What happens to the solids in a septic tank?

In a septic tank, the primary function is to provide a space for the initial treatment of wastewater that enters from a household. Solids in the septic tank settle to the bottom due to gravity, where they form a sludge layer. This layer undergoes anaerobic digestion, a biological process that occurs in the absence of oxygen, breaking down the organic matter present in the solids into simpler compounds. This process not only reduces the volume of the solids but also stabilizes them, making it safer for the environment.

The separation of solids from liquids is crucial because it prevents the solids from being discharged into the drain field, which could lead to clogging and system failure. The clarified liquid above the sludge layer eventually exits the tank and flows into the drain field for further treatment through soil absorption.

While other options suggest various outcomes for the solids, the key process in a septic system is this anaerobic digestion that occurs within the tank, effectively managing waste before it moves into the next stage of the septic system.