Organic wastewater treatment method and organic wastewater treatment device

A device for treating organic wastewater, the device comprising

• raw sludge removal means for removing raw sludge from organic wastewater,
• raw sludge concentration means for concentrating the raw sludge removed from the organic wastewater to a prescribed concentration to obtain concentrated raw sludge,
• a biological treatment tank for biologically treating the organic wastewater from which the raw sludge was removed,
• excess sludge separation means for separating excess sludge from the biologically treated organic wastewater,
• excess sludge concentration means for concentrating the separated excess sludge to a prescribed concentration to obtain concentrated excess sludge,
• a sludge mixing tank for mixing the concentrated raw sludge and the concentrated excess sludge to obtain mixed sludge, and
• a methane fermentation tank for performing a methane fermentation treatment on the mixed sludge,
• wherein the device for treating organic wastewater is characterized by comprising:
• a heating/sterilization device for heating and sterilizing the concentrated excess sludge retrieved from the excess sludge concentration means;
• and
• a control device for controlling the mixed sludge at a temperature adaptable to methane fermentation by adjusting at least one among (1) the temperature to which the concentrated excess sludge is heated in a sterilization step achieved by the heating/sterilization device, (2) the concentration of the concentrated raw sludge in a raw sludge concentration step achieved by the raw sludge concentration means and/or the concentration of the concentrated excess sludge in an excess sludge concentration step achieved by the excess sludge concentration means, and (3) the mixture ratio between the concentrated raw sludge and the concentrated excess sludge in a sludge mixing step achieved in the sludge mixing tank according to the fluctuations in the amount of raw sludge generated and the amount of the excess sludge generated.