chapter  12
16 Pages


The initial stage 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, including trash, garbage, and other debris, such as roots, rocks, rubber and plastic products, rags, bottles, and building materials (e.g., drywall, wood waste). The purpose of preliminary treatment is to protect plant equipment by removing these materials, which could cause clogs, jams, or excessive wear to plant machinery. In addition, the removal of various materials at the beginning of the treatment process saves valuable space within the treatment plant.