The role of sulfate-reducing bacteria on insolubilization of heavy metal ions at waste disposal sites

1993~1995年，对2个海基固体废物处置场和7个垃圾填埋场进行了硫酸盐还原细菌(SRB)的分布研究，结果表明SRB在垃圾填埋场的分布较为广泛。对SRB进行了积累，并对几种重金属离子进行了不溶实验。六价铬的增溶率很低，只有16%，但与硫化细菌产生的硫化氢反应48小时内，Cd、Cu、Fe、Zn离子就会析出。在Cd离子存在的情况下，通过扫描电子显微镜和能谱分析确定生成的沉淀物为硫化镉。在废物处置场中，SRBS对重金属离子的不溶解作用变得明显。其中硫杆菌属(Desulfotomaculum sp.)是孤立的。产甲烷细菌(MPB)也广泛分布于现场，钻孔样品中的MPB数量高于渗滤液样品中的MPB数量。当硫离子浓度在20 mg/L或以上时，SRB数大于MPB数。分离到两种MPB。一株是同时利用甲醇和醋酸的甲烷八叠球菌，另一株是嗜热甲烷微生物菌。激发波长为420 nm的荧光显微镜证实了MPB与其他细菌的差异，但荧光显微镜很难区分MPB和SRBS。

Distribution of sulfate-reducing bacteria (SRB) at two sea-based solid waste disposal sites and seven landfill sites were conducted from 1993 to 1995, resulting that SRB widely distributed in the sites. SRBs were accumulated and insolubilization experiments using several heavy metal ions were performed. Insolubilization rate of hexavalent chromium was very low of 16%, neverthless, Cd, Cu, Fe, and Zn ions were precipitated within 48 hr reaction with hydrogen sulfide produced by SRBs. In case of Cd ion, produced precipitate was determined as cadmium sulfide from SEM and EDX analysis. The role of SRBs for insolubilization of heavy metal ions in waste disposal sites turned evident. Among SRBs, Desulfotomaculum sp. was isolated. Methane-producing bacteria (MPB) were also widely distributed in sites and MPB number counted from boring-pits samples were larger than those of from leachates. If samples contained 20mg/l or more of sulfuric ion concentration, SRBs number were greater than MPB number. Two kinds of MPB were isolated. One was Methanosarcina sp., which utilized both methanol and acetic acid and the other was thermophilic Methanomicrobium sp. The difference between MPB and other bacteria was confirmed by fluorescence microscopy using 420nm of exciting wavelength, but it was difficult to differ MPB from SRBs by fluorescence microscopy.