A high recovery sulfate removal process comprises treating a feed water stream conditioned with antiscalant from a source with a reverse osmosis membrane system to produce a purified water permeate stream and a reject stream containing the retained or rejected ions and organic matter. The reject stream is further treated to remove dissolved and suspended species. The reject stream flows to a desaturation/clarification process. A preferred process includes a constant stirred tank reactor (CSTR) where co-precipitation agent is added followed by a clarifier. Water recycled from the clarifier overflow is blended with feed water stream. The removed solids are collected as sludge or a slurry and disposed of in a manner consistent with applicable regulations.