Which type of aerators have riffle plates?

• A. cone aerators
• B. spray aerators
• C. cascade aerators
• D. slat-and-coke tray aerators

Answer: (C)

Riffle plates are used in cascade aerators to create a stepped, turbulent flow that breaks the water into smaller streams as it moves from one plate to the next. This increases the surface area of water exposed to air and boosts oxygen transfer, making cascade aerators particularly effective at aeration.

Other aerator types achieve contact with air through different mechanisms and don’t use riffle plates. Cone aerators rely on diffusion and air entrainment within a conical chamber, spray aerators disperse water into a fine spray for rapid air contact, and slat-and-coke tray aerators spread water over trays to promote contact.