ABSTRACT
T HE initial stage of treatment in the wastewater treatment process (following collection and influent pumping) is preliminary treatment. Raw influent entering the treatment plant may contain many kinds of materials: rags, rocks, sand, metal, and other inorganics and disposables. The purpose of preliminary treatment is to protect plant equipment downstream by removing these materials that could cause clogs, jams, equipment breakdowns, or excessive wear to plant machinery. In addition to protecting downstream equipment, the removal of various materials at the beginning of the treatment process saves valuable space within the treatment plant.
