Which type of pump is useful for moving water that contains solids, as in raw-water intakes?

The correct answer is a mixed flow pump. Mixed flow pumps are specifically designed to handle fluids that contain solids, making them suitable for applications such as raw-water intakes where the water may carry debris and particulates. These pumps combine features of both centrifugal and axial flow pumps, allowing them to move water efficiently while minimizing the risk of clogging that can occur with solids.

In contrast, centrifugal pumps rely on rotational energy to move fluid, but they can struggle with solids, leading to potential damage or decreased efficiency. Jet pumps typically work by creating a vacuum to draw water, which is not ideal for applications involving larger solids. Submersible pumps are designed to be submerged and can handle some solids, but their construction may not handle large particles as effectively as mixed flow pumps, especially in high solid content situations. Thus, mixed flow pumps offer the best combination of efficiency and capability for transporting water with solid content in raw-water intake processes.