MEMBRANE-SEPARATION METHOD

摘要

A membrane separation method in which the concentration of free chlorine is reduced and the total chlorine concentration is increased using a small amount of chemicals and a simple operation, whereby it is possible to prevent even permeable membranes having low chlorine resistance from being contaminated by slime deposition based on microbial proliferation, and to efficiently perform membrane separation over a prolonged period of time, without any reduction in the removal rate or desalination rate due to degradation of the permeable membrane. When treated water containing free chlorine is fed from L1 to a membrane separation device (4) and subjected to membrane separation by a permeable membrane (4a), one or more sulfamic acid compounds selected from the group consisting of sulfamic acid, combined-chlorine sulfamic acid, and a salt of sulfamic acid or combined-chlorine sulfamic acid are added from L2 to the treated water to convert free chlorine to combined chlorine, and a reduction agent is added as required from L6 to remove residual free chlorine and prevent slime deposition in membrane separation.