What type of aerators have riffle plates?

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

Answer: (C)

Riffle plates are stepped, ridged plates that break the falling water into smaller streams and splashes. As water cascades over these plates, turbulence increases and more air is entrained, dramatically boosting the contact between air and water for oxygen transfer. This cascading action is the hallmark of cascade aerators, where the water flows down through a sequence of riffle plates to maximize aeration. Cone aerators rely on agitation from a rotating cone, not plate-induced cascading. Spray aerators achieve aeration by spraying water into air, not by passing over riffle plates. Tray-type aerators spread water over flat surfaces but don’t use the step-down plate cascade mechanism.