A chemical-free and no-microbe method for pre-treating a broad range of waste waters is presented. The said method involves electrocoagulation (EC) operated in synchronization with electrolytic ozone (EO3). In the combinatory method, each technique not only applies its own treatments, they also create synergistic effects from real-time reactions among the reagents generated by electrolysis. Two refractory waste waters, seawater and tannery effluent, are tested by the combinatory method, EC+EO3, to assess the viability of the said method. Without adjustment, each of the said waste waters is remedied by EC+EO3 from its raw state to a clean condition more effectively and more economically than that can be delivered by the respective prevailing processes of pretreatment for each of the said waste waters.