Human: What is the difference between a septic and a sewer system? Assistant: 
The main difference between a septic system and a sewer system is that a septic tank treats waste in an anaerobic environment, while a sewer system transports wastewater to treatment plants or other facilities for further processing. In addition, a septic tank can be used with a drain field to treat greywater, whereas sewer systems are only designed to handle blackwater (human waste).