pressure ro membrane u201c es 20 u201d manufactured by nitto denko corporation at a permeate flow of 60 l hr and a recovery rate of 80 the ro feed water had a ph of 5 5 treatment was performed under the same conditions as those in example 1 except that naclo in place of chloramine t was added to industrial water with a toc concentration of 1 mg l as c in such a manner that the concentration of free chlorine was 0 5 mg cl 2 l treatment was performed under the same conditions as those in example 1 except that chloramine t was added to the industrial water with a toc concentration of 1 mg l as c in such a manner that the concentration of combined chlorine was 0 5 mg cl 2 l example 2 0 8 mg cl 2 l example 3 1 mg cl 2 l example 4 or 3 mg cl 2 l example 5 treatment was performed under the same conditions as those in example 1 except that after chloramine t was added to the industrial water with a toc concentration of 1 mg l as c in such a manner that the concentration of combined chlorine was 1 mg cl 2 l coagulation filtration treatment was performed under conditions in which the amount of pac added was 10 mg l and the ph was 6 and then the water that had been subjected to the coagulation filtration treatment was passed through activated carbon at an sv of 10 hr u2212 1 example 6 15 hr u2212.