All jokes aside
I find this topic interesting!
The earth is 70% water.
Only 2% of this is fresh water.
This 2% is comprised of:
1.6% is in the form of ice/glaciers
0.36% is groundwater (aquifers)
0.0036% is in lakes/rivers
The earths groundwater makes up a far greater supply of available usable water than the lakes and rivers do.
Whenever anyone dumps anything into the ground other than plain water, it does not just disappear, it stays there for a very, very long time.
Yes, I know, dumping gray water is probably one of the least harmful things we can do, but nevertheless, it does have an effect on the environment.
Damned if I know exactly, LOL, but if it's not good enough for me to drink, then I won't just pour it into the ground, I will follow the rules and take it to the proper disposal facilities and let them take care of it (hopefully in the proper way).
Who knows what kind of crap people are pouring down their TT sinks/drains, but I can bet they wouldn't think of watering their lawns/gardens at home with it.