The effects of flow conditions and retention time in the pipe placed before and after pump on floc re-aggregation and the effect of floc re-aggregation on cake resistant of membrane were investigated in this study. The $R_f$ value was used to determine flow condition and $R_f$ value was changed from 117 to 1314 $(\sec^{-1})$. The EDSD (Effective Diameter for Shear-Induced Diffusion) was used to determine the polydisperse particle size. For the alumminium-based coagulants and charge neutralization condition it was found that, the broken floc can be re-aggregated in the pipe placed after pump. But only limited re-aggregation occurred in all cases, indicating a significant irreversibility of the floc re-aggregation process. It means that the re-aggregation floc size is smaller than the original floc. The $R_f$ value was important factor on re-aggregation process in the pipe. But, it is difficult to determine the effect of retention time on re-aggregation process in the pipe. The re-aggregation floc size increases when the $R_f$ value decreases under all condition. It was prove that, re-aggregation increased the permeate flux, and also decreased the cake resistance of membrane.
본 연구에서는 응집으로 인해서 커진 입자가 펌프를 통과한 후 다시 재 응집 되는 영향인자에 관한 연구를 진행하였다. 이 실험에서 $R_f$ 값은 실제 파이프관내의 유체의 특성을 나타내는데 사용하였으며 EDSD값은 다양한 입자크기가 존재하는 파이프관내 입자크기를 나타내기 위해서 사용하였다. 본 실험에서는 기본적으로 charge neutralization조건에서 재응집 실험을 하였다. 실험에서는 $R_f$ 값이 커질수록 관내 재응집 된 입자의 크기가 커지는 효과를 볼 수 있었다.
