The methane fermentation method is often used to process organic waste such as animal manure and garbage. The method attracts much attention since it works as a technology for producing renewable energy form organic waste, which changes organic waste into biogases such as methane and carbon dioxide. However, the methane fermentation process has a problem in that it involves large amounts of wastewater because organic waste is diluted with much water. In order to solve this problem, we devised a hydrolysis techn1que using an aerobic thermophilic bacterium, Anoxybacillus sp. MU3, as a pre-treatment method in methane fermentation under an aerobic high temperature environment (80°C).Solubilization of sewage sludge by strain MU3, isolated from a hot spring, was investigated as a pretreatment for the methane fermentation process. Strain MU3 could be grown at an optimum temperature of 60°C.
When strain MU3 was added to sewage sludge under the high temperature condition, the water-soluble CODcr value after 48 hours improved 40% compared with sample at the start of the test. The methane fermentation reactor (effective volume: 5 cubic meters) in which the sewage grime wonderment solubilization, was used to perform methane fermentation. At a SRT (sludge retention time) of 10 days, the VSS (volatile suspended solids) removal was 65%, the amount of biogas produced was 6,300/L, and the methane content in the biogas was 64%. The biogas yield per VSS removed was 1,133.6L/kg-VSS, that is, tow times greater than that of other sewage sludge treatment facilities.
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