We studied the electrochemical oxidation, on Pt anodes, of industrial wastewaters containing 5-amino-6-methyl-2-benzimidazolone (AMBI). Electrolysis of this non-biodegradable effluent produces simultaneous oxidation of AMBI and chloride ions. Highly oxidative chlorine intermediate species further boost the degradation of AMBI. Solution temperature, pH and current density affect little the degradation of AMBI. At our best conditions, AMBI was 100% degraded in 45 min. However, because the reaction intermediates exhibited high toxicity and non-biodegradability, the electrolysis had to continue for 3 more hours in order to obtain a biocompatible solution. Then, complete mineralization of the outputs from the electrolytic cells was readily achieved in a fixed bed biological reactor.