RECLAIMED WATER PRODUCTION METHOD AND RECLAIMED WATER PRODUCTION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a reclaimed water production method and a reclaimed water production system capable of stably producing reclaimed water from drainage while preventing clogging of a membrane surface at a low cost without requiring a large volume of ozone on a steady basis.SOLUTION: A reclaimed water production method includes a process to: treat raw water with ozone in a manner that injects the ozone generated by an ozone generator into the raw water in a normal mode; injects an aggregating agent into the raw water before or after treating the same with the ozone; and filtrate the raw water with a separation membrane after treating the same with the ozone and injecting the aggregating agent thereinto. Also, the reclaimed water production method: measures a transmembrane pressure difference between an upstream side and a downstream side of the separation membrane; and cleans the separation membrane by turning the normal mode to a cleaning mode when an increase rate of the transmembrane pressure difference exceeds a predetermined value and intermittently increasing a concentration of dissolved ozone in the cleaning mode with larger volume of ozone than the normal mode injected into the raw water for cleaning purpose.