Conventional processes of water disinfection can generate toxic composites. It is the case of the trihalomethanes (carcinogenic) formed in the contact of chlorine with organic substances present in the water. The electrolytic treatment can be a substitute for the chlorination process without the need for addition of chemical substances to the process. The effect of the electrolytic treatment using carbon cathode on the viability of the microorganism Bacillus subtilis was tested to determine the death process. By means of electronic microscopy, it was observed that the main cause of the microorganism's death was the cellular lysis due to the electroporation in the cell membrane.