Recycled Water for Drinking (Groundwater Replenishment)
Background
Unlike most forms of water recycling, recycling water for drinking involves increasing the public drinking water supply rather than substituting scheme use with an alternative supply.
One of the new drinking water supply options currently being considered by the Water Corporation is groundwater replenishment using recycled water.
Groundwater replenishment is a process where water from Perth’s wastewater treatment plants is treated to the highest standard through a process called reverse osmosis then pumped back into groundwater. The remaining high quality water then mixes with existing groundwater supplies and can be taken out many years later and treated again for use in Perth’s drinking water system.
There are a number of large scale recycled water for drinking schemes in the world, such as the Groundwater Replenishment System in California, the NEWater scheme in Singapore and the Goreangab Water Reclamation Plant in Namibia.
Queensland’s Western Corridor Recycled Water Project is Australia’s largest water recycling project and the first nationally to propose recycled water for drinking. The project is due for completion in 2008 and will recycle water from most of the wastewater treatment plants in Brisbane and Ipswich for a variety of uses, including public drinking water supply.
In addition to this project, water recycling to increase drinking water supplies is also being considered in Canberra. The Canberra water utility launched the Water2WATER proposal early in 2007, which may involve supplementing drinking water supplies by recycling Canberra’s wastewater. Community and scientific reviews are ongoing and a final decision on this scheme has not yet been made.
The Queensland and Canberra proposals involve adding the recycled water to their dams, rather than into groundwater.
In April 2007 the WA Premier announced the development of the State Water Recycling Strategy to improve water use efficiency and water recycling in Western Australia. This strategy supports the State Water Plan 2007 water policy framework to “use and recycle water wisely”. The Water Corporation participated in the development of this strategy which included consideration of groundwater replenishment as a long term source option for Western Australia.
Current Situation
The Water Corporation has committed to undertaking a three year trial, due to commence in 2009. It aims to demonstrate to the community and environmental and health regulators that groundwater replenishment is a safe and sustainable water source option for Perth.
To undertake the trial, a reverse osmosis plant will be built at the Beenyup Wastewater Treatment Plant in Craigie, and the high quality water sourced from the wastewater treatment plant will be injected into the groundwater at a depth of about 200 metres.
The trial will monitor:
- water quality, before and after the water is injected into the groundwater;
- any changes to the groundwater and water movement once the water is injected; and
- the performance of the treatment processes and associated equipment.
Following the three year trial and subject to approvals by the regulators and community support, the Water Corporation will consider developing a large scale groundwater replenishment scheme by 2015 which could deliver an additional 25-35 gigalitres of drinking water per year as a result of this process.
The water from the trial will not be used for drinking or for other purposes, but it will be closely monitored and tested as part of the trial and research program. It will not affect private bores in the area. Research and monitoring results from the trial will be made publicly available.
Groundwater replenishment has the potential to deliver a number of environmental benefits, including maintaining or preventing further decreases in groundwater levels as a result of abstraction or drying climate.
Future of Recycled Water for Groundwater Replenishment
Groundwater replenishment has the potential to contribute an additional 25-35 gigalitres a year to Perth’s water supply by 2015. This equates to about 10% of Perth’s annual demand. It is important to reserve water from the Beenyup Wastewater Treatment Plant to support this option.
In the long-term, it is possible that groundwater replenishment could contribute between 70-100 gigalitres each year by recycling water from Perth’s major wastewater treatment plants. This could account for approximately 25% of annual demand for scheme water supply.
Sustainability considerations
| Economic | Social and Cultural | Environmental |
| Not yet fully costed due to nature of trial. | Community acceptance is essential for the trial to continue into production. | Helps to maintain wetlands and vegetation dependent on groundwater for survival. |
| Can help to support existing public drinking water supply bores. | Various schemes being developed across Australia and the rest of the world will increase experience and support community confidence. | Reduces demand for new future water sources and sites. |
| Can allow water to be banked for future years – replaces need for additional costly storage. | Reduces wastewater discharges to the ocean/ environment. | More energy efficient than other large scale water solutions such as desalination. |
Potential source yield
If proven successful, groundwater replenishment could contribute 25 gigalitres a year into Perth’s water supply by 2015. This would be enough water to supply 100,000 houses with drinking water. By 2060, groundwater replenishment could contribute 100 gigalitres a year of additional scheme water from all of Perth’s major wastewater treatment plants.
Potential Cost
As regulatory and community standards have not yet been determined, early estimates indicate a range of possible costs of between $1.50-$3 a kilolitre.
More Information
- Singapore NEWater
- Groundwater Replenishment in Orange County, California
- Water Recycling, November 2006
Integrated Water Supply Scheme
Security through Diversity, 2005–2050 - Groundwater Replenishment
Key
Potential source yield (in 50 year planning horizon)
Potential Cost (2007 $)