Patent ID: 7368058

Claim:
A water processing method comprising the steps of: separating boron-containing water using at least two reverse osmosis membrane modules to provide a permeated water, wherein at least a part of the permeated water obtained in a first reverse osmosis membrane module is subjected to processing with a second reverse osmosis membrane module to produce a second permeated, water and a boron concentrated water, and subjecting at least a part of the concentrated water obtained in the second reverse osmosis membrane module to boron removal using an adsorbent, wherein the water subjected to the boron removal is mixed with the second permeated water not subjected to the boron removal to provide a mixed water, wherein the water processing efficiency in the second reverse osmosis membrane module is equal to or greater than 90%, wherein the first reverse osmosis membrane module uses a reverse osmosis membrane having salt rejection of 90% or more when a saline solution having a concentration of 35,700 mg/L at 25° C. pH of 6.5 is provided at 5.5 MPa. and wherein the second reverse osmosis membrane module uses a reverse osmosis membrane having flux of 0.8 m 3 /m 2 day or more when a saline solution having a concentration of 1500 mg/L at 25° C., pH of 6.5 is provided at 1.5 Mpa, and wherein a pH of water introduced to the second reverse osmosis membrane is 9 or more.