Electrochemical disinfection is quite attractive as a promising alternative technology to chlorination. It is still debated whether conventional electrochemical disinfection, which electrolyzes the solution with very high chloride concentration to produce excess amounts of chlorine species, will generate toxic disinfection byproducts (DBPs) and have the same health risks as chlorination. To resolve this critical issue, we explored the possibility of electrochemical disinfection based on electrogenerated free radicals but not on active chlorine. The germicidal efficiency of 99.99% was achieved with a contact time of 5 min and current density of 7 mA cm.2 for a chloride-free model wastewater contaminated by coliforms. Electron spin resonance detection clearly confirmed that hydroxyl radicals were the major germicidal species responsible for efficient electrochemical disinfection. This process would not generate poisonous DBPs due to the avoidance of dangerous chlorine species. pH in the range of 5-9 has little effect on the bacteria inactivation. Formation mechanism of hydroxyl radicals was discussed.