[Characteristics of nitrite accumulation in a hydrogenotrophic denitrification system]

A mathematic model for nitrite accumulation in a hydrogenotrophic denitrification system running in a sequencing batch mode was developed and denitrification coefficient alpha was defined to describe the process of nitrite accumulation. The reduction rates of nitrate and nitrite and the nitrite accumulation before/after the nitrite addition were investigated using a sequencing batch reactor. The result showed that in Run 1 the reduction rates of nitrate and nitrite were 6.52 mg/(L x h) and 4.40 mg/(L x h) respectively, accompanied with the remarkable nitrite accumulation. The reduction rate of nitrite increased to 4.89 mg/(L x h) after nitrite addition. In Run 2, the reduction rate of nitrate decreased to 3.94 mg/(L x h) and almost no nitrite accumulation was observed. The addition of nitrite changed both the reduction rates of nitrate and nitrite, and finally showed an effect on the accumulated concentration of nitrite. The process of nitrite accumulation was identical with the theoretical one calculated according to the model. The nitrite accumulation could be exactly reflected by the defined denitrification coefficient alpha. When alpha was less than 1, nitrite accumulation was observed obviously with the maximum concentration 11.06 mg/L. While when alpha was more than 1, accumulated nitrite concentration was lower than 0.30 mg/L.