Kurita Water Industries Ltd.

Isamu Katoh

Takafumi Murakami

Naoto Hitotsuyanagi

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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Tokyo, Japan

Isamu Katoh