Mount Stromlo water treatment plant (WTP) contains facilities for the chlorination, fluoridation and pH correction of all water drawn from the Cotter system.
It has the capability to treat water using two methods, allowing for more efficient water 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 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
- ultraviolet disinfection
- pH adjustment and stabilisation with lime and carbon dioxide
- fluoridation by sodium silico fluoride.
History of the Mount Stromlo water treatment plant
The original Mount Stromlo water treatment plant (WTP) was commissioned in June 1967. Since the 2003 bushfire damage to the Cotter River catchment however, 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 treatment of the Googong reservoir water involves conventional treatment such as:
- optional powdered activated carbon for organic matter removal, if required
- coagulation and flocculation
- dissolved air flotation and filtration (augmented plant) or clarification and filtration, depending on operation mode
- disinfection by chlorination
- pH adjustment and stabilisation with lime
- fluoridation by sodium silico fluoride.
At Googong dam, water is drawn from the storage and pumped to the adjoining water treatment plant. Treated water is then fed to Canberra's service reservoirs through the Googong bulk supply main.
The Queanbeyan River catchment, which feeds Googong dam, is an occupied rural catchment. This means extensive treatment is necessary to ensure a safe water supply. Recreational activities on Googong dam are controlled to avoid excessive turbidity (cloudiness) and contamination problems.
The Googong WTP has recently been augmented to enable it to meet the average daily summer demand of Canberra and Queanbeyan. This ensures that high quality treated water can be provided should the raw water quality in the Cotter or catchment deteriorate.
History of the Googong water treatment plant
The Googong Water Treatment Plant (WTP) was built in 1979 at the same time as the Googong dam.
Historically, water from Googong supply was distributed to consumers in Queanbeyan, north and south Canberra, and the Woden/Weston Creek area during the summer months when water consumption was high. In the low consumption winter months, water from the Cotter system was used and the Googong system shut down.
The Googong catchment supplied all of Canberra and Queanbeyan’s water in the immediate aftermath of the January 2003 bushfires, when the water quality from the Cotter catchment was poor.
The augmented Googong WTP was commissioned in December 2004. A parallel treatment process was added to the existing conventional treatment stream. The new dissolved air flotation and filtration process can be run in addition to or instead of the original clarification and filtration system. The augmentation has increased the capacity of the plant from 180 megalitres (million litres) a day up to 270 megalitres a day.