Whoa! I didn’t see this one coming!
It is possible to treat household wastewater so that it is acceptable for re-use. In the U.S., an estimated 10-15% of our wastewater is re-used annually mostly for irrigation, but some is reinjected into the aquafers.
But get this – some researchers have shown that attempting to conserve water reduces the flow of wastewater that can be reclaimed! It makes sense that if you use less water then you will not be able to reclaim as much.
I don’t know if this is critical, but it sure is interesting. There are probably always unseen consequences of our good intentions.