What does primary treatment specifically remove from wastewater?

Primary treatment in wastewater management is designed to remove larger solids and floating materials from the wastewater. This stage typically involves the physical processes of screening and sedimentation. During screening, large objects like sticks, leaves, and trash are removed to prevent damage to subsequent treatment processes. After screening, the wastewater undergoes sedimentation in a settling tank. Here, heavier solids settle to the bottom as sludge, while lighter materials can rise to the surface as scum, both of which are removed.

The primary treatment focuses not on killing pathogens, which is typically addressed in later processes, nor does it involve the removal of nutrients and minerals or the treatment of color and odor. Nutrient removal usually occurs in secondary treatment phases, where biological processes degrade organic matter and nutrients, while color and odor management often require advanced treatment techniques beyond primary treatment. Therefore, the correct identification of primary treatment's main function is specifically the removal of solids from the water.