To supply liquid including nitrate in a cathode chamber; and to raise electric power generation efficiency of microorganism electric power generation which performs reduction reaction by making use of denitrifying bacilli.
A negative electrode 21 is arranged in an anode chamber 11 wherein microorganisms are retained and a liquid including an electron donor is supplied. A positive electrode 22 is arranged in the cathode chamber 12 wherein denitrifying bacilli are retained. A positive electrode solution including nitric acid or nitrous acid is supplied to the cathode chamber 12. The positive electrode solution is supplied to the cathode chamber 12 by applying deoxidation treatment so as not to practically include dissolved oxygen. For example, a cathode circulation passage 42 for circulating the positive electrode solution to the cathode chamber 12 is arranged, and dissolved oxygen density of the liquid sent to the cathode chamber 12 practically becomes zero by arranging a deoxidation device 44 for removing oxygen in the middle of the cathode circulation passage.
ODA NOBUHIRO
KOMATSU KAZUYA
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