| 摘要 |
PROBLEM TO BE SOLVED: To provide a membrane filtering method for obtaining permeated water by membrane-filtering water to be treated like underground water, river water, lake water or secondary treated water of sewage capable of stable membrane filtration operation over a long period by reducing contamination of the membrane caused by continuous membrane filtration, and the membrane filtering system realizing it. SOLUTION: In this membrane filtration method of the water to be treated containing dissolved calcium by precise filtration membrane and/or ultrafiltration membrane, a compound capable of forming a complex with calcium is added to the water to be treated before membrane filtration, at an amount to keep the concentration of the compound within the range of 10μg/l-10g/l, and a filtration membrane allowing permeation of calcium and a calcium complex is used for membrane filtration. After the membrane filtration, the compound capable of forming the complex with calcium, and the calcium complex formed thereby are eliminated. COPYRIGHT: (C)2008,JPO&INPIT
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