Final step is to treat water with a disinfectants chlorine gas or ozone 400 people die every hour from diseases caused by drinking contaminated water Impure or contaminated water In UV light sources Portabl water out Water flow Figure 16.8 Small-scale water disinfecting units, such as the one shown here, hold great value in regions of the world where potable water is scarceFinal step is to treat water with a disinfectants, chlorine gas or ozone. 400 people die every hour from diseases caused by drinking contaminated water