Improvement of Methane Yield and Carbon Conversion Efficiency on Mesophilic Methane Fermentation of Swine Wastewater

概要

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The mesophilic methane fermentation performance of a swine wastewater treatment facility that has been in operation for about 4 years was examined. The methane fermentation reactor (effective volume: 3, 100 m3) is of special construction and operates with intermittent mixing connected with inflow to improve the microorganism concentration. At a VS loading rate of 1.7 kg/m3/day and an HRT of 19 days, the VS removal was 54%, the amount of biogas produced was 3, 210 m3/day, and the methane content in that biogas was 76%. The methane production per COD removed was 0.50 m3-CH4/kg-COD. The methane yield per VS removed was 0.866 m3-CH4/kg-VS, and 1.18-1.30 times greater than those of other swine wastewater treatment facilities. The approximate molecular formula of solids in the wastewater was C12H20O5N. The measured methane content and methane yield per VS removed were, respectively, 1.19 times and 1.43 times greater than the theoretically calculated values estimated by the approximate molecular formula and the stoichiometric equation reported to agree well with thermophilic methane fermentation experimental results. These results suggest that it is possible to improve the methane yield and carbon conversion efficiency per unit of influent VS in mesophilic methane fermentation with this operation.