Aeration in water treatment plants is used to:

• A. Lower pH
• B. Reduce Concentrations of Dissolved Gases
• C. Reduce Turbidity
• D. Stabilize Chlorine Residuals

Answer: (A)

Aeration’s main job is to strip dissolved gases from water and to introduce oxygen, which helps with taste, odor, and the oxidation of certain metals for easier removal later on. By exchanging gases with the air, dissolved gases such as carbon dioxide and hydrogen sulfide are carried away, lowering their concentrations in the water. This process can cause pH to rise (as CO2 leaves reduces carbonic acid), rather than lowering pH. It isn’t primarily used to reduce turbidity or to stabilize chlorine residuals, which are handled by other treatment steps. So, the best description is that aeration reduces concentrations of dissolved gases.