Not sure where you live, but in areas with public sewage of course the treatment plants remove as much as possible from the water before it reaches nature.
Of course the purpose of a sewage treatment plant is to remove as much as possible of the material in the water, regardless of what it is, ending up with water that is as pure as possible so it can be let out into nature.
The point is TP just becomes part of the solids and there's no need to separate it from the rest of the solids, it's complementary being derived from trees.
[0] https://en.wikipedia.org/wiki/Metropolitan_Water_Reclamation...
I think they're just finally going to start treating it this year (if they haven't already).