What is the primary function of a septic tank?

The primary function of a septic tank is to separate solids from liquids and facilitate anaerobic digestion. This process is essential in managing household wastewater effectively. When wastewater flows into the septic tank, it is held for a period that allows heavier solids to settle at the bottom, forming a layer of sludge, while lighter materials, such as grease, rise to the surface creating a scum layer. The anaerobic bacteria present in the tank then break down the organic matter in the sludge, reducing its volume and treating the waste.

This separation of solids and liquids, along with the biological treatment occurring within the tank, is critical for preventing overflow and ensuring that only partially treated liquid waste is sent to the leach field for further filtration and absorption into the soil. This maintains the effectiveness and longevity of the septic system while protecting the surrounding environment and water sources.

The other options do not accurately represent the purpose of a septic tank. For instance, while a septic tank does hold wastewater temporarily, it is not designed to store it indefinitely. Injecting chemicals for water treatment is not a typical function of septic systems; they rely on natural processes instead. Lastly, pumping waste directly into the water supply is not permitted and would pose serious health and environmental risks.