Denitrification kinetics indicates nitrous oxide uptake is unaffected by electron competition in Accumulibacter

WATER RESEARCH

卷:189

Article

Roy, Samarpita¹  Nirakar, Pradhan^2,5  Yong, N. G. How³  Stefan, Wuertz^2,4 

[1] Natl Univ Singapore, Singapore Ctr Environm Life Sci Engn, Singapore 119077, Singapore

[2] Nanyang Technol Univ, Singapore Ctr Environm Life Sci Engn, Singapore 637551, Singapore

[3] Natl Univ Singapore, NUS Environm Res Inst, 5A Engn Dr 1, Singapore 117411, Singapore

[4] Nanyang Technol Univ, Sch Civil & Environm Engn, Singapore 639798, Singapore

[5] Hong Kong Baptist Univ, Fac Sci, Dept Biol, Kowloon Tong, 224 Waterloo Rd, Hong Kong, Peoples R China

关键词: Nitrous oxide (N2O) emission;    Accumulibacter;    Electron competition;    Free nitrous acid;    Polyhydroxyalkanoates;   

DOI  :  10.1016/j.watres.2020.116557

来源: Elsevier

【 摘 要 】

Denitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate or nitrite as terminal electron acceptor. Denitrification is a multistep process, but many organisms do not possess the complete pathway, leading to the accumulation of intermediates such as nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance. Candidatus Accumulibacter organisms are prevalent in denitrifying phosphorus removal processes and, according to genomic analyses, appear to vary in their denitrification abilities based on their lineage. Denitrification kinetics and nitrous oxide accumulation in the absence of inhibition from free nitrous acid is a strong indicator of denitrification capabilities of Accumulibacter exposed long-term to nitrate or nitrite as electron acceptor. Thus, we investigated the preferential use of the nitrogen oxides involved in denitrification and nitrous oxide accumulation in two enrichments of Accumulibacter and a competitor - the glycogen accumulating organism Candidatus Competibacter. We modified a metabolic model to predict phosphorus removal and denitrification rates when nitrate, nitrite or N2O were added as electron acceptors in different combinations. Unlike previous studies, no N2O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not limit denitrification kinetics or lead to N2O accumulation in Accumulibacter or Competibacter. Despite the presence of sufficient internal storage polymers (polyhydroxyalkanoates, or PHA) as energy source for each denitrification step, the extent of denitrification observed was dependent on the dominant organism in the enrichment. Accumulibacter showed complete denitrification, whereas Competibacter denitrification was limited to reduction of nitrate to nitrite. These findings indicate that DPAOs can contribute to lowering N2O emissions in the presence of multiple electron acceptors under partial nitritation conditions. (C) 2020 Elsevier Ltd. All rights reserved.

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