1000 ppm is normally about ...
Published by Marco Rognoni, Owner at WET, Water Edge Technologies
1000 ppm is normally about the maximum that can be achieved with ion Exchange. Above that, the demin water requested for regeneration may even the capacity of the plant and reduce the net output down to zero.
Hence I believe that RO is the best solution among the two However there are other technologies which are better than RO for such low salinity, like electrodialysis, which I suggest because of lower energy consumption and good quality of the desalinated water.