The Headworks comprises the preliminary treatment consisting of fine screens to remove smaller particles, grit, oil and grease to avoid hindering treatment process.
Primary Sedimentation Tanks
As used water passes through the double-deck sedimentation tanks, heavy particles, mostly organics, settle out at the bottom as sludge. Scrapers move slowly along the floors of each deck to remove these solids.
After the heavier organic particles have settled out during primary sedimentation, the used water then flows into the bioreactors. Naturally occurring micro-organisms in the used water helps to consume and break down impurities and colloidal organic matter that are suspended in the used water. Air is released from the diffusers at the bottom of the bioreactor to provide an aerated condition that is conducive for micro-organisms to grow and agglomerate. Resulting biomass clumps can be settled out and remove. By keeping the right balance of organisms and food, most of the dissolved solids are removed.
Secondary Sedimentation Tanks and Outfalls
The heavy micro-organisms, known as the activated sludge, settle in the secondary sedimentation tanks and are recycled back to the bioreactors. Some are sent for solid processing.
Once the liquid treatment process is completed, the clear used water from the sedimentation tanks is then pumped and discharged from the effluent junction chamber, through the 5km long outfall pipes, into the Straits of Singapore. There, the treated used water, which has been treated to meet international standards, is dispersed in the swift currents more than 40m below the sea surface.