Our laboratory has been developing a sewage treatment system with UASB reactor for warm climate (average temperature: 15℃〜20℃). However, the performance of usual UASB such as organic matter removal decreases in winter because the decline of activities of methanogenic archaea due to low temperature. To overcome this problem, we are focusing on sulfate-reducing bacteria as an alternative terminal decomposer to methanogenic archaea, and have been developing a novel sewage treatment system using enhanced sulfur-redox cycle in combination with sulfur-oxidizing and sulfate-reducing bacteria, which is more tolerate for low temperature than methanogenic archaea.
During this research, an anaerobic sulfur oxidation phenomenon occurred in UASB reactor. In general, anaerobic sulfur oxidation occurs in presence of electron accepter such as nitrate. However, there are no potential electron accepters in the reactor, thus the fundamentals of this phenomenon was unclear. In this study therefore, trying to elucidate the exact nature of this anaerobic sulfur oxidation.