Quantification of nitrous oxide (N2O) emissions and soluble microbial product (SMP) production by a modified AOB-NOB-N2O-SMP model

- A modified AOB-NOB-N2O-SMP model was proposed for wastewater treatment modeling.
- AOB and NOB were considered the autotrophic biomass performing the nitrification.
- AOB denitrification was considered the N2O production kinetics.
- Modeling accuracy for N2O emission increased by 58% using the proposed model.
- Modeling accuracy for SMP production increased by 17% using the proposed model.

A modified AOB-NOB-N2O-SMP model able to quantify nitrous oxide (N2O) emissions and soluble microbial product (SMP) production during wastewater treatment is proposed. The modified AOB-NOB-N2O-SMP model takes into account: (1) two-step nitrification by ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), (2) N2O production by AOB denitrification under oxygen-limited conditions and (3) SMP production by microbial growth and endogenous respiration. Validity of the modified model is demonstrated by comparing the simulation results with experimental data from lab-scale sequencing batch reactors (SBRs). To reliably implement the modified model, a model calibration that adjusts model parameters to fit the model outputs to the experimental data is conducted. The results of this study showed that the modeling accuracy of the modified AOB-NOB-N2O-SMP model increases by 19.7% (NH4), 51.0% (NO2), 57.8% (N2O) and 16.7% (SMP) compared to the conventional model which does not consider the two-step nitrification and SMP production by microbial endogenous respiration.

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