Raw Water contains suspended matter and colour. To remove this turbidity and colour, a coagulant (aluminium sulphate) is injected into the raw water and thoroughly mixed in the Flash Mix Tank.
Aluminium sulphate (Alum) dosed water then passes into the clarifiers where the sedimentation process takes place.
The Alum reacts with the natural alkalinityof the water forming a ‘floc’. Being heavier than the water, the floc settles to the bottom taking with it suspended matter and algae. This forms a sludge on the floor of the clarifier which is collected and drained off.
Polyelectrolyteis added after the flash mix as an aid to the flocculation process, as well as a filter aid prior to filtration to improve filtration performance.
The Clarified Water leaving the clarifier still contains small amounts of floc. This is removed by passing the water through sand filters. The filters are periodically backwashed to remove the floc, which is sent to the recovered water tank.
The Filtered water then passes through to the clear water sump where its quality is checked by online instrumentation prior to chlorination.
Sodium Hypochlorite is then added to disinfect the water, which may contain micro-organisms and bacteria, making the water safe for human consumption and distribution. Water is then collected in the clear water reservoir and pumped to holding reservoirs from where it is reticulated to consumers.
Sludge that was collected in the clarifier during the sedimentation process and filter backwash water are all directed to the settled water tank. Sludge is then drawn off and sent to the sewer as trade waste and the recovered water is pumped to back and blended with raw water in storage for reuse.
The Gladstone Area Water Board proudly acknowledges the Byellee, Gooreng Gooreng, Gurang and Taribelang Bunda people as the Traditional Custodians of the Gladstone region. We pay our respects to Elders past and present, and recognise the ongoing connection of Aboriginal and Torres Strait Islander peoples to the land and water on which we rely.