CHEMICALS most commonly used as PRIMARY disinfectants are chlorine, chlorine dioxide, and ozone. Monochloramine usually referred to as chloramine, is used as a residual disinfectant for DISTRIBUTION.Properties of a good disinfectant:It should be persistent enough to prevent the regrowth of organisms in the distribution system so that the water will be safe from future recontamination.It must be toxic to micro-organisms at concentrations well below the toxic thresholds of humans and higher animals so that it cannot negatively AFFECT the animals or humans.It should have a FAST rate of kill of micro-organisms.It should be active and stable and environmentally safe.It should not leave damage and odour.