One of four primary clarifiers at GBMSD

Once the wastewater has been screened in headworks the wastewater flows into the primary clarifiers. Up to this point the wastewater has been moving pretty fast. The primary clarifiers are the first opportunity for the wastewater flow to slow down, and allow the solids that have been suspended in the water to settle out. The primary clarifiers remove the heavy solids that have settled out and also floating solids (scum and grease) from the incoming wastewater. The settleable solids settle by gravity to the bottom of the clarifier while the scum and greases float to the top. Both are then skimmed off and pumped to other processes.

Nearly 60% of the solids are removed before the wastewater leaves this step of the process and moves on to the Aeration Basins (or biological treatment).