| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for treating sewage sludge which solved the problem that when nitrate nitrogen and dissolved oxygen in the sludge are eliminated in the process of concentration and dewatering, phosphorus which was accumulated and fixed as polyphosphoric acid in the cells of microorganisms is released into water as orthophosphoric acid to increase the phosphorus concentration of wastewater. SOLUTION: In the method for treating sewage sludge generated in sewage works, in which phosphorus is removed biologically, comprising a concentration treatment process, a dewatering treatment process, and a drying or incineration treatment process, the sludge is concentrated and, without being allowed to stand at ordinary temperature for a long time, refrigerated while nitrate nitrogen is left in the sludge. In this way, the cell membranes of microorganisms in the sludge are broken so that phosphorus contained in the microorganisms is fixed as polyphosphoric acid, and the refrigerated sludge is melted, dewatered, and dried or incinerated.
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