What is the primary purpose of a septic tank in residential systems?

The primary purpose of a septic tank in residential systems is to store sewage temporarily. This is the first step in the treatment process for household wastewater. As wastewater flows into the septic tank, it is held there long enough for heavier solids to settle at the bottom, forming sludge, while lighter materials like grease and oils float to the top, creating a scum layer. This temporary storage allows for the decomposition of the solid waste by anaerobic bacteria, thereby reducing the volume of solid material.

After this initial treatment phase, the partially treated effluent exits the tank and is directed into a drain field, where it undergoes further treatment by the soil. Understanding the role of the septic tank in managing and treating household waste helps ensure that residential systems function effectively and protect public health and the environment.