零价铁对厨余垃圾高负荷厌氧消化体系微生物互营产甲烷的调控机制

Zero valent iron (ZVI) can significantly improve the capacity of anti-risk of excessive acidification in anaerobic reactor with high organic loading rates (OLRs) when dealing with kitchen waste. Therefore, analyzing the characteristics of microbial metabolism and the regulating effects of ZVI on the anaerobic metabolic process is a significant subject for improving the kitchen waste treatment efficiency and optimizing the management system of municipal solid waste. Three anaerobic batch reactors of “High OLR with ZVI dosing”, “High OLR with sodium hydroxide dosing” and “Low OLR with normal CH4 production” are to be set up in this project. Several molecular biotechnique and bioinformatics methods, such as high throughput sequencing (HiSeq), ecological network construction and quantitative polymerase chain reaction (qPCR), are applied in comparing the microbial diversity variations to find the rules of ZVI acting on the ecological network construction among different communities, and to identify the key microbial populations in various reaction phases in three different reactors. Furthermore, the microbial characteristics of certain key microbes in ZVI-reactor combining with environmental parameter variations in the reactors will be analysed to certify the positive impact of ZVI on enhancing interspecies hydrogen transfer. In addition, in the methanogenesis process, the effect of a certain electroactive microorganism discovered in ZVI-reactor, on extracellular electron transferring will be explored. The ZVI regulatory mechanisms for syntrophic methanogenesis in anaerobic treatment of kitchen waste at high OLRs will be illustrated, accordingly. Implementation of this project has a great significance for further understanding microbial metabolism of syntrophic methanogenesis in anaerobic reaction, and also provides theory basis for ZVI application in anaerobic digestion of kitchen waste, especially under high OLRs condition.

零价铁可显著提升高负荷厌氧反应器处理厨余垃圾时的抗酸化风险能力，分析该过程下微生物代谢特征以及零价铁对其的调控作用是提高厨余垃圾生物处理效率，优化生活垃圾处理系统的重要课题。本项目拟搭建“零价铁+高负荷”、“碱性药剂+高负荷”和“低负荷”三种工况的序批式反应器，采用高通量测序、微生物网络构建和qPCR等生物信息分析手段，对比解析各类反应器下微生物群落多样性的变化，揭示零价铁对共存微生物网络形成的作用规律，识别各阶段下网络中的关键物种。进一步，分析关键微生物的代谢特征，结合反应器环境参数的变化特点，证明零价铁对种间氢转移过程的促进作用；探索零价铁反应器中某些电活性微生物在胞外电子传递中的作用，进而阐明厨余垃圾高负荷厌氧消化体系下零价铁对互营产甲烷过程的调控机制。本项目的实施对进一步认识厌氧反应中微生物互营产甲烷代谢有重要意义，为零价铁在厨余垃圾高负荷厌氧消化中的应用提供理论依据。

本项目通过投加零价铁解决有机生活垃圾高负荷厌氧产甲烷反应器可能出现的严重酸化抑制现象这一技术难题，并提出零价铁对微生物群落结构及功能作用机制和互营产甲烷体系调控机制两个关键科学问题。在项目执行期间，分别开展了（1）零价铁投加对严重酸化体系下微生物群落的调控作用；（2）零价铁投加对体系共存微生物互作关系的影响规律；（3）零价铁对厌氧互营产甲烷体系的促成机制等方面研究。此外，还外延探究了（1）普通零价铁粉和纳米零价铁消除严重酸化体系对产甲烷代谢抑制，强化互营产甲烷过程作用机制的异同；（2）不同厌氧产甲烷代谢温度下，零价铁对厨余垃圾高负荷厌氧体系微生物互营产甲烷代谢的调控机制。研究结果显示，零价铁有效消除了高负荷厌氧反应器中的严重酸化现象，在有机负荷20gVS/L条件下，相比传统投加氢氧化钠方式，零价铁可以将酸化反应器恢复产甲烷的延滞期由29天缩短至22天，而由于零价铁对产酸代谢的促进，甲烷累计产率达414 mL/gVS，显著高于投加氢氧化钠反应器（336 mL/gVS）。基于微生物群落多样性数据的分子生态网络分析结果表明，零价铁可增强产甲烷菌与互营乙酸氧化菌（SAOB）间复杂的互营关系，从而实现VFAs的快速转化和产甲烷代谢。利用宏基因和宏蛋白等宏组学分析，进一步证明了零价铁一方面提高了产甲烷功能基因丰度，另一方面能够显著上调涉及碳水化合物和蛋白质类物质降解酶，以及嗜氢和嗜乙酸产甲烷代谢酶，从而证明了零价铁主要通过强化互营产甲烷代谢途径实现严重酸化现象的消除，而氢氧化钠仅通过酸碱中和实现体系pH升高。纳米零价铁和普通尺寸零价铁对酸化的厌氧产甲烷体系调控机制相似，但由于纳米零价铁会促进析氢腐蚀，因此需较低的投加量。中温和高温厌氧消化体系下，尽管零价铁均能在35 gVS/L负荷下实现酸化现象的消除，但在对群落组成影响和互营产甲烷代谢调控方面存在显著差异。本项目进一步探索和揭示了零价铁调控厌氧产甲烷代谢机制，为丰富厌氧理论有重要意义。