Producing potable water - our treatment process
AlburyCity, along with all other Local Water Utilities (LWUs) in NSW are required to have a potable water system that delivers treated water that complies with the Australian Drinking Water Guidelines (ADWG) and the NSW Health Act.
LWUs are also regulated by the water section of the NSW Department of Primary Industries (DPI – Water) and also require an EPA licence.
Albury’s Water Treatment Plants
AlburyCity has two Water Filtration Plants (WFPs), both on the same site, located in Water Works and Boundary Roads East Albury. Plant ‘A’ (WFP ‘A’) was constructed in 1980 and Plant ‘B’ (WFP ‘B’) was constructed in 1990.
Both plants are fully automated and operate 24 hours a day, 7 days a week. Each can process 70 megalitres of water per day - the equivalent of 28 Olympic-sized swimming pools.
Both plants use the ‘direct filtration’ process although WFP ‘B’ is soon to be converted to the dissolved air flotation filtration process which will increase its capacity to around 90 megalitres per day.
The treatment process
Raw (untreated) water is pumped directly from the Murray River to the Water Filtration Plant.
When the raw water arrives at the plant, it goes through the various treatment processes. Part of the process sees the water passing through a filter medium consisting of layers of gravel and sand, and topped with a layer of antracite (a hard filter coal). This process removes the dirt particles in the raw water.
The filters must be cleaned every eight to 24 hours depending upon the quality of the raw water. To clean the filters, clean water is pumped back through the filters to remove the accumulated dirt. The backwash water is then discharged to one of the four sludge lagoons, where the dirt settles out. The return water is then pumped back to the filtration plant and mixed with the incoming raw water. Approximately every 12 months, the lagoon is allowed to dry out and the dried sludge is either disposed of off-site or spread over the facility grounds as topsoil.
Part of the treatment process also sees specific chemicals being added to improve the treatment process and/or improve the water quality. These chemicals include:
- Alum (in the form of Aluminium Sulphate) and polyelectrolyte (a non-ionic polymer) are added to assist with the coagulation and flocculation process. Essentially, these chemicals cause the dirt particles to stick together so that it is easier to filter out the dirt
- Lime is added for pH correction, i.e. to control the acidic level that naturally occurs in water
- Chlorine (in the form of a gas) is added/used as a disinfectant to kill any microorganisms in the water
- Fluoride (in the form of Sodium silica fluoride [Na2SiF6] ) is added to improve the health of teeth (and is a requirement of NSW Health)
- Powdered Activated Carbon (PAC) is added to remove algal toxins and control the earthy smell of the water by reducing the levels of methylisoborneol (commonly known as MIB) and geosmin. This process usually only occurs in the months of February and March.
The addition of all of these chemicals and all treatment processes are closely monitored and testing occurs regularly on a daily basis. As part of the automated process of producing treated water the plant has the ability to shut-down if certain water standards or quality limits are not met.