二价铁作为电子供体的反硝化过程的分子生态学机理及调控策略研究

Microorganisms use organic matters as electronic donors to reduce nitrate and nitrite to nitrogen gas in traditional denitrification process, therefore, when this process is used to treat low C/N wastewater, extra organic carbon need be added to the bioreactor, which will significantly increase the operational cost. Nitrate-dependent anaerobic ferrous oxidation (NAFO) is an autotrophic denitrification process with many advantages, such as low cost and low sludge production. However, the current studies on NAFO process in wastewater treatment field mainly focused on the reactor operation and parameter optimization. The molecular ecology mechanisms of this process still remain largely unknown. In this project, NAFO process will be implemented in upflow blanket filter reactors and during the reactor startup and running high-throughput sequencing based metagenomic and metatranscriptomic approaches will be applied to investigate the structures and functions of microbial community involved in NAFO process. On one hand, the key microorganisms of the NAFO process and their functions on nitrogen and other pollutants removal will be investigated to elucidate the molecular ecology mechanisms of the NAFO process. At the same time, the bacterial community differences and the nitrogen removal efficiency differences between traditional denitrification and NAFO process will be revealed. On the other hand, the control and optimization methods of the NAFO will be explored based on the understanding of the characteristics of NAFO related bacterial community and the enrichment of specific NAFO bacteria. The outcome of this project is expected to provide theoretical and practical supports for the biological nitrogen removal from low C/N wastewater.

传统生物反硝化过程中微生物以有机物作为电子供体将硝酸盐和亚硝酸盐转化为氮气，用该方法处理低C/N 比的废水时需要外加碳源，成本高。依赖于硝酸盐的厌氧二价铁氧化（NAFO）是一种以二价铁作为电子供体的自养反硝化工艺，具有成本低、污泥产量少等优点。目前国内外对污水处理中NAFO的研究尚处于起步阶段，对于该过程的分子生态学机理还不清楚。本项目拟采用基于高通量测序的组学方法研究厌氧复合床中NAFO启动及运行过程中微生物群落结构和功能，一方面，从分子生态学的角度阐释反应器中NAFO关键菌群的群落结构和功能的演替及对环境条件变化的响应机制，比较其与普通反硝化过程在微生物群落结构和氮的去除效率方面的差异，探索NAFO过程的分子生态学机理；另一方面，从高效NAFO菌富集和筛选及微生物群落特性的角度探索NAFO反应器的优化控制及生物强化的原理和技术，为低C/N 废水生物脱氮处理提供理论依据和技术支撑。

传统生物反硝化过程中微生物以有机物作为电子供体将硝酸盐和亚硝酸盐转化为氮气，用该方法处理低C/N比的废水时需要外加碳源，成本高。以二价铁为电子供体的反硝化过程具有成本低、污泥产量少等优点。本项目系统研究了以二价铁为电子供体的自养反硝化过程的特点及相关的微生物群落结构和功能，并与异养反硝化过程进行了比较。研究发现二价铁为电子供体的自养反硝化过程可实现较好的脱氮除磷效果，但在该过程中很容易产生大量沉淀物将微生物包裹在内部，使微生物活性受到影响，从而降低反硝化效率。针对这一问题，我们从活性污泥中富集了铁自养反硝化菌群和硫自养反硝化菌群，并将其接种到以硫铁矿作为填料的反硝化滤池中，从而实现了持续的脱氮除磷。在此基础上，开发了一种基于硝化过程和硫铁矿自养反硝化过程的脱氮除磷方法，可有效去除水中的氮素并实现磷回收。此外，研究过程中还发现异养反硝化污泥可利用二价铁为电子供体进行自养反硝化，并且具有较高的反硝化效率，异养反硝化污泥的宏基因组分析结果表明，在41个基因组草图中有29个基因组携带有反硝化基因，其中有9个携带有铁氧化基因，8个基因组具有CO2固定功能，表明这些细菌可以在自养条件下生长。本研究结果为低C/N比废水生物脱氮处理提供了一定的科学依据和技术支撑。