Pathways and controls of N2O production in nitritation-anammox biomass

Chun Ma, Marlene Mark Jensen, Barth F. Smets, Bo Thamdrup

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Abstract

Nitrous oxide (N 2O) is an unwanted byproduct during biological nitrogen removal processes in wastewater. To establish strategies for N 2O mitigation, a better understanding of production mechanisms and their controls is required. A novel stable isotope labeling approach using 15N and 18O was applied to investigate pathways and controls of N 2O production by biomass taken from a full-scale nitritation-anammox reactor. The experiments showed that heterotrophic denitrification was a negligible source of N 2O under oxic conditions (≥0.2 mg O 2 L -1). Both hydroxylamine oxidation and nitrifier denitrification contributed substantially to N 2O accumulation across a wide range of conditions with varying concentrations of O 2, NH 4 +, and NO 2 -. The O 2 concentration exerted the strongest control on net N 2O production with both production pathways stimulated by low O 2, independent of NO 2 - concentrations. The stimulation of N 2O production from hydroxylamine oxidation at low O 2 was unexpected and suggests that more than one enzymatic pathway may be involved in this process. N 2O production by hydroxylamine oxidation was further stimulated by NH 4 +, whereas nitrifier denitrification at low O 2 levels was stimulated by NO 2 - at levels as low as 0.2 mM. Our study shows that 15N and 18O isotope labeling is a useful approach for direct quantification of N 2O production pathways applicable to diverse environments.

OriginalsprogEngelsk
TidsskriftEnvironmental Science & Technology
Vol/bind51
Udgave nummer16
Sider (fra-til)8981-8991
ISSN0013-936X
DOI
StatusUdgivet - 15. aug. 2017

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