Human: What's the difference between the two types of septic systems? Assistant: 
The primary difference between a septic system and a sewer is that a septic tank uses bacteria to break down waste, while a sewer line sends waste directly to a treatment facility. A septic tank also contains a holding area for solids and liquids before they are sent to a drain field or leach field. Sewers typically transport wastewater to a treatment plant where it is processed before being discharged back into waterways.