CHEMICAL SOLUTION CLEANING METHOD, WATER TREATMENT SYSTEM AND MEMBRANE FILTRATION APPARATUS

PROBLEM TO BE SOLVED: To provide a chemical solution cleaning method where the used amount of a chemical solution can be reduced and which is effective for reducing a running cost.SOLUTION: A chemical solution cleaning method of a hollow fiber membrane module 20 comprises: a discharge step of stopping the filtration operation of at least a part of a plurality of hollow fiber membrane modules 20 and discharging a liquid remaining in the hollow fiber membrane module 20; an interface adjustment step where a chemical solution is supplied from an upper part of the hollow fiber membrane module 20 via a treatment water header pipe 4 after the discharge step and the supply of the chemical solution is stopped at a position that the interface of the chemical solution is higher than the top edge of a hollow fiber membrane 21 in the hollow fiber membrane module 20 and does not reach the treatment water header pipe 4; and a cleaning step of settling the chemical solution after the interface adjustment step. 【課題】薬液の使用量を低減でき、ランニングコストの低減に有効な薬液洗浄方法を提供することを目的とする。【解決手段】中空糸膜モジュール２０の薬液洗浄方法であって、複数の中空糸膜モジュール２０の少なくとも一部の濾過運転を停止して中空糸膜モジュール２０内に残存する液体を排出する排出工程と、排出工程の後で、処理水ヘッダ管４を介して中空糸膜モジュール２０の上部から薬液を供給し、薬液の界面が中空糸膜モジュール２０の中空糸膜２１の上端よりも高く、且つ処理水ヘッダ管４に到達しない位置で薬液の供給を停止する界面調整工程と、界面調整工程の後で、薬液を静置する洗浄工程と、を備える。【選択図】 図１