| 摘要 |
PURPOSE:To remove efficiently the hardly biologically decomposable materials in waste water in the stage of treating said waste water, by changing the ferric hydroxide in formed sludge to secondary salt and reusing the same as a flocculating agent in a pretreatment for flocculation of the waste water. CONSTITUTION:Waste water contg. hardly biologically decomposable org. materials such as humic acid, fulvic acid or the like is put together with the supernatant liquid from the final stage into the 1st flocculation tank 1, where a pH adjusting agent or, if necessary, a flocculating agent 9 of ferric sulfate is added thereto to adjust the pH to 4-5. The org. materials are flocculated and separated in the 1st settling tank 2. The water is then put into a reaction tank 3 where iron salt 10 and H2O2 11 or further a sulfuric acid 12 are added to the water to oxidize the dissolved org. materials; thereafter the water is transferred into the 2nd settling tank 4 where an alkali agent 13 is added to the water to adjust the pH thereof. The formed flocs of ferric hydroxide are separated together with the org. materials in the waste water in the 2nd settling tank 5. The supernatant liquid is returned partly to the tank 1 and the settled sludge is added with a sulfuric acid 12 in a dissolution tank 6 whereby the ferric hydroxide is dissolved as ferric sulfate. |
