Abstract：
To overcome the significant challenges associated with nitrite supply and nitrate residues in mainstream anaerobic ammonium oxidation (anammox)-based processes, this study developed a combined solid-phase denitrification (SPD) and anammox process for low-strength nitrogen removal without the addition of nitrite. The SPD step was performed in a packed-bed reactor containing poly-3-hydroxybutyrate-co-3-hyroxyvelate (PHBV) prior to employing the anammox granular sludge reactor in the continuous-flow mode. The removal efficiency of total inorganic nitrogen reached 95.7 ± 1.2% under a nitrogen loading rate of 0.18 ± 0.01 kg N·m3·d-1, and it required 1.02 mol of nitrate to remove 1 mol of ammonium nitrogen. The PHBV particles not only served as biofilm carriers for the symbiosis of hydrolytic bacteria (HB) and denitrifying bacteria (DB), but also carbon sources that facilitated the coupling of partial denitrification and anammox in the granules. Metagenomic sequencing analysis indicated that Burkholderiales was the most abundant HB genus in SPD. The metabolic correlations between DB (Betaproteobacteria, Rhodocyclaceae, and Anaerolineae) and anammox bacteria (Candidatus Brocadiac and Kuenenia) in the granules were confirmed through microbial co-occurrence networks analysis and functional gene annotations. Additionally, the genes encoding nitrate reductase (Nap) and nitrite reductase (Nir) in DB primarily facilitated nitrate reduction, thereby supplying nitric oxide to anammox bacteria for subsequent nitrogen removal with hydrazine synthase (Hzs) and hydrazine dehydrogenase (Hdh). The findings provide insights into microbial metabolism within combined SPD and anammox processes, thus advancing the development of mainstream anammox-based processes in engineering applications.
摘要：
为了克服与主流厌氧氨氧化（厌氧氨氧化）工艺中的亚硝酸盐供应和硝酸盐残留相关的重大挑战，这项研究开发了一种组合的固相反硝化（SPD）和厌氧氨氧化工艺，用于在不添加亚硝酸盐的情况下进行低强度脱氮。在连续流动模式下使用厌氧氨氧化颗粒污泥反应器之前，在包含聚-3-羟基丁酸酯-共-3-羟基维甲酸酯（PHBV）的填充床反应器中进行SPD步骤。在0.18±0.01kgN·m3·d-1的氮负荷下，总无机氮的去除效率达到95.7±1.2％，需要1.02mol硝酸盐才能去除1mol的铵态氮。PHBV颗粒不仅是水解菌(HB)和反硝化细菌(DB)共生的生物膜载体,而且还有促进颗粒中部分反硝化和厌氧氨氧化偶联的碳源。宏基因组测序分析表明Burkholderiales是SPD中最丰富的HB属。DB(β变形菌，红环科，和Anaerolineae）和anammox细菌（CandidatusBrocadiac和Kuenenia）通过微生物共生网络分析和功能基因注释进行了确认。此外,DB中编码硝酸还原酶（Nap）和亚硝酸盐还原酶（Nir）的基因主要促进硝酸盐还原，从而向厌氧氨氧化细菌提供一氧化氮，用于随后用肼合酶（Hzs）和肼脱氢酶（Hdh）去除氮。这些发现为SPD和anammox过程中的微生物代谢提供了见解，从而推进了工程应用中基于厌氧氨氧化的主流工艺的发展。
