[danieltiIlett]

If it's made it through your body, it's likely to make it through the sewer... Not a lot of really reactive stuff there (cleaners/oils/detergents dissolve, not degrade), anything super reactive (e.g. bleach) exhausts itself chewing on poop. Microbial degradation is a thing, but it's not very different from human degradation so anything that's already been excreted is probably pretty stable.