Kurita Water Industries Ltd.

Naoto Hitotsuyanagi

Nobuhiro Orita

Takahiro Kawakatsu

Takafumi Murakami

Isamu Katoh

A detergent and a method for washing applicable to selectively permeable membranes for proposed, which can attain washing of selectively permeable membranes deteriorated in its membrane performance, such as the flux, in an efficient manner within a brief time at a higher detergent effect without causing deterioration of the selectively permeable membranes and without damaging safety to human and to environment with superior handling aspect. The detergent contains a polyol having a molecular weight not higher than 400 and, if necessary, an organic solvent.

Detergent for washing a selectively permeable membrane and method of washing

Dsiclosed is a method of treating fluoride-containing water, which comprises a reaction step where a calcium compound and/or an aluminium compound are/is added to fluoride-containing water while the pH value of the resulting suspended liquid is adjusted to fall within the range of from 6 to 8, and at least a part of the concentrated suspension to be formed in the membrane-separation step of the following stage is added to the suspended liquid and stirred and the resulting suspension is introduced into the circulation tank; a membrane-separation step where the suspension from the circulation tank is treated by membrane-separation to separate it into a permeated solution and a concentrated suspension; a circulation step where at least a part of the concentrated suspension to be taken out from the membrane-separation step is returned back to the reaction step while the remaining part thereof is circulated to the circulation tank; and a step where the permeated solution is taken out from the membrane-separation step as a treated water. The method is free from scaling disorder of the apparatus used and gives a treated water of high quality stably and efficiently.

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Kanagawa, Japan

Naoto Hitotsuyanagi