| 摘要 |
The pH value of excess sludge taken out from a biological oxidation tank ( 2 ) is adjusted to 8 to 14, and the pH-adjusted sludge is injected into a solubilizing device ( 3 ). The sludge taken out from the solubilizing device ( 3 ) is heated to 110° C. to 350° C. at a pressure higher than saturated steam pressure to solubilize the sludge to a state readily degradable by microorganisms. The solubilized sludge is returned to a biological oxidizing tank ( 2 ), and the pH value of the sludge in the biological oxidizing tank ( 2 ) to 5 to 9. The use of the above method of treating excess sludge and an apparatus therefore enables substantially reducing the volume of excess sludge with economic advantage.
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