Treated wastewater is the water discharged from a wastewater treatment plant after it has been processed to reduce nutrients and other contaminants. Wastewater can undergo a high level of treatment which results in water that is suitable for a similar range of non-potable uses as harvested stormwater.
Recycled wastewater is a climate independent source of water that can contribute to South Australia’s water security. Desalinated seawater is the only other water sources that is fully independent of climate. As climate independent sources these two water sources are likely to become increasingly important in the future with changing rainfall patterns as a result of climate change.
Wastewater recycling in South Australia today
South Australia is recycling more wastewater than ever, reusing one in every three litres of treated wastewater in irrigating vineyards, other horticulture crops and city parklands.
SA Water provides wastewater services for almost 90% of the state's population across Adelaide and the major towns. Twenty of the twenty-five wastewater treatment plants operated by SA Water support reuse.
In 2018–19 SA Water recycled 35.9% of the wastewater that it treated, with recycled water used in both urban and rural areas.
Examples of large scale wastewater recycling projects include:
- Virginia Pipeline Scheme supplies 20 billion litres of recycled water per year from the Bolivar Wastewater Treatment Plant to growers on the northern Adelaide plains which includes the largest greenhouse area in Australia.
- Willunga Basin Water Company supplies 6 billion litres of recycled water per year from the Christies Beach Wastewater Treatment Plant to irrigate vineyards in the McLaren Vale region.
- Glenelg to Adelaide Pipeline supplies 4 billion litres of recycled water per year from the Glenelg Wastewater Treatment Plant to businesses and council facilities across Adelaide including for Adelaide Airport toilets, and irrigating the Adelaide Oval and Adelaide Parklands offsetting the “heat island’ effect of the city.
- The Northern Adelaide Irrigation Scheme, which is currently being constructed will supply 12 billion litres of recycled water per year from the Bolivar Wastewater Treatment Plant to provide additional recycled water to the Northern Adelaide Plains.
- Approximately 450 million litres per year of recycled water is supplied in separate dual reticulation or “purple pipe” networks across Adelaide for non-drinking uses such as toilet flushing and irrigation including:
- At Mawson Lakes a mixture of recycled wastewater and stormwater is supplied to 10,000 residents in 4000 homes as well as 6000 workers and 7500 students in educational institutions.
- At Seaford Meadows recycled wastewater from the Christies Beach WWTP supplies 8000 homes.
- At Bowden recycled water from Glenelg is provided for toilet flushing.
Local councils are responsible for effluent and some sewage collection, treatment and disposal services for the country towns not serviced by the state government. In these towns, wastewater is managed by local councils through Community Wastewater Management Systems (CWMS). There are 175 CWMS in 50 councils throughout the state, most are owned and operated by the local council.
Many regional towns use water from the CWMS to irrigate parklands, golf courses or crops. The Mount Barker District Council operates the largest council wastewater treatment plant and recycled water scheme in SA, targeting 100% reuse of treated wastewater.