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by Annabelle Powell, Journalist, Utility magazine

Australia is projected to see up to ten per cent less rainfall across the south of the country by 2030, and 20 per cent by 2050. Alternative water sources, such as desalination, will play an increasingly vital role in providing the population with fresh water as we face the impacts of climate change.

Desalination is the process of removing the salt and impurities from seawater to make it drinkable. Desalination facilities withdraw enormous amounts of seawater through large pipes along or beneath the seafloor, which is then processed and treated to make it safe for consumption.

Desalination plants operate independent of rainfall, and with the high risk of events like heat waves, bushfires and cyclones gaining intensity in the coming decades, desalination plants can provide a critical backup supply.

Following the devastating effects of the Millennium Drought – Australia’s worst drought in living memory – concern rose that the country could run out of fresh water.

Six major desalination plants were constructed across the states following the Millennium Drought, with the largest in Victoria, the state hit hardest by the dry conditions.

As Australia’s droughts become longer and more frequent, the existing desalination plants may have to function at a higher capacity than they are already. In addition, new plants continue to be planned and developed in coastal cities around the country.

From seawater to drinking water

There are two main methods that are used to produce desalinated water: distillation and membrane processes.

• Distillation: This process occurs naturally through evaporation or through very simple methods such as boiling salty water and condensing the steam. Commercial desalination plants using this process have been in operation for decades

• Membrane processes (reverse osmosis): Currently, the more widely used method relies on a semi- permeable membrane with microscopic pores that separate bacteria, viruses, salt and other impurities leaving only fresh water. Most desalination plants built recently in Australia use reverse osmosis

Around 40 per cent of the water that goes through the desalination plant comes out as fresh drinking water. The remainder, known as brine, is pumped back into the ocean.

Drinking water produced by desalination plants is monitored and tested in the same way as water from a Filtration plant and must meet the standards of the Australian Drinking Water Guidelines (2006).

Australia’s major desalination plants

Major coastal cities in Australia have invested in desalination plants to improve water security. In Perth, long-term reductions in rainfall have had a significant impact on dam flows, and desalination plants have become a base load provider of water.

In 2020-21, water produced by the Perth and Southern Seawater Desalination Plants made up 47 per cent of the city’s water supply. In other coastal cities, desalination plants provide an insurance policy that ensures the population does not run out of water. Australia’s major desalination plants are:

• Perth and Southern Seawater Desalination Plants (Western Australia): The Perth Seawater Desalination Plant, located in Kwinana, was completed in late 2006. It produces 45 billion litres of fresh drinking water a year and around 17 per cent of Perth’s water supply. The Southern Seawater Desalination Plant in Binningup produces 100 billion litres of drinking water per year.

• Kurnell Desalination Plant (New South Wales): The plant is located in Sydney and was completed in 2010. It is currently the largest plant in the country and has the capacity to supply about 250 million litres of drinking water per day, supplying 15 per cent of Sydney’s water needs.

• Wonthaggi Desalination Plant (Victoria): The plant is located in Wonthaggi and was completed in 2012. The plant can produce 150 billion litres of water a year with the capability to expand to 200 billion litres a year.

• Gold Coast Desalination Plant (Queensland): The plant is located at Tugun and was completed in February 2009. It can produce up to 45 billion litres per year of drinking water for the Gold Coast, Logan and Brisbane.

• Adelaide Desalination Plant (South Australia): The plant was completed in 2011 and has the ability to  produce up to 100 billion litres of water per year.

Planning for the future

New desalination plants are in various stages of construction across Australia, in Kangaroo Island, Belmont and Eyre Peninsula. In South Australia, Kangaroo Island’s new desalination plant is expected to improve drinking water security and support the island’s tourism and agricultural industries.

The plant aims to add a layer of bushfire resilience. During the Black Summer bushfires, the higher-than-usual demand for water, primarily from fire-fighting use, was only able to be met through network reconfigurations and carting water from the mainland.

Desalinated water would provide a backup supply to firefighters in the event of another severe bushfire. Planning has also been approved for a new desalination plant in Belmont, New South Wales, to provide an enduring supply of water for the Lower Hunter Region.

The new plant is expected to produce up to 30 million litres a day of drinking water, in response to droughts that have ravaged the Hunter
region in recent years.

SA Water’s planned Eyre Peninsula seawater desalination plant is reviewing its location, following ongoing engagement with the Eyre Peninsula community. The utility is set to explore more cost-effective alternatives compared to the current preferred site near Sleaford Bay.

The Australian Government invested $20 million in funding to the National Centre of Excellence in Desalination Australia (NCEDA) in 2009 to conduct research supporting the development and commercialisation of innovative technologies in desalination.

Some of the projects objectives are to secure Australia’s water supply by:

• Providing leadership in accelerating ground-breaking research on energy efficient desalination technology for water supply being developed in Australia

• Investigating ways of optimising and adapting desalination technology for use in Australia’s unique circumstances

The Federal Government has continued to invest in the NCEDA over the years, indicating its desire to innovate desalination technology as the population grows and the need for freshwater becomes more urgent.

Addressing environmental concerns

Most forms of desalination are energy intensive and have the potential to increase greenhouse gas emissions. Many Australian plants attempt to offset these emissions by using wind power or purchasing renewable energy certificates.

An additional environmental concern around desalination are the impacts of releasing brine back into the ocean. The salts and minerals extracted from the seawater forms a hyper saline slurry leaving it with a much higher salt concentration than seawater.

The high density and salinity of this brine waste can accumulate in and around disposal areas, smothering bottom dwelling species and altering coastal ecosystems.

While diffusers are used to mix brine with seawater and disperse it at several different discharge points from desalination facilities, the large-scale uptake of desalination could overtake these protective measures.

Currently, there is an absence of detailed scientific studies on the impact desalination plants could have on marine ecosystems. By 2025, more than 2.8 billion people in 48 countries are likely to be short of water. To adapt to this new way of life, our alternative water sources will become vitally important.

As desalination technology continues to innovate, there is an opportunity to address environmental concerns and evolve the industry into a sustainable long-term solution.

 

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