Recycled water - the future for irrigation
by Vincent Ciccarello
The
people of Toowoomba weren’t prepared to drink it, but South
Australians are comfortable with it being sprayed on their
vegetables and vineyards.
Water recycled from treated sewage elicits a range of emotive reactions - but it has the potential to alleviate the pressure on irrigators, industry and the environment from persistent drought and climate change.
Now, Research Chair of Environmental Science, Professor Nanthi Bolan and researchers in the Centre for Environmental Risk Assessment and Remediation (CERAR) are working to expand the science behind recycled water from sewage, stormwater, dairy and pig farms and other sources.
"Recycled water can play an important role as an irrigation source for sustainable production and environmental protection," Prof Bolan said.
"And while it is not going to be a complete substitute for freshwater, recycled water can be an important complementary source."
Prof Bolan said recycled water has the potential to take the pressure off freshwater supplies, bringing with it a number of added benefits.
"If we increase the use of alternative sources such as treated sewage and stormwater for non-potable purposes, this will reduce the use of freshwater for industry and irrigation," he said.
"Also, if we minimise the amount of wastewater entering our rivers by using it for irrigation, we reduce the effort required to treat the water to drinking water quality."
And in the case of Australia’s generally fragile soils, recycled water can bring much needed nutrients such as nitrogen, phosphorous and carbon to improve soil quality.
"More science is needed, though, to establish the long-term impact of recycled water on soils and plants, such as the effect of high nutrients and salt loadings," Prof Bolan said.
But it is in "ecosystem servicing", or providing water for environmental purposes, that recycled water may be of greatest benefit. With the competition for freshwater likely to result in priority given to domestic and industrial users, Prof Bolan said recycled water could fill a lack of water in other forms of irrigation.
"Irrigation is used not just for agricultural and horticultural purposes," Prof Bolan said.
"Parks, sports fields and other recreational facilities, which could make effective use of recycled water, also rely on irrigation. So, too, could environmental remediation projects."
CERAR already has a number of projects on the go.
It is currently working with businesses in Port Augusta to look at the potential value of recycled water in the revegetation of mine sites.
Closer to home, CERAR is working with the Turf Research Institute and Horticulture Australia Limited to see how recycled stormwater could be used to irrigate sport turf.
And CERAR is about to embark on a project with the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment to see if untreated wastewater can be used to grow non-edible plants as biomass for energy uses.
Prof Bolan said thanks to continued drought, community attitudes to recycled water are fast changing, pointing to the use of recycled water in South Australia on market gardens in Virginia and vineyards in McLaren Vale.
"Drinking recycled water might be a last resort but not long ago it was unthinkable that water recycled from sewage would be sprayed on salad and vegetable crops," he said.
Before coming to UniSA, Prof Bolan was Professor of Soil Science in the Institute of Natural Resources at New Zealand’s Massey University for 22 years. He is a Fellow of NZ Soil Science Society and was named Communicator of the Year (1998) by the NZ Institute of Agricultural Sciences and the NZ Society for Horticultural Sciences. He received the Massey University Research Medal in 2005 for research supervision and the ML Leamy Award from the NZ Soil Science Society in 2004 in recognition of his contribution to soil science. He serves as a member of the Editorial Board of Nutrient Cycling in Agroecosystem and Environmental Geochemistry and Health, and as an Associate Editor of Journal of Environmental Quality.