MFC-AA/O反应器中生物反硝化阴极的功能强化方法及电子传递机理研究

Embedding Continuous flowing membraneless biocathode microbial fuel cell (MFC) in the conventional AA/O wastewater treatment process could enhance the biological nitrogen and phosphorus removal efficiency of AA/O process and produce electricity simultaneously, which would efficiently solve the conflict of enhancing the treatment efficiency and reducing the energy input in wastewater treatment. Therefore, it offered a new approach for the practical application of MFC and would have wide application prospect in the fields of environment and energy. The previous study of the applicant has revealed the microbiological mechanism of the improved nitrogen and phosphorus removal of MFC-AA/O bioreactor by studying the changes of the microbial community structures. However, the electricity output of MFC-AA/O bioreactor was still not high enough, which was possibly because of the low efficiency of the key component - biocathode and the uncertainty of the electron transfer mechanism of biological denitrification cathode. Therefore, this project plans to explore methods to enhance the functions of the biological denitrification cathode of MFC-AA/O bioreactor through two aspects: one is to modify the cathodic material by using conductive polymers to form nanostructures on the surface of carbon materials, and the other is to study the colonization and richness of the microorganisms on the biocathode of MFC-AA/O reactor who are capable of high efficient simultaneous electricity production and denitrification. Furthermore, based on the researches above, the electron transfer mechanism of the biological denitrification cathode will be systematically studied through the transcriptome analysis of the denitrifying metabolic system, the comparison of the key proteins in the simultaneous electricity production and denitrification process and the metabolite analysis, which will lay a solid theoretical foundation for the further functional enhancement of biological denitrification cathode and the practical application of MFC-AA/O bioreactor.

申请人提出了在AA/O污水生物脱氮除磷工艺中嵌入无膜生物阴极MFC，可以在强化其脱氮除磷效率的同时产生电能，有效解决污水处理行业既要求效率高又要节能降耗的矛盾，为MFC实际应用拓展新途径，在环境能源领域具备广阔的应用前景。申请人前期从微生物群落变化的角度研究了MFC强化AA/O反应器脱氮除磷的机理，但目前MFC-AA/O反应器效能仍不够高，深究原因与其关键部件生物阴极性能不高及电子传递机理不清有关。因此，本项目分别从阴极材料表面导电高分子纳米结构修饰改性和生物阴极高效同步产电反硝化菌定殖富集两个角度，探索强化生物反硝化阴极功能的方法，并在此基础上通过反硝化代谢系统转录组、产电反硝化关键功能蛋白差异分析以及反硝化细菌代谢特征分析，从基因、蛋白以及代谢产物变化等角度系统阐释生物反硝化阴极的电子传递机理，从而为进一步强化阴极产电反硝化性能、实现MFC-AA/O反应器实际应用奠定重要理论基础。

反硝化生物阴极生物电化学系统（Bioelectrochemical system, BES）利用电极自养型反硝化菌的代谢作用，以电极为电子供体，在自养条件下完成硝酸盐去除过程，将其与传统污水处理工艺—厌氧-缺氧-好氧工艺（Anaerobic/Anoxic/Oxic, AA/O工艺）结合，有望在强化生物脱氮除磷效率的同时产出电能，有效解决城市污水处理行业既要求处理效率高又要求节能降耗的矛盾。但其效能与传统异养反硝化工艺相比较低，电极自养型反硝化菌的电子传递机理尚不明确也制约了反硝化生物阴极BES的推广应用。本项目首先从电极材料表面修饰改性角度出发，制备了石墨烯/聚苯胺复合修饰的碳布电极，发现改性后的电极具有更大的比表面积和更高的电化学活性，以改性后电极构建的反硝化生物阴极BES的还原电流和硝态氮去除能力提高了41%和13%，电极表面微生物多样性的下降和Pacacoccus属微生物的丰度增加是其性能提高的原因之一。随后，本项目从富集电极自养型反硝化菌的角度出发，探究了种源对反硝化生物阴极BES的影响，并比较了极性反转培养方式和种源接种启动方式下反硝化生物阴极BES的性能差异。研究发现，以极性反转培养方式获得的反硝化生物阴极BES具有较高的还原电流和硝态氮去除能力，而种源接种启动方式下BES的性能则较差。在此基础上，进一步通过宏转录组学揭示了Geobacter和Afipia是BES中的关键微生物，细胞色素c和甲酸脱氢酶分别参与了两种微生物摄取电极电子还原硝态氮的过程。此外，本项目进一步探索了纯培养Shewanella在反硝化生物阴极BES的应用，揭示了S. loihica PV-4具有双向电子传递特性，可直接以电极为电子供体还原硝态氮，S. loihica PV-4的产电性能和胞外可生化有机物浓度之间以及亲电性能与硝酸盐浓度之间均具有良好的正相关性，项目基于此建立了一种水体BOD和硝酸盐同步检测的方法，可在1h内完成BOD和硝酸盐检测，准确度超过80%。本项目为提高反硝化生物阴极BES的效能并拓展其应用提供了理论依据。