What is the primary function of a septic tank?

The primary function of a septic tank is to act as a subsurface treatment system for wastewater management. Septic tanks are designed to receive and hold wastewater from households, enabling the separation of solids from liquids. In this system, the heavier solids settle at the bottom, forming a sludge layer, while lighter materials like grease and scum float to the surface. This natural separation allows for the liquid effluent, which is relatively treated, to flow out of the septic tank into the drain field or leach field for further treatment and absorption into the soil.

By effectively managing the initial stages of wastewater treatment, septic tanks help prevent pollution and protect groundwater resources. The completed treatment process takes advantage of the soil's natural filtration and biological breakdown processes, making it an efficient option for managing wastewater in areas without centralized sewage systems. The other options do not align with the primary function of a septic tank, as they pertain to different systems and purposes outside of this specific wastewater management role.