R/O water is rather pure, Some think it is too pure,, (I happen to be one of them but that's a topic for another thread)
There was a demonstration many years ago of a Sewage to fresh water maching in Detroit, Mi... Folks who were there and who knew the diference between you know what and the famous hole in the ground, labeled it a Fraud, and explained why.
I was not there, but have the needed training and skills to read their report, and ... They were accurate, it was fraud.
Of course, newer technology exists today, nearly half a century later,, So I do not know.. But I remain speptical of any waste water purification system other than natures.