Where is floatable scum typically removed from wastewater?

Floatable scum is typically removed from wastewater in the primary clarifier. This process occurs in the primary treatment stage of wastewater treatment, where larger solids are settled out by gravity. As the wastewater undergoes primary clarification, lighter materials such as oils, grease, and other floating debris rise to the surface, forming a layer of scum.

The primary clarifier is designed specifically to facilitate this separation, allowing the heavy solids to settle to the bottom and the lighter materials to be skimmed off the surface. This scum removal is essential, as it helps reduce pollutants before the wastewater moves on to secondary treatment, where the remaining organic matter is taken care of by biological processes.

In contrast, the secondary clarifier focuses on the settlement of biological solids resulting from microbial activity, and floatable scum is not a significant concern in that stage. The final filter is primarily for polishing treated effluent, and the aeration tank is where oxygen is supplied to promote the growth of microorganisms that break down organic substances in the wastewater, not for the removal of floatable scum.