人工湿地污水处理潮汐运行强化总氮脱除机理研究

Nitrification process is normally recognized as the rate-limiting step with ammonium oxidation to nitrate of total nitrogen removal in traditional horizontal and vertical constructed wetlands, due to their low capacity of oxygen transfer into the wetland bed. Thus, the enhancement of oxygen refreshment in constructed wetlands might be very important to increase the nitrification process and further intensify total nitrogen removal efficiency. Tidal flow constructed wetlands are newly developed wetlands and their higher capacity of nitrification was reported in previous studies due to the enhanced transfer of oxygen by the operation strategy of periodical flood and drain. However, the denitrification process in tidal flow constructed wetlands is often inhibited which further limited the total nitrogen removal efficiency. Therefore, in the present study,the dynamics of transformations of nitrogen compounds and microflora response will be experimented to investigate the mechanism of intensified total nitrogen removal in tidal flow constructed wetlands. In order to intensify the denitrification process coupled with a high nitrification capacity in tidal flow constructed wetlands, the effect of different flood drain ratios, ammonium adsorption characteristics and oxygen refreshment controls on the removal of nitrogen, capacity of nitrification and denitrification would be deeply discussed. In addition, a mathematical/quantitative model to predict the nitrogen transformations and removal efficiency in tidal flow constructed wetlands will be established based on the data obtained from the proposed experiments. The findings of this study will post a more clear understanding of nitrogen transformations under tidal operation in constructed wetlands and also inspire new ideas to the enhancement of total nitrogen removal. Moreover, valuable suggestions from both aspects of scientific research and engineering application will be concluded to forward the development of tidal flow constructed wetlands for wastewater treatment.

硝化过程往往是氧环境较差的传统人工湿地处理系统总氮脱除的限速步骤，这使得合理改善湿地床氧环境对强化湿地系统总氮脱除效果至关重要。前期研究证明人工湿地在潮汐运行方式下具有较强的复氧效果和氨氮去除效率，但反硝化能力较弱进而限制了脱氮效率。本课题拟针对人工湿地污水处理系统，通过实验手段分析氮素污染物在潮汐运行过程中的迁移转化规律和微生物菌群响应，深入探讨人工湿地在潮汐运行方式下的强化总氮脱除规律。对比不同淹没排空时间比、基质氨氮吸附性能、复氧调控方式等因素下的总氮脱除效果、硝化反硝化强度以及脱氮菌群变化，完善潮汐湿地床在周期性淹没排空下的强化脱氮机理，力求在维持潮汐人工湿地强硝化能力的基础上协同强化反硝化能力，提高总氮脱除率。根据潮汐湿地脱氮能力与不同运行条件之间关系构建耦合多因素潮汐流湿地脱氮模型。研究成果将是对潮汐人工湿地污水强化处理的重要补充，对推动湿地污水处理技术发展具有重要的理论意义。

传统人工湿地有限的复氧能力和较差的氧环境使得氨氮的硝化过程往往成为湿地污水处理系统脱氮的限速步骤。合理提高人工湿地复氧能力和改善湿地中的氧环境对提高氨氮氧化能力进而提高湿地总氮脱除效果至关重要。潮汐流湿地床的强复氧能力可以强化氨氮氧化效率，但如何在维持潮汐流人工湿地强硝化能力的基础上优化系统反硝化能力，提高总氮去除率将成为潮汐流人工湿地技术脱氮发展的新挑战。本课题通过分析氮素污染物在潮汐运行过程中的迁移转化规律，探讨了潮汐流人工湿地脱氮机理。针对淹没排空时间比、基质氨氮吸附性能、复氧调控方式等因素，探究了潮汐流湿地床的脱氮优化机制，揭示潮汐流湿地脱氮能力与不同运行工艺之间的关系。同时基于污染物传质及微生物降解动力学的关系，初步建立了潮汐流人工湿地氨氮及总氮脱除效率预测模型。结果为有效地提高潮汐流湿地床脱氮效果拓展新思路，对进一步推动潮汐流人工湿地污水处理技术的发展具有重要的理论意义和工程应用价值。主要结论如下：（1）通过研究淹没排空时间和排空速率对潮汐流人工湿地总氮强化脱除的影响，发现淹没排空时间3 h:3 h更有利于系统硝化和反硝化反应的协同交替进行，相对较慢的排空速率有利于提高铵根离子与湿地基质的接触时间，增大基质的吸附量，也更有利于氧气在基质层间隙中的均匀分布，使湿地床的硝化能力大幅提高。（2）利用分别装有沸石、石英砂、生物陶粒、火山岩的潮汐流人工湿地，通过进出水氨氮和总氮的降解效率以及基质的比表面积、阳离子交换能力、电镜扫面及微生物菌群丰度和结构等表征指标，证明了基质类型对潮汐流人工湿地强化脱氮效率的影响机制。（3）通过分别模拟脉冲式氨氮进水浓度和有机物COD进水浓度以及监测潮汐流人工湿地污染物去除对脉冲负荷的响应，证明了人工湿地潮汐运行可以显著提高湿地系统对较高污染负荷的抗冲击能力。（4）探讨了潮汐流湿地耦合电化学强化脱氮除磷规律。结果表明耦合电化学的潮汐流人工湿地组合系统将潮汐流人工湿地强硝化能力与电化学强硝酸盐和磷酸盐脱除能力进行了优势互补，在潮汐过程中氨氮氧化去除效率维持在90%以上，电化学过程产生的氢离子作为点子供体推动了硝酸盐的异化还原过程，牺牲铁电极产生的絮凝剂不仅提高了磷酸盐的吸附沉淀，同时络合沉淀了硫酸盐异化还原过程中产生的硫化氢，不仅实现了污染物的高效去除，同时实现了污水的无味处理。