An apparatus for decontaminating water in an ice machine or a beverage-dispensing machine comprising an ultraviolet radiation source, an ozone source and a controller. As potable water enters the apparatus via a conduit, the potable water is decontaminated by an ultraviolet (UV) light source, which irradiates the potable water, and by an ozone generation system that provides ozone to be injected into the potable water to oxidize contaminants. Because water is often circulated within ice machines, the circulating water conduits and reservoir are also treated with ozone and UV radiation. The present invention also provides a controller for optimizing the decontamination process by providing UV light and ozone production only when required for decontamination. Typically, ozone generation and UV radiation are required whenever makeup potable water is brought into the apparatus or when the refrigeration compressor is running.