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Nitrous oxide production in autotrophic nitrogen removal granular sludge: A modeling study.
- Source :
-
Biotechnology and bioengineering [Biotechnol Bioeng] 2019 Jun; Vol. 116 (6), pp. 1280-1291. Date of Electronic Publication: 2019 Feb 06. - Publication Year :
- 2019
-
Abstract
- The sustainability of autotrophic granular system performing partial nitritation and anaerobic ammonium oxidation (anammox) for complete nitrogen removal is impaired by the production of nitrous oxide (N <subscript>2</subscript> O). A systematic analysis of the pathways and affecting parameters is, therefore, required for developing N <subscript>2</subscript> O mitigation strategies. To this end, a mathematical model capable of describing different N <subscript>2</subscript> O production pathways was defined in this study by synthesizing relevant mechanisms of ammonium-oxidizing bacteria (AOB), nitrite-oxidizing bacteria, heterotrophic bacteria (HB), and anammox bacteria. With the model validity reliably tested and verified using two independent sets of experimental data from two different autotrophic nitrogen removal biofilm/granular systems, the defined model was applied to reveal the underlying mechanisms of N <subscript>2</subscript> O production in the granular structure as well as the impacts of operating conditions on N <subscript>2</subscript> O production. The results show that: (a) in the aerobic zone close to the granule surface where AOB contribute to N <subscript>2</subscript> O production through both the AOB denitrification pathway and the NH <subscript>2</subscript> OH pathway, the co-occurring HB consume N <subscript>2</subscript> O produced by AOB but indirectly enhance the N <subscript>2</subscript> O production by providing NO from NO <subscript>2</subscript> <superscript>-</superscript> reduction for the NH <subscript>2</subscript> OH pathway, (b) the inner anoxic zone of granules with the dominance of anammox bacteria acts as a sink for NO <subscript>2</subscript> <superscript>-</superscript> diffusing from the outer aerobic zone and, therefore, reduces N <subscript>2</subscript> O production from the AOB denitrification pathway, (c) operating parameters including bulk DO, influent NH <subscript>4</subscript> <superscript>+</superscript> , and granule size affect the N <subscript>2</subscript> O production in the granules mainly by regulating the NH <subscript>2</subscript> OH pathway of AOB, accounting for 34-58% of N <subscript>2</subscript> O turnover, and (d) the competition between the NH <subscript>2</subscript> OH pathway and heterotrophic denitrification for nitric oxide leads to the positive role of HB in reducing N <subscript>2</subscript> O production in the autotrophic nitrogen removal granules, which could be further enhanced in the presence of a proper level of influent organics.<br /> (© 2019 Wiley Periodicals, Inc.)
Details
- Language :
- English
- ISSN :
- 1097-0290
- Volume :
- 116
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- Biotechnology and bioengineering
- Publication Type :
- Academic Journal
- Accession number :
- 30684360
- Full Text :
- https://doi.org/10.1002/bit.26937