_____ aerators draw water into the blade of the aerator and throw water into the air in tiny droplets.

• A. Draft
• B. Cascade
• C. Surface
• D. Bubble

Answer: (C)

The correct choice highlights surface aerators, which are specifically designed to enhance the oxygen transfer in water treatment processes. Surface aerators function by drawing water into the rotating blades of the aerator. As the blades spin, they throw the water into the air, creating a splash that breaks the water into tiny droplets. This action greatly increases the surface area of the water exposed to the air, which in turn promotes the diffusion of oxygen into the water.

In contrast, the other options represent different aeration techniques or designs. Draft aerators are typically used for inducing air through a submerged diffuser and don't break water into droplets. Cascade aerators involve water flowing over steps or weirs, allowing some air contact but not effectively creating droplets. Bubble aerators, often using diffusers to release air bubbles, primarily focus on introducing air bubbles into the water rather than throwing water into the air. Thus, surface aerators stand out for their effectiveness in generating droplets for enhanced aeration.