Modeling electron competition and pH factor interactions improve cognitions of nitrite accumulation during denitrification.

Electron competition (EC) and pH stress are two key factors influencing NO production during denitrification, but their dominance and interactions in the full pH range are poorly understood. In this study, we propose a concise Electron Competition Inhibition (ECI) model to clarify the contribution of EC and pH stress to NO production by characterizing the denitrifying kinetics in batch tests. The model exhibits good fitting results on NO accumulation across a wide NO/NO ratio range from 0 to 9, demonstrating its excellent ability in describing the EC effect and determining rate constants for NO and NO reductions.

Reactive and microbial inhibitory mechanisms depicting the panoramic view of pH stress effect on common biological nitrification.

pH is a crucial factor of microbial nitrification, which often combines with high-strength ammonium to influence nitrogen removal pathway in wastewater treatment. However, the detailed inhibitory mechanisms of pH stress are not sufficiently disclosed yet. In this study, the pH stress effect on nitrification was comprehensively studied by a set of experiments which identified the reactivity of nitrification processes and activity of nitrifiers, the time dependence of inhibition effect and the hybrid pH stress effect with ammonium.