What is the main function of a septic tank?

The main function of a septic tank is to treat wastewater and provide initial treatment. Septic tanks are designed as part of a decentralized sewage treatment system. When household wastewater enters the tank, the solid waste settles to the bottom, forming sludge, while lighter materials, like grease and oils, float to the top, creating scum. This separation allows the tank to treat the wastewater by anaerobic digestion, where bacteria break down the organic matter over time.

This initial treatment process is crucial before the wastewater is distributed to the drain field or absorption area, where it undergoes further treatment through soil filtration. Option B accurately captures this multifunctional role of the septic tank in managing household wastewater effectively and safely.

Other choices do not reflect the primary function of the septic tank correctly. While tanks do store waste, they do far more than just storage. They do not eliminate the need for an absorption area, as this area is essential for further treating the effluent. Lastly, while septic tanks do filter some solids, they are not designed to filter out all types; they primarily focus on solids that settle and float, leaving some smaller particles to exit the tank with the effluent.