What is the purpose of an aeration step in water treatment, and in what scenarios is it used?

• A. To add oxygen for biological processes.
• B. To remove dissolved gases and improve taste/odor.
• C. To disinfect the water.
• D. To remove dissolved gases (e.g., radon, H2S) and improve taste/odor; used in degassing and odor control.

Answer: (D)