碳纳米管介导的硫酸盐有机废水产甲烷及电子竞争机制研究

There was electron competition between sulfate reduction and methane production during the anaerobic digestion of sulfate-containing organic wastewater. Usually, the efficiency of methane production would be decreased by sulfate reduction. Meanwhile, sulfide produced from sulfate reduction would lead to foul smell and corrosivity. Moreover, the methanogenesis would even break down caused by the toxicity of sulfide. Generally, the nitrate was always added to inhibit sulfate reduction. However, this operation complicated the process and increased the cost. Many researchers reported that direct interspecies electron transfer (DIET) could be enhanced by conductive materials, i.e., DIET during methanogenesis would be enhanced and then the efficiency of methanogenesis would be promoted. Therefore, conductive anaerobic granular sludge in UASB would be formed via adding carbon nanotube in this project which aimed to control the electron competition. The process of methanogenesis with carbon nanotube under different running conditions would be studied. The electron competition between methane production and sulfate reduction would be mainly investigated. The dynamics of biochemical reaction, electron distribution and microbial community would be researched in this project via advanced analytical method and imaging technique. The possibility of sulfate reducing bacteria participation in DIET would also be explored. Finally, the electron transfer pathway based on the conductive anaerobic granular sludge would be established. This project would provide new possibility to enhance methanogenesis of sulfate-containing organic wastewater. This project also help to better understand the electron competition in other conductive systems.

硫酸盐有机废水厌氧消化过程中，硫酸盐还原和产甲烷存在电子竞争关系，硫酸盐还原会降低产甲烷效率，且生成的硫化氢具有恶臭和腐蚀性，其毒性甚至会导致产甲烷过程中止。传统工艺中采取添加硝酸盐等方式抑制硫酸盐还原，增加了工艺复杂程度和维护费用。大量研究表明导电材料可以强化产甲烷过程中的直接种间电子传递，从而提高产甲烷效率。因此，本项目拟通过添加碳纳米管在UASB中构建厌氧“导电”颗粒污泥，以调控产甲烷和硫酸盐还原过程的电子分配，以期提高产甲烷过程竞争力。研究不同运行条件下碳纳米管介导的硫酸盐有机废水产甲烷过程，重点考察电子竞争机制。拟充分运用先进的分析手段和成像技术，考察不同运行条件下生化反应动力学、电子分配及微生物种群结构的响应规律，并探讨基于厌氧“导电”颗粒污泥的微生物种群电子传递路径。本项目有望实现硫酸盐有机废水高效产甲烷的目的，并为其它导电生物体系中电子竞争的研究提供参考价值和新的研究视角。

硫酸盐还原过程会大大降低甲烷资源回收的效率，因此，寻找一种工艺简单、成本较低，且可以使电子更多的流向产甲烷过程同时减弱硫酸盐还原，以实现高效产甲烷的途径是一项十分重要的研究课题。以电子传递代替氢气传递可以极大地提高反应速率，可以提高有机物厌氧降解产甲烷的速率。因此，本项目拟通过UASB反应体系中添加导电材料，以期能实现强化产甲烷过程电子竞争力的目的，从而提高产甲烷效率。首先，研究了导电材料对有机物厌氧产甲烷过程的影响。其次，探讨了导电材料对产甲烷过程中协同乙酸氧化菌和产甲烷菌之间的电子传递的影响。在此基础上，对导电材料介导的硫酸盐有机废水产甲烷过程进行系统研究，考察产甲烷和硫酸盐还原过程的电子竞争、分配及微生物种群结构，并深入探讨了主要功能微生物种群之间的电子传递路径。.研究结果表明，导电材料的添加明显促进了高温条件下有机物厌氧降解产甲烷速率，这一研究结果为实现高温条件下高浓度有机废水的高效降解及甲烷资源回收提供了理论依据，亦为其他难降解废水的生物处理提供了参考价值。在高乙酸浓度和高温条件下导电材料促进了产甲烷的速率，该过程主要是有协同乙酸氧化菌和产甲烷菌完成的。此外，群落结果表明，协同乙酸氧化菌Coprothermobacter和Thermacetogenium在此过程中发挥着重要的作用，导电材料的添加使协同乙酸氧化菌群得以富集，以及强化了两者之间的直接种间电子转移途径，是该系统甲烷产率提高的本质原因。此外，导电材料磁铁矿颗粒的投加可以显著促进乙酸和丁酸为碳源的体系中最大产甲烷速率并缩短反应的停滞期。在乙醇和葡萄糖为碳源的体系中，磁铁矿颗粒仅在高浓度硫酸盐条件下对产甲烷过程起促进作用。在丙酸为碳源的体系中，磁铁矿颗粒甚至会抑制产甲烷过程。在乙酸为碳源的体系中COD/SO42-=0.5和葡萄糖体系COD/SO42-=1条件下，磁铁矿颗粒的投加可以显著提升最大产甲烷量。在绝大部分情况下，磁铁矿颗粒的投加能够显著富集产甲烷菌的丰度，这一过程可能和直接种间电子传递有关，且各碳源体系中Methanosaeta均占据主导地位。