Mt. Stromlo Water Treatment Plant

The original Mount Stromlo Water Treatment Plant (WTP) was commissioned in June 1967. It contained facilities for the chlorination, fluoridation and pH correction of all water drawn from the Cotter River system.

The 2003 bushfire damage to the Cotter River catchment meant that the existing water treatment plant was not adequate to treat the potentially turbid (cloudy) water drawn from the dams in the burnt-out catchment. A substantial upgrade of the water treatment plant was undertaken to ensure the quality of Canberra’s drinking water was protected during the Cotter River catchment’s lengthy recovery. The new, more sophisticated Mount Stromlo WTP was commissioned in November 2004.

Many of the old Mount Stromlo WTP components, such as the chlorination and fluoridation systems, were incorporated into the new water treatment plant.

The new water treatment plant provides for two methods of treatment:

  • Direct Filtration: used when the raw water quality is good
  • Dissolved Air Flotation and Filtration: used together when the raw water quality is relatively poor.

The availability of the two different treatment processes allows for more efficient water treatment. The plant is typically run in direct filtration mode, which is the more cost effective of the two processes. The dissolved air flotation system is used to ensure the quality of treated water continues to meet stringent driking water quality criteria even when the raw water quality deteriorates.

Additionally in 2007, ultraviolet (UV) light disinfection was installed at the treatment plant. The UV treatment stage of the plant gives ACTEW an increased ability to use water from the Murrumbidgee River for town supply. The UV system was installed to ensure there are adequate treatment barriers in place for pathogen reduction. Before the UV system was in place, extraction of water from the Murrumbidgee River needed to be restricted to ensure the drinking water supply could be maintained within acceptable quality limits. This reduced the time period and volume of water that ACTEW could draw from this source.

The water treatment plant has a production capacity of 250 megalitres (million litres) per day. The treatment process involves the following steps:

  • coagulation and flocculation
  • optional dissolved air flotation
  • dissolved air flotation and filtration or direct filtration
  • disinfection by chlorination
  • ultraviolet disinfection
  • pH adjustment and stabilisation with lime and carbon dioxide
  • fluoridation by sodium silico fluoride.

ActewAGL operate the water and sewerage assets on ACTEW's behalf. For more information visit www.actewagl.com.au