What is the function of a septic tank?

The function of a septic tank is primarily to treat sewage and wastewater by separating solids from liquids. In a septic system, wastewater flows into the septic tank where it undergoes a natural biological process. This process involves the settling of solid waste to the bottom of the tank, forming sludge, while lighter materials, such as oils and grease, float to the surface, creating scum.

The design of the septic tank allows for the anaerobic digestion of solids, which reduces the volume of waste. The liquid effluent, after undergoing this preliminary treatment, then flows out of the tank into a drain field, where it is further treated by soil filtration and microbial activity. This process is crucial for maintaining a safe and effective sewage disposal system in areas that are not connected to centralized sewer systems.

Understanding the role of a septic tank in wastewater treatment helps in recognizing its importance in sanitation and environmental health, especially in rural and suburban settings. The other choices primarily address functions unrelated to the treatment of sewage, such as rainwater collection, water storage for irrigation, or filtration of stormwater runoff, which are not the primary purposes of a septic tank.