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ab s t r ac tThis study concerns electromagnetic treatment-doubled electrocoagulation of humic acid (HA) using response surface method and raw waters of two Dams (Ghrib and Boukerdene). This paper has two principal aims to achieve: firstly, enhance the efficiency of removal of HA by electrocoagulation (EC) adopting the following approach: EC in series using two electrocoagulators (BI-EC, doubled EC) and BI-EC assisted by electromagnetic (EM) field or in other words EM treatment (EMT) followed by EC in series (EMT-BIEC); secondly, substitute coagulation process (which is used in water treatment chain) with BI-EC or EMT-BIEC process in performing tests on raw waters (Boukerdene and Ghrib Dam's, Algeria) using different electrodes (Al, Fe and stainless steel). According to the obtained results, BI-EC and EMT-BIEC processes are globally efficient in HA removal and water treatment. Indeed, removal of microorganisms and reduction of turbidity, conductivity and organic matter (OM) suggest that these processes would be used on an industrial scale for drinking water treatment especially for EMT-BIEC process using Al electrodes. EMT contribution does not seem constantly efficient for these two raw waters especially for their OM removal. However, for HA solution, EMT alone achieve a medium reduction (52% at pH 3, 25% at 12 and 30% at 7) and behaves similarly to EC.

Laboratory experiments were carried out to investigate electrocoagulation (EC) of Ghrib Dam's water (Algeria) in batch using aluminium and iron electrodes without addition of chemicals, without pH modifi cation, and without agitation. The optimal conditions are an applied voltage of direct current of 8 V and a current density 74 A m −2 (0.35 A) during 45 min for both electrodes. The microbial pollution is completely removed by essentially electrical field whereas conductivity and turbidity are reduced at 27 and 85% respectively for Fe electrodes and 22 and 97% for Al electrodes by metallic cations. These results prove that water treatment by EC using Al electrodes (fl otation) for low turbid water (7 NTU) is more convenient than Fe electrodes (sedimentation) for both turbidity and organic matter removal. A new parameter to be taken in consideration for EC reactor design the ratio r active volume on reactor volume which is full of water is introduced where the active volume is the active surface multiplied by the distance between the electrodes.