The objective of this study is to examine the effectiveness of the removal of polymeric humic matter during coagulation-flocculation and to highlight stoichiometric relationships between the coagulant dosage and the organic substance content. It is therefore a question of assessing the influence of reaction parameters such as the dose of aluminum sulfate, the concentration of humic acid, the pH and the saline composition of the water during the coagulation-flocculation treatment.

To establish correlations between the initial organic compound content and the coagulant dosage, humic acid was dissolved at levels of 1 to 20 mg/l in distilled water and mineralized groundwater from the Biskra area at different pH values. Then, solutions were coagulated by increasing doses of aluminum sulfate. The organic compound final concentrations are deduced from the calibration curves, which were previously established for the tested compound in the various dilution media.

The results obtained indicate that the process efficiency as well as the coagulant dosage depend on the pH, the organic compound initial concentration and the characteristics of the dilution medium. The findings also showed that increasing water salinity had a promoting effect on humic acid removal. The predominant mechanisms of the tested organic acid removal process were complexation phenomena or ligand exchange with soluble or insoluble aluminum species. Demonstration of the stoichiometry of the reactions showed that the relationships linking the dosage of the coagulant to the initial concentration of humic acid essentially depended on the pH and the salinity of the different waters tested.‎


Humic acid, Coagulation-flocculation, pH, Salinity, Mechanisms, Stoichiometry

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