What is e coli in water from?

Misdirected sewage: E coli is an inhabitant of the colon and is involved in digestion. It is easily dealt with in modern sewage treatment. If it gets loose into the soil or water supply, then it can become a hazard. It gets there from badly designed or old sewage systems or sometimes from septic systems too close to wells, and other water sources.

Poop: E. coli is a germ found in almost every digestive tract in animals/humans. In nature, every animal that poops in/near the stream where they drink adds to the E.coli load. It is a real issue if a dairy is located upstream from a community lake/water source. It is even found in sea water from direct ship discharges. The amount is a common gauge of water contamination.