Nitrous Oxide Production in Co-Versus Counter-Diffusion Nitrifying Biofilms

Publication Type:
Journal Article
Scientific Reports, 2016, 6
Issue Date:
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For the application of biofilm processes, a better understanding of nitrous oxide (N 2 O) formation within the biofilm is essential for design and operation of biofilm reactors with minimized N 2 O emissions. In this work, a previously established N 2 O model incorporating both ammonia oxidizing bacteria (AOB) denitrification and hydroxylamine (NH 2 OH) oxidation pathways is applied in two structurally different biofilm systems to assess the effects of co-and counter-diffusion on N 2 O production. It is demonstrated that the diffusion of NH 2 OH and oxygen within both types of biofilms would form an anoxic layer with the presence of NH 2 OH and nitrite (), which would result in a high N 2 O production via AOB denitrification pathway. As a result, AOB denitrification pathway is dominant over NH 2 OH oxidation pathway within the co-and counter-diffusion biofilms. In comparison, the co-diffusion biofilm may generate substantially higher N 2 O than the counter-diffusion biofilm due to the higher accumulation of NH 2 OH in co-diffusion biofilm, especially under the condition of high-strength ammonium influent (500 mg N/L), thick biofilm depth (300 μm) and moderate oxygen loading (∼1-∼4 m 3 /d). The effect of co-and counter-diffusion on N 2 O production from the AOB biofilm is minimal when treating low-strength nitrogenous wastewater.
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