Which type of aerator consists of a propeller-like mixing blade mounted on the end of a vertical shaft driven by a motor?

• A. Mechanical aerator
• B. Diffuser aerator
• C. Gravity aerator
• D. Static mixer

Answer: (A)

The type of aerator that features a propeller-like mixing blade attached to the end of a vertical shaft driven by a motor is known as a mechanical aerator. This device functions by utilizing mechanical means to introduce air into water, creating turbulence and increasing the transfer of oxygen into the liquid. Mechanical aerators are commonly employed in wastewater treatment processes where efficient oxygenation is critical for the growth of aerobic microorganisms.

In contrast, a diffuser aerator uses porous materials or devices to release air as fine bubbles within the water, which increases the surface area for contact but does not involve a moving part like the propeller in a mechanical aerator. A gravity aerator typically relies on the flow of water to draw in air without mechanical assistance, while a static mixer involves fixed components to blend fluids but lacks the active mixing and aeration capabilities of a mechanical aerator. These distinctions clarify why the mechanical aerator is the correct choice for the question.