Our favorite science illustrators AsapSCIENCE have just waded into some murky waters. Yes, they're talking about poop - specifically what happens after you flush.
Here's the short version: You poop, it goes down a tube, all the poop pebbles get separated out, cleaned and used to build your toilets (how's that for full circle). After that, people have to remove all the condoms and stuff that you flush down the toilet (don't do that) by hand. Gross. Then there's some terribly disgusting oil separation, at which bacteria start to eat away bad stuff. Liquid waste gets treated and put back into society, while solid waste gets treated and is used to power the very treatment plant it's housed under. What's left is used to grow your radishes. Then you eat them and poop it out again.
There's nothing as glamourous as the poop cycle, my friends: