潜流型人工湿地植物碳源对低碳氮比污水脱氮作用机制研究

Direct discharge of tailwater with high nitrogen from municipal sewage plant has caused water eutrophication in rivers and lakes. It has become a serious problem for water environment governance, which requires advanced nitrogen removal in the tailwater. There are many advantages of the subsurface constructed wetlands in treating the tailwater with low C and high N content. However, the role of endogenous plant carbon sources in removing nitrogen from low C/N sewage treatment has been neglected in the subsurface constructed wetlands. In this study, the correlation between plant carbon and microorganism with different periods and layers will be analyzed by investigating the carbon and nitrogen composition, microbial activity and community structure. Further, the microcosm incubation experiments with root exudate and plant residue will be conducted to find out the relationship of nitrification, denitrification and anaerobic ammonia oxidation, and their contribution to nitrogen removal in low C/N sewage. Meanwhile, the composition and abundance of critical microorganisms related to nitrogen transformation will be determined by 13C-DNA-SIP combined with high-throughput sequencing of related functional gene amplicons. The objective of this project is to understand the effects of plant carbon on microbial molecular mechanism of nitrogen removal in low C/N sewage, in order to provide scientific bases in improving nitrogen removal efficiency in subsurface constructed wetlands, reducing nitrogen pollution and protecting the quality of water environment.

高氮含量的市政污水厂尾水直接排放所导致的水体富营养化已经成为水环境治理面临的严峻问题，对其进行深度脱氮处理迫在眉睫。潜流型人工湿地在处理该类低碳高氮污水中有诸多优势，然而，目前在潜流型人工湿地对低碳氮比污水脱氮研究中忽视了内源植物碳的作用。本项目拟通过分析基质层碳、氮组分、微生物活性和结构变化特征，阐释不同时空尺度上植物碳源与微生物的相关关系；进一步通过根系分泌物和植物残茬培养试验，剖析植物碳源作用下硝化、反硝化和厌氧氨氧化过程在低碳氮比污水脱氮中的作用与相互联系；同时结合稳定性同位素核酸探针（13C-DNA-SIP）和高通量测序技术，辨识发挥作用的氮转化关键功能微生物的丰度和群落结构，阐明植物碳源作用下低碳氮比污水脱氮机制，为提高潜流型人工湿地脱氮效率、减少氮素污染、提升水环境质量提供科学依据。

本项目以潜流型人工湿地脱氮效率和微生物机制为研究核心，分析了植物种类和不同生长阶段脱氮效果和基质微生物活性与群落结构差异，探究了植物和碳氮比对氮转化速率和微生物群落结构的影响，阐释了氮转化功能微生物空间分布特征和对碳源及可溶性氧的响应机制。研究结果表明：（1）种植植物提高了湿地NO3-和TN去除效率，增加了基质微生物碳源代谢强度; 种植植物在夏季促进了基质微生物的生长繁殖，而在冬季降低了基质微生物的丰富度和多样性指数。（2）种植植物处理的湿地基质硝化强度、反硝化速率和厌氧氨氧化速率均高于不种植物处理；种植植物处理的基质反硝化速率和硝化强度在高碳氮比条件下高于低碳氮比条件；而不同碳氮比对不种植物处理的基质氮转化速率无显著影响。（3）添加碳源和碳源耦合曝气处理分别改变了水平潜流型人工湿地基质前端和后端的细菌群落组成；曝气显著增加了湿地前端硝化菌的相对丰度，Sphingomonas是主要的氨氧化菌，Nitrospira是主要的亚硝酸盐氧化菌；添加碳源和碳源耦合曝气处理分别增加了湿地前端和后端的反硝化菌相对丰度，主要的反硝化菌是Acinetobacter、Gaiella、Pseudomonas和Rhizobium。（4）添加秸秆处理、秸秆与生物炭组合处理以及秸秆、生物炭、聚丁二酸丁二醇酯组合处理均增加了湿地基质细菌丰富度和多样性指数。秸秆和生物炭处理显著改变了湿地基质细菌群落组成，降低了主导菌相对丰度，秸秆处理增加了反硝化菌相对丰度，而生物炭处理增加了好氧菌相对丰度。