Issue 37 March 2006
As dam levels ebb away, two thirsty Australian towns have turned to the challenging notion of topping up drinking supplies with recycled water from their sewage treatment plants.
Councils in Toowoomba on the Darling Downs in Queensland and Goulburn in southern New South Wales are asking residents to accept that about a quarter of their drinking water may come from recycled water.
Mayors under pressure: Goulburn Mulwaree’s Paul Stephenson at a barren Goulburn
Coliban Water, which supplies Bendigo, has also raised it as a distant possibility, and Perth is examining ways of storing recycled water in aquifers for drinking years later.
There are a few examples overseas of using recycled water for drinking, but none is up and running in Australia.
Communities are struggling with the ‘yuck factor’ and the question of whether potable reuse (drinking recycled water) is a safe and workable answer to chronic water shortages around Australia.
Recycled water is increasingly used for agriculture, parks and gardens and toilet flushing, but could it be made safe enough to drink?
Toowoomba and Goulburn have applied to the National Water Commission for Federal Government funding. Both say they are prepared to go through the critical community education and consultation stages with or without this funding, although the Federal Parliamentary Secretary responsible for water policy, Malcolm Turnbull, is a supporter.
“You can treat wastewater with modern technology to a level that makes it safe to drink,” Mr Turnbull says.
Toowoomba plans to build an advanced treatment plant to purify recycled water from the sewage treatment plant, then use it to recharge the Cooby Dam. About 25 per cent of the city’s drinking supply would come from this source.
Toowoomba is further down the track and more bogged down in controversy over its $68 million proposal, epitomising the difficulty of being first to flag such a radical plan.
Mayor Dianne Thorley says Toowoomba, which has been on water restrictions for 14 years, could run out of water within two years.
“We’ve been surviving on groundwater, but that is a huge drain on those reserves,” she says. “We have already cut water consumption by a third, but it’s not enough, and less rain may be part of a long-term pattern of climate change.
“Sewage treatment plants have been putting effluent into rivers that people drink from for years, and they don’t clean it to hospital grade like we plan to. I think every sewage plant should have to clean up their effluent to a much higher standard before they’re allowed to put it into a river system.
”Toowoomba’s proposal is backed by the Queensland Government and local supporters including the group Pure H2O, which is petitioning the Federal Government to approve the proposal.
Toowoomba’s plan to clean its recycled water
But it also has its detractors including Citizens Against Drinking Sewage, which is concerned that the proposal could damage the town’s reputation.
In Goulburn Mulwaree council, Engineering Services Director Phil Hansen says as well as severe drought, his council is under pressure not to increase the amount of water already drawn by Goulburn from the Sydney water catchment.
“A significant part of our local government area is in the Sydney drinking water catchment, and combined with the drought, that led us to look at alternative drinking supplies,” Mr Hansen says.
Under the $35 million recycling plan, high quality recycled water would be returned to Sooley Dam to make up some 30 per cent of the town’s supply. The water would then go through the normal treatment process before being piped to residents.
Council has approved the first $200,000 community education and engagement phase, but the plan will go no further unless this stage is successful, Mr Hansen says.
“It’s heavily dependent on the reaction we get from the community and from NSW Government regulators,” he says.
“We’re very aware that the concept of potable reuse is difficult to accept, and people are justifiably concerned about health and safety issues. We intend to have that debate; we’re not shying away from it.
”Melbourne Water’s John Poon, who is Manager of Strategy and Planning in Water Recycling, agrees that while it is rare for cities to deliberately plan for potable reuse, it often happens in an ad hoc way. It is common for sewage treatment plants to discharge upstream from where other communities draw drinking water. The Murray, Thames and Rhine are examples.
“This situation has occurred over time without any deliberate action or thought, and it becomes the norm,” Mr Poon says.
The world’s first potable reuse plant began operating in Windhoek, Namibia, in 1968. During emergencies or drought, recycled water produced using advanced methods is sent directly to consumers’ taps, without the intermediate step of a river or reservoir.
Since then, several ‘indirect’ potable reuse schemes have sprung up, including in Orange County, North Virginia and Scottsdale, Pretoria and Cape Town. Indirect schemes put high quality recycled water back into a river, reservoir or aquifer to mix and rest with ‘natural’ water before being treated again using normal methods.
Perhaps the most famous example is Singapore’s NEWater project, which began full operation in 2003. Mr Poon, a civil engineer, worked on the scheme, running a pilot plant that undertook a three-year study of human health risks, and chemical and microbial risks.
In the NEWater project, recycled water is produced using advanced membrane filtration and ultraviolet disinfection technologies. The study found that this treatment reduced contaminants such as suspended solids, microbes – viruses, bacteria and protozoans – and chemicals to safe levels.
“When we begin to think about using recycled water for drinking, questions are raised about the longer-term health impacts from unknown contaminants at such extremely low concentrations that we are unaware of them,” Mr Poon says. “Singapore has gone to great lengths to try to address these concerns.”
NEWater is a key part of Singapore’s sustainable water supply, but not much of it ever reaches household taps. Most goes to water-intensive industries such as petrochemical and cooling, or silicon chip wafer making and microelectronics, which need water that is cleaner than drinking water.
Singapore is investing heavily in clearing the public perception hurdle. More than five million bottles of NEWater have been handed out to promote the benefits and familiarise people with the look, feel and taste.
No single technology is foolproof, and potable reuse is not a silver bullet, Mr Poon says. It should be considered alongside other water conservation measures and alternative sources.
“New compounds are being invented and discovered every day and understanding the health implications of thousands of chemicals and emerging pathogens is an enormous and ongoing scientific challenge,” he says.
toowoombawater.com.au
www.goulburn.nsw.gov.au
www.pub.gov.sg/NEWater
The view from Melbourne
Drinking recycled water from a bottle
Communities tend to turn to potable reuse only after other options for securing drinking water supplies have been exhausted. This is not the case for Melbourne, says Melita Stevens, Manager of Water Quality Research for Melbourne Water.
“There are many other things we would do before we would consider putting recycled effluent back into the supply,” she says. “We don’t need now, or in the short or medium term, to turn to potable reuse.
”The idea has generated a lot of discussion in the water industry, she says, but Melbourne can meet its needs for the next 30 to 50 years from supply and demand management measures already in train.
Melbourne draws most of its exceptionally high quality water from protected, forested catchments. Mixing this water with reclaimed, treated effluent would negate the purpose of having protected catchments, Dr Stevens says.