Eli5: what exactly does it mean when sewage is treated them released into a river?

Question

So the city it talking about treating sewage before dumping it into a river that I see tons of people swimming and fishing in. How does this work?

In: 11

Answer 1

Large scale treatment plants use gravity to remove the top layer of cleaner water while junk (poop) settles to the bottom and gets scooped away. Some chemicals are used for binding to make some stuff heavier and sink.