Drinking Water

How is my water treated?

Here’s how the treatment process works.

Siphon

Water is taken from the river by siphon to draw the flow into a concrete main. This travels five kilometers downstream to reach the plant.

Storage Ponds

Once it reaches the plant, only the amount of water required is stored in three holding ponds until it's needed. Unused water returns to the river. When the river is in flood and dirty, the flow is shut off and the plant can run on its stored capacity for 3-4 days.

Coagulation

From the ponds, water is let into a large concrete vessel or clarifier, where the chemical coagulants PAC (poly aluminium chloride) and polyelectrolite are added to form small floc particles, these attract the fine suspended silt and clays present in the water. These drop to the bottom of the clarifier as sludge.

Filtration

Five sand filters are used to “polish” the water to a high degree of clarity and remove any residual floc particles. The filtered water is then piped to a covered clear water pond.

Chlorine, fluoride & lime

Metered dosing is carried out at the clear water pond, using chlorine (disinfectant to give protection from micro-organisms that may enter the distribution system), fluoride (for prevention of dental cavities in children), and lime (to raise the pH of the water making corrosion of pipes less likely).

Reservoirs

The last storage point before water enters the town water mains is the Upper Plain Reservoir, supplemented by smaller reservoirs on Lansdowne hill. The supply is almost all gravity fed from our reservoirs, with only a limited amount needing to be pumped to the highest point.