What is the primary function of a septic tank?

The primary function of a septic tank is to collect and treat wastewater. Septic tanks are designed to receive effluent from household plumbing, which includes water from sinks, toilets, and showers. Inside the tank, the wastewater undergoes a natural treatment process, where solids settle at the bottom and form a sludge layer, while lighter materials float to the top, creating a scum layer.

The treated liquid, known as effluent, is then discharged from the tank into the drain field, where it further undergoes filtration and microbial treatment before entering the groundwater. This process helps to ensure that harmful pathogens and contaminants are reduced, thereby protecting both public health and the environment. Hence, the correct choice reflects the vital role that septic tanks play in managing and processing household wastewater safely and effectively.