In this work, the removal of orthophosphate from synthetic wastewaters is studied by the electrocoagulation (EC) process using respectively aluminum and iron electrodes connected in monopolar configuration. The effects of current intensity, initial phosphate concentration, initial solution pH, treatment time and electrode type were investigated by experimental design methodology (EDM). The factorial design (FD) used in the first time shows that the current intensity and the electrolysis time have a positive effect on the orthophosphate removal rate while the pH and the initial concentration have a negative effect on it. Using Aluminum electrode, phosphate removal rate were higher than those recorded with iron electrode. A central composite design (CCD) was then used to optimize the removal rate while minimizing the mass of sludge produced. The optimal conditions obtained are the following: for aluminum electrodes (intensity 1.09A, concentration 48.55 mg / L, pH 4 and time 59.19 min) and for iron electrodes (Intensity 0.85A, concentration 26.8 mg/L, pH 3 and time 47.48 min). Under these conditions, 99.33% (48.21 mg/L) of phosphate was removed by using aluminum electrode with metallic residues of 2.1 g. By comparison, 80.74% (21.63 mg/L) of phosphate was removed using iron electrode with metallic sludge residues generated of 1.01 g. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.