氢-硫电子供体协同驱动污水深度脱氮的增效机制研究

Autotrophic denitrification has been widely concerned due to its advantages of no requirement for additional organic carbon, clean reaction products and low operation cost in advanced nitrogen removal process of wastewater. This study supposes that coupling hydrogen autotrophic denitrification and sulfur autotrophic denitrification not only overlaps their nitrogen efficiency, but also creates synergistic promotions on nitrogen removal. Thus, a hydrogen-sulfur driven autotrophic denitrification system would be constructed in this study, in which the hydrogen gas supplement is controllable. The synergistic effect on nitrogen removal would be enhanced through optimizing the system structure and operation parameters. Targeting the low start-up efficiency, slow recovery after back-wash and low nitrogen removal capacity of sulfur autotrophic denitrification technique, the regulation strategies for various of operating conditions and wastewater qualities would be developed via optimizing the quantity and method of hydrogen supplement. The chemical and biological mechanisms of the synergistic effects would be revealed from different perspectives of pH balance, element sulfur dissolving, electron donor increment and microbial augmentation. It would provide the significant theoretical directions for optimizing the hydrogen supplement modes, seeking out the threshold value of hydrogen supplement, increasing the utilization efficiency of electrons, enhancing the nitrogen removal process and developing the regulation strategies. Also, it would establish a theoretical foundation for the application of hydrogen-sulfur driven autotrophic denitrification in the future.

自养反硝化技术凭借其在对废水深度脱氮处理过程中无需外加有机碳源、产物清洁、运行成本低等优势被广泛关注。本研究推断：将氢、硫自养反硝化技术进行耦合在二者脱氮效能叠加的基础上，还会产生协同增效作用。因此，本研究将构建供氢可控的氢-硫协同驱动自养反硝化体系，并通过对体系结构和运行参数的优化，强化体系的协同增效作用。针对传统硫自养反硝化体系存在的酸碱失衡、工艺启动效率低、反冲洗恢复速度慢、脱氮负荷低等问题，通过优化供氢量和供氢模式，建立以供氢调节为手段的应对不同运行工况和废水水质条件的调控策略。另外，本研究将从酸碱平衡、硫单质溶出、电子增量、微生物强化多角度重点解析氢-硫协同驱动自养反硝化体系增效作用的化学机制和生物学机制，为优化体系供氢模式，找出供氢“平衡阈值”，提高电子利用效率，强化深度脱氮效能以及构建供氢调控策略提供重要的理论指导，也为氢-硫协同驱动自养反硝化体系的应用奠定理论基础。

本项目针对二级生化出水受季节及上游水质波动导致单质硫自养反硝化滤池难以实现灵活调控导致出水总氮不达标的问题，通过引入传质效率更高的液/气相外源电子供体与单质硫生物滤池进行协同脱氮。本研究在实验室阶段探究了不同外源电子供体（氢气、硫代硫酸盐）加入后对于系统脱氮的强化效能，考察了EBCT，温度，外源电子施加量等因子对体系脱氮效能的影响，从去除负荷、亚硝酸盐的累积过程、低温的抑制作用、生物量及群落结构变化等方面解析了协同脱氮过程中的增效机制。这种增效机制主要源于：（a）在硝酸盐转化为氮气的还原过程中，硫代硫酸盐的加入交替强化了硝酸盐和亚硝酸盐的还原速率；（b）外源电子供体的引入增强了微生物对电子的利用效率，促进了群落结构的向脱氮功能菌群演替。不同外源电子与单质硫的复合系统对模拟二级生化出水处理的研究表明，复合系统对总氮的去除效率均显著高于单独硫自养反硝化系统。本研究提出的引入外源电子与硫自养生物滤池协同脱氮技术为污水处理厂二级生化出水总氮的深度去除提供了一种低能耗、零碳耗、可持续性好的新型技术途径。为了进一步为实际工程提供理论指导，在中试阶段下研究了单质硫生物滤池全年度不同季节的运行情况，从工艺不同温度下的去除负荷，总氮出水浓度以及不同反冲洗方式下滤池恢复效率等方面考察了工艺实际应用的可行性，结合实验室中对于外源电子供体的强化能力考察，为深度脱氮的滤池工艺的设计提供了一种新的视角。