Evaluation of the process performance of comammox-like nitrospira dominant down-flow hanging sponge reactor with reduced nitrous oxide emissions
Sota Kabasawa (Nagaoka University of Technology)
Takahiro Watari (Nagaoka University of Technology)
Yuki Sato (Nagaoka University of Technology)
Yuga Hirakata (National Institute of Advanced Industrial Science and Technology (AIST))
Masashi Hatamoto (Nagaoka University of Technology)
Tsutomu Okubo (National Institute of Technology, Kisarazu College)
Carols Lopez Vazquez (IHE Delft Institute for Water Education)
Jules B. van Lier (TU Delft - Sanitary Engineering, IHE Delft Institute for Water Education)
Takashi Yamaguchi (Nagaoka University of Technology)
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Abstract
Nitrification/denitrification mitigates excess nitrogen in wastewater and reduces nutrient pollution in recipient surface waters but emits substantial amounts of nitrous oxide (N₂O). Complete ammonia-oxidizing (comammox) bacteria provide novel opportunities to mitigate N₂O emissions from wastewater treatment systems. In this study, a down-flow hanging sponge (DHS) reactor with low-strength ammonia-based synthetic wastewater was used to culture comammox bacteria, to study the microbial community structure, and to assess the nitrogen removal performance. The results showed a high NH4+-N removal efficiency of 98 ± 4 % and complete nitrification during the entire experimental period. 16S rRNA gene sequencing and metagenomic analysis showed that comammox-like Nitrospira dominated the DHS-retained sludge, and that comammox-like Nitrospira and ammonia-oxidizing archaea may have coexisted symbiotically. The dissolved N₂O emissions per NH4+-N removed from the DHS reactor were much lower than those from conventional activated sludge processes, indicating that the DHS reactor could be effective in reducing N₂O emissions during wastewater treatment.
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