WATER PRODUCTION METHOD

摘要

Provided is a process for producing water including generating a water to be filtrated wherein a water to be treated is treated to generate a water to be filtrated; filtration wherein the water to be filtrated is filtrated through a separation membrane module having a separation membrane to generate a filtrated water; back washing wherein the substance to be removed by filtration which has blocked the separation membrane in the step of filtration is washed away by using a cleaning water; and drainage wherein cleaning drainage generated in the step of back washing is drained; wherein the step of generating the water to be filtrated has a coagulation substep of adding a first pH adjuster and a cationic coagulant to coagulate the substance to be removed by filtration in the water to be treated to thereby generate the pretreated water; the water to be filtrated used in the step of filtration satisfies the following expression (i); and the step of back washing has at least first back washing substep wherein the separation membrane is back-washed by the cleaning water satisfying the following expressions (ii) and (iii):;4.0≦pH of the water to be filtrated≦6.5  (i);pH of the cleaning water≦9.0  (ii);pH of the cleaning water−pH of the water to be filtrated≧1.0  (iii).

主权项

1. A process for producing water comprising:
a step of generating a water to be filtrated wherein a water to be treated is treated to generate a water to be filtrated; a step of filtration wherein the water to be filtrated is filtrated through a separation membrane module having a separation membrane to generate a filtrated water; a step of back washing wherein a substance to be removed by filtration which has blocked the separation membrane in the step of filtration is washed away by using a cleaning water; and a step of drainage wherein cleaning drainage generated in the step of back washing is drained; wherein the step of generating the water to be filtrated has a coagulation substep of adding a first pH adjuster and a cationic coagulant to coagulate the substance to be removed by filtration in the water to be treated to thereby generate the pretreated water; the water to be filtrated used in the step of filtration satisfies the following expression (i); and the step of back washing has at least first back washing substep wherein the separation membrane is back-washed by the cleaning water satisfying the following expressions (ii) and (iii):
4.0≦pH of the water to be filtrated≦6.5  (i)pH of the cleaning water≦9.0  (ii)pH of the cleaning water−pH of the water to be filtrated≧1.0  (iii).