Stroud water supply
MidCoast Water Services provides water to approximately 440 customers in Stroud and Stroud Road.
The scheme was developed to overcome water quality problems with the previous supply. In the past, water was pumped directly from a weir on the Karuah River to the Stroud reservoirs, for distribution to homes. Treatment of the supply was minimal - there was just a screen on the pump to stop large objects, such as sticks and leaves, from getting into the water and chlorine was added at the reservoirs.
In times of high flow, from heavy rains or flood and also during low flow periods, the water quality deteriorated significantly. To overcome the problem, an off stream storage unit and water treatment plant were added in 1997.
The water treatment plant is capable of treating two million litres a day. Water is pumped from the Karuah River to the treatment plant. Prior to entering the plant, sodium hypochlorite (liquid chlorine) is added to assist oxidisation of soluble metals. Activated carbon can be added before water enters the treatment plant to remove taste and odour issues, however this is rarely needed.
Just before entering a flocculation tank, ACH (aluminium chlorohydrate) is added to promote coagulation. This helps particles in the water to stick together so they can be easily removed. Sodium carbonate (soda ash) can be added to the tank if required to adjust pH.
Water then travels to settling lagoons where the larger particles sink to the bottom. Clear water is drawn from the top of the settling lagoons and travels to the off-stream storage. This storage can hold 50 million litres of water. Chlorine can be added to the storage if required. Two solar powered destratifiers are used to keep the storage well mixed.
From the off stream storage, water is pumped to sand filters to help remove smaller particles. When the clean water leaves the filters, chlorine is added for disinfection and fluoride is added for dental hygiene. Water is stored in a clear water tank until it is pumped to the reservoirs and reticulation system. There are three reservoirs in the system: two at Stroud and one near Stroud Road.
More information is available on the chemicals used in the Stroud water treatment process