초록 ▼

A process for treatment of water via membrane separation equipment. Hardness and non-hydroxide alkalinity are removed from feedwaters to very low levels, preferably by simultaneous removal in a weak acid cation ion exchange resin. Then, ionization of sparingly ionizable components in the feedwater i

A process for treatment of water via membrane separation equipment. Hardness and non-hydroxide alkalinity are removed from feedwaters to very low levels, preferably by simultaneous removal in a weak acid cation ion exchange resin. Then, ionization of sparingly ionizable components in the feedwater is substantially accomplished by increasing the pH of the feedwater preferably up to about pH 10.5, or higher. In this manner, species such as silica become highly ionized, and (a) their rejection by the membrane separation process is significantly increased, and (b) their solubility in the reject stream from the membrane process is significantly increased. Passage of weakly ionized species such as boron, silica, and TOC is reduced by a factor of ten or more. Recovery ratio of ninety percent (90%) or higher is achievable with most brackish feedwaters, while simultaneously achieving a substantial reduction in cleaning frequency. The method is particularly useful for the preparation of high purity water. Although the silica level in the reject water in this process is increased from the conventional range of approximately 150 ppm to a level of 450 ppm or better (thus increasing recovery rates), significantly improved levels of silica contamination in the ion-exchanged polished permeate are achieved. New Ultra Pure Water (UPW) systems utilizing this process will have thirty to fifty percent lower capital costs and at least twenty five percent lower operating costs compared to conventional UPW systems.

대표청구항 ▼

[ I claim:] [1.] 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 com

[ I claim:] [1.] 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, and(iii) at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution;(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, wherein TOC is rejected at least 95%(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, and(ii) a low solute containing product stream.