METHOD FOR REMOVING BORON IN WATER TO BE TREATED, BORON REMOVAL SYSTEM, ULTRAPURE WATER PRODUCTION SYSTEM, AND METHOD FOR MEASURING BORON CONCENTRATION

摘要

To provide a method for removing boron from water to be treated, capable of stably, efficiently, and controlling a boron concentration in RO membrane permeated water to a desired low level at a low operating cost.SOLUTION: There is provided a method for removing boron from water to be treated, including the steps of: subjecting the water to be treated to reverse osmosis membrane treatment; subjecting at least a portion of permeated water of the reverse osmosis membrane treatment to a cation removal treatment; and measuring a boron concentration in the permeated water after the cation removal treatment; and controlling at least one of the following (a) to (e) based on the measured boron concentration: (a) a recovery rate of the water to be treated in the reverse osmosis membrane treatment, (b) temperature of the water to be treated, (c) pH of the water to be treated, (d) supply pressure of the water to be treated applied to the reverse osmosis membrane in the reverse osmosis membrane treatment, and (e) replacement time of a reverse osmosis membrane used in the reverse osmosis membrane treatment.SELECTED DRAWING: Figure 1