To economically treat an ammonia-containing waste liquid by properly controlling the quantity of an alkali to be added into a liquid to be treated to prevent the unnecessary increase of the quantity of the alkali to be added into the liquid to be treated in a treatment of the ammonia-containing waste liquid by the ammonia stripping method.
This treating method comprises controlling the quantity of the alkali to be added into the liquid to be treated on the basis of the pH of the treated liquid after brought into contact with steam or air. For example, the quantity of the alkali to be added into the liquid to be treated from an alkali feed line 8 is controlled to fix the pH of the treated liquid flowing in a treated liquid flow-out line 22 connected to a stripping tower 14, in which the liquid to be treated is brought into gas-liquid contact with steam or air.
TAKAHASHI HIDENORI
NAKAMURA MIEKO
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