Water Journal : Current May 2016
www.awa.asn.au Resource recovery 59 Each day, Australians send many billions of litres of wastewater into the sewers. There s much more than water in that wastewater, of course, including minerals such as phosphorus, nitrogen and potassium. The fact excess levels of these cause downstream problems, such as eutrophication, means wastewater treatment plants expend many resources reducing concentrations. At the same time, farmers are spending billions of dollars each year on fertilisers to boost soil nutrient levels, consuming an estimated 450,000 tonnes of phosphorus alone. Not surprisingly, finding some way to profitably tap into resources washed down the sewer has been high on the water industry s wish list for years. So where does the science stand? TECHNICAL HURDLES Recovering all the resources in wastewater could deliver a $5 billion annual windfall to Australia, according to a recent Academy of Technological Sciences and Engineering (ATSE) report, Wastewater -- an untapped resource? Lead Author Professor John Burgess said the potential value going unexploited brought to mind sunshine. "There s plenty of solar energy there, if only we could work out a way to get it really cheaply," he said. Phosphorus has been the focus of the most research, which has begun to bear feasible fruit in recent years. Overseas, phosphorus is being extracted as struvite, a magnesium ammonium phosphate slow-release fertiliser. The poster child for global struvite recovery is Vancouver-based Ostara Nutrient Recovery Technologies, which partners with wastewater treatment plants across north America and Europe. The struvite production process involves placing the liquid extract from sludge into a fluidised bed 'Pearl reactor and using chemical precipitation to form crystalline pellets of struvite. Ostara dries, packages, and markets the struvite as a commercial fertiliser. University of Technology Sydney Institute of Sustainable Futures Deputy Director Professor Cynthia Mitchell said Ostara s approach had been particularly clever. "They set up the inner workings of their business model so that utilities benefit from doing the right thing -- from giving them a better feed stream -- and [Ostara] take all of the product management work away from utilities." Struvite recovery has been considered in Australia, where naturally phosphorus-poor soils and the agricultural sector make Australia the world s fifth-largest consumer of phosphate fertilisers. However, Melbourne Water Senior Project Scientist Kelly Brooks said uptake is slow on home soil. "We did a couple of feasibility studies on phosphorus recovery through struvite production several years ago now, but financial analysis showed it wasn t viable for at least 10 years," she said.
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Current August 2016