This invention is directed to a method system and apparatus (10) for the treatment fluids. An apparatus (10) for the treatment of a fluid comprises a fluid chamber (16) and at least one ultraviolet light unit (12 13) arranged at a periphery of the fluid chamber (16). The at least one ultraviolet light unit (12 13) comprises at least one ultraviolet light emitting diode (13) and an ultraviolet light directing element (12). The ultraviolet light directing element (12) is configured to collimate at least a portion of the light emitted from the at least one ultraviolet light emitting diode (13) in use such that the ultraviolet light rays emitted from each ultraviolet light unit (12 13) are parallel in a first plane. Also described is a method for the cooling a light emitting diode in a fluid treatment system.
