Abstract
Blowing water used for cooling blast furnace slag from the iron-making process is expected to be strongly alkaline because alkaline components of blast furnace slag are dissolved in it. However, actual blowing water in a water supply tank has a neutral pH. On the assumption that bacteria in blowing water cause pH to decrease, we conducted incubation experiments using blowing water controlled at a pH of 10 or higher. The pH of blowing water decreased at 60°C upon the addition of sodium thiosulfate. The concentration of sulfate also increased. DNA sequencing results revealed that the proportion of Thermi in this thiosulfate-stimulated blowing water increased to 83%. Thus sulfur-oxidizing bacteria that exist in high-temperature, high-pH blowing water oxidized thiosulfate into sulfate and hydrogen ion, so that the blowing water was neutralized. This bacterial reaction in a water supply tank is crucial for wastewater treatment of blowing water to decrease its pH and oxidize sulfur compounds.
