TY - JOUR

T1 - Model-based identification and testing of appropriate strategies to minimize N2O emissions from biofilm deammonification

AU - Freyschmidt, A.

AU - Beier, M.

N1 - Funding Information: This work was carried out as part of the MiNzE project (‘Minimization of the CO2 footprint by adapted process development in process water treatment – testing of the MiNzE process in an immersed fixed bed’, FKZ: 02WQ1482B). We thank the German Federal Ministry of Education and Research for financial support. Publisher Copyright: © 2022 IWA Publishing. All rights reserved.

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Based on a one-year pilot plant operation of a two-step biofilm nitritation-anammox pilot plant, N 2O mitigation strategies were identified by applying a newly developed biofilm modeling approach. Due to adapted plant operation, the N 2O emission could be diminished by 75% (8.8% → 2.3% of NH 4-N oxidized_AOB). The results (measurement and simulation) confirm the huge importance of denitrification as an N 2O source or N 2O sink, depending on the boundary conditions. A significant reduction of N 2O emissions could only be achieved with a one-step deammonification system, which is related to low nitrite and HNO 2 concentrations. Increased oxygen concentrations in the bulk phase are not related to decreased emissions. N 2O formation by ammonium-oxidizing bacteria (AOB) just shifts deeper into the biofilm; zones with low oxygen concentrations are not avoidable in biofilm systems. Low oxygen concentrations in the bulk phase, however, result in a reduction of the total net N 2O formation due to increased activity of heterotrophic bacteria directly at the source of N 2O formation (outer biofilm layer). For the model-based identification of mitigation strategies, the standard modeling approaches for biofilms were expanded by including the factor-based N 2O formation and emission approach. The new model 'Biofilm/N 2O ISAH' was successfully validated using data from pilot-scale measurement campaigns. Altogether, the investigation confirms that the employed digital model can strongly support the development of N 2O mitigation strategies without the need for specialized measurement inside the biofilm.

AB - Based on a one-year pilot plant operation of a two-step biofilm nitritation-anammox pilot plant, N 2O mitigation strategies were identified by applying a newly developed biofilm modeling approach. Due to adapted plant operation, the N 2O emission could be diminished by 75% (8.8% → 2.3% of NH 4-N oxidized_AOB). The results (measurement and simulation) confirm the huge importance of denitrification as an N 2O source or N 2O sink, depending on the boundary conditions. A significant reduction of N 2O emissions could only be achieved with a one-step deammonification system, which is related to low nitrite and HNO 2 concentrations. Increased oxygen concentrations in the bulk phase are not related to decreased emissions. N 2O formation by ammonium-oxidizing bacteria (AOB) just shifts deeper into the biofilm; zones with low oxygen concentrations are not avoidable in biofilm systems. Low oxygen concentrations in the bulk phase, however, result in a reduction of the total net N 2O formation due to increased activity of heterotrophic bacteria directly at the source of N 2O formation (outer biofilm layer). For the model-based identification of mitigation strategies, the standard modeling approaches for biofilms were expanded by including the factor-based N 2O formation and emission approach. The new model 'Biofilm/N 2O ISAH' was successfully validated using data from pilot-scale measurement campaigns. Altogether, the investigation confirms that the employed digital model can strongly support the development of N 2O mitigation strategies without the need for specialized measurement inside the biofilm.

KW - aeration strategies

KW - control algorithms

KW - denitrification

KW - GHG Emissions

UR - http://www.scopus.com/inward/record.url?scp=85140144077&partnerID=8YFLogxK

U2 - 10.2166/wst.2022.307

DO - 10.2166/wst.2022.307

M3 - Article

VL - 86

SP - 1810

EP - 1820

JO - Water science and technology

JF - Water science and technology

SN - 0273-1223

IS - 7

ER -