A fluid treatment apparatus comprises a plurality of elongate UV lamps 13 mounted in a duct 10 and a cleaning assembly 14 comprising a plurality of cleaning heads 20 which are rotated around respective lamps and are simultaneously driven longitudinally thereof to clean the lamps 13 and the internal surface of the duct 10. The cleaning heads 14 each comprise a plurality of portions 28 of titanium dioxide which are biased against the surface of the respective lamps 13 and which produce hydroxyls and oxygen free radicals in the presence of water and oxygen. Hydroxyls and oxygen free radicals are highly reactive and will break down the cells and molecules of the accumulated material on the lamps.