Which of the following is NOT a process involved in primary treatment?

In the context of primary wastewater treatment, the goal is to remove large solids and settleable organic material from the wastewater. Screening, comminuting, and grit removal are all essential processes in this stage of treatment.

Screening involves the physical removal of large debris, such as sticks and plastics, that can damage equipment or hinder the treatment process. Comminuting refers to the process of grinding or shredding materials into smaller pieces to facilitate easier handling and subsequent treatment. Grit removal focuses on the elimination of heavier inorganic particles like sand, gravel, and other granular materials that settle quickly.

Filtration, on the other hand, is typically associated with secondary treatment or tertiary treatment stages rather than primary treatment. In primary treatment, the primary methods focus on the physical separation of solids, while filtration is a more refined process occurring at later stages to remove smaller particles and impurities after the wastewater has been subjected to primary treatment processes. Thus, filtration does not fit in the category of processes involved in primary treatment.