An aerobic septic system also known as an aerobic treatment system (ATS), is a small-scale sewage treatment system similar to a septic tank system, but which uses an aerobic method to digest sewages rather than just the anaerobic process used in septic systems.

An aerobic septic system works like a septic tank system, but the aerobic septic system uses an aerobic process instead of the anaerobic process.

These systems are often found in rural areas where there are no public sewers and can be used for a single residence or for a small group of houses.