Following a precipitation system, with good filtration, an reverse osmosis system makes sense when properly sized. When used in this manner the thing to watch for is precipitation in the membrane when the concentration is taken too high and the flow is too low. The disadvantage is that there is no reduction of sludge volume using this method. Type 2 - Deionization type ion exchange. When a system is primed with deionized water, only the chemistry you add to the system is removed.
Incoming water is eliminated as a source of ions.
A deionization type system removes all ions from solution and recycles deionized water. The metal, Sodium, Potassium, and other cations are removed on one resin, and the anions such as sulfate, fluoride, chloride, sulfamate, EDTA, etc. are removed on another resin. The quality of the water recycled is very high. When regenerated you get all of these ions back in the regenerant which then has to be dealt with. Metals can be plated out of the cation regenerant.