Patent ID: 6537456
Filing Date: 2003-03-25
Classification: B01D,C02F,Y10S

Abstract:
A process for treatment of a feedwater stream in membrane separation equipment, said membrane separation equipment comprising at least one unit having a membrane separator, to produce a low solute containing product stream and a high solute containing reject stream, said process comprising:(a) providing a feedwater stream containing solutes therein, said solutes comprising (i) hardness, (ii) alkalinity, (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 one or more of (1) at least some TOC, or (2) at least some silica, or (3) at least some boron; (b) concentrating said feedwater stream in a first unit of said membrane separation equipment after reducing the tendency of said feedwater to form scale 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: (i) removing hardness from said feedwater stream; (ii) removing substantially all 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 product from step (a) to a selected pH of at least about 8.5, to urge said at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution toward increased ionization; (d) passing the product from step (c) above through said membrane separation equipment, said membrane separation equipment substantially resisting passage of dissolved species therethrough, to concentrate said feedwater to said preselected concentration factor, to produce (i) a high solute containing reject stream, (ii) a low solute containing product stream, and (iii) wherein TOC in said product stream is less than five percent (5%) of said at least some TOC in said feedwater.