零价铁驱动异化铁还原强化微生物电催化厌氧甲烷化的调控机制及耐盐机理研究

The inhibition of wastewater with high salinity on microorganisms is a big challenge of research in anaerobic treatment process. To overcome the inhibition of high salinity, it is critical to improve the salinity tolerance and the biodegradation ability of anaerobic microorganisms. The construction of an iron enhanced microbial electrolysis cell (MEC) of anaerobic methanogenesis system, combining the anodic oxidation of MEC and direct anaerobic methanogenesis, is liable to accelerate the conversion of organic acids to methane. The formation of Fe(III) oxides via Fe(0) oxidation is expected to enrich electro-active microorganisms - iron-reducing bacteria and enhance the salinity tolerance of microorganisms through the production of microbial extracellular polymers (EPS). Moreover, high salinity may lower the ohm internal resistance and improve the efficiency of anodic oxidation, which may accelerate the rate of electron transfer between electrodes. Based on the enrichment of iron-reducing bacteria and enhancement of anaerobic digestion by the introduce of iron oxides formed from Fe(0), this study intends to investigate the transport and transfer mechanism of iron oxidization and microbial iron (III) reduction under high salinity environment. Meanwhile, the impacts of microbial iron (III) reduction on the production of extracellular polymers (EPS) and salinity tolerance of anaerobic microorganisms will be comprehensively studied with the aim to clarify the effects of microbial iron (III) reduction and high salinity on the physiological and electrochemical properties of electro-active microorganisms. By means of molecular biology methods, the changes of metabolic pathways of microorganisms on the surface of electrodes will be analyzed to explore the mechanism of salt tolerance of microbes. Overall, this study aims to provide a scientific basis for the development of new waste-to-energy technology for high-salt wastewater treatment, and to provide theoretical and methodological support for the engineering application of this technology.

高盐有机废水对微生物的抑制是厌氧生物处理的难点。提高微生物的耐盐性和降解能力是克服盐度抑制的关键。零价铁强化微生物电解池（MEC）耦合厌氧甲烷化系统，利用MEC阳极氧化和厌氧直接产甲烷的特点，可加速有机酸甲烷化。零价铁氧化形成的铁氧化物可富集电活性微生物-铁还原菌并有望在胞外聚合物（EPS）生成等方面促进微生物的耐盐性；另外，高盐度可降低MEC-厌氧甲烷化系统的欧姆内阻，提高阳极氧化效率，有望提高电极间的电子传递速率。本课题以零价铁形成的铁氧化物富集铁还原菌和强化厌氧甲烷化过程为基础，研究零价铁的铁氧化和异化铁(III)还原的迁移转化规律，探讨铁还原过程对促进EPS产生与提高微生物耐盐性的影响，明确铁还原和盐度对电活性微生物的生理效应和电化学特性的影响。进一步运用分子生物学手段，分析电极微生物代谢通路的演变规律，揭示微生物的耐盐机理，以期针对性地为高盐废水处理技术的发展提供理论依据和方法。

高盐有机废水/废物含有大量无机盐类例如钠盐、钾盐，高浓度的Na+会导致沼气产量下降，甚至导致厌氧消化系统的失效。提高微生物的耐盐性和降解能力是克服盐度抑制的关键。本课题构建了零价铁强化微生物电解池（MEC）耦合厌氧甲烷化系统，利用MEC阳极氧化和厌氧直接产甲烷的特点，加速有机酸甲烷化。另外，高盐度降低MEC-厌氧甲烷化系统的欧姆内阻，提高阳极氧化效率，提高电极间的电子传递速率。运用分子生物学手段，分析电极微生物代谢通路的演变规律，揭示微生物的耐盐机理，为高盐废水/废物处理技术的发展提供理论依据和方法。以高盐餐厨废水/废物为研究对象，系统考察了铁-碳微生物电解池与厌氧消化反应器耦合在中温和高温条件下的耐盐机制以及强化甲烷化过程的作用机理。主要研究结论如下：.（1）高温条件下添加零价铁可显著提高甲烷产量，实现高效的餐厨垃圾处理及能源产生。添加零价铁可获得最大产甲烷量为0.46±0.06L·g-1 VS·d-1，相对餐厨垃圾的热预处理和水热预处理而言，CH4产量高出约6％和48％。.（2）中温条件下将铁-碳微生物电解池耦合厌氧消化反应器可以显著提高反应器用于含盐餐厨垃圾产甲烷的效果。当体系含盐量为20g/L Na+时，铁-碳微生物电解池中的有机物的去除率最高，而控制组的产甲烷能力明显受到抑制。铁-碳微生物电解池强化了有机物的水解酸化过程，从而为甲烷化创造了有利的环境。宏基因组和宏蛋白质组分析表明，铁-碳微生物电解池富集了包括细菌和古菌在内的大量耐盐微生物，具有更高的微生物细胞活性，强化了高盐度体系下微生物的产甲烷性能和耐盐能力。.（3）高温条件下，铁-碳微生物电解池耦合厌氧消化反应器可以显著提高含盐餐厨垃圾厌氧消化产甲烷性能，增强了丙酸转乙酸过程，从而为甲烷化创造了有利的环境，宏基因组分析表明，铁-碳微生物电解池提高了微生物的耐盐能力，并且通过富集Methanobacterium、Methanomassiliicoccus和Methanothrix促进甲酸和H2/CO2产甲烷、甲基途径产甲烷及种间电子传递。