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?
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Usually a bacteria is used in a big vat that eats the poo. This leaves the water.
Other chemicals may be used that clean the poo water by killing bacteria and viruses that are left. This is then put back in the river
Sewage treatment plants exist to convert raw sewage into relatively clean water.
The effluent of sewage treatment plants, particularly in developed countries with decent pollution regulations, is mostly just water — the nasty stuff was either left behind in a digester/settling tank or scraped off a semi-permeable membrane.
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.
The “grey water” is “bubbled” to separate the stuff less dense than water. This is skimmed off the top and held off to the side. The solids are separated using a sedimentation tank (those big circular tanks at your local sewer plant).
At this point it’s effectively just water with some stuff dissolved in it. Typically something is done to balance the PH and if nothing else is wrong (or nothing else can be done) then the water is released into the local water way. Fun fact, there are significantly more female fish than male fish in US rivers because estrogen from women’s pee can effect fish genders. The estrogen comes from two sources, pregnant women, and women on birth control. The proliferation of hormonal birth control has thrown the gender ratios of fish out of whack. So that’s a fun sentence.
The stuff that had been removed typically gets cooked in a kiln (to kill any bacteria or parasites) and then the waste can be used as a fertilizer additive.
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