Which principle is used in the separation of grease from wastewater?

The principle of flotation is the correct method utilized for the separation of grease from wastewater. This process involves introducing air into the wastewater, causing grease and other lighter substances to rise to the surface. As air bubbles are generated, they attach to the grease particles, allowing them to float. Once at the surface, the accumulated grease can be skimmed off, resulting in the clarification of the wastewater.

Flotation is particularly effective for treating wastewater containing a high concentration of fats, oils, and grease, which are less dense than water. This makes the separation process efficient, as the lighter materials can be easily removed without the need for extensive mechanical processes.

In contrast, filtration relies on physical barriers to separate solids from liquids, which may not effectively target grease that floats. Absorption involves the adherence of substances to solid surfaces, and while it can help with removal, it does not specifically facilitate the separation of floating grease. Activated sludge refers to a biological treatment method that uses microorganisms to break down organic matter but is not designed specifically for grease separation.