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Denitrification as an N 2 O sink

Monica Conthe, Pawel Lycus, Magnus Ø Arntzen, Aline Ramos da Silva, Åsa Frostegård, Lars R Bakken, Robbert Kleerebezem, Mark C M van Loosdrecht

Water Res. 2019 Mar 15;151:381-387.

PMID: 30616050

Abstract:

The strong greenhouse gas nitrous oxide (N2O) can be emitted from wastewater treatment systems as a byproduct of ammonium oxidation and as the last intermediate in the stepwise reduction of nitrate to N2 by denitrifying organisms. A potential strategy to reduce N2O emissions would be to enhance the activity of N2O reductase (NOS) in the denitrifying microbial community. A survey of existing literature on denitrification in wastewater treatment systems showed that the N2O reducing capacity (VmaxN2O→N2) exceeded the capacity to produce N2O (VmaxNO3→N2O) by a factor of 2-10. This suggests that denitrification can be an effective sink for N2O, potentially scavenging a fraction of the N2O produced by ammonium oxidation or abiotic reactions. We conducted a series of incubation experiments with freshly sampled activated sludge from a wastewater treatment system in Oslo and found that the ratio α = VmaxN2O→N2/VmaxNO3→N2O fluctuated between 2 and 5 in samples taken at intervals over a period of 5 weeks. Adding a cocktail of carbon substrates resulted in increasing rates, but had no significant effect on α. Based on these results - complemented with qPCR and metaproteomic data - we discuss whether the overcapacity to reduce N2O can be ascribed to gene/protein abundance ratios (nosZ/nir), or whether in-cell competition between the reductases for electrons could be of greater importance.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP12022025 Ammonium heptafluorotantalate(V) Ammonium heptafluorotantalate(V) 12022-02-5 Price
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