That’s been a solved problem, engineering-wise, for a while.
The advanced treatment stages take care of it. Between UV, ozone, and nanofiltration, etc. we can remove the pharmaceuticals.
Actually the problem is the water comes out too pure out of a well designed water reuse system, to the point where the mineral content can be too low and you need to add some back in.
Cite for it being solved? All the articles I can find have it as ‘active and growing problem with some potential mitigations which are not universally applied’.
All the recycled water systems I’m aware of still have PCC issues and excess ion contamination problems too still.
Admittedly my knowledge was based on work I did in academia, and I now work in transportation, so I suppose it’s possible I’m in error, but I’d be surprised if much survives the RO stage, and isn’t eaten up by the oxidation stage. My understanding was that the water needs to actually get remineralized to protect the distribution system. And that it’s very devoid of pharmaceutical contaminants by that point. I was unaware of this being an issue in real world potable reuse systems. Though, I suppose different jurisdictions may have different standards. My state was pretty strict.