Purified Recycled Water

Water is a precious resource, and it doesn’t always rain where and when we need it to.

Purified recycled water is a safe method of re-treating and re-using water that would otherwise go to waste.

By using purified recycled water to replenish south-east Queensland’s largest water storage, Lake Wivenhoe, we have a safe and sustainable way to supplement our drinking water.

What is membrane filtration (microfiltration)?

What is reverse osmosis?

What is ultraviolet advanced oxidation?

How our purified recycled water plants work

Purified recycled water is made using treated wastewater, which would otherwise be released into our waterways and into Moreton Bay.

We make this water safe through:

  • membrane filtration
  • reverse osmosis
  • ultraviolet advanced oxidation
  • disinfection.

In very simple terms, these processes firstly filter out anything larger than a water molecule, such as particles and contaminants like bacteria and viruses.

Then the water is exposed to hydrogen peroxide along with intense UV light to destroy any trace amounts of impurities.

The water is then safe for drinking and meets the stringent standards set by the Australian Drinking Water Guidelines.

This pure water is then used to replenish Lake Wivenhoe, blending it with captured rainwater already in the lake, before it is treated once again at our Mount Crosby Water Treatment Plants.

A comprehensive testing and monitoring program means water quality is verified multiple times a day.

Water is recycled all the time in the environment through the natural water cycle. We are simply speeding up the water cycle so we can reuse it more quickly. There is no new water, we are drinking the same water the dinosaurs drank.

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  • How do you make the water safe?

    We have the knowledge, technology and testing regimes available to be certain purified recycled water is safe for drinking.

    Very simply, used water is firstly treated at a wastewater treatment plant to break down organic matter before it arrives at our purified water treatment plants. Then the processes of membrane filtration and reverse osmosis filter out microscopic particles like silt, chemicals, hormones and microorganisms like bacteria. Ultraviolet advanced oxidation then degrades remaining organic compounds. Water used to replenish Lake Wivenhoe would be very high quality, far exceeding that which the dam receives from run-off after rainfall.

    The treatment process is closely monitored by engineers and water scientists and water quality is verified multiple times a day. We have a comprehensive testing and monitoring program, with multiple critical control points designed to prevent purified recycled water from entering Lake Wivenhoe if it has not met all critical limits.

    In 2012-13, we monitored and tested the purified recycled water we were supplying to power stations. We tested for more than 360 biological, radiological and chemical constituents and no public health concerns were identified. The assessment considered more than 74,000 tests (32,000 on purified recycled water and 42,000 on the treated wastewater provided to the purified water treatment plant).

    In the decade since our purified recycled water plants were constructed, there has been a substantial increase worldwide in other water recycling schemes for drinking water supply including in Perth, Western Australia and countries such as the US, the UK and Singapore.

    It's important to note that all sources of water, including water from lakes and rivers, contain impurities that need to be removed.

    How does purified recycled water fit into South East Queensland's water supply plan?

    South East Queensland’s water supply plan includes measures to ensure our region’s water supply remains secure, especially during extreme climatic events like drought.

    Purified recycled water is a source of drinking water that is less reliant on rainfall than dams.

    The purified recycled water plants and pipelines were built during the Millennium Drought to provide drinking water. After replenishing rain filled our water storages, the plants were placed into care and maintenance mode.

    Purified recycled water is critical to our ability to respond to drought in South East Queensland should our Water Grid dam levels decline.

    The program to restart the scheme has been designed so that all three purified recycled water plants need to be fully operational within two years of re-start.

    There may be an opportunity to progressively release purified recycled water into Lake Wivenhoe as each plant comes on line but only after full Government approvals, including from public health and drinking water quality regulators.

    In the longer term, to help meet population growth and increased demand for water, the purified recycled water plants in conjunction with the desalination plant, will supplement our drinking water supply on a more regular basis.

    With rainfall becoming less reliable, and our population growing, purified recycled water is a key part of our future water supply plans. With the SEQ Water Grid, the Gold Coast Desalination Plant and the adoption by communities of water efficient behaviours, purified recycled water can help us achieve a more sustainable water future for South East Queensland.

    When does this start?

    Under South East Queensland’s Drought Response Plan, the decision to remobilise the plants for our drinking water supply needs to be considered should Grid dam levels reach 60% capacity. This will be a decision at the time for the State Government.  

    Seqwater is ready to recommission the purified recycled water scheme if required to make sure the water is ready to be released into Lake Wivenhoe when it’s needed.

    The remobilisation process is expected to take up to two years to have all three purified recycled water plants fully operational. This includes the rigorous validation process of all three plants and pipelines involving Queensland Health and the Queensland Water Supply Regulator to make sure the water produced meets the required public health standards.

    In 2018, Seqwater recommissioned a small part of its Luggage Point purified recycled water plant to supply pure water for the operation of the Swanbank gas-fired power plant near Ipswich. We test the water supplied daily, and this testing has shown that we continue to make recycled water that meets the very high standard set for drinking water, even though it is then used for industrial purposes.

    Who will be drinking purified recycled water?

    The purified recycled water will be used to replenish Lake Wivenhoe, blending it with captured rainwater already in the lake before being treated again at our Mt Crosby Water Treatment Plants and introduced into the region’s water grid.

    Purified recycled water will not be directly added to the bulk water supply from the purified recycled water treatment plants, without first going through this process.

    Purified recycled water, like desalination, will help supplement the SEQ Water Grid supply which moves drinking water around our region every day. 

    Central Brisbane, Ipswich, Lockyer Valley and Logan currently receive their drinking water primarily from the Mount Crosby plants. The SEQ Water Grid can move water around the region, so suburbs such as Moreton Bay, Redlands and suburbs in Brisbane’s north could receive purified recycled water depending on the operation of the Water Grid.

    What happens to the water once it has been treated at our purified recycled water treatment plants?

    In Queensland, the legislation governing recycled water for drinking requires purified recycled water to be stored in an aquifer, lake or dam. As such, Seqwater would use purified recycled water to supplement our drinking water supply in Lake Wivenhoe by blending purified recycled water with rainfall captured by the lake. The water in Lake Wivenhoe is then treated again at the Mount Crosby Water Treatment Plants before supply through the SEQ Water Grid to homes and businesses. All water from Mount Crosby Water Treatment Plants is re-tested, as usual, to make sure it meets drinking water quality standards. 

    What makes purified recycled water a more beneficial option over building more dams?

    Across South East Queensland we have 26 dams, with the most recent, Wyaralong Dam, constructed in 2011.

    Even if previously considered dams, such as Wolffdene and Traveston had been built and were at full supply level, they would only store a maximum of 6% more water in the SEQ Water Grid and not offer the insurance provided by purified recycled water and desalination during periods when our region is experiencing drought.

    Dams will continue to be the major drinking water source in South East Queensland but dams alone will not be enough for a sustainable and resilient water future for our region.

    For future water security, it makes sense to invest in climate-resilient water infrastructure. Dams rely on rainfall, which isn’t always reliable -  especially when we are in drought.

    Isn’t purified recycled water and desalination more expensive?

    Purified recycled water and desalination are more expensive to operate compared to most other, existing water sources in SEQ. This is why these sources are among the last of SEQ’s current water sources to be used in a drought. At the same time, these sources provide water supply security for a region which has experienced severe droughts in the past and will again.

    Seqwater is continuing to investigate ways to reduce the operational costs for both purified recycled water and desalination.

    While dams will continue to be the main supply of drinking water for SEQ well into the future, purified recycled water and desalination provide more resilience and supply reliability whether it rains or not.