Methods and apparatus of embodiments of the invention relate to treating water including contacting a liquid stream with a source comprising inorganic and/or divalent ions and separating the stream into an effluent and a fluid comprising less sulfate than the stream, wherein the effluent comprises more sulfate and more inorganic and/or divalent ions than the stream. Methods and apparatus relate to treating water including a reaction unit comprising an inlet for feed fluid and an inlet for inorganic and/or divalent ions and a separator unit comprising an inlet for output from the reaction unit, an outlet for effluent, and an outlet for fluid comprising less sulfate than the feed fluid. Some embodiments include introducing the fluid comprising less sulfate than the stream into a subterranean formation.