US 6,537,456 B2Granted

Method and apparatus for high efficiency reverse osmosis operation

OwnerDebasish Mukhopadhyayinventor

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Abstract

A process for treatment of water via membrane separation to remove hardness and non-hydroxide alkalinity by simultaneous removal in a weak acid cation exchange resin. The process includes ionization of sparingly ionizable components, such as silica, by adjusting the pH up to about 10.5 or higher. Their separation by the membrane is significantly increased. The passage of boron, silica and TOC is reduced by a factor of ten or more. Recovery of 90% or higher is achievable with most brackish feedwaters, while substantial reduction in cleaning frequency is simultaneously achieved. The apparatus used for the water treatment process includes reverse osmosis membrane(s) (30), mixed bed ion exchange unit (44, 46), micron filter (48), ultraviolet sterilization unit (49), decarbonation unit (20), and electrodeionization unit (150).

Claims36

Dependent claims

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.

13 more elements

(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 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 effectively eliminating 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 non-hydroxide alkalinity from said feedwater stream;
(iii) removing dissolved gases, whether initiallly 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 by adding a selected base thereto, 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 to produce a reject stream and a product stream, 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 permeate 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.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/242,249Filed 28 Sep 1999 · us provisional application
Priority: 12 Aug 1996
Published: US 2002/0125191 A112 Sep 2002
Granted: 25 Mar 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification23 codes

B01D 61/58
Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary…
B01D 61/026
Reverse osmosis; Hyperfiltration: comprising multiple reverse osmosis steps
B01D 61/04
Reverse osmosis; Hyperfiltration ; Nanofiltration: feed pretreatment
B01D 65/08
Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes: prevention of membrane…