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Recycled water (Werribee)

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Werribee recycled water update

Melbourne Water has alerted Southern Rural Water that Blue Green Algae has been detected in Class A recycled water supplied for irrigation.  

While this doesn’t currently affect the supply of Class A recycled water, our Werribee customers are reminded to minimise their exposure.

Blue-green algae is a naturally occurring group of micro-organisms present in both fresh water and salt water. Under certain environmental conditions, these cells can grow rapidly or ‘bloom’. The lagoon treatment process at Melbourne Water’s Western Treatment Plant for Class A recycled water contains nutrient rich water which – when combined with warmer weather – create conditions for a variety of algae species to grow, including blue-green algae.

The Victorian blue-green algae circular, published by the Department of Energy, Environment and Climate Action (DEECA), includes guidance on the limits (cells/mL) beyond which blue-green algae is considered a public health risk.

Melbourne Water follows the recommendations set by DEECA and will cease supply of Class A recycled water if the blue-green algae cell count exceeds the limit published in this guide for swimming. Southern Rural Water notifies our customers when the cell count reaches 10 percent of the limit as a safety reminder.

More information about blue-green algae can be found on our blue-green algae warning page.

What's the current focus in this space?

Southern Rural Water is committed to ensuring recycled water supply is available for our Werribee customers to use. Together with Melbourne Water, we are working together to seek solutions through research and interim interventions to mitigate blue green algae outage risks, while pursuing longer term funding options. The interim interventions include:

  • A large-scale peroxide dosing trial planned to start on 5 January 2026.
  • An ultrasound system installation planned for Q3 2026.
  • A key component of these trials is to monitor for unintended side effects, particularly environmental, to inform the feasibility and timelines for a scale-up of these methods.  

Melbourne Water committed to investing in improvements to recycled water infrastructure as part of its Price Submission 2026-31. The investments included: the renewal and improvement of chlorine treatment infrastructure to be delivered by 2028/29; additional treatments for blue green algae to provide reliability in 2027; and carbon dioxide dosing upgrade to improve pH and reliability.

What's being done to secure a longer-term solution?  

Southern Rural Water and Melbourne Water are both committed to securing a high-quality, reliable recycled water product for Werribee growers through the Werribee System Reconfiguration project.  

Growers and our project partners Department of Energy, Environment and Climate Action, Melbourne Water and Greater Western Water have pledged their support for the preliminary business case.  

We submitted a funding application for further developing the business case to the National Water Grid Authority and we’re awaiting a final decision.  

  • Introduction of the Recycled Water scheme

    The Werribee Irrigation District is an important vegetable growing area on the western fringe of metropolitan Melbourne. Using water from the Werribee River, the aquifer below and the recycled water scheme, over 400 growers produce lettuces, broccoli, cabbages and many other vegetables for local consumption and export.

    During 2004 the then Victorian Minister for Water, John Thwaites, announced the Werribee Irrigation District Recycled Water Scheme would be established. The scheme was designed to assist in overcoming water shortages due to drought and to secure water for greater production in the future.

    During 2004 grower representatives, project partners (Department of Energy, Environment and Climate Action, Melbourne Water and Southern Rural Water), and regulators (EPA Victoria and Department of Health) took up the challenge of bringing the scheme to fruition.

    More than $20 million was invested in additional water treatment at Melbourne Water’s Western Treatment Plant, a connecting pipeline into the Werribee Irrigation District, environmental investigations and approvals, and the operating arrangements for the scheme. Growers received the first deliveries of Class A recycled water under the scheme in January 2005.

  • Class A recycled Water

    Class A recycled water is supplied by Melbourne Water and delivered to participating growers by Southern Rural Water through its existing irrigation channels and pipelines.

    Class A recycled water is water that has been collected from the sewage catchment and treated to make it safe for a wide variety of non-drinking uses.

    The process used to ensure the Class A recycled water is safe for its intended use is strictly regulated by the Environment Protection Authority (EPA) Victoria.

    The treatment process consists of multiple stages of treatment that remove different types of compounds. At the Western Treatment Plant (WTP) we use three stages of treatment, primary, secondary and tertiary:

    • Primary treatment involves physical removal of large pollutants such as plastics, rags and other material that will sink or float.
    • Secondary treatment involves biological removal of compounds like ammonia, nitrogen, carbon and other dissolved compounds.
    • Tertiary treatment involves disinfection to kill residual pathogens left in the water, such as bacteria, protozoa and viruses.

    It is important to remember that although Class A recycled water has been treated for reuse, it should only be used for its intended purpose. For more information on recycled water, visit Melbourne Water.

  • Uses of Class A recycled water

    Class A recycled water can be used for a wide range of non-drinking purposes including for the irrigation of food crops intended for raw or unprocessed consumption. 

    It should not be used for drinking, cooking, showering, filling domestic swimming pools or drinking water for pigs. 

    Class A recycled water is supplied by Melbourne Water who follow strict state and national guidelines for producing recycled water.

  • 2024/2025 recycled water outage

    Recycled water customers were provided with a rebate in recognition of the extended recycled water outage for the time the plant was not in operation during the 2024/25 irrigation season. This included a prolonged outage from 1 February to 7 May 2025, resulting from an outbreak of Blue Green Algae at Melbourne Water’s Western Treatment Plant.  

    Melbourne Water provided Southern Rural Water with a rebate in recognition of the extended recycled water outage for the time the plant was not operating during the 2024/25 irrigation season.  

    Southern Rural Water passed on this rebate in full to its customers.  

    Melbourne Water calculated the rebate based on the cost savings achieved when the plant was not in operation. This was equally applied to each customer proportional to their contract volume.  

 

Using Class A recycled water for irrigation

For information on Shandy Mix salinity levels visit Waterline. 

Western treatment plant recycled water quality

Click the links below to access the “western treatment plant recycled water quality – Post disinfection” report for the corresponding month.