An Heng, Wang Qiang, Lu Xinyi, Ruan Tianqi, Ma Chenxiao, Yao Lu, Tang Yadong, Wu Zhenbin, Zhou Qiaohong, Xiao Enrong
Research Division for Water Environmental Science and Engineering, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Research Division for Water Environmental Science and Engineering, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan 430074, China.
Bioresour Technol. 2026 Jan;439:133295. doi: 10.1016/j.biortech.2025.133295. Epub 2025 Sep 8.
Constructed wetlands (CWs) treating nitrate-rich wastewater often face incomplete denitrification and elevated NO emissions due to insufficient electron donors. Pyrrhotite as a CW substrate demonstrated potential for enhancing autotrophic denitrification through coupled sulfur and iron biological oxidation. However, the impact of pyrrhotite layer positioning on regulating NO emissions and underlying mechanisms remains unclear. This study evaluated the effect of pyrrhotite layer placement (top, middle and bottom) on S/Fe-coupled denitrification and NO release under organic carbon-free with varying nitrogen loads. Results showed that the bottom layer achieved 32.36-65.86 % complete denitrification (2.37-5.68 times higher than middle/top layers), while B-CW limited NO emission to only 0.36 % of converted nitrate (39.60-53.60 % lower than M-CW/T-CW). Enhanced performance in B-CW correlated with higher oxidation amounts of reduced sulfur (50.51 vs. 25.27-28.97 mg/L) and ferrous iron (36.83 vs. 18.43-21.12 mg/L), with efficient utilization. Network analysis revealed increased modularity and functional clustering in the bottom layer, with Ralstonia co-occurring with key sulfur/iron-cycling bacteria (Thiobacillus, Undibacterium) to form stable denitrifying consortia. Microbial analysis revealed enrichment of nitrate-reducing bacteria, primarily Ralstonia (14.69 %) in the bottom layer, driving 66.58 % inorganic electron utilization via sulfur oxidation-coupled complete denitrification. Electron and nitrogen mass balances revealed that 81.84 % of reduced nitrate was converted to N Additionally, synergistic interactions among nitrate-reducing bacteria (24.19 %), sulfur-/iron-oxidizing bacteria (16.29 %/4.46 %), organic matter-degrading bacteria (23.23 %), and electroactive bacteria (8.12 %) supported the process. These findings highlight pyrrhotite layer depth as a critical regulator of NO mitigation in CWs, providing a sustainable inorganic strategy for low-carbon and sustainable nitrogen removal.
处理富含硝酸盐废水的人工湿地（CWs）由于电子供体不足，常常面临反硝化不完全和一氧化氮排放增加的问题。磁黄铁矿作为人工湿地的基质，通过耦合硫和铁的生物氧化，显示出增强自养反硝化的潜力。然而，磁黄铁矿层位置对一氧化氮排放调控的影响及其潜在机制仍不清楚。本研究评估了磁黄铁矿层放置位置（顶部、中部和底部）对无有机碳且氮负荷不同情况下硫/铁耦合反硝化和一氧化氮释放的影响。结果表明，底层实现了32.36% - 65.86%的完全反硝化（比中层/顶层高2.37 - 5.68倍），而底部人工湿地将一氧化氮排放限制在转化硝酸盐的0.36%，（比中层人工湿地/顶部人工湿地低39.60% - 53.60%）。底部人工湿地性能的增强与还原态硫（50.51对25.27 - 28.97mg/L）和亚铁（36.83对18.43 - 21.12mg/L）的氧化量更高以及有效利用相关。网络分析表明底层的模块性和功能聚类增加，其中罗尔斯通氏菌与关键的硫/铁循环细菌（硫杆菌属、未培养细菌属）共同出现，形成稳定的反硝化聚生体。微生物分析显示底层中主要是罗尔斯通氏菌（14.69%）的硝酸盐还原菌富集，通过硫氧化耦合完全反硝化驱动66.58%的无机电子利用。电子和氮质量平衡表明81.84%的还原态硝酸盐转化为氮气。此外，硝酸盐还原菌（24.19%）、硫/铁氧化细菌（16.29%/4.46%）、有机物降解细菌（23.23%）和电活性细菌（8.12%）之间的协同相互作用支持了这一过程。这些发现突出了磁黄铁矿层深度是人工湿地中一氧化氮减排的关键调节因素，为低碳和可持续的氮去除提供了一种可持续的无机策略。
