To examine the effects of different coagulants on membrane fouling in the coagulation/aid⁃coagulation/ultrafiltration process for high turbidity surface water purification, Malvern laser particle size analyzer and micro⁃scale ultrafiltration unit were used to investigate membrane fouling caused by the flocs formed by coagulants (i.e. aluminium polychlorid (PACl), ferric trichloride (FeCl3)) and aid⁃coagulant (polyacrylamide (PAM)). The results indicated that, with the constant dosage of combined coagulants (PACl=FeCl3=3 mg/L), the PAM dosage of 0-0.4 mg/L rendered the d50 of flocs exhibited an obvious increase ( eventually reached to 1 000μm) compared to those with single coagulant dosage of PACl(3-370μm) or FeCl3(360-420μm). With the dosage of PAM increased, specific membrane flux increased (PACl:0.56-0.64;FeCl3:0.71-0.76) and cake resistance decreased (PACl:0.90×10-11-0.52×10-11 m-1;FeCl3:0.47×10-11-0.28×10-11 m-1). However, when the dosage of PAM increased to 1.0 mg/L, the membrane flux decreased significantly to 0. 48 while cake resistance increased to 1. 55 × 10-11 m-1 . An optimum flocculant dosage (0.4 mg/L) that caused the minimum membrane fouling was confirmed. Furthermore, the results obtained from Nanoseries Zetasizer and scanning electron microscopy ( SEM) demonstrated that cake layer was the dominant fouling mechanism under different conditions and membrane pore blocking was severe with higher PAM dosage.%为考查混凝剂种类对混凝－助凝－超滤工艺处理较高浊度地表水时膜污染的影响，采用动态测絮体粒径的马尔文粒度仪和微型超滤系统研究聚合氯化铝（ PACl）和三氯化铁（ FeCl3）与助凝剂聚丙烯酰胺（ PAM）联用形成的絮体对超滤膜污染的影响．结果表明，固定混凝剂投量（PACl 和 FeCl3为3 mg／L），当PAM投量在0～0．4 mg／L时，絮体粒径增至1000μm，相对于单一投加PACl（3～370μm）和FeCl3（360～420μm）时增长明显，且随投量增加比通量增大（PACl：0．56～0．64；FeCl3：0．71～0．76）、滤饼层阻力减小（PACl：由0．90×10－11降至0．52×10－11 m－1；FeCl3：由0．47×10－11降至0．28×10－11 m－1）；然而当PAM投量增大为1．0 mg／L时，比通量明显减小至0．48，而滤饼层阻力显著增加至1．55×10－11 m－1．因此，助凝剂 PAM 存在最优投量（0．4 mg／L）膜污染最小．结合纳米粒度仪和扫描电镜证明滤饼是主要污染机理，但膜孔堵塞在PAM投量高时明显．
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