Full Description

Fully-grown flocs in a mixing tank of membrane filtration with dead-end membranes are rupturedwhile passing through a pump and the ruptured flocs are aggregated again in a membrane-feed-pipe(MFP). To look at more details, this study relates the reaggregation to a parameter of mixingintensity in the MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter,friction factor and average velocity in the MPF. To deal with the polydispersity condition, the authors developed arepresentative particle size called Effective Diameter for Polydispersecondition in Dead-end filtration (EDPD). The experimental results show that as the G-value increases, theEDPD decreases, and also the cake resistance increases. An in-line injection system, which injectscoagulant just before a pump and has no mixing tank, is also tested for comparison. Resultssuggest that as the G-value goes above 3,100sec-1, the floc sizes at an inlet to the membraneincrease in the case of in-line injection compared to the one with a mixing tank. The cake resistancedecreases. Given that most treatment plants operate with the G-value larger than 3,100sec-1, thissuggests that there is a strong possibility of replacing the mixing tank for coagulation and flocculationwith an in-line injection system. Includes 16 references, figures, tables.

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Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 35File Size: 1 file , 1000 KB