“The proposal in the [strategy] is to develop a demonstration plant and that’s an excellent way to enable people to come and see what it’s all about,” he said.

“People will be able to see the technology, understand the safety measures in place, and get to observe the high-quality water that is produced.”

The report noted Sydney was far more reliant on rainfall than other major Australian cities. The Harbour City can meet only about 23 per cent of daily water demand if its desalination and existing recycling plants are operating at full tilt, compared with 34 per cent in Melbourne and about half in Perth and Adelaide.

“Our preliminary analysis shows that, over the past 30 years, average inflows to Sydney’s dams have been half the long-term average since records began in 1910, while significant flooding events have also occurred,” it said. “Future climate risks and extreme events mean we cannot meet our water needs by only using traditional water supply approaches.”

Ensuring the desalination plant operates more constantly could produce an extra 20 gigalitres water a year. That tally, though, would still leave a projected short-term deficit of as much as 70 gigalitres a year. (Current sustainable supply levels are between 515 and 540 gigalitres a year, or about the amount of water held by Sydney Harbour.)

“Increasing our rainfall-independent supply means we can enter periods of drought with higher storage levels in our dams, slow down storage depletion rates in times of drought and improve our response to shocks in the system, such as when bushfires or floods pose water treatment challenges,” it said.

Purified recycled water could provide as much as 200 gigalitres of water a year for a range of uses, although the report acknowledges the public would be wary of it coming out of their taps.

“While communities have indicated an openness to new supply options, engagement and consultation with customers and communities will be needed around the idea of using purified recycled water for drinking purposes,” it said.

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Sydney’s west, particularly around the new airport, might be the obvious place to build a demonstration plant, not least because the area is expected to have rapid population growth and has limited additional supply options.

The planned Upper South Creek Advanced Water Recycling Centre could treat as much as 100 million litres of waste water a day from about half a million local residents.

“The project will include a diversified approach to water recycling that includes the potential for purified water to be used for environmental flows, supply to third pipe systems for urban greening, cooling and industry, and ultimately the potential to supply purified recycled water for drinking,” the report said.

The two main water purification processes are reverse osmosis, using the same membrane technology as the desalination plant, and carbon trains using ozone and filters.

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