F22
Issued 1/5/1999

91 Hammond Avenue, PO Box 456
Wagga Wagga NSW 2650
Phone 02 6922 0608 Fax: 02 6921 2241
Email: admin@rwcc.com.au

The type of water treatment used by Riverina Water depends on whether the water is from a surface (rivers, creeks) or underground (bore) source.

The Murrumbidgee River provides the surface water that is treated at Wagga Wagga. The river has a large catchment area including a number of tributary creeks.

Clay particles resulting from the surface run-off into the river and creeks cannot be easily filtered. A process called flocculation and sedimentation removes most of these clay particles. Filter Alum (aluminium sulfate) is used for flocculation.

Now that the water is mostly clear, a final filtering through layers of sand and gravel "polishes" it by removing the particles that escaped the flocculation process.

Hydrated lime is added to neutralise the slightly corrosive nature of the water, created by the use of alum. Chlorine is added to destroy any bacteria and pathogens present in the water source, and to maintain disinfection properties while water is being stored in reservoirs.

Fluoride is added in strictly controlled doses to safeguard the dental health of children during their formative years.

The water treatment process is carefully controlled by regular monitoring of the water quality throughout the day.

Underground water supplies are generally very clean and mostly free of bacteria requiring very little treatment. The water is aerated to remove dissolved gases such as carbon dioxide and hydrogen sulfide. Chlorine is again used to destroy bacteria and maintain disinfection properties.

Most underground water sources have a natural fluoride content of about ½ the recommended dose for dental health. At some locations fluoride is added to achieve a recommended dose of 1mg per litre, (one part per million).