To provide a method for digesting sludge capable of remarkably reducing the volume of sludge without generating excess sludge at the time of biologically digesting an org. concd. sludge by making the org. matter difficult to biologically decompose contained in a soluble org. matter (VDS) formed in a high-temp. solubilization tank low molecular and converting the low molecular org. matter completely to inorg. matter in the succeeding medium-temp. digestion.
High-temp. digestion and medium-temp. digestion are alternately conducted to biologically digest a concd. org. sludge 10 (raw sludge). In this case, the sludge solubilized in the high-temp. digestion 12 is oxidized with ozone in a tank 14 for ozone oxidation and then digested at a medium tamp. in a tank 16.
KATSURA KENJI
MIURA MASAHIKO
YOKOYAMA HIDEKI
