| 摘要 |
PURPOSE:To facilitate the removal of a phosphate ion, by a method wherein water to be treated containing the phosphate ion is passed through a hydroxyapatite fine crystal suspension being a precipitation material and a calcium ion subsequently is added to the water to be treated to precipitate the phosphate ion as apatite. CONSTITUTION:Water to be treated is introduced into a stirring tank 2 from a raw water inflow pipe 1. A hydroxiapatite fine crystal is present in the water of the stirring tank 2 and stirred by a stirrer 3. Calcium is added to the stirring tank 2 from a calcium inflow pipe 4 corresponding to the concn. of the phosphate ion in water to be treated and alkali is added to said tank 2 from an alkali inflow pipe 6 so as to obtain a predetermined pH value. The phosphate ion in water to be treated is precipitated on the precipitation material comprising the hydroxyapatite fine crystal and the treated water is introduced into a solid-liquid separation tank 8 to perform solid-liquid separation. By this method, the phosphate ion can be efficiently removed.
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