Aeration is defined as which of the following?

• A. The process by which air is circulated through, mixed with or dissolved in a liquid or substance.
• B. A substance that increases hydrogen ion concentration
• C. A bacteria that requires oxygen to grow
• D. A binding to surfaces

Answer: (A)

Aeration is the process of introducing air into a liquid to circulate, mix with, or dissolve air. In wastewater treatment, this supplies dissolved oxygen to microorganisms that break down organic matter, enabling aerobic digestion and improving treatment efficiency and odor control. The definition that matches this is the option describing air being circulated through, mixed with, or dissolved in a liquid. The other descriptions refer to an acid (increasing hydrogen ion concentration), a bacterium that requires oxygen to grow (an organism, not the process of adding air), and binding to surfaces (adsorption), none of which define aeration.