基于铁基材料与固相碳源协同强化脱氮的新技术研究

Heterotrophic denitrification with the addition of carbon source has been well demonstrated as a promising technology for treating the low C/N ratio wastewater under aerobic condition. But the high cost of carbon source is one of the concern for its wide application. Zero-valent-iron facilitated autotrophic denitrification can directly transfer the electron to nitrate and release the ferrous ion, which can participate the metabolic activity of bacteria to enhance its growth. And iron material is well known to be easy to achieve and economic. Based on the idea of combining Heterotrophic denitrification with the addition of carbon source has been well demonstrated as a promising technology for treating the low C/N ratio wastewater under aerobic condition. Zero-valent-iron facilitated autotrophic denitrification can directly transfer the electron to nitrate and release the ferrous ion, which can participate in the microbial metabolisms and enhance microbial growth. This study aims to explore a kind of optimized iron/solid carbon source composite, which is based on solid carbon sources and iron based materials, to achieve the efficient nitrogen removal by two denitrificaiton approaches toward to low C/N ration waste water. The research is mainly focused on: 1) the development of the low-cost solid carbon sources based on biomass, and the study of their performances of nitrogen removal and reaction mechanisms; 2) the development of the iron based materials, and the study of their performances of nitrogen removal and reaction mechanisms; 3) the development of the novel integrated bio-carrier based on iron based materials and solid carbon sources, and the study of their performances of nitrogen removal and reaction mechanisms; 4) the optimization of process parameters and the long-term stable operation of the biofilter supporting with the novel integrated carrier. This study is significantly meaningful to arise a potentially possible solution to further improve the water quality from the wastewater treatment plant and resolve the serious eutrophication problem in China.

固相碳源反硝化脱氮能有效突破低有机污染水、好氧条件下脱氮的技术瓶颈；零价铁可为硝酸盐氮的化学还原提供电子且生成的Fe2+能促进微生物代谢活动。通过研制固相碳源、铁基材料以及铁基-碳源复合载体，探讨零价铁化学还原脱氮与生物脱氮协同效应及其影响因素，开发一种基于铁基-固相碳源协同脱氮的新材料，实现好氧、低C/N比下的低成本、高效、快速的脱氮。研究内容包括：1）低成本生物质固相碳源的制备、脱氮特性研究及脱氮机理解析；2）铁基材料的制备、脱氮特性研究及脱氮机理解析；3）铁基材料-固相碳源复合载体的研发制备、脱氮特性研究及脱氮机理解析；4）基于铁基-固相碳源复合载体强化脱氮的生物滤池反应器的工艺参数优化与长效稳定运行研究。研究成果对污水处理厂尾水提标升级，解决国内日益严重的水体富营养化问题，有着重要的理论意义和广阔的应用前景。

水体富营养化一直是我国当前面临的重大水环境问题，污水处理厂出水中氮、磷的深度控制对满足受纳水体水生态健康的要求具有重要意义。为强化尾水的深度脱氮，本项目研发了脱氮性能优异的低成本生物质共混碳源，并借助利用宏基因组学技术，首次从功能基因水平揭示了体系内微生物的碳氮代谢的协同过程。为进一步解决固相反硝化技术难以同步除磷的技术瓶颈，本项目基于所开发的低成本生物质共混碳源，制备出零价铁-固相碳源复合载体，利用固相碳源与零价铁的协同效应解决了尾水的同步脱氮除磷的问题，并运用高通量测序、高通量qPCR等技术手段对微生物群落和功能基因丰度进行解析，揭示脱氮除磷机理。研究取得以下结论：.（1）低成本生物质共混碳源（PHBV/木屑）具有良好的强化脱氮效果，在实际污水处理厂二级出水的深度脱氮中，实现了出水总氮浓度稳定低于1.0 mg/L，且突破了富氧条件对反硝化脱氮的限制，在较高DO（4.1-8.0 mg/L）进水条件下仍然能实现反硝化生物脱氮过程； .（2）借助利用宏基因组学技术，首次从功能基因水平揭示了生物质碳源在木质纤维素菌群的作用下，分解释放出易于利用的小分子碳源，实现了生物质固相碳源系统的反硝化脱氮持久碳源供应和系统脱氮效果稳定的长效机制。.（3）30%零价铁含量的零价铁/固相碳源复合载体具有较高的脱氮除磷效率。复合载体中固体碳源与零价铁在促进脱氮速率、限制铁的还原硝酸盐成氨、维持铁的持续腐蚀稳定除磷三个方面具有耦合促进效应；.（4）零价铁在复合载体反应器微生物群落演变过程中具有富集发酵菌群梭菌纲成为优势菌群的作用，该优势菌群在反应器运行后期可通过降解难降解有机物如木质素、纤维素为反硝化过程提供可利用的小分子碳源，有利于系统稳定脱氮；.（5）铁的代谢菌属 Desulfitobacterium、Ferritrophicum 在复合载体反应器微生物协作网络中成为发挥微生物联系作用的关键菌属。零价铁对系统微生物分子生态网络协作关系的促进作用有利于微生物群落保持结构稳定性从而维持反应器稳定的脱氮能力。.（6）零价铁/固相碳源复合载体调节了微生物功能基因的结构，编码碳降解（manA、gam和mxa等）和氮转化（nirS 和nosZ）的基因显著上调，且刺激了DHA（脱氢酶）和NIR（亚硝酸盐还原酶）的表达。从基因水平和酶代谢水平解释了复合载体中固相碳源和零价铁协同强化脱氮的优势。