Adsorption refers to which process?

• A. When oxygen dissolves
• B. When bacteria replicate
• C. When food or other bacteria get caught in the slime layer
• D. When food sticks to the surface

Answer: (C)

Adsorption is the adhesion of dissolved or dispersed substances to the surface of a solid. In wastewater treatment, that surface is often the slime layer or biofilm that forms around particles and microorganisms. When food particles or other bacteria become trapped in that slime layer, they’re being held on the surface, which is exactly what adsorption describes.

Oxygen dissolving is a dissolution process, not adsorption. Bacteria replication is growth, not attachment to a surface. While food sticking to a surface is related to surface adhesion, adsorption specifically refers to substances being retained at the surface, such as being caught in the slime layer.