Stabilization of a geothermal power plant operation by repressing of sulfur bacteria in the cooling water system

本研究的目的是通过抑制硫细菌来减少地热发电厂冷却水系统中硫垢的形成量。在上野台地热发电厂，产井产生的硫化氢有10%被氧化为硫酸，2%被转化为单质硫。这些变化主要发生在冷却塔。从冷却塔、冷凝器和管道的硫垢中分离出许多硫氧化细菌。此外，从河流污泥中分离出了某种细菌。河水被用作电厂的冷却水。16S核糖体DNA分析表明，电厂内部分离的硫氧化菌在设备中占主导地位，来源于河流。还从冷却塔和冷凝器底部分离出硫酸盐还原菌。在这些设备中，微生物硫氧化和还原是同时进行的。为减少硫垢的形成，在上野台地热发电厂冷却水中加入戊二醛和阳离子表面活性剂G-50。在一年的作业中，大约25%的结垢地层被减少。

The purpose of this study is to reduce the amount of sulfur scale formation in the cooling water system of a geothermal power plant by repressing sulfur bacteria.At Uenotai geothermal power plant, 10% of hydrogen sulfide derived from production well was oxidized to sulfuric acid, and 2% was converted to elemental sulfur. These changes were mainly occurred in the cooling tower. Many strains of sulfur oxidizing bacteria were isolated from sulfur scale sampled from the cooling tower, the condenser and pipelines. Also, some kind of bacteria was isolated from the river sludge. This river water is used for the cooling water of the power plant. The 16S ribosomal DNA analysis indicates that the sulfur oxidizing bacteria isolated from inside of the power plant are dominant in the equipments and derived from the river. Sulfate reducing bacteria were also isolated from bottoms of the cooling tower and the condenser. In these equipments, microbial sulfur oxidation and reduction occur simultaneously.To minimize the formation of sulfur scale, glutaraldehyde and cationic surfactant (G-50) were added to the cooling water of Uenotai geothermal power plant. About 25% of the scale formation was reduced for one year operation.