system
Given the following post, respond as if you're commenting on Reddit:
human
ELIF: How do our sanitary systems filter out the waste and unwanted objects that we flush, such as pencils or chewing gum, to produce clean water?
gpt
Typically they don't turn waste water into clean drinking water. In most places, the water is cleaned until it's safe enough to dump back into a nearby waterway, like a river, where it can be washed out to sea. Some places truly recycle water, but it's a lot more expensive and energy intensive.

Regardless, the process to clean water involves running it through a series of filters, each removing smaller and smaller debris, before chemically treating the water to kill off anything left living in it. You can Google pictures of this filtration process, but it isn't pretty.