| 摘要 |
In a multistage osmosis treatment method including: subjecting liquid to reverse osmosis treatment in a first-stage reverse osmosis separation module (31); adding an alkali agent to the obtained permeated water (5) to adjust a pH value of the permeated water (5) in an alkaline region; and further subjecting the permeated water (5) to reverse osmosis treatment in second and subsequent stage reverse osmosis separation modules (32), the supply water (5) to the second-stage reverse osmosis separation module (32) is subjected to at least one treatment selected from deferrization, demanganization, decarboxylation, and addition of a chelator and a scale inhibitor. Because of this, multistage reverse osmosis treatment is provided, in which the separation performance of the second and subsequent stage reverse osmosis membrane modules is enhanced, and liquid can be separated and purified to a high degree, and boron and the like that are not dissociated in a neutral region can be separated at a high blocking ratio. <IMAGE> |
