What is the main function of a sedimentation tank in wastewater treatment?

The primary function of a sedimentation tank in wastewater treatment is to allow solids to settle out of the wastewater. This process is essential for separating heavier particles from the liquid, which is critical for the effective treatment of wastewater.

In a sedimentation tank, wastewater flows slowly, providing sufficient time for the suspended solids to settle at the bottom due to gravity. This settled material, known as sludge, is then removed from the tank, while the clarified liquid, or supernatant, can move on to further treatment processes. By efficiently removing solids at this stage, sedimentation tanks help improve the overall efficiency and effectiveness of the wastewater treatment process, reducing the load on subsequent treatment steps.

Other functions mentioned in the options, such as aeration, mixing chemicals, and disinfection, are important aspects of overall wastewater treatment but do not pertain to the specific role of a sedimentation tank. Aeration is more relevant to biological treatment processes that promote the breakdown of organic material, while mixing chemicals is typically carried out in separate tanks designated for chemical treatment. Disinfection occurs as a final step in the treatment process to eliminate pathogens before the treated water is released or reused.