Recycled water supply update - 20 February

Werribee recycled water update

Melbourne Water supply Class A recycled water to Southern Rural Water, who in turn supply the water to our Werribee Irrigation District customers.

Melbourne Water paused supplying recycled water to Southern Rural Water on Tuesday, 30 December 2025, because the Blue Green Algae cell count exceeded the acceptable supply limit.

What is the current BGA count now?

The BGA count on 19 February 2026 was 150,8000 cells/ml.

The count needs to drop below 50,000 cells/ml for three days in a row before recycled water supply can resume.

Melbourne Water and Southern Rural Water cannot provide certainty on when this level will be reached, meaning we cannot provide a definite timeframe for when recycled water services will be resumed.

What is Blue Green Algae?

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 is Melbourne Water doing to seek to lower the BGA count?

A large-scale peroxide dosing trial started on 5 January 2026.

This is the third year of peroxide trials that Melbourne Water has progressively scaled up from laboratory testing and small-scale pilot plant studies, through to a series of 24-hour tests at full-scale operation. Tests are advancing to continuous full-scale dosing over the whole bloom season. 

So far, trials demonstrate scalability and efficacy, and it's likely to be the most feasible solution for blue-green algae control at waste stabilisation ponds.

When is the ultrasonic trial planned?

A trial using a commercially available ultrasound unit for controlling blue-green algae is planned to be implemented in mid-2026. However, this trial will not be available in time for the 2026 bloom season.

What other trials have been investigated?

Copper based algaecides are commonly used to control blue green algae at small scales, particularly in water bodies that don't discharge to marine environments. Melbourne Water conducted a small-scale trial using coper-based algaecide in 2022 to determine its effectiveness and the rate at which copper was removed from the system.

Copper is toxic to shellfish and other marine species at relatively low concentrations. Unfortunately, the trial showed that copper remained persistent in the process and was ineffective at controlling the algal bloom, making it not a viable option.

No further trials using copper-based algaecides to control blue-green algae are planned.

Investigations found that a small-scale trial using ozone would not be safe for staff to implement without costly and complex control measures. 

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.  

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.

Contact us         

If you wish to lodge a complaint, Southern Rural Water is committed to responding or passing on complaints or feedback as appropriate.

Please call 1300 139 510 or email srw@srw.com.au

Our Customer Charter can be found here.