Fully-grown flocs in a mixing tank of membrane filtration with dead-end membrane are ruptured while passing through a pump and the ruptured flocs are aggregated again in a membrane-feed-pipe (MFP). To look at more details, this study tries to relate the reaggregation to a parameter of mixing intensity in MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter, friction factor and average velocity in MPF. To deal with polydispersity condition, we develop a representative particle size called in this study EDPD (Effective Diameter for Polydisperse condition in Dead-end filtration). The experimental results show that as the G-value increases, the EDPD decreases and also the cake resistance increases. An in-line injection system which injects coagulant just before a pump and has no mixing tank is also tested for comparison. Our results suggest that as the G-value goes above 3,100sec~(-1), the floc sizes at an inlet to the membrane increase in the case of in-line injection compared to the one with a mixing tank. The cake resistance decreases. Given most of treatment plants operate with the G-value larger than 3,100sec~(-1), this suggests that there is a strong possibility of replacing mixing tank for coagulation and flocculation with in-line injection system.
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