Edinburgh Napier University

  The killing of bacteria on surfaces by two types
of UV sources generated by microwave radiation is
described. In both cases, UV radiation is produced by gasdischarge
electrodeless lamps (Ar/Hg) excited by microwaves
generated by a power supply from a standard
domestic microwave oven. For UV lamp excitation, one of
these sources makes use of a coaxial line with a truncated
outer electrode that allows the excitation of gases and
gaseous mixtures over a wide range of pressures at a
comparatively low microwave power. In the second source,
UV lamps are placed inside a microwave oven. Ultraviolet
generated by the two sources was used to destroy vegetative
Escherichia coli bacteria dispersed in thin films and in
droplets on surfaces. Two types of UV lamps were used in
the study. The first was constructed of quartz that filtered
UV below 200 nm preventing the dissociation of oxygen in
air and, hence, ozone production. The second type of tube
was transparent to UV below 200 nm facilitating ozone
production in air surrounding it. It was shown that bacterial
cells dispersed in films on surfaces are killed more rapidly
than cells present in droplets when using the lamps producing
ozone and UV radiation. The UV sources described
can effect rapid killing and constitute a cost-effective
treatment of food and other surfaces, and, the destruction of
airborne viruses and bacteria. The lamps can also be utilised
for the rapid eradication of microorganisms in liquids