Water treatment

Our water treatment process uses disinfection and filtration to produce safe drinking water. We then monitor the water along multiple points in the supply system, keeping your drinking water safe as it travels through the network to reach your tap.

Our different supply systems use different treatment methods depending on where the water catchment is located and the unique properties of the water. 

Water sourced from unprotected catchments requires both filtration and disinfection due to nearby agricultural and urban activity. 

The majority of Melbourne's water only requires disinfection, as it's mostly sourced from protected catchments.

Filtration

We operate 7 water filtration plants (WFP). Most of our plants use a Dissolved Air Flotation Filtration (DAFF) treatment process. All our filtration processes produce high quality water with minimal chemical use. 

DAFF is an energy-efficient filtration system. It uses chemicals to force particles to stick together in clumps. Air bubbles then lift these clumps to the surface where they can be easily removed.  

Merrimu WFP uses a sedimentation-filtration process. This involves separating particles by giving them time to settle, then filtering them.  

Disinfection 

Disinfection is an important part of the treatment process that destroys harmful pathogens in the water supply. Disinfection kills bacteria and viruses and provides ongoing protection as the water travels through our network. 

We use methods like chlorination, as well as powerful ultraviolet light to disinfect the water. The method we use depends on the supply system.

Chlorination 

Chlorination is the addition of chlorine to the water supply to destroy microorganisms. Bulk water coming from the Melbourne supply system is disinfected by chlorination, with additional dosing carried out in our service region. 

Chloramination 

Chloramination is the addition of ammonia to chlorine, which forms chloramines. 

Chloramines are effective at maintaining disinfection of the water supply over long networks. 

Correcting pH levels 

We correct pH levels to ensure water is not too acidic or alkaline. We do this by adding substances like lime, carbon dioxide, or sodium carbonate.  

Maintaining a neutral pH level of water protects our pipes from corrosion and improves the efficiency of any additional chemical dosing. 

Ultraviolet light 

Ultraviolet (UV) disinfection treats water by using powerful ultraviolet light to neutralise harmful microorganisms. It adds an extra layer of protection by effectively targeting microorganisms that can be found in open catchments.  

UV disinfection is a sustainable water treatment process that doesn’t impact the taste or smell of drinking water.  

Fluoridation   

Fluoride is a natural element found in rocks, soil, water and plants, and is added to drinking water to improve dental health. 

Fluoridation is used in the Melbourne supply system and at our Merrimu and Rosslynne WFPs, using fluorosilicic acid or sodium hexafluorosilicate. Our smaller plants don’t add fluoride. 

For more information about fluoride, visit the Department of Health and Human Services.