Methods for reducing boron concentration in high salinity liquid

Abstract

Methods of treating a high salinity liquid, such as seawater, containing boron are provided, including adjusting the pH of the liquid to about 8 to about 9.5, optionally adding a scale inhibitor to the liquid, passing the liquid through a reverse osmosis device, and recovering a permeate having a boron concentration less than about 2 ppm. One embodiment includes removing colloidal matter from the liquid using a membrane filtration system, such as ultrafiltration or microfiltration, prior to passing the liquid through the reverse osmosis device, and preferably prior to adjusting the pH of the liquid.

1 . A method of reducing boron concentration in a high-salinity, boron-containing liquid comprising the following steps:
 (a) increasing a pH of a non-softened, high salinity liquid to about 8 to 9.5;   (b) passing the pH-increased, non-softened high salinity liquid through at least one reverse osmosis device; and   (c) recovering a permeate from the at least one reverse osmosis device wherein the permeate has a boron concentration of less than about 2 ppm,   
     further comprising at least before step (b) adding at least one coagulant chemical to the high salinity liquid and treating the high salinity liquid with a membrane filtration system to remove at least one suspended solid from the liquid. 
   
   
       2 . The method of  claim 1 , wherein the high salinity liquid is seawater. 
   
   
       3 . The method of  claim 1 , wherein the seawater comprises about 4 to about 7 ppm boron. 
   
   
       4 . The method of  claim 1 , wherein the pH of the high salinity liquid is increased to about 8 to about 9.3. 
   
   
       5 . The method of  claim 1 , wherein step (a) comprises adding a base to the high salinity liquid. 
   
   
       6 . The method of  claim 5 , wherein the base is selected from the group consisting of calcium hydroxide, sodium hydroxide, and lime. 
   
   
       7 . The method of  claim 1 , wherein the at least one reverse osmosis device comprises an array comprising at least one reverse osmosis membrane. 
   
   
       8 . The method of  claim 7 , wherein the at least one reverse osmosis membrane is a polyamide-type membrane. 
   
   
       9 . The method of  claim 7 , wherein the at least one reverse osmosis membrane is selected from the group consisting of a spiral wound membrane and a hollow fiber membrane. 
   
   
       10 . The method of  claim 1 , wherein the method further comprises adding a scale inhibitor to the high salinity liquid before step (b). 
   
   
       11 . The method of  claim 1 , wherein the permeate has a boron concentration of less than about 1 ppm. 
   
   
       12 . The method of  claim 1 , wherein the permeate has a boron concentration of less than about 0.5 ppm. 
   
   
       13 . The method of  claim 1 , wherein the membrane filtration system is selected from the group consisting of an ultrafiltration system and a microfiltration system. 
   
   
       14 . The method of  claim 13 , wherein the membrane filtration system comprises a membrane module selected from the group consisting of an ultrafiltration membrane module and a microfiltration membrane module. 
   
   
       15 . The method of  claim 14 , wherein the ultrafiltration or microfiltration membrane module comprises a membrane selected from the group consisting of spiral wound and capillary type membranes. 
   
   
       16 . The method of  claim 1 , wherein the pH of the high salinity liquid is increased to about 8.5 to 9.5 in step (a). 
   
   
       17 . The method of  claim 16 , wherein the pH of the high salinity liquid is increased to about 8.5 to about 9.3. 
   
   
       18 . The method of  claim 1 , wherein the at least one reverse osmosis device is a high pressure reverse osmosis device. 
   
   
       19 . The method of  claim 1 , wherein step (b) comprises passing the pH-increased, non-softened, high salinity liquid through two reverse osmosis devices. 
   
   
       20 . A desalination treatment method for high salinity, boron-containing liquid, including reducing a boron concentration in the high salinity, boron-containing liquid, the method comprising the following steps:
 (a) treating a non-softened, high salinity liquid with a membrane filtration system to remove at least one suspended solid from the liquid;   (b) subsequently increasing a pH of the non-softened, high salinity liquid to about 8 to 9.5;   (c) passing the pH-increased, non-softened, high salinity liquid through at least one reverse osmosis device; and   (d) recovering a permeate from the at least one reverse osmosis device wherein the permeate has a boron concentration of less than about 2 ppm.