人工湿地生物质发酵与琨基电子传递耦合强化反硝化机制研究

Advanced nitrogen removal in municipal sewage plant is the key point of wastewater reuse in the world. The use of constructed wetlands is an important technology for polishing the wastewater effluent, and the addition of plant biomass as the carbon sources can improve the denitrification efficiency. However, the unstable supply of carbon sources can hardly match the variations of the influent nitrate load, resulting in relatively high concentrations of nitrate in the effluent. Concerning the challenges above, the integration of plant biomass as electron donors and plant biochar as electron shuttles was proposed. It can achieve the sink of electrons when the carbon source is overloaded, and release the electrons when the carbon source is insufficient. The objectives of this project are to develop the method of production of plant biochar; to investigate the denitrification efficiencies under different biomass/biochar ratios and environmental factors; to clarify the mechanisms of denitrification with electron shuttle adjustment of quinone (transfer-storage-resupply); to reveal the mechanisms of coupling effect between biomass and biochar-driven denitrification; to propose the engineering regulation strategies of efficient nitrogen removal based on the matching mechanisms of biomass and biochar. The results of this research are expected not only to clarify the mechanisms of denitrification in complex systems, to overcome the defects in the traditional solid-carbon based denitrification, but also to guarantee the safety of wastewater reuse.

城镇污水处理厂深度脱氮是基于全球污水回用背景下亟待解决的关键问题。人工湿地是污水深度处理的重要技术单元，利用生物质补充碳源可一定程度改善系统的反硝化效能。然而，生物质碳源的释放无法与波动的硝酸盐负荷精确匹配，导致系统出水硝态氮浓度季节性偏高。本项目围绕上述问题，提出以生物质为电子供体辅以生物炭琨基调节电子传递的方法，实现反硝化过程中多余电子的储存（碳源过量时）与赋存电子的重新释放（碳源不足时）。重点研究人工湿地系统中富琨基植物生物炭的制备方法，探寻关键环境因素影响下不同生物质/生物炭配比的最佳反硝化效能，阐明系统反硝化过程中琨基调节电子传递（分流-储存-再供给）的过程机制，揭示复杂环境系统中生物质与生物炭反硝化的耦合作用机制，建立基于生物质（炭）定量匹配机制的高效脱氮调控策略。研究结果对于完善复杂系统反硝化过程的科学机理，克服传统固态碳源反硝化技术的缺陷，保障污水回用安全具有重要意义。

人工湿地被广泛地应用于城镇污水深度净化，但反硝化效能较低，造成系统出水硝态氮浓度季节性偏高。本项目以湿地植物为原料制备具有电化学活性的生物炭材料作为湿地基质，重点考察了不同湿地植物来源、不同温度对生物炭电化学活性（得失电子能力）的影响；探究了生物炭在不同水质条件下对温室气体排放的影响；通过分子生物学与电化学结合的方式探究了生物炭驱动反硝化的过程机制；阐明了低温环境下固定化生物炭提高脱氮效能的机制。研究结果表明，300℃条件下，芦苇生物炭的电子传递能力最大（1.35mmol e-/g）；香蒲原料下，中低温生物炭的电子传递能力最强（约0.63 mmol e-/g）。将300℃香蒲生物炭作为填料应用到人工湿地中，在不同COD/N条件下都可显著降低N2O的排放；在常温条件下（28℃），300℃制备的生物炭可提高硝酸盐氮去除率27%，降低N2O释放通量78%，生物炭主要是通过促进微生物系统的电子传递能力以及四种反硝化关键酶活提高脱氮效能。而在低温条件下（6±2℃），固定化300℃生物炭可提高反硝化速率76.8%，N2O减排82.5%，机理研究表明，固定化生物炭通过提高糖酵解关键酶活（电子产生）、电子传递系统活性（电子传递）、反硝化酶活性（电子消耗）等多种方式强化反硝化。研究结果完善了复杂系统反硝化过程的科学机理，克服了传统固态碳源反硝化技术的缺陷，成果正在四川、河北等地开展工程示范，且在本项目的资助下，项目组成员已发表SCI论文11篇，参加国内外会议7次，培养研究生3名。