Groundwater replenishment - the process of returning treated wastewater to the aquifer system for purification - was an under-utilised way of improving water security in response to climate change, an urban water expert from the University of NSW has argued.
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Using recycled water to replenish groundwater has been successful in other parts of the world such as Orange County, California since the 1970s.
Water recycling schemes are also used to supplement drinking water supplies in Singapore and in Windhoek, Namibia
Australia's first full-scale groundwater replenishment scheme is located in north Perth suburb of Craigie.
It started recharging recycled water to Perth's deep aquifers in 2017.
The project's first stage has the capacity to recharge the Leederville and Yarragadee aquifers with up to 14 gigalitres of purified water per year.
The development of stage 2 of the scheme is also underway with the construction of a second advanced water treatment plant as well as construction of new recharge bores and an associated recharge pipeline.
This second stage is expected to be completed this year and will double the scheme's capacity to 28 gigalitres per year
It is estimated groundwater replenishment could supply 10 per cent of Perth's drinking water by 2060
Brisbane will also recommission its water recycling plants as soon as dam levels drop to below 60 per cent.
Although not a groundwater replenishment scheme, recycled water is deposited into Lake Wivenhoe. When fully operational the Brisbane scheme will recycle 80 gigalitres of water a year.
Stuart Khan, a professor of civil and environmental engineering at the University of NSW, said most state's struggled to effectively manage waste water systems and has called for the reform of a "broken system"
He said groundwater replenishment was capable of providing extremely high quality drinking water at a much lower cost compared to seawater desalination.
"Innovative approaches to water recycling offer the opportunity to keep costs down for customers and mitigate climate change impacts at the same time," he said.
"Unfortunately NSW is dragging the chain on innovative solutions to water recycling so there is not a high level of community awareness about these types of treatment options."
Dr Khan described typical water recycling schemes installed in new housing developments, as a "niche solution" which only went part way to realising the potential of wastewater reuse.
"It's never really cost-effective. The high level of treatment needed for a whole separate supply system, plus monitoring, generally costs more per kilolitre than what the water is retailed for," he said.
"Risk management has been a significant ongoing problem with non-potable water supplies. You'd think it would be simple, but problems with cross-connections appearing between non-potable and potable systems have occurred on practically every scheme"
Hunter Water is conducting a review of the Lower Hunter Water Plan, the state government's blueprint for securing water security in the region.
The Lower Hunter's water supply draws about 20 per cent of its total yield from the Tomago and Tomaree Sandbed aquifers.
A Hunter Water spokeswomen said seven water supply and demand option types, including groundwater options, were being considered as part of the review.
A study undertaken in 2018 identified the Hunter palaeochannel, or ancient river channel, as a potential groundwater source beneath the existing Tomago Sandbeds.
"Hunter Water has begun preliminary investigations, including drilling approximately 70 metres deep, to understand the technical feasibility of this option and its potential for water production," the spokeswoman said.
"We will continue to explore further the feasibility of groundwater options over the coming months."
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- Recycled water is keeping water bills low
- Orica cuts its potable water usage by 90 per cent in less than a decade
- Water regulation not keeping up the demands of industrial users
- The Lower Hunter is now viewed as a piece of an inter-connected water management puzzle
- Water Pressure: Government says 'no way' to revisiting Tillegra Dam
- About 400 megalitres of treated effluent could be transferred from Sydney to the Hunter a day
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