| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an apparatus for treating wastewater which can extremely reduce the amount of generated sludge at a low running cost and in which a solubilization tank can be miniatured. SOLUTION: The apparatus for treating wastewater is provided with a biological treatment system (5) for biologically treating the wastewater (4), a solid- liquid separation device (6) for obtaining treated water and returning sludge by solid-liquid separation of the biologically-treated wastewater, a means for obtaining taken-out sludge (11) from a part of the returning sludge, an alkaline treatment vessel (1) for alkaline treating the taken-out sludge at normal temperatures and pressures under anaerobic and oxygen-free or microaerophilic conditions at pH 7.5-8.9 with a holding time of 3-24 hours, a biological- solubilization vessel (3) for biologically solubilizing the alkaline treated sludge at normal temperatures and pressures under anaerobic and oxygen-free or microaerophilic conditions and at pH 7.0-7.8 with a holding time of 1-3 days, and a sludge returning means (13) for returning the solubilized sludge to the biological treatment system.</p> |
