In wastewater primary treatment, which unit is primarily used?

In wastewater primary treatment, primary settling basins are the primary units utilized. The purpose of primary treatment is to remove large particles and settleable solids from wastewater before it undergoes secondary treatment. Primary settling basins, also known as sedimentation tanks, allow the wastewater to remain still for a period of time, enabling heavier solids to settle to the bottom as sludge, while lighter materials, such as fats and oils, rise to the surface as scum.

This process is key for reducing the load on later treatment stages and improving overall efficiency. The design and functioning of primary settling basins are focused on gravity separation, ensuring that the solids are effectively removed without the need for elaborate chemical or biological processes, which are reserved for subsequent treatment phases. Therefore, they are essential in the initial stage of wastewater treatment, effectively preparing the effluent for further processing.