Water Journal : Current May 2016
www.awa.asn.au 79 Stormwater harvesting Fitzroy Gardens is known for being "uniquely Melbourne". There was just one problem back in 2008: Melbourne was increasingly priding itself on sustainability measures, and keeping the thirsty gardens green was proving unsustainable. Soaking up an estimated 117 million litres of prime drinking water each year, it became apparent that the 26-hectare heritage- listed site needed to tap into water from an alternative source. Enter the Fitzroy Gardens stormwater harvesting system, which since 2013 has been capturing, treating and storing enough stormwater to replace 59% of the drinking water -- or 70 million litres -- previously used for irrigation. The system was funded as part of the Eastern Melbourne Parks and Gardens Stormwater Harvesting Scheme, which received a total of $4.8 million from the Australian Government's Water for the Future initiative in 2011. The cost of water over the lifespan of the system will be $2.49 per kilolitre, with ongoing maintenance expected to cost around $28,000 per year. The treatment process begins with a gross pollutant trap that removes large pollutants, such as litter and leaves. Water then flows to a sedimentation chamber, where suspended particles of pollution such as fine sands and oils are removed. Next to the chamber is the primary storage tank, which stores up to four million litres of partially treated water. From here, water is pumped to the surface where a biofiltration bed naturally removes invisible pollutants such as nitrogen and phosphorus -- which once would have spilled into the Yarra River and Port Phillip Bay. One million litres of treated stormwater then sits in a secondary tank, which passes UV light tubes to kill any remaining bacteria before being pumped into the irrigation network. KEEPING THE GARDENS GREEN WHEN YOU VE GOT AN ABUNDANCE OF WATER, YOU CAN HAVE HIGH-VALUE PUBLIC URBAN SPACES ... AND THAT STIMULATES ECONOMIC DEVELOPMENT. was plucked, leaving only the more expensive and complicated projects left to pursue -- exacerbating the aforementioned cross- jurisdictional problem. "Projects were previously funded by grants or councils as they were the easier ones to do with good payback periods," he said. "Now we are left with complex, large-scale projects which are less cost-effective and therefore harder to fund." That said, there are still a myriad of smaller scale stormwater projects being undertaken across the nation. The Green Square water-harvesting project in Sydney is a prime example. Run in conjunction with the City of Sydney, it will be Australia s biggest residential stormwater harvesting scheme. Green Square is one of the fastest growing in Sydney, with nearly 10,000 new apartments due for completion over the next four years. Enough water to fill three Olympic-sized swimming pools will be pumped out of the Green Square stormwater drainage system each week, purified in a recycling plant and then stored in tanks before being distributed to buildings for use in bathrooms, laundries and gardens. There are also a number of successful projects in Melbourne [see box above], while newly re-elected Brisbane Lord Mayor Graham Quirk pledged $10 million during his campaign to irrigate city sports fields with stormwater harvested from nearby creeks. AECOM Principal Environmental Scientist Courtney Henderson said the value that lush sports fields, public parks Courtney Henderson, AECOM Principal Environmental Scientist and botanical gardens provide for an urban society shouldn t be underestimated. "When you ve got an abundance of water, you can have high-value public urban spaces," he said. "So people feel comfortable in their cities, they enjoy being there, and that stimulates economic development. It also makes the cities cooler, which means people aren t heat-stressed." BMT WBM s David Kirby agrees. "If you have aesthetically pleasing waterways, and parks and ovals it provides people with a place to exercise, which reduces obesity issues." "Stormwater treatment can remove a lot of pollutants that would otherwise end up in receiving water courses, which is not only an environmental issue, but also a social issue if the waterway quality is so bad that you can t swim in it and don t want to walk along the side of it." Or, surf at the entrance of it.
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