Azo dye wastewater treatment was enhanced in an acidogenic reactor (A1) by Fe-0 dosing. Both COD (50%) and color (60%) removal in A1 were stable when the dye concentrations were increased from 200 to 800 mg/L. However, the performances of a Fe-0-free control reactor (A2) showed low COD (34%) and color (32%) removals. The reason was attributed that Fe-0 dosing enhanced the activity of fermentative bacteria, which played an important role in acidogenesis and decolorization. The methanogenic reactor fed with the effluent of A1 exhibited higher removal efficiency and treatment stability. These results suggested that Fe-0 powder dosing was helpful to improve acidogenesis and decolorization to create a favorable feeding condition for the subsequent methanogenic treatment. (C) 2012 Elsevier Ltd. All rights reserved.