Major Projects

Ultraviolet disinfection at the Mt Stromlo Water Treatment Plant

ACTEW has successfully completed the installation and commissioning of an ultraviolet (UV) light disinfection system at the Mt Stromlo Water Treatment Plant. This makes the plant the largest drinking water ultraviolet facility in Australia.

The UV treatment stage of the plant gives ACTEW an increased ability to use water from the Murrumbidgee River for town supply.

Why add UV to our treatment process?

The UV system was installed to ensure there are adequate treatment barriers in place for pathogen reduction, particularly when taking water from the Murrumbidgee River.

While the existing treatment processes at Mt Stromlo readily remove most pathogens, two key pathogens - Cryptosporidium and Giardia - are not as effectively removed by filtration and chlorination barriers. However, both pathogens can be inactivated by UV disinfection, a system used in many places around the world.

The presence of these pathogens is very low in the Cotter catchment due to no or a very small human, cattle and sheep populations. However, at times these pathogens are present in the Murrumbidgee River.

Before the UV system was in place, extraction of water from the Murrumbidgee River needed to be highly controlled to ensure the drinking water supply could be maintained within acceptable quality limits. This limited the time period and volume of water that ACTEW could draw from this source.

The implementation of the UV system has significantly expanded the period when water can be safely drawn from the river.

All water passing through Mt Stromlo is now treated through the UV system, which came at a cost of approximately $8 million.

How UV works

UV disinfection is a physical process. Water is exposed to UV light as it passes through a pipe. The UV light damages the DNA and RNA in pathogens and prevents their cells from replicating, rendering them unable to infect other cells. At Mt Stromlo, a UV dose of approximately 27 mJ per cm2 is used to make the treatment work effectively.

Other work

Other work undertaken at the Mt Stromlo Water Treatment Plant as part of this project included the installation of an additional sludge thickening tank and emergency generators.

Linked to the UV project is also the upgrade of the Cotter Pumping Station, which has included a full engineering and heritage upgrade of this historic facility.