1. Field of Invention
This invention relates to fluid treatment apparatus and more particularly, but not solely, to an apparatus for treating drinking water.
2. Description of the Prior Art
Drinking water may be contaminated with foreign matter such as parasites, bacteria, viruses, worms, protozoa, moulds and mould spores, which can be particularly harmful to human beings if ingested. Such foreign matter is often extremely difficult to treat by conventional means, especially if they are resistant to chlorine and other biocides. However some types of foreign matter are susceptible to extremely high doses of ultra-violet radiation.
Conventional ultra-violet fluid treatment apparatus, such as the one disclosed in GB 2175779, comprise an elongate tubular chamber having an axially extending ultra-violet light source. The dose of radiation supplied by the apparatus is equal to the product of the radiation intensity of the light source and the retention time of the fluid inside the chamber. A high fluid flow rate is needed, but it is impractical to increase substantially the radiation intensity of the light.