This study brings out a disinfection process of bacteria Escherichia coli using a hydrodynamic cavitation method. The method used different contactors, orifice plate and venturi injector. The experiment result shows that an orifice plate with initial concentration of 104 CFU/mL has decreased into zero CFU/mL after 20 minutes, while venturi injector has decreased into zero CFU/mL after 30 minutes. The orifice plate gave a better, more effective and faster disinfection than the venturi injector.