Method for treating waste water

Abstract

In wet-oxidizing organic waste water containing cyanogen i.e. inorganic-CN, or a compound capable of forming cyanogen under oxidative conditions, if the wet oxidation is conducted in the presence of copper or a copper compound and a specific ammonium salt, COD and the cyanogen concentration can be reduced at highly improved removal ratios. Copper ions resulting from the copper component made present at the wet oxidation step can be effectively removed by precipitation or ion exchange. Accordingly, this treatment method does not cause secondary pollution at all. In case recovery of the copper ions is performed by ion exchange, good results are obtained when the oxidized liquid from the wet oxidation step is flashed at a temperature higher than 100.degree. C. and the pH of the oxidized liquid is adjusted to 4-7 after the cyanogen decomposition step but before the ion exchange treatment. A weakly acidic ion exchange resin is preferably employed. When recovery of the copper ions is performed by precipitation, good results are obtained when sulfide type insolubilizing agents are employed.

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