Data underlying the publication: Nitrous Oxide as a Major Product of Anoxic Bioanode Ammonium Oxidation: Pathway Insights and Implications

Anoxic ammonium (NH₄⁺) oxidation at bioanodes offers a feasible alternative to conventional biological nitrogen removal (BNR), eliminating the need for aeration and enabling direct nitrogen gas (N₂) production. However, the extent of nitrous oxide (N₂O) emissions in this process remains unclear. This study examines N₂O emissions during anoxic NH₄⁺ oxidation at a polarized bioanode (+0.55 V vs Ag/AgCl), focusing on the roles of key intermediates—hydroxylamine (NH₂OH) and nitrite (NO₂^-)—in N₂O formation, and microbial functional groups involved in N₂O production, aiming to elucidate the underlying N₂O production pathways during bioanodic NH₄⁺ oxidation. Results show that up to 40% of oxidized NH₄⁺ was converted to N₂O, while NO₂^- and NO₃^- remained at relatively low levels (2.1%–11.1%). NH₂OH oxidation was identified as the dominant N₂O production pathway, likely involving nitric oxide (NO) as an intermediate. NO₂^- reduction also contributed to N₂O formation, albeit to a minor extent, while in situ N₂O reduction—considered to be mediated by denitrifiers—offers potential for mitigating its emissions. In parallel, an electro-anammox-like pathway, which does not involve nitrifiers, facilitated direct NH₄⁺ conversion to N₂ without N₂O formation. These findings highlight the potential for substantial N₂O emissions from bioanode-based systems and underscore the importance of pathway control to mitigate greenhouse gas release.

生物阳极（bioanode）上的缺氧氨（NH₄⁺）氧化为传统生物脱氮（BNR）提供了可行替代方案，无需曝气即可直接生成氮气（N₂）。然而，该过程中一氧化二氮（N₂O）的排放水平仍未明确。
本研究考察了极化生物阳极（相对于Ag/AgCl参比电极为+0.55 V）上的缺氧氨氧化过程中的N₂O排放，重点关注关键中间体——羟胺（NH₂OH）与亚硝酸盐（NO₂⁻）在N₂O生成中的作用，以及参与N₂O产生的微生物功能菌群，旨在阐明生物阳极氨氧化过程中N₂O生成的潜在途径。
研究结果显示，高达40%的被氧化氨会转化为N₂O，而亚硝酸盐（NO₂⁻）与硝酸盐（NO₃⁻）的残留水平相对较低（2.1%~11.1%）。研究证实羟胺氧化是N₂O生成的主要途径，该过程可能以一氧化氮（NO）作为中间体。亚硝酸盐还原同样对N₂O生成有贡献，但占比极小；而由反硝化菌（denitrifiers）介导的原位N₂O还原则为缓解其排放提供了潜在可能。
与此同时，一条无需硝化菌（nitrifiers）参与的类电厌氧氨氧化途径，可直接将氨转化为氮气（N₂）且不会产生N₂O。
上述研究结果凸显了基于生物阳极的系统存在显著N₂O排放的潜力，并强调了调控反应途径以缓解温室气体释放的重要性。