Coagulation par fe(iii) de substances humiques extraites d'eaux de surface: effet du ph et de la concentration en substances humiques

Abstract

Numerous studies (e.g. Kavanaugh, 1978; Van Breemen et al., 1979; Babcock and Singer, 1979; Semmens and Field, 1980; Reckhow and Singer, 1983; Dempsey et al., 1984; Semmens and Ayers, 1985; Jekel, 1986; Reckhow anu Sibony, 1986; Legube et al., 1988; Paillard et al., 1988a) have been reported concerning the coagulation performance at acidic pH with aluminium and iron salts for reducing the concentration of organic matter in drinking water, expressed in terms of u.v.-absorbance, TOC, THM and TOX formation potential removal. The capacity to remove high molecular weight organics by coagulation with iron salts at pH = 5.5 has been already shown concerning humic substances (Semmens and Ayers, 1985; Sinsabaugh et al., 1986) and algogenic organic matter (Bernhardt et al., 1985). The influences of pH, coagulant dose, initial fulvic acid (FA) concentrations and fulvic acid origin were studied from reconstituted water containing fulvic acid (Tables 1 and 3) with laboratory apparatus including coagulation-flocculation, sedimentation and filtration treatment steps shown in Fig. 1. The removal of fulvic acid by coagulation was followed by the ratio of organic matter content after filtration on organic matter content before coagulation, expressed in u.v.-absorbance measurements (at 254 nm) and total carbon analysis.