Determination of partial denitrification kinetic model parameters based on batch tests and metagenomic sequencing

In this study, a model was developed to investigate the partial denitrification(PD) process. The heterotrophic biomass (X_H) proportion in the sludge was determined to be 66.4% based on metagenomic sequencing. The kinetic parameters were first calibrated, then validated using the batch tests results. The results showed rapid decreases in the chemical oxygen demand (COD) and nitrate concentrations and gradual increases in the nitrite concentrations in the first four hours, then remained constant from 4 to 8 h. Anoxic reduction factor (η_NO3 and η_NO2) and half saturation constant (K_S1 and K_S2) were calibrated at 0.097, 0.13, 89.28 mg COD/L, and 102.29 mg COD/L, respectively. Whereas the simulation results demonstrated that the increase in carbon-to-nitrogen (C/N) ratios and the reduction in X_H contributed to the increase in the nitrite transformation rate. This model provides potential strategies for optimizing the PD/A process.