Mechanism of filter fouling in coagulation-membrane water treatment process

水处理工艺的主要目的是从水中分离杂质，即固/液分离。 杂质通常以颗粒聚集体（絮凝物）的形式存在。 成功去除水中的絮凝物可以减少消毒剂的剂量及其致癌副产物。 许多市政当局正在探索用先进的固/液分离工艺取代传统的固/液分离工艺。 例如膜过滤。 然而，水源通常含有高浓度的化合物（污垢），其有效地堵塞膜过滤器。 这些污染物可以有效地固定在膜过滤预处理过程中形成的絮体上。 一旦吸附到絮凝物上，污垢就不能再渗透到膜内部;相反，它们在过滤器表面上形成多孔滤饼。 这种滤饼通常可以通过膜的物理清洁来去除。 本研究旨在探讨膜过滤器的堵塞机理。 将使用光学显微镜和医学科学中使用的先进方法分析过滤器堵塞饼的结构。 将使用分形几何的概念来建立滤饼渗透率的数学模型。 本研究的实验室结果的现场验证已安排在位于马尼托巴的两个膜水过滤厂进行。 许多供水系统可能不得不考虑膜过滤，以满足饮用水质量的严格规定。 污垢无法避免，但可以通过仔细设计过滤预处理工艺来控制。 膜污染的控制允许更长的过滤运行和更少的水被丢弃，这与工厂的运行成本直接相关。

The main objective of a water treatment process is the separation of impurities from water, that is solid/liquid separation. The impurities are usually in the form of particle aggregates (flocs). The successful removal of flocs from the water reduces the dose of disinfectant and its carcinogenic by-products. Many municipalities are exploring replacing conventional solid/liquid separation processes with advanced processes such as membrane filtration. However, water sources often contain high concentration of compounds (foulants) that effectively clog membrane filters. These foulants can be effectively immobilized on the floc formed in the membrane filtration pre-treatment process. Once adsorbed onto the floc, the foulants can no longer penetrate inside the membrane; rather they form a porous cake on the surface of the filter. This cake can usually be removed by physical cleaning of the membrane. This research proposes to study mechanisms of membrane filters clogging. The structure of the filter clogging cakes will be analyzed using optical microscopes and advanced methods used in medical science. Mathematical models of the cakes permeability will be developed using concepts of fractal geometry. Field verification of the laboratory results of this study has been arranged with the two membrane water filtration plants located in Manitoba. Many water supply systems may have to consider membrane filtration to meet the stringent regulations for potable water quality. Fouling cannot be avoided but it can be controlled with careful design of filtration pre-treatment processes. Control of membrane fouling allows for longer filtration runs and for less water to be rejected, which is directly related to the operating cost of the plant.