Why purified recycled water is vital to Australia’s water future

As water scarcity intensifies across Australia, purified recycled water (PRW) is emerging as a powerful source within the water security portfolio. Here, SUEZ Water Reuse Discipline Manager Flavia Zraick shares why PRW is not only a viable option, but vital.

As the official Circular Economy Thought Leadership sponsor for Ozwater’25, SUEZ has been working within the PRW space across the global water sector for decades, making the organisation particularly well positioned to help tackle water security planning.

Zraick said Australia’s water security challenges are shaped by a unique combination of factors, including increasingly extreme heat events, shifting rainfall patterns and longer fire seasons.

“Not only is Australia hot and dry, it’s facing more frequent heat extremes and changes to when and how rain falls,” she said.

“On top of that, the population is heavily concentrated in major cities, many of which depend on vulnerable surface water resources. In places like France, Italy and even parts of Spain, groundwater provides a buffer for water supply.

“The exception in Australia is Perth, where the groundwater aquifer offers an additional source, although even that is under pressure.”

Zraick said the reliance on lakes, reservoirs and rivers is already becoming problematic in some areas as the climate changes, with droughts and extreme weather events creating vulnerability and volatility within current surface waters that may become scarce or polluted.

"Surface storages are more vulnerable, not only to variations in quantity, but also quality, which impacts production systems,” she said.

"Incorporating diverse water resources will become crucial in creating more resilient water supply schemes.”

PRW versus desalination

When it comes to comparing PRW and desalination for water security, context is always key, but Zraick said there are certainly financial benefits of leaning into PRW where and when available before considering further investment in desalination.

“Water reuse, particularly PRW, relies on sophisticated treatment processes that seem challenging; it’s definitely more expensive than using water from a clean river or aquifer,” she said.

“But when it comes to finding new resources, it is often cheaper than the alternatives. I like to say that desalination is water reuse’s best friend. When the alternative is desalination, PRW suddenly looks very attractive. Desalination is very energy-intensive and expensive.”

Costs aside, Zraick said it’s impossible to ignore one of the biggest boons of moving towards PRW, which is to utilise existing water assets already in place.

“It all narrows down to one issue – transport,” she said.

“People don’t always realise that the cost of both the infrastructure and the pumping to transport water to off-takers can represent more than the treatment infrastructure itself. And if we’re not treating to PRW level quality, we need a special delivery mechanism to take that water to off-takers.

“Delivery infrastructure for agriculture, street cleaning or industrial customers can be really expensive, if not just very difficult to put in place, as off-takers are rarely positioned right beside wastewater treatment plants.”

Zraick said one of the key advantages of treating water to potable reuse standards is the ability to use existing infrastructure – the pipes and storage systems are already in place and ready for use.

“Potable reuse allows us to match, and often exceed, the quality of conventional drinking water by implementing multiple barriers,” she said. “This means we can tap into current delivery networks and improve the overall economic viability of supply.”

A major driver for potable reuse is avoiding costly upgrades to wastewater systems as cities expand. Instead of building new mains to transport wastewater to the coast, authorities can treat and reinject it into reservoirs or the supply network.

An increasingly important factor – particularly in cities like Sydney – is the tightening of regulations on wastewater discharge. As authorities move towards near-zero nutrient levels, the treatment required already approaches potable reuse quality, making the leap to full PRW more cost-effective and efficient.

Striking the balance

When it comes to how this burgeoning new resource should be used, supplementing drinking water supplies is an option, but Zraick prefers a balanced approach that also places water back into the environment via Indirect Potable Reuse schemes.

In places where groundwater recharge is an option, Zraick said taking this approach can help on multiple fronts.

“If we’re reinjecting water into an aquifer, we tend to set very high standards for water quality. So, the logic around PRW treatment that fits drinking water standards also makes the water quality appropriate to restore our pristine natural resources. When the geology is right, aquifers can serve as reservoirs and even transport systems,” she said.

“And that’s what happens in some cases. In Perth, there’s a double interest. There is the hydraulic barrier to protect from saline intrusion, but also the restoration of the aquifer. And we’re capable of doing all of this in the absence of precipitation.

“Releasing PRW into reservoirs, lakes and aquifers allows natural systems to provide an additional treatment barrier while also serving as a buffer. Drinking water treatment plants benefit from a safe supply of clean water for production.

“The natural environment also plays a very beneficial role in overcoming barriers in public perception.

"Community acceptance is crucial to the success of water reuse, and sending water back through the environment is sometimes an easier way to facilitate acceptance.”

Key challenges

To make sure PRW works to promote water security now and in future, Zraick said innovation is needed to improve cost-efficiency, online process control and brine management.

“It’s going to be important to work on reverse osmosis processes that are less energy intensive. Can we get more water through the system? Can we reduce chemical consumption by managing fouling issues and other elements like that?” she said.

“Even if we know the system works, we still have to reassure our clients that the system is operating as designed and that we’re managing risks appropriately. What are the right parameters and instruments that will allow us to detect any malfunction and react in real-time?

"Brine management is also a crucial issue, particularly in the context of circular economy. What do we do with the concentrate from reverse osmosis? How do we depollute it in a way that makes it safe to return to the environment?”

Technical hurdles can also provide opportunity. SUEZ creates value in its process called brine valorisation, where resources are extracted from the brine byproduct for use elsewhere.

Lastly, Zraick encourages any discussion of PRW and water security to consider very closely the issue of human resourcing.

“Even from a science and challenge perspective, water reuse, especially PRW, is about a new generation of expertise and experts. When it comes to cultivating new talent, we need people who can cooperate across disciplines, understanding the biology in wastewater treatment, the chemistry in drinking water production and the hydrogeology of natural resources."

SUEZ invests more than $120 million (euro) every year on new technologies, developed and tested at its laboratories and implemented throughout the world.

Zraick said this investment provides a wonderful training ground for the next generation of water engineers and the PRW plants it has operating throughout the globe.

“There are very few people who are able to interact intelligently with all the different stakeholders in a circular scheme. It’s a really interesting area for the future for our young scientists and engineers, to develop skills that achieve these aims," she said. 

Interested in hearing more from SUEZ on all things Circular Economy Thought Leadership? Register for Ozwater’25 and join us at Australia's leading water sector conference in Adelaide this May.