Yang Risen, Jiang Jianhong, Wu Sha, Jin Jiao, Din Mohd Fadhil Md, Sanjaya Eli Hendrik, Chen Hong, Liu Zhihua, Wang Binquan
School of Hydraulic and Ocean Engineering, Changsha University of Science & Technology, Changsha, 410114, China; Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, Changsha, 410114, China.
China Machinery International Engineering Design & Research Institute Co., Ltd, Changsha, 410007, China.
Environ Res. 2025 Aug 8;285(Pt 4):122543. doi: 10.1016/j.envres.2025.122543.
The single-stage partial nitritation-anammox (PNA) process is widely regarded as a sustainable strategy for nitrogen removal from high-strength ammonium wastewater, yet its stability remains challenged under elevated ammonium conditions. In this study, a lab-scale airlift inner-circulation reactor with a working volume of 1.9 L was continuously operated for 247 days to evaluate the synergistic effects of calcium ion addition on process performance, microbial structure, and gene expression. The influent ammonium concentration was progressively increased from 850 mg/L to 1800 mg/L, while calcium ion concentration, added as calcium chloride dihydrate, was raised from 0 mg/L to 100 mg/L. Moderate calcium addition between 40 mg/L and 100 mg/L promoted significant sludge granulation, with mixed liquor volatile suspended solids nearly tripling and sludge volume index decreasing markedly, indicating enhanced biomass retention and sedimentation. Accompanying this, the secretion of extracellular polymeric substances, particularly tightly bound protein and polysaccharides, was substantially stimulated, resulting in a more compact and cohesive matrix. High-throughput 16S rRNA gene sequencing revealed that Ca addition selectively enriched key autotrophic taxa, such as Candidatus Brocadia and Nitrosomonas, while metagenomic analysis showed upregulation of functional genes. The increased abundance of these genes suggests an enrichment of functional microorganisms involved in autotrophic nitrogen metabolism, which may contribute to enhanced nitrogen transformation capacity, thereby supporting stable total inorganic nitrogen removal performance above 85 % despite increasing ammonium stress. These findings deepen the mechanistic understanding of calcium's synergistic role in reinforcing microbial aggregation, regulating EPS biosynthesis, and enhancing nitrogen-converting functionality, providing theoretical guidance for the robust application of PNA systems in treating ammonium-rich industrial wastewaters.
单级部分亚硝化-厌氧氨氧化（PNA）工艺被广泛认为是一种从高浓度铵废水中去除氮的可持续策略，然而在铵浓度升高的条件下，其稳定性仍面临挑战。在本研究中，一个工作体积为1.9升的实验室规模气升式内循环反应器连续运行247天，以评估添加钙离子对工艺性能、微生物结构和基因表达的协同作用。进水铵浓度从850毫克/升逐步提高到1800毫克/升，同时以二水氯化钙形式添加的钙离子浓度从0毫克/升提高到100毫克/升。在40毫克/升至100毫克/升之间适度添加钙促进了显著的污泥颗粒化，混合液挥发性悬浮固体几乎增加了两倍，污泥体积指数显著下降，表明生物量保留和沉降得到增强。与此同时，细胞外聚合物的分泌，特别是紧密结合的蛋白质和多糖，受到显著刺激，形成了更致密和有凝聚力的基质。高通量16S rRNA基因测序表明，添加钙选择性地富集了关键的自养类群，如“Candidatus Brocadia”和亚硝化单胞菌属，而宏基因组分析显示功能基因上调。这些基因丰度的增加表明参与自养氮代谢的功能微生物富集，这可能有助于提高氮转化能力，从而在铵胁迫增加的情况下仍支持稳定的总无机氮去除性能高于85%。这些发现加深了对钙在增强微生物聚集、调节胞外聚合物生物合成和增强氮转化功能方面协同作用的机理理解，为PNA系统在处理富含铵的工业废水中的稳健应用提供了理论指导。
