REVERSE OSMOSIS TREATMENT METHOD, REVERSE OSMOSIS TREATMENT SYSTEM, SODIUM REMOVAL DEVICE, AND SODIUM REMOVAL METHOD

摘要

To provide a reverse osmosis treatment method and a reverse osmosis treatment system, capable of improving the quality of treated water in two or more steps of a reverse osmosis treatment of water to be treated containing at least 3 mg/L of free carbon dioxide.SOLUTION: There are provided a reverse osmosis membrane treatment method and a reverse osmosis membrane treatment device, employing a first reverse osmosis treatment device (a first reverse osmosis treatment process) 10 for obtaining first permeated water and first concentrated water by causing water to be treated containing at least 3 mg/L of free carbon dioxide to flow through a first reverse osmosis membrane, and a second reverse osmosis treatment device (a second reverse osmosis treatment process) 12 for obtaining second permeated water and second concentrated water by causing the first permeated water to flow through a second reverse osmosis membrane, with at least the second reverse osmosis membrane being a polyamide-based reverse osmosis membrane with a difference between the maximum sodium-ion blocking rate and the minimum sodium-ion blocking rate in a pH range of 5 to 7 being at least 1%.SELECTED DRAWING: Figure 1