纳米银在污水处理系统中迁移转化规律及对微生物活性影响机制研究

With the rapid development of nano technology, a large amount of nano-materials were discharged into urban water, and caused the potential hazards to urban water ecological environment and human health. Focus on the occurrence state and pollution levels, typical environmental behaviors and fate, transportation and transformation law of silver nanoparticle in urban wastewater treatment system, and its influence effect and mechanism on microbial activity, the behavior characteristics of Ag-NP in activated sludge system, including adsorption/ desorption, biotic absorption and transformation, physical aggregation, abiotic oxidation and transformation, ect, were investigated, and influence mechanisms of environmental factors on Ag-NP transportation and transformation were explored to obtain the behavior characteristic parameters. The transfer process, speciation transformation and distribution law of Ag-NP in multi-medium were also studied to construct the fate model. The influence law of Ag-NP on the decarbonization, nitrogen removal and dephosphorization in activated sludge system were investigated, and the inhibitory effects and molecular mechanisms of Ag-NP on activated sludge microorganism were revealed on the genetic level by adopting the microbial molecular ecology methods, such as FISH, PCR-DGGE, and fluorescence probe, ect. This project could provide the important basic data and technical support to understand the existing state and ecological environment effect of Ag-NP in urban water treatment system.

随着纳米技术的飞速发展，大量纳米材料排放到城市水体中，对城市水生态环境及人体健康造成潜在的危害。本课题以城市污水处理系统中银纳米颗粒（Ag-NP）赋存状态与水平、典型环境行为与归趋、迁移转化规律及对水中微生物活性影响及机制为核心，考察活性污泥处理系统中Ag-NP的吸附解吸、生物吸收及转化、物理聚集、非生物氧化及转化等行为特征，探讨环境因子对其迁移转化的影响机制，获取行为特征参数；探明其在多相多介质中的传输过程、形态转化与分布规律，构建Ag-NP迁移转化归趋模型；考察Ag-NP对活性污泥处理系统脱碳、脱氮及除磷功能的影响规律，采用FISH、PCR-DGGE、荧光探针等微生物分子生态方法，从基因水平上揭示Ag-NP对活性污泥中微生物活性的抑制作用及分子机制。本研究为明确城市水处理系统中Ag-NP的存在状态及生态环境效应提供重要基础数据和支持。

随着纳米技术的飞速发展，大量纳米材料排放到城市水体中，对城市水生态环境及人体健康造成潜在的危害。本项目以明确污水中纳米银的污染特征及对微生物活性的影响机制为目标，主要开展了以下研究工作：纳米银在污水厂的污染特征、纳米银在污水系统中的迁移转化机制及纳米银对水处理系统微生物的影响机制。为了明确城市水系统中纳米银的污染水平，系统研究了污水中银纳米颗粒的富集分析方法，开发出基于浊点提取富集-ICP/MS检测的实际水体中纳米银分析方法，优化出最佳的提取pH值为3.5左右，加入10mM的硫代硫酸钠能促进相分离，并降低银离子对纳米银提取的干扰，最大富集因子可以达到200，同时发现存在35mg/L的腐殖酸对提取没有影响。当注入纳米银浓度为0.1-100 μg/L时，本方法的回收率介于53-127%。实际污水中总银浓度在0.93-2.63μg/L，出水介于0.27-0.69μg/L，总去除率73-84%；污水中纳米银介于0.69-2.11μg/L，出水介于0.11-0.38 μg/L，总去除率81-90.7%. 研究了纳米银对SBR工艺营养物质去除及微生物群落结构的影响。发现当纳米银浓度大于0.1mg/L时，纳米银对系统的抑制效果并不明显；而当纳米银浓度大于1.0mg/L时能明显的影响系统的脱碳、脱氮及除磷功能，且随纳米银浓度和暴露时间的增加，抑制效果增强；还发现大部分纳米银累积在活性污泥中；高通量测序表明，纳米银明显改变系统的群落结构。研究了纳米银对典型反硝化细菌（Brachymonas denitrificans）的影响机制。当AgNPs投加浓度低于1mg/L时，细菌反硝化活性几乎不受影响，细菌形态结构比较完整，LDH释放率以及ROS含量都较低。当投加AgNPs浓度逐渐增大时，细菌反硝化活性受到明显影响，细菌数量逐渐降低，细菌细胞形态出现畸形，细胞膜发生破裂，通过能谱扫描可在细菌胞内检测到Ag含量。通过对比纳米银与Ag+毒性效应，发现细菌对Ag+更加敏感，毒害影响更加明显，说明纳米银毒性与其释放的溶解性Ag+含量密切相关。本项目为明确城市水系统中纳米颗粒的环境效应提供了基础数据和技术支持。