絮凝时间对混凝-超滤工艺的膜污染特性影响

为了考察混凝条件对混凝-超滤工艺中有机物去除效果和膜污染的影响，采用静态超滤试验装置对引黄水库水进行了试验研究。研究了絮凝时间对有机物去除效果、絮体特性和超滤膜过滤特性的影响，分析了膜污染的影响因素。试验结果表明：溶解性有机污染物质( DOC、UV254)的去除作用主要发生在快速混合和凝聚过程，后续的絮凝反应过程对溶解性有机污染物质的去除效果没有影响。絮凝反应时间对絮体特性和膜污染特性的影响显著，过短或过长的絮凝时间均会产生不利影响，絮凝时间10 min时絮凝指数处于最佳范围，絮体二维分形维数最小，膜比通量最大，膜总阻力最小，滤饼层阻力最小，膜孔阻力趋于稳定。混凝剂投加量为20 mg/L、絮凝10 min时，絮体特性和超滤膜过滤性能均达到最佳。欠投药和过投药都会对混凝效果、絮体特性和膜阻力特性产生显著影响。

Effect of Flocculation Time on Fouling Characteristics in Coagulation-Ultrafiltration Process

To exam the effect of coagulation conditions on organic removal efficiency and membrane fouling of the coagulation-ultrafitration process, Yellow Biver reservoir water was studied by using the static ultrafiltration device. Effect of flocculation time on organic removal, flocs characteristics and ultrafiltration characteristics during the ultrafiltration process was investigated in this study and membrane fouling factors were also analyzed. Results indicate that the dissolved organic matter ( DOC, UV254 ) removal mainly attributes to the condensing process, the following flocculation process has no influence. Coagulation time had significant influence on flocs characteristics and membrane fouling, and both shorter and longer time had negative influence. The flocculation time of 10 mins was in the range of optimum, at which the fractal dimension, the normalized flux, the total membrane fouling resistance and the cake fouling resistance up to their minimum. However the normalized flux decline was the biggest and the pore blocking resistance lay in the stable state. 20 mg/L dosage of PAC and 10min of flocculation time is the optimal optimum coagulation conditions in coagulation-ultrafiltration process, while achieving a good flocs property and ultrafiltration characteristics. Insufficient and excessive dosage of PAC would have a great influence on coagulation, flocs and cake layer characteristics.