| 摘要 |
PURPOSE:To reduce the addition amount of an alkali agent and to reduce the load in post-treatment, by adding slaked lime to ammonia nitrogen containing water while performing aeration treatment by using an oxygen containing gas with an oxygen concn. of 30-70%. CONSTITUTION:Slaked lime is added to ammonia nitrogen-containing water as a neutralizing agent to bring the pH thereof to 6.5 or more and the phosphoric acid ion in sewage is converted to insoluble calcium phosphate while the precipitation property of sludge is improved. Subsequently, this treated water is subjected to aeration treatment by using oxygen-containing gas with an oxygen concn. of 30-70%. The oxygen concn. of the oxygen-containing gas is pref. 40-60% and, as the mode of an oxygen supply means and an aeration tank, one, wherein a porous plate is used to generate fine air bubbles, is used. In addition, by using oxygen-containing gas with oxygen concn. of 30-70% even to sewage containing NH4-N in a high concn., pH lowering is suppressed and the amount to be used of an alkali agent can be reduced.
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