High purity water produced by reverse osmosis

A composition matter consisting essentially of water and dissolved solutes, said composition of matter provided as a low solute containing product water stream from continuous treatment of a feedwater stream in a first reverse osmosis membrane separation unit that produces a low solute containing product water stream and a high solute containing reject stream, said process consisting of:

• (a) providing a feedwater stream containing solutes therein, said solutes comprising
• (i) hardness,
• (ii) alkalinity, and
• (iii) at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution, said at least one molecular species comprising boron;
• (b) pretreating the feedwater stream to remove scale forming substances from said feedwater stream to substantially eliminate scale accumulation in said first reverse osmosis membrane separation unit when said feedwater is concentrated to a preselected concentration factor at a selected pH, by effecting, in any order, two or more of the following, before concentrating said feedwater stream in said first reverse osmosis membrane separation unit:
• (i) removing hardness from said feedwater stream;
• (ii) removing substantially all non-hydroxide alkalinity associated with hardness from said feedwater stream;
• (iii)removing dissolved gas from said feedwater stream, whether initially present or created during said hardness or said alkalinity removal step;
• (c) raising the pH of the pretreated feedwater stream to a selected pH of at least about 8.5, thereby increasing the ionization of one or more of said at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution;
• (d) passing the pH adjusted pretreated feedwater stream through said first reverse osmosis membrane separation unit, said first reverse osmosis membrane unit rejecting said at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution by at least 95% while concentrating said feedwater stream to said preselected concentration factor, to produce a low solute containing product water stream and a high solute containing reject stream.