Raw sewage is well known to decompose in the environment into harmless things. Unlike the majority of chemicals we invented in the last 100 years or so.
Errr.....no? Human waste in water is a major cause of disease. Sure, a turd or two won't be a problem. And sure, it'll decompose. But all kinds of pathogens remain. There are billions of people, and as the eponymous book says: everyone poops.
People have been pooping for millions of years without filling our oceans with poop. We have been creating new chemicals for a hundred years and have created a huge waste problem. The last time pooping had a big impact on the global ecosystem was during the Great Oxygenation Event, afaik.
