METHOD FOR REMOVING SOLUBLE COMPONENT INCREASING COD

PURPOSE:To remove soluble components increasing COD at a high rate of removal by subjecting sewage or industrial waste water to flocculation and precipitation treatments, mixing produced and drawn sludge contg. acidic metal ions with raw water contg. soluble components increasing COD and dehydrating the resulting mixed sludge. CONSTITUTION:In order to remove soluble components increasing COD from sewage or industrial waste water, this sewage or waste water 1 is sent to a chemical injection tank 4, mixed with a neutralizing agent 3 and subjected to flocculation treatment in a flocculation tank 5 and precipitation treatment in a precipitation tank 6. Produced sludge 9 contg. acidic metal ions is drawn from the bottom of the tank 6 and mixed with raw water 19 contg. soluble components increasing COD. The resulting mixed sludge is dehydrated with a dehydrator 12 and solid-liq. separation is carried out. The separated water is discharged at treated water 8 or added to sewage or industrial waste water to be treated.