The type of pump most frequently used to pump thickened sludge is the ___________ type:

The piston type pump is most frequently used to pump thickened sludge due to its ability to handle high viscosity fluids effectively. These pumps operate by using a reciprocating motion to create pressure and move the sludge through the pump system. This design allows for a more consistent flow and the ability to manage denser materials, which is essential when dealing with thickened sludge that can be more challenging to transport.

Piston pumps are particularly advantageous because they can generate higher pressures than many other types of pumps, ensuring that thickened sludge can be moved through pipes or systems without significant backflow or pressure drop. Additionally, they can provide a high level of control over the flow rate, which is crucial in wastewater treatment processes where precise management of sludge is necessary.

While other types of pumps like centrifugal pumps or gear pumps have their applications, they are often better suited for less viscous fluids. Centrifugal pumps, for instance, rely on high rotational speeds to generate flow, which can be inefficient or even ineffective when handling thicker materials. Gear pumps can handle viscous fluids but are generally more suitable for lower flow rates and less thick materials compared to piston pumps. Thus, the piston type pump is distinctly favored for the specific needs of thickened sludge pumping in sewage treatment.