Observation and mathematical description of the acceleration phenomenon in batch respirograms associated with ammonium oxidation

Two-step nitrification models are generally calibrated using short-term respirometric batch experiments. Important discrepancies appear between model predictions and experimental observations just after the pulse addition since a fast transient in the OUR profile is experimentally observed. Acceleration of the OUR appears ongoing between the substrate addition and attainment of the maximum OUR value.This work proposes a simple methodology to successfully describe (not to explain) the acceleration phenomenon estimating only two parameters. This methodology consists of introducing a Gaussian-like expression in the model.