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There are many places around the world that recycle water to add to their drinking water supplies. The key difference between the methods is where they put the water after it is treated.

Our groundwater replenishment trial followed the same approach used in California where treated wastewater undergoes additional treatment and is then recharged to groundwater before being accessed for drinking water supplies. However, in other places such as Canberra and Queensland, proposals for recycling water for drinking water involved adding the water to their dams.

Western Corridor Recycled Water Project – Queensland, Australia

In 2009 the Queensland Government completed a $2.5 billion water grid to treat and supply recycled water to South East Queensland. This water is used by the region’s three main power stations, industrial and agricultural users, and also to supplement drinking water supplies through Wivenhoe Dam. To date, this is the largest recycled water scheme in Australia.

  • Source: domestic and industrial wastewater
  • Treatment: micro-filtration, reverse osmosis and ultraviolet disinfection with hydrogen peroxide disinfection (advanced oxidation).

Groundwater Replenishment System – California, USA

Orange County, California, originally began groundwater replenishment in 1976 to help minimise salt water intrusion into the aquifers. This helped build a case for groundwater replenishment for drinking water. Every day, about 57 million litres of recycled water is blended with groundwater and then pumped into the groundwater system to replenish drinking water supplies and prevent saltwater intrusion. In 2007 the scheme was expanded to pump 265 million litres per day into aquifers which supply up to 50 per cent of Orange County's water (about 600,000 residents).

  • Source: domestic and industrial wastewater
  • Treatment: micro-filtration, reverse osmosis and ultraviolet disinfection with hydrogen peroxide disinfection (also known as advanced oxidation)
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NEWater – Singapore

Singapore’s national water agency completed its first NEWater plant in May 2000. NEWater is highly treated recycled water that has been strongly endorsed as a safe and sustainable source of water because it exceeds the drinking water standards of the World Health Organisation (WHO).

Approximately 11 million litres of water a day is added to a reservoir then further treated as part of Singapore's normal drinking water treatment system. Currently, there are four NEWater plants which meet 30 per cent of the nation’s water needs.

  • Source: domestic and industrial wastewater
  • Treatment: ultra-filtration and micro-filtration, reverse osmosis and ultraviolet disinfection

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Hampton Water Treatment Works - London

United Kingdom water company, Thames Water, draws water from the River Thames and pumps it to storage reservoirs. On arrival at Hampton, the stored water is fed into the Grand Junction Reservoir. This small reservoir is predominantly used to blend different sources of water and balance the flow into the plant.

When the water is passed through primary rapid filters, it gravitates under the Grand Junction Reservoir and is lifted into the ozone plant by six pumps. It then undergoes ozone dosing before passing through slow sand filters. Ozone is the activated form of oxygen and the dosing helps to reduce pesticide concentrations.

  • Source: water from the River Thames, stormwater and industrial wastewater
  • Treatment: advanced water treatment using rapid gravity filters, ozone treatment and sand filters

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Unplanned water recycling

Many communities also drink recycled wastewater through what is called ‘unplanned potable reuse’. This happens where one community collects and treats its wastewater, discharges the cleaned product into a river and, downstream, another community uses the same river as its main drinking water source.

For example, towns on the River Thames upstream of London (Oxford, Reading, Swindon and Bracknell) discharge their treated sewage into the river which is used to supplement London’s water needs.

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 pre-treated drinking water.

In Australia, a number of farms, towns and cities draw some of their drinking water from, and also discharge their wastewater into, rivers and tributaries of the Murray-Darling System. Canberra, Albury and Wagga are examples of such cities. The Murray River is also Adelaide’s primary drinking water supply source.

The difference between planned and unplanned water recycling is how they are designed and regulated. There are more stringent water quality and environmental requirements for the planned schemes, such as groundwater replenishment, which means public health and the environment are protected.