Sand can damage or ...

Sand can damage or deteriorate equipment. There are several way to remove sand from water or wastewater entering a process. Essentially all rely on the fact that sand is much denser than other materials that may be contained in the influent stream. Slowing flow velocity to about less than 2 ft/s (0.6 m/s) will cause sand to settle. This can be done in a dedicated container called a "grit chamber". There are also hydrodynamic separators that use centrifugal force to achieve the same results with less moving parts. A good textbook on the fundamentals of wastewater treatment will contain more detailed information.