Mount 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 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 catchment. A substantial upgrade of the water treatment plant was undertaken to ensure the quality of Canberra’s drinking water during the Cotter catchment’s lengthy recovery. The new, more sophisticated Mount Stromlo WTP was commissioned in November 2004.
Many of the old Mount Stromlo WTP systems 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 more cost effective. The dissolved air flotation system is used to ensure the quality of treated water remains high if the raw water quality deteriorates.
The water treatment plant has a production capacity of 250 megalitres (million litres) a 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
- pH adjustment and stabilisation with lime and carbon dioxide
- fluoridation by sodium silico fluoride.