Variations in backwash efficiency during colloidal filtration of hollow-fiber microfiltration membranes

    Authors

    S. K. Hong; P. Krishna; C. Hobbs; D. H. Kim;J. W. Cho

    Comments

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    Abbreviated Journal Title

    Desalination

    Keywords

    colloidal fouling; microfiltration; backwashing efficiency; cake layer; structure; water treatment; CROSS-FLOW MICROFILTRATION; DRINKING-WATER TREATMENT; PARTICLE-SIZE; FLUX DECLINE; WASTE-WATER; ULTRAFILTRATION; CHARGE; SUSPENSIONS; REMOVAL; MODEL; Engineering, Chemical; Water Resources

    Abstract

    A series of filtration experiments was performed systematically to investigate physical and chemical factors affecting the efficiency of backwashing during microfiltration of colloidal suspensions. In this study, all experiments were conducted in dead-end filtration mode utilizing an outside-in, hollow-fiber module with a nominal pore size of 0.1 mu m. Silica particles (mean diameter = 0.14 mu m) were used as model colloids. Using a flux decline model based on the Happel's cell for the hydraulic resistance of the particle layer, the cake structure was determined from experimental fouling data and then correlated to backwash efficiency. Modeling of experimental data revealed no noticeable changes in cake layer structure when feed particle concentration and operating pressure increased. Specifically, the packing density of the cake layer (1-cake porosity) in the cake layer ranged from 0.66 to 0.67, which corresponds well to random packing density. However, the particle packing density increased drastically with ionic strength. The results of backwashing experiments demonstrated that the efficiency of backwashing decreased significantly with increasing solution ionic strength, while backwash efficiency did not vary when particle concentration and operating pressure increased. This finding suggests that backwash efficiency is closely related to the structure of the cake layer formed during particle filtration. More densely packed cake layers were formed under high ionic strength, and consequently less flux was recovered per given backwash volume during backwashing.

    Journal Title

    Desalination

    Volume

    173

    Issue/Number

    3

    Publication Date

    1-1-2005

    Document Type

    Article

    Language

    English

    First Page

    257

    Last Page

    268

    WOS Identifier

    WOS:000228118500006

    ISSN

    0011-9164

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