基于硫循环调节电子供给强化潜流人工湿地反硝化机制与调控

The total nitrogen concentration of municipal sewage plant effluent can not meet the demand for wastewater reuse, and enhanced nitrogen removal for the secondary effluent is imperative. The use of constructed wetland (CW) is an important technology for the polish of secondary effluent, and the addition of plant fermentation broth helps to enhance the denitrification potential in CW. However, the stability of carbon supply can not coincide with the periodic and random variations of the influent nitrate load, which constrains the denitrification potential in the CW and weakens the stability of the CW effluent quality. Based on the engineering challenges above, the objectives this project are to investigate the functional mechanism of carbon source quantity and quality and interventional mechanisms of interspecies hydrogen transfer for nitrate and sulfate reduction, and identify the limiting factors of electron transfer; to ascertain the mechanisms of sulfide transformation and distribution as well as sulfur deposition, and quantify the critical thresholds of main factors of electron distribution and storage; to recognize the coupled mode of heterotrophic and autotrophic denitrification, and obtain the rate-limiting threshold of transmembrane mass transfer in the process of autotrophic denitrification; to clarify the mechanisms of denitirfication in subsurface-flow constructed wetlands with electron supply adjustment (shunt and transfer-distribution and storage-resupply) of sulfur cycle (reduction-deposition-oxidation), and propose the engineering regulation strategies of efficient nitrogen removal. The results of this research are expected not only to clarify the cycles of carbon, nitrogen and sulfur in complex systems, but also to introduce novel technical approaches to control the risks of wastewater reuse.

城市污水处理厂尾水总氮浓度与污水回用标准之间差距甚大，深度脱氮势在必行。潜流人工湿地是深度处理的重要技术单元，外加生物质发酵液有助于发挥系统反硝化潜能。然而，稳定的碳源投加量无法与周期性并伴随一定随机性波动的硝酸盐负荷相吻合，限制了系统反硝化潜能的高效发挥，削弱了出水水质的稳定性。本项目围绕上述工程问题，揭示碳源数量及品质与种间氢传递对异养反硝化和硫酸盐还原的作用机制与干预机制，辨识电子转移效率的限制因子；探究硫化物转化及分配与单质硫沉积机制，定量电子分配与贮存主控因子的临界阈值；识别异养与自养反硝化耦合模式，探明自养反硝化电子再供给的跨膜传质限速阈值；从而阐明基于硫循环（还原-沉积-氧化）调节电子供给（分流与转移-分配与贮存-再供给）强化潜流人工湿地反硝化的作用机制，建立系统高效脱氮的调控策略。研究结果不仅可以加深人们对复杂系统中碳氮硫循环的认识，还能为保障污水回用安全提供新的技术途径。

污水厂尾水的深度脱氮是保证城镇污水再生回用的重要举措。人工湿地是城镇污水厂尾水深度处理的重要技术单元，外加碳源有助于发挥系统的反硝化潜能。本项目聚焦稳定的碳源投加量无法与波动的硝酸盐负荷相吻合的工程问题，在潜流人工湿地中开展了以下研究：（1）潜流人工湿地硫循环及其电子传递机制；（2）碳氮比与植物对潜流人工湿地电子传递影响及其作用机制；（3）硫氮比与植物对潜流人工湿地电子传递影响及其作用机制；（4）基于胞内聚合物和铁硫循环调控潜流人工湿地反硝化机制。主要结论如下：.（1）硫酸盐还原、硫沉积与沉积硫氧化实现了硫循环对电子的捕获、固定与再供给，表明硫循环能够作为有机物与硝酸盐之间的媒介进行电子传递。.（2）碳氮比的增加能够对有机物向硫酸盐的电子传递速率（ra）、沉积硫向硝酸盐的电子传递速率（rb）、还原态硫向三价铁的电子传递速率（rc + rd）、沉积铁向硝酸盐的电子传递速率（rf）和有机物向三价铁的电子传递速率（re）产生直接的正面影响。栽种植物仅对有机物向硝酸盐的电子传递速率（rg）具有直接的负面影响。铁硫循环电子传递效率（ηET）与碳氮比具有显著的负相关关系，而与是否栽种植物无显著相关关系。.（3）硫氮比的增加能够对ra、rb、rc + rd和rf产生正面影响。栽种植物能够对ra、re和rg产生直接的负面影响，而对rc + rd与rf产生直接的正面影响。栽种植物能够显著提升ηET，硫氮比与ηET无显著相关性。.（4）在基于胞内聚合物调控潜流人工湿地反硝化效能过程中，各系统总氮去除率随着进水硝酸盐波动程度的增加而增加，而基于铁硫循环调控时则相反。同时，前者的总氮去除率较高，出水中不含有具有毒性的硫化物。因此基于胞内聚合物的调控过程脱氮效果更佳。.上述研究结果加深了人们对复杂系统中碳氮铁硫循环的认识，为潜流人工湿地高效稳定脱氮提供了工程设计参数与运行调控策略，为保障污水回用安全提供了新的技术途径。