Producing recycled water

We produce high quality recycled water at our Eastern and Western treatment plants, using highly specialised treatment processes unique to each plant.

The plants process most of the treated wastewater to a Class A standard. In Victoria, Class A is the highest class of recycled water and is safe to use for a range of non-drinking purposes.

Learn about the process for producing recycled water at our treatment plants.

​Eastern Treatment Plant

The Eastern Treatment Plant is a world-class wastewater treatment plant that also produces high quality recycled water. It is one of the few plants in the world designed to treat all incoming wastewater to a standard suitable for reusing, rather than only a small percentage.

The plant was upgraded to include advanced tertiary treatment in 2012. The upgrade minimises the impact of discharge on the receiving marine environment at Boags Rocks, and has the additional benefit of producing Class A recycled water.

We conducted significant research to choose a treatment method that best suited the plant’s location and wastewater quality. You can read more about this project:

Process for producing Class A recycled water

​Step 1

​After undergoing primary and secondary treatment, treated wastewater is pumped into the advanced tertiary treatment plant.

Ozone injection

Biological media filters

UV disinfection

Chlorine contact basins

​Step 2

​Ozone is added to reduce colour and odour.

​Step 3

​A physical filter removes any residual litter, suspended solids, oil and grease and foam from the secondary effluent.

The filters contain naturally occurring bacteria that help to further reduce the ammonia in the water to very low levels. Reducing ammonia benefits the marine environment, and improves the efficacy of chlorine disinfection in later stages.

​Step 4

​More ozone is added for disinfection inside large concrete tanks.

​Step 5

​From the ozone disinfection tanks, the water passes through large vessels where ultraviolet light is used for further disinfection.

​Step 6

​Treated water enters two large basins, where chlorine is added as part of the final disinfection process.

​Step 7

​Class A recycled water is then pumped to the South Eastern Pipeline where it is supplied to water retailers and customers. The remainder is discharged into the ocean under EPA Victoria licence.

Animation of the tertiary treatment process


Western Treatment Plant

The Western Treatment Plant was the first plant in Victoria to produce recycled water to a Class A standard.

To do this, we use a sustainable, low-energy process that makes use of our existing lagoon system, combined with additional ultraviolet light and chlorine disinfection.

Step 1

​Following secondary treatment, wastewater enters maturation lagoons, where solids and bacteria settle to the bottom. Ultraviolet radiation in sunlight helps naturally disinfect the water.

After 30 to 35 days, the water reaches the end of the lagoon system. At this point the water meets Class C recycled water quality requirements. We use this water at the treatment plant to maintain habitat for migratory birds and for agricultural activities onsite.

​Step 2

​To produce Class A water, the water leaving the lagoon needs further disinfection. The first disinfection step uses ultraviolet light.

​Step 3

​The water then enters a large covered basin where chlorine is added for final disinfection. At this point the water is classified as Class A recycled water.

​Step 4

​Some recycled water is used for irrigating food crops and public open spaces, such as sports grounds and gardens.

Other Class A recycled water undergoes additional treatment by City West Water to reduce the salt content, before it can be supplied to residential customers. This is because wastewater in the west has a higher salt content than the east.

Did you know?

Our disinfection processes reduce biological pathogens in the source water by more than 99.999%.


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