新型湿地高效处理养殖废水的脱氮过程及其微生物机制

Swine wastewater is high nitrogen organic wastewater. Using constructed wetland dispose of swine wastewater is effective method of nitrogen removal. In the previous field experiment had been confirmed that a new type Myriophyllum elatinoides constructed wetland could high efficiently remove nitrogen, the removal rate of ammonia nitrogen and total nitrogen was reached 90%. But research of nitrogen removal process and microbiological mechanism is less. In this study, we select two types of wetland plant Eichhornia crassipes and Alternanthera philoxeroides which compare to M. elatinoides constructed wetland. We will sample sediments in different seasons. We will adopt physicochemical methods of the chlorate inhibition method and acetylene inhibition method and molecular analysis method of Miseq high-throughput sequencing. Our research is conducted to study dynamic changes of metabolic activity of nitrifying and denitrifying bacteria, genetic abundance, microbial structure in different seasons，compare to the other two wetland. We will discuss contribution rate of nitrogen removal of nitrification and denitrification of sediment, respectively. Combining the multivariate statistical analyses, we study the relations of interaction between environmental factor and nitrogen removal microbial structure. By above systematic further studying, we reveal microbiological mechanism of nitrogen removal in new type constructed wetland. This study provides data support to perfecting nitrogen cycle theory and nitrogen removal mechanism of constructed wetland system.

养殖废水是氮含量高的有机废水，采用人工湿地处理是有效的脱氮方法。在前期野外模拟试验已证实在高效脱氮的绿狐尾藻新型湿地中，对氨氮和总氮的平均去除效率高达90%以上，但存在脱氮过程及其微生物机制认识不足。本研究选择常见的两种湿地植物水葫芦、水花生与绿狐尾藻构建野外对比试验，在不同季节进行底泥采样，采用氯酸盐抑制法和乙炔抑制法的理化手段，研究不同植物湿地硝化和反硝化代谢活性变化规律，揭示绿狐尾湿地中硝化和反硝化作用相对于其他湿地对氮素去除的贡献，再运用Miseq高通量测序等分子手段，研究硝化和反硝化微生物基因丰度和群落组成动态变化，探讨绿狐尾藻湿地与其他湿地硝化和反硝化微生物群落变化不同规律。应用多元数理统计方法，分析湿地脱氮微生物群落结构与环境因子相互作用关系。从而深入研究对比几种湿地微生物，揭示新型湿地处理养殖废水的脱氮微生物机制，为完善人工湿地氮循环的理论和氮的去除机理提供数据支撑。

通过本项目发现新型湿地高效处理养殖废水脱氮过程中，硝化功能基因AOB基因丰度高于AOA，反硝化功能基因nirK基因丰度高于nirS，说明该系统中硝化过程主要以AOB起主导作用，反硝化过程主要以nirK起主导作用。湿地系统中一周年硝化潜势变化范围为2.3–120.7 mg N kg-1 底泥 d-1，反硝化潜势变化范围为512–8806 mg N kg-1 底泥 d-1，均高于其他植物湿地系统。同时发现这两种功能基因分别与硝化和反硝化潜势呈强烈的正相关性，这一结果阐明了新型湿地高效处理养殖废水脱氮的分子机理。通过高通量测序结果发现，多级湿地系统中前段主要以厌氧微生物为主，随着水质DO和Eh的升高，后段主要以好氧微生物为主，该结果进一步明确新型湿地氮素循环的过程和特征。对完善人工湿地去除氮的分子机理具有重要意义。通过对新型湿地高效处理养殖废水脱氮的分子机理的研究，可以为该湿地应用于养殖废水治理提供科学理论依据和数据支撑。