生物电化学-厌氧消化耦合系统缓解高浓度氨氮抑制并实现沼气纯化的过程及机制研究

Anaerobic digestion of cyanobacteria is a technology by which the treatment of cyanobacteria and the recovery of clean energy could be both achieved. However, ammonia inhibition could be occurred during the anaerobic digestion process of cyanobacteria, which is the main challenge for application of this technology. Nowadays, the strategies applied for alleviation of ammonia inhibition are economically unattractive or environmentally unfavorable. Moreover, the application of biogas produced during anaerobic digestion could be highly limited due to the low content of methane. .Therefore, a novel three chambers bioelectrochemical system (BES) coupled with anaerobic digestion (anode chamber for producing electricity, desalination chamber for ammonia removal, cathode chamber for producing hydrogen) would be used for alleviation of ammonia inhibition, recovery of nutrients and hydrogen assisted biogas upgrading. In order to improve the efficiency of ammonia recovery and hydrogen production, the cathode electrode would be modified for increasing electron transfer efficiency in this study, which could be the foundation of achieving conquering ammonia inhibition and hydrogen assisted biogas upgrading. Moreover, the composite cathode electrode was characterized by XPS, FTIR and SEM. The results would reveal the mechanism of improving electron transfer efficiency by modifying cathode electrode..After increasing the hydrogen production in cathode chamber, hydrogen would be added into the anaerobic digestion chamber (desalination chamber) to achieve hydrogen assisted biogas upgrading. Afterwards, the acidic solution in anode chamber would be pumped into the anaerobic digestion chamber to neutralize the increasing pH during the hydrogen assisted biogas upgrading process. Moreover, by selecting different hydrogen partial pressure and stirring speed in anaerobic digestion chamber, the detail process and the interaction between anaerobic digestion and hydrogen assisted biogas upgrading would be explored. The key factors that improve the reaction process would also be identified and the efficiencies of anaerobic digestion and hydrogen assisted biogas upgrading in anaerobic digestion chamber could be further increased. In addition, by extracting DNA from microbial samples in anaerobic digestion chamber and high-throughput sequencing, qPCR analysis, the coexisted mechanism of anaerobic digestion and hydrogen assisted biogas upgrading process in this system would be also revealed. Finally, different applied voltages, initial ammonium concentrations and other ionic species would be used to identify the optimal parameters for the entire system. Furthermore, the energy balance of this system could also be calculated and the results would be used to evaluate the advantages of this novel system in energy cost compared with other anaerobic digestion and biogas upgrading process. Overall, this study could offer new insights for treatment of cyanobacteria by using BES coupled with anaerobic digestion technology in future.

高浓度氨氮的抑制作用是制约对太湖蓝藻进行厌氧消化的一大瓶颈，而厌氧消化产生的沼气因为其甲烷纯度不足、热值较低，被极大限制了用途。因此，本课题拟采用一套新型三极室生物电化学(BES)-厌氧消化耦合系统（阳极室产电、中间室脱氮、阴极室产氢）来同时解决缓解蓝藻底物高浓度氨氮毒性、营养物质回收与沼气纯化的难题。为促进阴极室的氨氮回收与产氢效率，本研究通过改性修饰阴极电极材料来提高电子传递效率，也为本系统高效缓解氨氮抑制与实现沼气纯化奠定了基础。阴极室所产氢气导回中间室进行沼气纯化后，本研究将通过调控不同氢分压等因素促进中间室厌氧消化与沼气纯化反应效率的提升；随后采用分子生物学手段进一步揭示中间室两个反应的共存机制。最后，采用不同参数来优化系统的最佳反应条件，并进行能量衡算，评估本系统相比于其它工艺在能耗方面的优势。综上，本研究将为厌氧消化与BES的耦合系统高效处理太湖蓝藻底物提供新思路。

高浓度氨氮的抑制作用是制约对太湖蓝藻进行厌氧消化的一大瓶颈，而厌氧消化产生的沼气因为其甲烷纯度不足、热值较低，被极大限制了用途。因此，本课题采用了一套新型三极室生物电化学(BES)-厌氧消化耦合系统（阳极室产电、中间室脱氮、阴极室产氢）来同时解决缓解蓝藻底物高浓度氨氮毒性、营养物质回收与沼气纯化的难题。通过实验发现当初始氨氮浓度为1000 mg NH4+-N/L，外接电压为0.4 V时，BES-厌氧消化耦合系统中的甲烷产量可达到发酵瓶反应器的3.18倍。微生物分析的结果表明在高浓度氨氮环境条件的胁迫下，厌氧消化过程的产甲烷阶段由嗜乙酸产甲烷途径向嗜氢气产甲烷途径进行了转化，而嗜氢气产甲烷菌也成为了产甲烷阶段的优势菌种。研究结果表明BES-厌氧消化耦合系统可以有效缓解高浓度氨氮对厌氧消化过程的抑制作用。此外，本研究运用BES-厌氧消化耦合系统将迁移至阴极室的氨氮作为阴极产氢微生物的氮源加以利用，并将阴极室所产氢气通入中间室实现了沼气纯化。实验结果显示在反应第0天通入0.25 bar氢气的反应器比对照组反应器中的甲烷产量提高了22.98%，甲烷组分浓度较对照组反应器也提升了14.04%；同时相比于发酵瓶反应器内提纯效果最佳的甲烷纯度（53.63%），第0天通入0.25 bar氢气的反应器的甲烷纯度也提高了22.10%。另外，我们还通过高通量测序分析以及PICRUSt的关键酶与功能基因预测发现，外源氢气的添加量和通入时间均会对中间室厌氧消化过程中的各个阶段（水解、产酸和产甲烷阶段）产生重要影响；在反应第0天就通入0.25 bar氢气可以有效促进厌氧消化中的水解过程以及胞外电子的传递过程，进而实现反应器内甲烷产量的提升。综上，本研究将为厌氧消化与BES的耦合系统高效处理太湖蓝藻底物提供新的思路。