Killing bacteria present on surfaces in films or in droplets using microwave UV lamps

The killing of bacteria on surfaces by two typesof UV sources generated by microwave radiation isdescribed. In both cases, UV radiation is produced by gasdischargeelectrodeless lamps (Ar/Hg) excited by microwavesgenerated by a power supply from a standarddomestic microwave oven. For UV lamp excitation, one ofthese sources makes use of a coaxial line with a truncatedouter electrode that allows the excitation of gases andgaseous mixtures over a wide range of pressures at acomparatively low microwave power. In the second source,UV lamps are placed inside a microwave oven. Ultravioletgenerated by the two sources was used to destroy vegetativeEscherichia coli bacteria dispersed in thin films and indroplets on surfaces. Two types of UV lamps were used inthe study. The first was constructed of quartz that filteredUV below 200 nm preventing the dissociation of oxygen inair and, hence, ozone production. The second type of tubewas transparent to UV below 200 nm facilitating ozoneproduction in air surrounding it. It was shown that bacterialcells dispersed in films on surfaces are killed more rapidlythan cells present in droplets when using the lamps producingozone and UV radiation. The UV sources describedcan effect rapid killing and constitute a cost-effectivetreatment of food and other surfaces, and, the destruction ofairborne viruses and bacteria. The lamps can also be utilisedfor the rapid eradication of microorganisms in liquid