モリブデン欠乏下での硝化脱窒現象

抄録

Nitrification and denitrification process is a useful means of nitrogen removal of wastewater including night soil. A current concern about the process is the possibility that N₂O, a green-house effect gas could be released by the nitrogen removal. The mechanism of so called “aerobic denitrification” also remains to be elucidated. In this study, two lab-scale models of the nitrification denitrification process of a mixed liquor recycle type were operated under conditions similar to those of “High Rate Process” amply adopted in night soil treatment and characterized by high MLSS concentration and high volumetric loads of nitrogen and organic matter. During the operation, the content of nutritional metals (Cu, Fe, Zn, Mn, Co and Mo) in the influent was varied to investigate the effects of the metals on nitrification and denitrification. The deficiency of Mo in the influent resulted in a halt of the oxidation of NO₂^-to NO₃^-, which accompanied a prominent aerobic denitrification concomitantly releasing N₂O in a large amount. This finding suggests that Mo is a metal essential for preventing N₂O emission from the nitrification denitrification process.