Dai Jingyi, Zhao Shuyuan, Xian Zhihao, Zhang Xin, Wu Hao, Guo Fucheng, Chen Yi
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400045, PR China; College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400045, PR China; College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
Water Res. 2024 Dec 1;267:122490. doi: 10.1016/j.watres.2024.122490. Epub 2024 Sep 20.
The ammonium (NH) removal efficiency in constructed wetlands (CWs) is often limited by insufficient oxygen. In this study, an extract of Eucalyptus robusta Smith leaves was used to prepare multivalent manganese oxides (MVMOs) as substrates, which were used to drive manganese oxide (MnO) reduction coupled to anaerobic NH oxidation (Mnammox). To investigate the effects and mechanisms of MVMOs on ammonium nitrogen (NH-N) removal, four laboratory-scale CWs (0 %/5 %/15 %/25 % volume ratios of MVMOs) were set up and operated as continuous systems. The results showed that compared to controlled C-CW (0 % MVMOs), Mn25-CW (25 % MVMOs) improved the average NH-N removal efficiency from 24.31 % to 80.51 %. Furthermore, NO emissions were reduced by 81.12 % for Mn25-CW. Isotopic tracer incubations provided direct evidence of Mnammox occurrence in Mn-CWs, contributing to 18.05-43.64 % of NH-N removal, primarily through the N-producing pathway (73.54-90.37 %). Notably, batch experiments indicated that Mn(III) played a predominant role in Mnammox. Finally, microbial analysis revealed the highest abundance of the nitrifying bacteria Nitrospira and Mn-cycling bacteria Pseudomonas, Geobacter, Anaeromyxobacter, Geothrix and Novosphingobium in Mn25-CW, corresponding to its superior NH-N removal efficiency. The enhancement of NH oxidation, first to hydroxylamine and then to nitrite, in Mn25-CW was attributed to the upregulation of ammonia monooxygenase genes (amoABC and hao). This study enhanced our understanding of Mnammox and provided further support for the use of manganese oxide substrates in CWs for efficient NH-N removal.
人工湿地（CWs）中铵（NH）的去除效率常常受到氧气不足的限制。在本研究中，用大叶桉树叶提取物制备多价锰氧化物（MVMOs）作为底物，用于驱动与厌氧氨氧化（厌氧氨氧化菌）耦合的锰氧化物（MnO）还原。为了研究MVMOs对铵态氮（NH-N）去除的影响及机制，设置了四个实验室规模的人工湿地（MVMOs体积比分别为0%/5%/15%/25%）并作为连续系统运行。结果表明，与对照C-CW（0% MVMOs）相比，Mn25-CW（25% MVMOs）将平均NH-N去除效率从24.31%提高到了80.51%。此外，Mn25-CW的NO排放量减少了81.12%。同位素示踪培养提供了厌氧氨氧化菌在含锰人工湿地中发生的直接证据，其对NH-N去除的贡献率为18.05 - 43.64%，主要通过产N途径（73.54 - 90.37%）。值得注意的是，批次实验表明Mn(III)在厌氧氨氧化菌中起主要作用。最后，微生物分析显示，Mn25-CW中硝化细菌硝化螺菌属以及锰循环细菌假单胞菌属、地杆菌属、厌氧粘细菌属、地丝菌属和新鞘氨醇菌属的丰度最高，这与其卓越的NH-N去除效率相对应。Mn25-CW中NH首先氧化为羟胺然后氧化为亚硝酸盐的过程增强，归因于氨单加氧酶基因（amoABC和hao）的上调。本研究增进了我们对厌氧氨氧化菌的理解，并为在人工湿地中使用锰氧化物底物高效去除NH-N提供了进一步支持。
