Before raw water from our catchments enters the water supply system, it is purified, filtered and treated to ensure the community receives safe drinking water that complies with the Australian Drinking Water Guidelines.
At the beginning of the process, lime is mixed into the water to minimise the risk of pipe corrosion, taste and odour problems, and ineffective disinfection as the water travels through the system. Carbon dioxide is also added to assist with the coagulation stage of the treatment process.
When necessary, the raw water is dosed with potassium permanganate so that soluble manganese can be easily removed. This reduces the possibility of discoloured water entering the water supply system.
Coagulation / flocculation
Liquid aluminium sulfate (Alum) and polymers are added to separate clear water from tiny particles of silt and mud - this process is called coagulation. The water is then stirred vigorously so that particles form larger, heavier clumps called floc which are easier to remove - this is called flocculation.
The water and floc then move slowly into large horizontal sedimentation tanks. As the flow of water decreases, heavy floc settles to the bottom of the tanks and becomes sludge. This is then pumped into sludge lagoons and the water moves on to the next stage of the treatment process.
The clarified water is dosed with chlorine so that any remaining soluble manganese particles can be removed by the sand filters.
Water flows vertically into slow sand filters which sieve suspended organic material from the water before it enters the clear water storage tank. Any solids that become trapped in the sand are removed by backwashing the filter.
The water is then disinfected with chlorine to destroy harmful micro-organisms before it enters the water supply system. Chlorine is used because of its immediate and long-lasting anti-bacterial effect. Council carefully controls and monitors this process to ensure the residual chlorine concentration poses no risk to health.
The water is then Fluoridated to increase the natural concentration to 1.0 part per million. Fluoride levels are continually monitored to ensure they remain within the optimal concentration range determined by the NSW Department of Health.
Finally, the water is set back to its neutral pH level so that it can travel safely to your tap.