What little I know about RO is that it is primarily a de-salinization tool. At one time many cruise ships augmented their fresh water with RO, but could only run it at sea, not in port. Sewage and heavy metals in river run-off prevented usage.
I don't know how much has changed with the RO technology since then.

I thin I remember Ben had looked into a chemical that could clear cyanuric acid, but I forgot what it was, how successful it was, or how expensive and involved a process.