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There are a number of large-scale recycled water for drinking schemes in the world - including California, Singapore and the Goreangab Water Reclamation Plant in Namibia.  There are also small schemes in Europe.

The Groundwater Replenishment Trial follows the approach used in California where treated wastewater undergoes additional treatment and is added to aquifers before use in drinking water supplies.  The treatment processes to be used in the Trial are similar to those used in Singapore.

Singapore
Singapore has been developing recycled water plants since the late 1990s.  Approximately 11 megalitres per day of highly treated wastewater is added to a reservoir then further treated as part of Singapore’s normal drinking water treatment system.  This water currently provides approximately 1% of Singapore’s daily requirements, and the volume of recycled water will increase to 2.5% by 2011.

USA
Orange County, California, blends 57 megalitres per day of highly treated wastewater with groundwater and then pumps it into the groundwater system to augment drinking water supplies and prevent saltwater intrusion.  This process has been operating since early 1976.  In 2007 the scheme was expanded to pump 265 megalitres per day into aquifers which supply up to 50% of Orange County’s water.

In various states of America, including California, Colorado, Florida, Northern Virginia, Texas and Washington, trials have been undertaken since the 1970s and have proven to be highly successful.  These trials have resulted in some full schemes being developed.

Australia
Other Australian states including Canberra and Victoria are investigating recycled water for drinking; however these proposals involve adding the water to their dams, rather than into groundwater.

The Queensland Government is currently developing a $9 billion Water Grid to provide up to 232 megalitres per day of highly treated wastewater from three large wastewater treatment plants at Bundamba, Luggage Point and Gibson Island.  This water will be used to supplement Wivenhoe Dam, a drinking water supply, as well as supply power stations, industry and agriculture.  The project is expected to be complete by the end of 2008.

Unplanned potable re-use
Many communities also drink recycled wastewater in what is called “unplanned potable re-use”.  This happens where one community collects and treats its wastewater, the cleaned product of which is output to a river up-stream of another community using the same river as their main drinking water source.

There are many large towns on the River Thames upstream of London (Oxford, Reading, Swindon, Bracknell) that discharge their treated sewage into the river, which is used to supply London with water downstream.  The same happens in the United States, where the Mississippi River serves as both the destination of sewage treatment plant effluent and the source of potable water.

In Australia the Murray-Darling River is an example of unplanned potable reuse, where towns and farms upstream discharge their wastewater into the river.  Canberra, Albury and Wagga each rely on the Murray as the source of their drinking water, as well as their main mechanism for wastewater discharge.  The Murray is also Adelaide’s primary drinking water supply source.

The difference between planned and unplanned potable reuse is in how they are designed and regulated.  More stringent water quality and environmental requirements are in place for the planned wastewater recycling schemes such as groundwater replenishment in order to protect public health.