COMPARISON OF ORGANIC-COMPOUNDS REMOVAL BY COAGULATION-FLOCCULATION AND BY ADSORPTION ONTO PREFORMED HYDROXIDE FLOCS

The coagulation process is traditionally described in terms of the destabilization of colloids present in a water supply. Many studies show that coagulants are not only used to destabilize organic or inorganic colloidal particles, but also to remove natural organic matter. The removal of this organic matter from the bulk water can occur by direct precipitation or by adsorption of the organic matter onto metal hydroxides. The goal of this study is to compare the removal of organic compounds by coagulation and by adsorption onto preformed flocs with aluminium and iron salts who are the most used coagulants in drinking water treatment. Various studies (Chadick and Amy, 1987; Dentel and Gosset, 1988; Edwards and Amirtharajah, 1985; Hundt and O'Melia, 1988; Jekel, 1986; Randtke, 1988; Tipping et al., 1988) have been reported concerning the removal of humic substances and the removal of low molecular weight compounds (Lefebvre, 1990; Lefebvre et al., 1990). Only a few studies show the interactions between preformed hydroxide flocs surface and these organic compounds.