外置植物碳源人工湿地系统反硝化脱氮过程中N2O释放机理及控制研究

Plant material could be supplied as carbon source to the constructed wetlands to improve the efficiency of nitrogen removal. The most important operating problem met in engineering practice was the fresh plant material supplementary and old plant material removal. In this project, a new type of constructed wetland system was proposed, in which, plant material was supplied in another place, outside of the constructed wetland instead of inside. The purpose of this design thought was to solved the above-mentioned operating problem and extend the application of constructed wetland system in practice. The emission mechanism and reducing method of N2O in this type of constructed wetland microcosm was investigated. The influence of plant species, dissolved oxygen and hydraulic retention time on N2O emission during denitrification was studied. PCR-DGGE method and Substrate-induced respiration (SIR) inhibition method were combined used to analyze the denitrified microbial diversity in the constructed wetland. And the relationship between the N2O emission characteristic and the denitrified microbial diversity was investigated. The results would be helpful to explain the characteristic and mechanism of N2O emission in the constructed wetland supplied with plant material as carbon source. And the results would provide theoretical suggestion to help choosing good plant material as carbon source and to reducing N2O emission.

向人工湿地系统中补充植物材料作碳源可以有效的提高反硝化脱氮效果，但在工程应用中存在植物碳源补充和移除困难的问题。本项目提出一种新型人工湿地系统- - 将植物碳源材料补充于人工湿地系统体外，以提高反硝化脱氮效果的同时解决上述工程难题，推广人工湿地在工程实践中的应用。本项目拟在此构建的人工湿地系统模型中，就"反硝化脱氮过充中N2O释放机理及控制"开展系统深入的研究。研究在不同植物材料种类、溶解氧、水力停留时间等因素条件下反硝化脱氮过程中N2O释放的特点和规律；采用微生物分子生态学的方法并结合基质诱导呼吸抑制法研究系统中反硝化微生物群落结构的组成及反硝化作用强度；研究系统中反硝化微生物群落组成与系统N2O释放特点的相关关系。研究结果为揭示外置植物碳源人工湿地系统反硝化脱氮过程中N2O释放的特点及微生物作用机理，筛选优质植物碳源材料，减少N2O释放的控制措施提供理论依据和技术指导

针对添加植物碳源来解决人工湿地系统处理低C/N污水脱氮过程中可能导致的N2O释放及植物碳源更换困难的问题，本论文在自行构建的植物碳源外置型人工湿地系统中，研究了芦苇（Phragmites australis）和梧桐（Platanus orientalis）树叶分解规律、不同类型碳源对人工湿地污水处理系统脱氮效果的影响以及添加植物碳源后系统N2O释放情况。论文主要研究内容及结论如下：.（1）通过控制植物材料分解区的水位，模拟不同DO条件下芦苇和树叶的分解及释放情况。无论是处在何种水淹状态下，芦苇干重及有机碳的损失都大于树叶，芦苇和梧桐树叶的干重损失分别为46.71%和16.70%，芦苇和树叶有机碳的减少量分别为18.85%和7.80%；与之相应，芦苇释放到水体中有机碳、TN含量也高于梧桐树叶。.（2）研究了葡萄糖和芦苇、梧桐树叶分别作为反硝化碳源时对人工湿地脱氮效率的影响。葡萄糖作为碳源（DOC/N=2）时的脱氮效率一直都很高，脱氮率稳定在90%以上；芦苇和梧桐树叶作碳源时，在试验初期（前20d）由于植物材料本身分解释放出较多的碳、氮、磷等营养物质，会导致出水中有机物浓度较高，浓度范围为15~30mg/L，且脱氮效率低于葡萄糖作碳源。随后，出水中有机物浓度低至3 mg/L左右，脱氮效率稳定地维持在90%左右。.（3）研究了添加碳源后人工湿地系统N2O的释放量。在本试验研究条件下，添加植物碳源的系统N2O的释放通量虽然大于葡萄糖作碳源的系统，但是要小于碳源不足的对照系统。单个批次内空白组、树叶组、芦苇组、葡萄糖组N2O的平均释放量分别127.45μg.m-2.h-1、34.16μg.m-2.h-1、40.91μg.m-2.h-1、6.20μg.m-2.h-1，表明采用植物材料作为解决低碳氮比污水脱氮时的外加碳源具有可行性。.（4）采用PLFA方法对人工湿地单元基质中的微生物组成和数量进行分析，结果表明：添加碳源系统微生物数量大于空白实验组，这与添加碳源系统的脱氮效率大于空白对照组的现象一致。添加碳源组真菌PLFAs含量正好和N2O的释放量呈正相关关系，说明真菌的含量可能直接影响N2O的产生。不同碳源通过影响微生物群落组成和数量来影响脱N效率及N2O的释放。.