ABSTRACT
The initial stage of treatment in the wastewater treatment process (following collection and influent pumping) is preliminary treatment. Process selection normally is based upon the expected characteristics of the influent flow. Two of the processes used in preliminary treatment include screening and grit removal. These processes include shredding, flow measurement, preaeration, chemical addition, and flow equalization. Except in extreme cases, plant design will not include all these items. This chapter describes typical calculations used in two of these processes: screening and grit removal. Wastewater operators responsible for screenings disposal are typically required to keep a record of the amount of screenings removed from the flow. Grit removal may be accomplished in grit chambers or by the centrifugal separation of biosolids. Processes use gravity/velocity, aeration, or centrifugal force to separate the solids from the wastewater.
