Which mechanism adds oxygen to aerobic ponds during daylight?

• A. Algae growth
• B. Algae growth and mechanical aeration
• C. Chemical dosing
• D. Heat exchange

Answer: (B)

During daylight, algae perform photosynthesis, using light to convert carbon dioxide and water into glucose and oxygen. The oxygen produced by algae dissolves into the water, increasing the dissolved oxygen (DO) in the pond. Mechanical aeration then comes into play by moving the water and increasing its contact with air, which speeds up the diffusion of oxygen from air into the water and helps distribute that oxygen throughout the pond. Therefore, the combination of algae growth (which generates oxygen) and mechanical aeration (which enhances oxygen transfer) adds the most oxygen during daylight. Chemical dosing can raise DO but isn’t a daylight-driven mechanism, and heat exchange mainly affects DO by changing solubility with temperature rather than adding oxygen directly.