To provide a drainage purification method by which treated water of very low fluorine concentration can be obtained by removing fluorine contained in fluorin-containing drainage to the utmost without necessitating a large quantity of a calcium compound such as calcium chloride and calcium hydroxide or a flocculant and discharging a large quantity of sludge.
This drainage purification method comprises the steps of: adding the calcium compound to the fluorine-containing drainage to produce calcium fluoride; subjecting a calcium fluoride-containing reaction product to solid-liquid separation such as a flocculating/settling method to remove the calcium fluoride; adjusting the pH of the calcium fluoride-removed treated water; adding hydrotalcite to the pH-adjusted treated water to adsorb remaining fluorine on hydrotalcite (called a fluorine adsorption step); subjecting the treated water containing fluorine-adsorbed hydrotalcite to solid-liquid separation such as the flocculating/settling method to remove the fluorine-adsorbed hydrotalcite; desorbing fluorine from the fluorine-adsorbed hydrotalcite (called a fluorine desorption step); adding the fluorine-desorbed hydrotalcite again at the fluorine adsorption step and; mixing the fluorine-containing drainage before calcium fluoride is produced with the fluorine-containing water produced at the fluorine desorption step.
ITO KENICHI
AKITA NASEISHI
KANEKAWA KOJI
SATO TSUTOMU
Shigeyuki Motoi
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