微污染水源表面流人工湿地生源性水质突发恶化和功能衰退演变机理

Part slightly polluted rivers and lakes in China have the functions of life drinking water. Using surface flow constructed wetlands for their water quality maintenance and promotion is a common and effective means. However, after a long-term operation most large constructed wetlands emerge function degradation such as decline in treatment efficiency, increase in operation cost and even paroxysmal deterioration in water quality. So how to maintain constructed wetlands operating steady and efficiently is the key technical problems to be solved. In this research, field observation in situ, laboratory experiment and mathematical model are combined to distinguish characterization and physical characteristics of paroxysmal deterioration of water quality in SFCW for micro-polluted water; to investigate ascertain long term evolution process of the decline of purification performance; to clarify short-term mechanism of paroxysmal deterioration of water quality under the drive of hydrodynamic conditions, plant and sediment in SFCW; to study transport mechanism of characterization elements such as dissolved oxygen, pollutants and odor-causing microbes in the atmosphere-water-sediment multi interface; and to explore the dominant influencing factors of the decline of pollutants removal in SFCW’s different operation periods. A multi-factor coupling simulation technology including meteorological, hydrology and sediment transport is expected to reenact the evolution of the decline of SFCW function and predict the paroxysmal deterioration of water quality event. In addition, the ways and consequences of the paroxysmal deterioration of water quality in SFCW will be evaluated and optimal adaptive control measures are proposed to protect the long-term effective operation of SFCW. The results are supposed to have significant technical recommendations for the scientific design, construction and operation management of constructed wetlands in China.

我国部分微污染河湖承担了生活饮用水源的功能，利用表面流人工湿地进行其水质维护和提升是常用的有效手段，而多数大型人工湿地长期运行后陆续出现处理效率下降、运维成本增加，甚至生源性水质突发性恶化等功能衰退的系列问题，如何保持人工湿地持续稳定高效运行是亟待解决的关键技术难题。本项目将室内外实验和数学模拟相结合，研究微污染水源表面流人工湿地生源性水质突发恶化表征现象，探索水动力-植物-底质复合驱动下水质突发恶化的短期骤变机理和水质净化功能衰退的长期演变过程；解析特征元素在大气-水体、水体-底泥、氧化-还原界面的运移机制，探索湿地水质净化功能衰退的诱变因子与灾变机制；开发水动力-植物-底质耦合的人工湿地污染物运移数学模型，反演与预测人工湿地生源性水质突发恶化现象和水质净化功能衰退的全过程，提出保障表面流人工湿地长效运行的适应性调控措施，预期成果以期为我国表面流人工湿地的建设和长效运维提供技术支撑。

饮用水水源地水质安全保障已经成为我国社会经济可持续发展中迫切需要解决的关键问题。利用表面流人工湿地对微污染水源进行水质提升和维护是我国常用的有效措施，然而运行年限不断增长，表面流人工湿地出现了由底泥污染累积，植物疯长倒伏、根系腐烂变质等原因造成的人工湿地水质净化能力显著下降等功能衰退的系列问题，成为微污染水源表面流人工湿地保障水源地供水安全亟待研究和解决的关键技术难点。本项目将室内实验、野外监测和数学模拟相结合开展微污染水源表面流人工湿地生源性水质恶化和功能衰退演变机理研究。具体为（1）利用典型表面流人工湿地在水质恶化的前、中、后时期湿地进水水源的水位-水量-水质立体观测数据，研究人工湿地不同水文特征以及微污染的水质特性条件下湿地出水水质的变化规律以及湿地内部污染物迁移转化过程，揭示微污染水源水位-水量-水质特征对水质恶化的影响机理。（2）利用表面流人工湿地长序列水质和底泥观测数据，定量表征湿地底泥污染物垂向累积特征及氧化层理化性质，明确湿地底泥与上覆水污染物的短期动态交换通量，揭示湿地长期运行条件下底泥污染程度及污染物释放规律。（3）构建表面流人工湿地水动力-植物-底质耦合模型，从优化湿地运行效率的角度出发，模拟不同运行条件对湿地净化效果的影响并进行对比分析，获取改善水质的有效途径。以上研究成果可为我国表面流人工湿地的建设和长效运维提供理论基础和技术支撑。