纳米改性填料强化垂直流人工湿地脱氮的机理研究

The Vertical-flow constructed wetland (VFCW)is widely used for the treatment of sewage because of small footprint and high removal efficiency . However, the nitrogen removal has always been an urgent technical problem in the Vertical-flow constructed wetland.The technical problem has become a bottleneck, which restricted the populary of VFCW. According to our previous study, the removal effect of nitrogen can significantly be improved because of nano modified substrate, but the mechanism of nitrogen removal of nano modified substrate is not yet clear. Therefore, the Vertical-flow constructed wetland (VFCW) based on nano modified substrate will be researched in this project. Firstly, this study seeks to understand the relationships between nano-modified substrate adsorption characteristics of ammonia nitrogen and the physical and chemical properties of substrate in VFCW through isothermal adsorption test. The degree of relationship of various physical and chemical indicators and ammonia nitrogen adsorption can be elucidated. Secondly, effect of colony of bacteria and nitrogen transport and transformation will be researched in VFCW through the simulated sylinders test. The number, activity and faunal composition of total bacteria, nitrification bacteria, denitrification bacteria, nitroso-bacteria will be searched out in the nano modified substrate wetland. The nitrogen removal molecular mechanism of nano modified substrate will be stated. Finnally, the effect and cooperative action of nano modified substrate in nitrogen removal will be analyzed through considering the combine function of nano modified substrate, microorganisms and plant. which will provide a theoretical an practice basis for the optinum of nitrogen removing methods and the improvement of the sewage treating efficiency by VFCW.This study will provide valuable results to the scientific research on new substrate of VFCW.

垂直流人工湿地占地面积小、处理效率高，应用广泛，而氮去除效果差是其面临的难题。本课题组前期研究表明，纳米改性填料能显著提高垂直流人工湿地的氮去除率，但其脱氮机理尚未明确。因此，本项目以纳米改性填料湿地系统为研究对象，首先采用等温吸附试验，考察纳米改性填料物理、化学性质对脱氮的影响，明确不同填料的氨氮吸附量、吸附去除率与物理、化学指标的相关关系，利用Langmuir方程对其进行数据拟合，确定填料物理、化学性质与氨氮吸附去除的显著程度；其次采用室外模拟试验，研究纳米改性填料对系统脱氮微生物功能菌群及氮迁移转化的影响，弄清硝化菌、亚硝化菌及反硝化菌的数量、活性、区系组成等与氮去除之间的关系，阐明纳米改性填料微生物脱氮的分子机制；最后综合填料、微生物和植物的作用，分析纳米改性填料在脱氮方面的作用率以及其协同作用率的大小，揭示纳米改性填料垂直流人工湿地脱氮机理，为其高效脱氮新填料的选择提供科学依据。

垂直流人工湿地占地面积小、处理效率高，应用广泛，但脱氮除磷效果差一直是其面临的技术难题。而纳米材料的添加提高了垂直流人工湿地的处理效果，特别是提高了垂直流系统对TN的去除效率。不管是在温度较高的夏季还是温度较低的冬季，纳米混合填料人工湿地的硝化强度均要高于普通填料的硝化强度，随着硝化时间的延长，其硝化强度呈逐渐递减的趋势，即24h>48h>72h的硝化强度，而硝化强度的高低直接反映的是系统对氨氮去除率的大小差别,因而纳米混合填料系统对氨氮的去除率在夏季可达98%以上；同时研究结果表明，纳米改性填料去除的氮量占污水带入系统总氮量的35%，而普通填料只能去除24%，植物能去除12%，因而不同填料系统在氮的去除方面的贡献率呈现出：微生物＞填料＞植物的趋势，而磷的去除则表现出填料＞微生物＞植物的规律；试验中发现纳米改性填料人工湿地系统中微生物种群的数量要高于普通填料系统，这表明纳米改性填料的存在有利于提高系统的微生物数量（如硝化和反硝化细菌等），这些微生物对污水中的污染物质起到了吸收降解的作用，从而明确了纳米改性填料对垂直流人工湿地脱氮起促进作用的因素。确定了硝化菌、亚硝化菌及反硝化菌数量等与氮去除之间的关系以及纳米改性填料微生物脱氮的初步机制；另外，通过对纳米改性填料进行电镜扫描以及有关吸附氨氮、总磷的特征与填料的物理和化学性质的关系研究，弄清了纳米改性填料的粒径、容重、孔隙度等对填料去除污染物饱和浓度的影响，获得纳米改性填料湿地系统氨氮吸附达到饱和的时间是36年（系统高140cm），其次是高炉渣，为31年，最短的是煤灰渣，为29年，纳米改性填料因其具有较小的容重,较大的孔隙度和比表面积等特征，导致其脱氮除磷的效率明显提高，这为人工湿地填料的选择及推广应用提供了理论依据。