Five scenarios were implemented and evaluated for their potential to reduce N2O emissions. The boundary conditions varied for each scenario are summarized in Table 1. For the modeling study, only those parameters were selected that on the one hand can be easily modified during operation and on the other hand have a strong impact on N2O formation by denitrification. The dosage of additional carbon was not considered, as its influence is only relevant for substrate-limited conditions. Moreover, as the N2O load is low compared to the total N load, the organic C released from the hydrolysis of dead biomass is expected to be sufficient for N2O denitrification.
Varied boundary conditions for each scenario (deamm.: deammonification, interm.: intermittent aeration, cont.: continuous aeration, bold: changes compared to baseline scenario)
| scenario . | process . | aeration . | pH . |
|---|---|---|---|
| baseline | nitritation | direct interm. (1.5 mg/l) | 5.8 |
| S1 | one-step deamm. | direct interm. (1.5 mg/l) | 5.8 |
| S2 | one-step deamm. | direct interm. (1.5 mg/l) | 7.0 |
| S3 | nitritation | direct interm. (3 mg/l) | 5.8 |
| S4 | nitritation | indirect cont. (1.5 mg/l) | 5.8 |
| S5 | one-step deamm. | indirect cont. (1.5 mg/l) | 7.0 |
| scenario . | process . | aeration . | pH . |
|---|---|---|---|
| baseline | nitritation | direct interm. (1.5 mg/l) | 5.8 |
| S1 | one-step deamm. | direct interm. (1.5 mg/l) | 5.8 |
| S2 | one-step deamm. | direct interm. (1.5 mg/l) | 7.0 |
| S3 | nitritation | direct interm. (3 mg/l) | 5.8 |
| S4 | nitritation | indirect cont. (1.5 mg/l) | 5.8 |
| S5 | one-step deamm. | indirect cont. (1.5 mg/l) | 7.0 |