| 摘要 |
PURPOSE:To remove phosphoric ion from waste water at a low cost, by stripping waste water containing phosphoric ion, and bringing it into contact with the crystal seeds of calcium phosphate in the presence of Ca. CONSTITUTION:Phosphate-contg. raw water 11, e.g. treated water of night soil, sewage or industrial waste water, is adjusted to a pH of 3-5 by the addition of an acid 13 such as sulfuric acid. Said raw water is introduced into a decarboxylation column 15 and stripped therein by releasing air from a lower side. CO2- contg. stripping gas is discharged through a line 17, while the decarboxylated raw water is withdrawn through a line 19. Said raw water is adjusted to a pH above 6 by the addition of an alkaline Ca agent 21 such as slaked lime. Thereafter, the raw water is sent into a crystallization dephosphorizer column 23 and brought into contact with crystal seeds containing calcium phosphate, e.g. hydroxyapatite, fluoroapatite or trilime phosphate, charged in the column to crystallizedly dephosphorize phosphoric ion as calcium phosphate on the surfaces of said crystal seeds. The dephosphorized raw water is introduced into a neutralizer column 27, neutralized therein with the stripping gas 17 and then drained.
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