The purpose of this study was to investigate the disinfection efficiencies for total coliform and total bacteria by ozone, UV, electron beam and gamma ray and to evaluate an alternative of the disinfection of water and wastewater. The disinfection efficiencies by the electron beam and gamma ray were 99.8% at a dose of 0.2 kGy and revealed much better efficiencies than UV and ozone. At a 90% of the disinfection efficiency, the electric powers consumed during the experiments 1.8 wh/(L/day) by ozone, 7 wh/(L/day) by UV and 4.8X 10³ wh/(L/day) by E-beam respectively. The electron beam was found to be more economical than the ozone and UV.