中文摘要：

混凝过程产生的絮体会对后续膜过滤性能产生一定的影响。实验中利用激光粒度仪研究2种混凝剂（AlCl3和PAC）在不同投加量下的絮体性质，混凝出水（不经过沉淀）直接进入纳滤膜（NF270）装置进行过滤实验。研究表明，投加量低（〈0．20mmol／L）的情况下，混凝出水反而使纳滤通量衰减发生恶化，随着投加量的增加，纳滤膜通量衰减得到有效的减缓。直接过滤腐殖酸（HA）的膜通量衰减（J／J0）为0．65，投加量为0．50mmol／L时，AlCl3，和PAC2种混凝剂产生的通量衰减（J/J0）分别为0．78和0．75。滤饼层阻力受到絮体尺寸的影响较大，絮体尺寸越大，形成的滤饼层透水性更好。通过污染模型分析，混凝出水的纳滤膜污染机理主要是滤饼层阻力。

英文摘要：

Flocs formed by coagulation process will also affect the performance of membrane filtration. Floc characteristics of coagulants-conventional A1 salt （A1Cl3 ） and polyaluminum chloride （PAC） under different dosages were investigated by using a laser diffraction instrument. The results showed that membrane flux decline was deteriorated less than 0.20 mmoi/L dosages. With the dosages increasing, membrane flux decline decreased significantly. The flux decline （J/Jo） with only humic acid （HA） was 0.65. Adding 0.50 mmol/L A1C13 and PAC coagulants, the flux declined 0.78 and 0.75, respectively. Cake resistance was more obviously affected by floc size. The bigger floc size is, the better permeability of cake is. The mechanism of nanofiltration membrane fouling was mainly pore blocking by fouling model analysis.