本研究では，経済的な下水汚泥からの金属類の除去を目的とし，下水汚泥中に存在する硫黄酸化細菌と，嫌気性消化ガスの脱硫過程で生成する硫黄廃棄物の利用可能性について検討した。硫黄酸化細菌は，嫌気性消化汚泥を含む様々な性状の汚泥のいずれにも存在し，汚泥と元素硫黄を混合することにより容易に活性化し，分離できることが分かった。また，下水汚泥から分離した硫黄酸化細菌は嫌気性消化ガスの脱硫過程で生成する含硫黄廃棄物を基質として利用できることが明らかとなった。さらに，下水汚泥に硫黄廃棄物のみを添加することにより，汚泥中の硫黄酸化細菌の働きで硫酸が生成し，下水汚泥のpHが低下して金属類を溶出させることができた。これより，下水処理場内で必要な物質が全て供給される，新しい下水汚泥からの金属類の溶出システムを提案した。 ; The availability of indigenous sulfur-oxidizing bacteria and sulfur waste produced by desulfurization of digester gas was studied in order to achieve economical metal leaching from anaerobically digested sewage sludge. Indigenous sulfur-oxidizing bacteria were confirmed to exist in the various sewage sluge and activation and isolation were carried out by adding elemental sulfur. The utilization of sulfur waste as a substrate for indigenous sulfur-oxidizing bacteria was investigated in batch experiments. It was found that the addition of sulfur waste caused the production of sulfuric acid by bacteria and a decrease in pH, resulting in effective elution of heavy metals. Then, elution of the metals in sewage sludge using indigenous sulfuroxidizing bacteria and sulfur waste was carried out in semi-batch experiments. The optimum sludge retention time was found to be 3 days, when the sludge concentration was 2% and the amount of sulfur waste was 5g/ l. It was shown that the biological leaching of heavy metals from sewage sludge can be carried out in a closed system, where all required materials are obtained in a sewage treatment plant.