零价铁协同厌氧氨氧化微生物脱氮过程解析和协同机理研究

Anaerobic ammonium oxidation (anammox) is an attractive alternative to the traditional biological nitrogen removal technology. However, the application of anammox in engineering is limited by the relatively slow growth rates and strict external environment requirements of anammox bacteria, which lead to a relatively long start-up time. The low total nitrogen removal which is caused by the subsequent produced nitrate is also obsessed the widespread application of anammox process. To deal with these limitations, a new nitrogen removal system is built by introducing zerovalent iron (ZVI) to traditional anammox system. In this way, the chemical reaction and microbial process will be combined to enhance the microbial activity and to integrate nitrogen degradation in chemical and microbial pathways. Through the 15N isotopic tracing technique and analysis of water samples, the migrating and transforming course of nitrogen in ZVI and anammox cooperation system will be revealed. The nitrogen degradation pathway in new-built system will be illustrated by calculating the mass balance and the stoichiometric relationship. By determining the key enzyme activity during degradation process, this study aims to establish the corresponding correlations between special enzymes and ZVI. The diversity and variation rules of microorganism communities will also be studied by molecular biological techniques in this research. Thus, the enhanced nitrogen removal mechanism in the ZVI and anammox cooperation system will be revealed from the enzymology and community level. This subject aims to effectively solve the bottleneck problems in anammox process, such as the immobilization of anammox bacteria, the long start-up time especially the low total nitrogen removal rate. The results may help to provide useful theoretical basis to the application promotion and regulatory process of anammox system.

厌氧氨氧化是传统废水生物脱氮技术的有效替代，但应用受到了微生物敏感且世代周期长，工艺启动时间长,自身产生的硝氮使得总氮去除率低等限制。本课题通过在厌氧氨氧化过程中引入零价铁构建协同脱氮体系，改良生境以提高菌群活性，化学还原生物过程生成的硝氮为氨氮并进一步生物降解，实现氮在生物和化学途径上的协同降解；通过15N 同位素示踪和水样分析追踪氮在协同体系中的形态变化，揭示氮素的迁移转化过程；结合反应物料平衡的化学计量学关系，明确零价铁协同厌氧氨氧化体系中氮降解途径；测定降解历程中起关键作用的酶，建立特种微生物酶与零价铁的响应关系；利用分子生物技术解析微生物群落多样性与演绎变化规律，从酶学和群落水平上揭示零价铁协同厌氧氨氧化微生物脱氮的机制。课题旨在有效应对厌氧氨氧化工艺应用中的微生物富集困难、启动周期长和出水硝氮累积等关键问题，为厌氧氨氧化技术的应用推广与过程调控提供理论依据。

本项目针对厌氧氨氧化工艺中存在的问题，提出在厌氧氨氧化体系中引入零价铁（ZVI）构建新的协同体系，研究了新体系中氮素的迁移转化过程，揭示了ZVI协同作用的机制，优化了ZVI强化厌氧氨氧化微生物过程的操作条件。主要结论如下：. 1、采用同步球磨和化学原位沉积法（B&C）制备了高活性零价铁，蒙脱土实现了对Ni/Fe双金属的固定化，从而避免了纳米材料在使用过程中的团聚、流失和环境安全等问题。. 2、在反应器中填装ZVI及海绵铁可促进硝态氮向氨氮转化，对冬季低温（约15 ℃）和突变氮素负荷均有较强的适应能力，负荷可达1.1 kg N/m3/d。ZVI可以有效的增强微生物表面的电负荷和疏水性能，从而促进颗粒凝聚，还可以通过抑制nosZ基因的数量来减少N2O的产生。. 3、氮去除效率正比于基因浓度的对数， hzo和hzs功能基因更适用于评定厌氧氨氧化活性。零价铁的投加可显著增加接种污泥胞外聚合物(EPS)的分泌量，EPS含量可作为表征厌氧氨氧化菌活性的指标。ZVI作用机制可能是Fe2+、Fe3+参与到anammox菌呼吸中的电子传递过程以及铁硫蛋白和c型细胞色素等物质的合成过程。. 4、ZVI-厌氧氨氧化反应器内anammox 16S rRNA的含量提高了约29.0%，Hzo基因含量提高了62.2%；ZVI促进了AOB及反硝化菌的生长繁殖。ZVI有利于反应器内厌氧氨氧化菌的富集，可以影响微生物群落的多样性，尤其是浮霉菌门、变形菌门下的微生物的数量与分布，厌氧氨氧化菌中Candidatus Brocadia属的适应性相较其他更强，更容易富集。. 5、不同类型ZVI（mZVI和nZVI）均显著缩短了厌氧氨氧化工艺的启动时间，nZVI效果更好；50 mg/L的ZVI反应器启动时间最短，但抗冲击负荷能力较差；1000 mg/L 的反应器微生物活性先受到抑制，50天后，微生物适应了高浓度ZVI环境，微生物活性和富集得到促进；通过外置一定强度的磁场可以进一步缩短反应器的启动时间，增强反应器的稳定性。. 本项目结果为厌氧氨氧化技术的应用推广与过程调控提供了理论依据，对于有效应对厌氧氨氧化工艺应用中的微生物富集困难、启动周期长和出水硝态氮累积等关键问题具有工程指导意义。