Instead of quality of life, and living within our natural limits, GDP and economic growth are both given disproportional priority in government management. We need to curtain massive costs of living and water infrastructure costs through population stabilization.

    • Hi VivKay. Yes we do. Our small contribution to the debate is to help understand what water resources we have and the costs and benefits associated with different water sources. Did you read the groundwater article? In this country of all places we should be storing our water under the ground.

  • Heather

    We wouldn’t need the desalination plants if every home and business had water tanks. Desalination plants use too much energy resulting in making our climate even drier.

  • Hi Heather, as a member of the rainwaterharvesting association of australia, i agree with you. It doesnt mean there isnt a place for desalination as an emergency supply but it should be one of a range of water supply solutions.

    The numbers back rainharvesting up, its not just the cost of energy for desalination its also the cost of energy to pump it from the desal plant to your house. The rainwater harvesting tank is free water right where you need it, although it also has energy costs if you are using a pump they are less than desal costs.

    In terms of volume, absolutely it will make a difference. In a city of a million homes rainwater tanks could supply 50,000 litres/household/year. That is 50 gigalitres (GL) comparable to many desalination plants.