基于"后絮凝"控制的膜法饮用水处理单元设计机理研究

To solve the re-flocculation phenomenon & the instability influence onthe water qulity question，the water treatment units processes with membrane technology is carried out in this researches based on the re-flocculation controlling. By marking on the Fe3+ flocculation，the floc morphological analysis and fluorescent probe labeling technology are organically combined together. The migration and distribution law of the coagulant in the unit within the system are judged and analyzed, the collaborative units and process design scientific idea of re-flocculation inhibiting is put forward. Based on the process of quantitative controlled combination of coagulation and membrane filtration process, the techniques experiment, numerical simulation and image information analysis are used to improve membrane in the process integrated design. Through the regulation of the coagulation process parameters, the analysis of flocs sediment on membrane fouling layer mechanism, simulation and optimization of the hydraulic environment in coagulation membrane filtration process unit, establishing the security and efficiency model of coagulation application in the coagulation-membrane filtration process, in the aspect of operation mode and design theory, and further improve and modify the process design and operation of coagulation-membrane filtration in drinking water treatment in the theoretical system. Through this research, the theoretical foundation of low agent consumption, short process, high efficiency drinking water treatment system with membrane technology is constructed.

针对混凝-膜过滤工艺中"后絮凝"及现象及给工艺系统水质稳定性带来的影响，本课题提出基于"后絮凝"控制的膜法饮用水工艺单元设计及优化研究。通过对Fe3+絮凝的标记, 将絮体形态学分析和荧光探针标示技术有机结合在一起, 判断和分析混凝剂在单元系统内的迁移分布规律,形成抑制后絮凝的单元协同调控与设计的学术构想。基于定量化可控混凝与膜过滤组合的工艺形式，采用工艺实验、数值模拟和图像信息分析相结合的手段，完善膜法处理中工艺集成化设计。通过对混凝过程参数的调控；膜面絮体沉积污染层机理的解析；混凝-膜过滤工艺单元内水力环境的模拟与优化；混凝剂安全高效的应用模式的建立，在设计理论、运行模式层面进一步完善混凝-膜过滤饮用水处理工艺设计与运行理论体系。通过本课题的开展，完善和补充以"膜终端"过滤为核心的饮用水净化理论， 为实现"低药耗、短流程、高效能"的膜法饮用水处理工艺系统奠定理论基础。

混凝-膜过滤组合工艺目前已被广泛应用于处理水质恶化和微污染水体，尤其是在饮用水净化领域。但混凝-膜过滤反应器在工程实践中还存在诸多不足。本文针对混凝-膜过滤工艺中的“后絮凝”现象及给工艺系统水质稳定性带来的影响，开展基于“后絮凝”控制的膜法饮用水工艺单元设计及优化研究。.针对微污染水源的水质特点研究混凝-膜过滤工艺的混凝动力学特征，探究混凝-膜过滤中混凝的最佳调控规律。随着混凝剂投加量的逐渐增加，絮体粒径和分形维数逐渐增大，絮体结构密实，对水中污染物去除率逐步提高，膜污染趋于减缓。当混凝剂的投加量为20mg/L时，絮体粒径增长幅度变缓，混凝反应对污染物去除效果最好。.基于罗丹明类Fe3+荧光探针对铁离子污染的辨识功能，构建探针Ⅰ。研究表明，微量Fe3+浓度范围内，探针Ⅰ在580nm处的荧光强度与铁金属离子浓度具有良好的线性关系。混凝-膜过滤实验中，用探针Ⅰ检测污染后膜面的荧光反应，来表征膜面滞留的Fe3+混凝剂含量。混凝剂投加量在20mg/L时系统中混凝过程最为充分，继续提高投量将使膜面滞留的Fe3+浓度出现明显增加，一部分Fe3+开始透过膜引发“后絮凝”现象。.对比常规混凝膜过滤工艺，循环絮凝-膜过滤工艺通过调节混凝剂和回流絮体的浓度比例，能够提高亲水性有机物的去除率，并促进絮体生长，减缓膜污染。同时，循环絮凝可提高混凝剂的利用率，从而有效控制“后絮凝”现象的发生。.利用CFD模拟对混凝-膜过滤工艺不同停留时间比和膜组件填充密度进行流场分析，优化工艺单元设计。结合实验将絮体平均粒径与模拟得到的微涡旋尺度λ0进行对比，结果表明，混凝-膜过滤停留时间比为2:1时，形成的水力学条件有利于絮体的碰撞、聚集，使混凝反应更充分。反应器中膜组件的填充密度为1.6，气水比为15：1时，膜单元可得到有效的清洗，同时有利于形成较大的絮体，减小曝气过程对絮体的破坏作用。