What is the primary function of a primary treatment stage in wastewater treatment?

The primary treatment stage in wastewater treatment focuses on the physical separation of solids from the liquid portion of wastewater. During this stage, processes such as screening and sedimentation are employed to remove larger particles and settleable solids. This physical separation is essential for reducing the load on subsequent treatment stages, particularly secondary biological treatment, which is designed to further reduce organic matter.

By effectively removing a significant portion of suspended solids and some biodegradable materials, primary treatment aims to improve the overall efficiency of the treatment process. This ensures that pathogenic organisms and organic matter are effectively addressed in later treatment stages, allowing for cleaner and safer effluent to be discharged or treated further. Though aspects of biological degradation and chemical treatment may take place in later stages, they are not functions of primary treatment, which primarily concentrates on physical processes.