The water treatment process
Capalaba Treatment Plant
Destratification system
Compressed air is pumped into pipes near the bottom of the Leslie Harrison Dam. Air bubbles from the pipes float to the surface and ensures the water is circulated before it is removed through the Intake Tower.
Intake tower
The Intake Tower is 24.5 meters high. When the dam is 100% full only about 6m of the tower is visible above the water’s surface. Water is taken from the dam into the tower just below the water’s surface. Water is not taken from the surface level in order to avoid algae and other surface bugs and it is not taken from the lowest intake point in order to avoid mud and other particles closer to the bottom.
Treatment plant
This water is then moved via a pumping station to the Capalaba Treatment Plant where the ‘raw’ or untreated water is treated to Australian Drinking Water Standards.
What happens at Capalaba Treatment Plant
Stage 1 Clarification
Lime and alum are added to water to assist the fine light particles to form larger particles which settle to the bottom of the clarifier. This removes excess colour and clay particles and the majority of the microbiological organisms.
Stage 2
The clean water spills out the top of the clarifier and is passed through a chamber with chlorine being added to remove excess manganese – a major cause of discoloured water. Lime is also added to correct the pH balance.
Stage 3 Filtration
The water is passed through a sand bed to remove any remaining suspended particles.
Stage 4 Final correction / clear water storage tank
The water is moved into the main reservoir site where it undergoes a final pH correction by adding lime and final disinfection by adding chlorine to kill bacteria.
Stage 5 Distribution
Water is pumped to the distribution systems.
Telemetry system
The treated water is then pumped to the main reservoir site off Vienna Road in Alexandra Hills. At this site there are four surface reservoirs and one elevated reservoir. From there the water is reticulated to the Redlands through over 1,000 kilometres of water pipes or ‘water mains’ to over 44,000 properties. This process is monitored by a computer-based telemetry system.