The present study aimed the characterization of the fouling formed on anion-exchange membrane during electrodialysis treatment of model salt solutions at different Mg/Ca ratio (0, 1/20, 1/10, 115 and 2/5). The membrane fouling was characterized by membrane parameters (membrane thickness and electrical conductivity) and identified by membrane surface analysis (elemental analysis and X-ray diffraction). The mineral deposit was identified as Ca(OH)(2) when no magnesium was present in the model salt. As soon as magnesium was present in the model salt solution for neutral pH(concentrate) conditions a mix between CaCO3 and Ca(OH)(2) was formed. This study is the first one to report the influence of magnesium in solution on the formation of CaCO3 fouling at the interface of anion-exchange membrane during electrodialysis. (c) 2008 Elsevier Inc. All rights reserved.