During which treatment stage do solids settle and grease get skimmed off?

The stage where solids settle and grease is skimmed off is known as primary treatment. This phase focuses on the physical processes used to remove large solids from wastewater. During primary treatment, the wastewater undergoes sedimentation in large tanks, allowing heavier particles to settle at the bottom, forming sludge, while lighter materials, such as grease and oils, float to the surface. These floating materials can then be skimmed off.

This separation of solids and fats is essential because it reduces the load on subsequent treatment processes and improves the overall efficiency of the wastewater treatment system. Primary treatment serves as an effective preliminary step and is crucial for preventing clogging and wear on equipment used in later treatment stages.