I wish I could answer that question absolutely. I'm sure pressurizing your waste water enough to filter through a RO system would eliminate solids but I'm not sure about nitrates. If not, I wonder if a UV filter would help with organic waste leftovers at least enough to keep bio load reduced? Would carbon block help here?
I'm not sure I'm helping but just throwing ideas out there. JamesW is a good water guy. Hopefully he can provide some advise???