微生物-光-电三元耦合工艺强化水中碳、氮污染物协同去除及调控机制

As toxic recalcitrant organic and nitrite residual become more common in sewage effluent, the safety reuse wastewater has a potential environmental and health risks, and we have to pay intensive attention on the development of adapted advanced technology for efficient carbon and nitrogen removal. In this program, we propose a novel integrated process that was combined carbon contaminant removal in photoanode and nitrogen contaminant removal in microbial catalyzed cathode. The program selects the sewage effluent of dyeing industry as research object. Research will probe into the optimized integrated mode of the selective denitrification at biocathode and organic contaminant degradation at photoanode, as well as the principle of system operation to develop the novel microbial-photo-electrochemical (MPE) process with the function of carbon and nitrogen contaminants removal. For the MPE process, the research is goes on to analyze and understand the contaminants transformation route and degradation regulation on the electrodes, as well as the function of cathodic bacteria, to clarify the function differentiation and synergy of involved reactions, such as photo catalytic oxidation, microbial catalyzed electrochemical reduction, microbial redox et.al., which would further guide the system optimization and operation. The program is expected to provide an adaptable technology for advanced carbon and nitrogen contaminants removal from industrial sewage effluent.

目前，工业废水二级处理后，出水中难降解有机物、硝酸盐等污染物残留现象越来越普遍，废水安全回用面临着较大的环境和健康风险，亟待开发适用性强的碳、氮污染物深度去除技术。本研究提出一种光阳极强化脱碳和生物阴极强化脱氮相结合的新型工艺模式。以印染废水二级出水为研究对象，深入探讨生物阴极选择性脱氮和光阳极催化降解有机物分解两个过程的优化匹配模式和系统操控要点，构建具有碳、氮污染物协同去除功能的“微生物-光-电三元耦合”工艺。同时，解析污染物在阴、阳极的转化途径与降解规律，以及阴极活性微生物的功能地位，阐明光催化、生物电催化和生物氧化还原等反应过程的功能区化与功能协同效应，指导系统优化和定向调控。为工业二级出水中碳、氮污染物深度去除提供技术基础。

本项目针对污水处理二级生化出水碳、氮污染物深度去除问题，通过将强氧化能力的光阳极和反硝化脱氮生物阴极相耦合，构建了一种能够同步去除水中难降解有机污染物和硝态氮的新型微生物-光-电三元耦合系统（MPES）。在国际上率先报道了微生物利用光生电子进行反硝化脱氮的行为，并将这一行为命名为“光电营养型生物反硝化”（microbial photoelectrotrophic denitrification, PEDeN）。系统研究了光阳极/生物阴极尺寸比例、光照强度、污染物浓度等因子对MPES体系脱氮效能的影响，阐明了光电转化、电子从阳极向阴极转移、微生物从阴极捕获电子进行反硝化脱氮等关键过程的热力学机制。发现MPES同步去除难降解有机污染物和硝态氮的两个过程存在协同效应，其主要体现在：a)硝酸盐在生物阴极的还原过程由于消耗电子拉动光阳极“空穴-电子”分离，从而加速了有机污染物在光阳极的去除；b)有机污染物在光阳极的降解消耗光生空穴、拉动“空穴-电子”分离，使得阴极微生物能够获得更多电子从而加速反硝化脱氮；c)有机污染物同时存在吸光效应，降低光阳极表面实际接受辐照强度，从而减弱光电转换效率，当此效应大于其拉动“空穴-电子”分离能力时，表现出光电流降低、阴极反硝化脱氮速率下降。该效应与有机污染物种类相关，偶氮染料和腐殖酸产生的吸光效应大于酚类和小分子有机酸。利用MPES对模拟生化二级出水处理的研究表明，MPES对于总氮和二级生化出水中的典型有机污染物的去除负荷均显著高于单独光电催化系统和单独生化系统。本研究提出的“微生物-光-电三元耦合体系”为污水处理厂二级生化出水碳、氮污染物深度去除提供了一种系统集约型高、可持续性好、零药耗的新型技术途径。通过工艺系统实现的“光电营养型生物反硝化”过程对于未来探究富含天然半导体/导体矿物的自然水体中，阳光对微生物氮素循环的贡献和影响提供了一种新的视角。