In wastewater treatment, what is the main purpose of using a settling tank?

The primary function of a settling tank, also known as a sedimentation tank, is to remove solids from wastewater. During the wastewater treatment process, heavier particles and settleable solids can be effectively separated from the liquid by allowing the wastewater to sit in the tank for a period of time. As the wastewater sits, gravity causes these solids to settle to the bottom, forming a sludge layer. This solid material can then be removed for further treatment or disposal, while the clarified liquid can proceed to the next stages of treatment.

Choosing this option reflects an understanding of the physical processes involved in wastewater treatment, specifically the importance of reducing the solid load before biological treatment or further filtration steps. By facilitating the removal of suspended solids, settling tanks play a critical role in improving the overall effectiveness and efficiency of the wastewater treatment system. Other processes, such as aeration or chemical injection, serve different functions and do not primarily focus on solid removal, highlighting the unique and essential role of settling tanks in the treatment process.