CBU is used to pre-treat wastewater before entering the WWTP. It performs three operations: screening; grit removal and grease removal. 

Wastewater passes through the screen, where bigger particles are removed: the screw screen also wash and compact the screenings before discharge. Wastewater flows toward the settling tank, where the grit sedimentation take place. In order to improve this process a special buffle is used to obtain a laminar flow as well as to redece the temperature gap.

Settled grit is collected toward the accumulation pit and than removed by an inclined screw conveyor.
Suspended particles, such as oil, grease and other matters, are removed by the scum screaper and collected in a side tank. An air blowing system along the settling tank’s side improve the grease separation and the settling
process, rising the overall plant’s efficiency.