What is a characteristic of a positive displacement pump?

A positive displacement pump is defined by its method of operation, which involves physically moving a specific amount of fluid with each cycle through mechanical means. This type of pump captures a fixed volume of liquid and displaces it to create flow, making it distinct from other pump types that generate movement via velocity or pressure alone.

In a positive displacement pump, mechanical components like gears, diaphragms, or pistons are essential for drawing in and expelling the fluid, thus making the movement direct and consistent per cycle. This characteristic allows these pumps to be efficient in applications requiring precise dosing or handling of viscous fluids.

The operation contrasts with pumps that depend on velocity, like centrifugal pumps, which use impellers to create flow, or with those that lack mechanical components entirely, relying instead on different principles. Therefore, the defining trait of positive displacement pumps lies in their mechanical mechanism, which is crucial for understanding their application and efficiency in various environments in wastewater treatment.