PROBLEM TO BE SOLVED: To stir and transfer a fermentation treatment object liquid with no power by utilizing biogas generated by fermentation in the technology of treating organic components contained in the fermentation treatment object liquid by the fermentation. SOLUTION: The fermentation treatment of the fermentation treatment object liquid containing the organic components is performed in a plurality of fermentation tanks 1, 2 whose lower parts are communicated with each other. By the pressure P1of the biogas generated in the fermentation tank 1 on the upstream side, the fermentation treatment object liquid L1is transferred from the fermentation tank 1 on the upstream side to the fermentation tank 2 on the downstream side. Also, the fermentation treatment object liquid L2in the fermentation tank 2 on the downstream side is made to overflow and transferred out of a system. By opening the pressure P1of the biogas stored in the fermentation tank 1 on the upstream side, a part of the fermentation treatment object liquid L2in the fermentation tank 2 on the downstream side is made to flow back to the fermentation tank 1 on the upstream side. Thus, the fermentation treatment object liquid is stirred and transferred with no power. COPYRIGHT: (C)2011,JPO&INPIT
