Not disagreeing with Don, but just for clarity I want to point out we
are talking about two different things.

He is talking about bacteria in the drinking water system.

I am talking about bacteria living in the sewer system.

Surprisingly, I've seen a number of cases in my 16 years of facility
management where the two got confused, and an expensive fix was tried
instead of an easy one.

If you have bacteria in the water pipes you'd have to try something
like Don suggests. But that's overkill if you have bacteria in the
drain. When you run water it stirs up the air and crud in the drain
and you can smell it, and think it's the water. (I have this
happening right now in a large gymnasium shower room, and it is hard
to convince them the problem is in the drain because they don't smell
it until they run the water.) And yes, the smell is the same.

Like I said, low probability, but worth trying.