What is the primary function of the secondary clarifier in wastewater treatment?

The primary function of the secondary clarifier in wastewater treatment is to separate solids from liquid. After biological treatment processes, such as activated sludge or biological aerated filters, the wastewater contains a mixture of clarified liquid and suspended solids, including live microorganisms and organic mater. The secondary clarifier allows these solids to settle to the bottom, forming a sludge that can be removed for further processing. The supernatant, which is the liquid that remains above the settled solids, can then be further treated or discharged. This separation is crucial for enhancing the quality of the treated water and ensuring the efficient removal of contaminants.

Other processes mentioned, such as aeration, disinfection, and nutrient addition, occur at different stages of wastewater treatment and are not the primary purpose of the secondary clarifier. Aeration is typically handled in earlier stages to promote microbial growth, disinfection is done to eliminate pathogens before discharge, and nutrients may be added to support biological processes but are not the focus of the secondary clarifier’s function.