STRUCTURED MODELING OF DENITRIFICATION INTERMEDIATES

Two mathematical models have been formulated to describe the turnover of denitrification intermediates. Batch experiments with different nit rite concentrations have been performed to calibrate the models, In th ese experiments the concentration of oxygen in the reactor has been va ried from 4 g O(2)m(-3) to O g O(2)m(-3). Model I includes the reducti on of nitrate, nitrite, and nitrous oxide. Non-competitive inhibition of these processes by oxygen and nitrite has been included in the kine tics. The estimated parameters indicate that the net production of N2O at low oxygen concentrations can be explained by different oxygen inh ibition of the three reduction steps, Model II works with structured b iomass to improve the description of the data from the experiments, In addition to Model I, the synthesis and decay of denitrification enzym es are described to allow correct predictions of nitrate, nitrite and N2O concentrations. Model II has been used to simulate the effect of c ell saturation with enzymes in a wastewater treatment process. Low dis solved oxygen concentrations in the anoxic reactor reduce the denitrif ication efficiency equally by inhibiting enzyme activity and enzyme sy nthesis: at 0.5 gm(-3) O-2 enzyme decay causes a cell saturation of be low 40%. The benefits of modelling with structured biomass are shown: The comprehension of experimental observations is improved and plant d esign and operation can be optimized. However, the multitude of unknow n parameters still may restrict the application of complex models.