Which of the following is a type of positive displacement pump?

A gear pump is a type of positive displacement pump, which means it moves fluid by trapping a fixed amount of it and forcing that volume into the discharge pipe. This is achieved through the action of gears, which rotate and create a cavity that carries the fluid from the inlet to the outlet. As the gears intermesh, they effectively displace a precise volume of liquid with each rotation, making gear pumps highly efficient for delivering a consistent flow rate, especially in applications requiring high pressure.

Positive displacement pumps are characterized by their ability to deliver the same amount of fluid regardless of the pressure at the discharge, which is crucial in various wastewater treatment processes. They can handle thick fluids and offer reliable performance even against varying back-pressure conditions.

In contrast, the other pump types listed do not function as positive displacement pumps. Axial pumps are typically used for high flow applications and move fluid using a propeller action, turbine pumps use centrifugal force to move fluid, and an educator is designed to mix fluids rather than displace a set volume of fluid. Understanding the operational principles of gear pumps and their classification as positive displacement pumps helps clarify their importance and usage in wastewater systems.