| 摘要 |
When a separation membrane ( 3 ) is washed with a chemical solution that is a sodium hypochlorite solution, which has a high concentration, diluted with membrane treated water stored in a chemical solution tank ( 6 ), an ammonic nitrogen concentration in membrane-treated water is monitored with a monitoring device ( 9 ), and a control device ( 8 ) controls a chemical solution dosing pump ( 7 ) using the concentration measured by the device ( 9 ) to adjust a dilution rate. Thereby, even when water quality of membrane-treated water varies, a sodium hypochlorite concentration in backwashing water can be retained constant, and fluctuation in the chemical washing effect can be prevented.
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