I try to be green in most things, but brewing is my biggest indulgence, because I use RO from my I house system for brewing. Even so, my water is well water from an aquifer beneath my rural lot and the spent waste water of all types generated in my house returns to the aquifer by running off directly through the ground or via a septic leach field, so I don't see it as truly wasted in the course of generating the RO water for my brewing.
If I were on City water that was treated, I would feel differently, I suspect.