Granules and floc in the aerobic granular sludge (AGS) reactor undertook different roles in the nitrogen removal process and displayed significant disparities in microbial communities. This study quantified the contribution of different nitrogen removal pathways and analyzed the nitrogen removal mechanisms inside granules and flocs by metagenomics sequencing. The results showed that the AGS reactor performed excellent nitrogen removal efficiency and the removal efficiencies of NH-N and total nitrogen were more than 90.0 % and 60.0 %, respectively, with the main nitrogen form of NO-N in the effluent. Batch experiments indicated that the nitrogen removal pathway was principally shortcut nitrification and denitrification (SCND), accounting for 51.6 %, followed by anaerobic ammonium oxidation (Anammox) accounting for 26.1 % and the remaining 22.3 % was simultaneous nitrification and denitrification (SND). The metagenomic sequencing results pointed out that the abundance of SCND-related genes in the granules was 0.18 %, and the abundance of Anammox-related genes was 0.02 %, which indicated that the granules mainly reduced nitrogen via SCND, and minor nitrogen was removed through Anammox. Inside the flocs, nitrogen was mainly reduced via the unconventional SND pathway (HAND). The in-depth analysis of the nitrogen removal process in the reactor with granules and flocs provides an important reference for further exploring the nitrogen removal mechanism, and supplies foundation for expanding the application of AGS.

中文翻译：

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颗粒与絮体共存的好氧颗粒污泥反应器脱氮途径及微生物群落结构


好氧颗粒污泥（AGS）反应器中的颗粒和絮体在脱氮过程中发挥着不同的作用，并且微生物群落表现出显着的差异。本研究量化了不同脱氮途径的贡献，并通过宏基因组测序分析了颗粒和絮凝物内部的脱氮机制。结果表明，AGS反应器具有良好的脱氮效率，出水中NH3-N和总氮的去除率分别达到90.0%和60.0%以上，其中氮的主要形态为NO-N。批量实验表明，脱氮途径以短程硝化反硝化（SCND）为主，占51.6%，其次为厌氧氨氧化（Anammox），占26.1%，其余22.3%为同时硝化反硝化（SND）。宏基因组测序结果显示，颗粒中SCND相关基因的丰度为0.18%，Anammox相关基因的丰度为0.02%，说明颗粒主要通过SCND还原氮，少量通过厌氧氨氧化。在絮凝体内部，氮主要通过非常规 SND 途径 (HAND) 减少。深入分析颗粒和絮体反应器的脱氮过程，为进一步探索脱氮机理提供了重要参考，也为扩大AGS的应用奠定了基础。