Abstract: The present invention relates to a method for treating opaque fluids, comprising the steps of placing a treatment unit inside a volume of fluid to be treated, which treatment unit comprises a UV radiation member capable of emitting UV radiation, 5 radiating said volume of fluid with UV radiation, whereby said UV radiation is capable of creating radicals in said fluid, which radicals react with matter in the fluid, thereby treating it.

Abstract: An arrangement for use in a liquid treatment unit, which includes a generally tubular housing having a liquid inlet in one end and a liquid outlet in the opposite end, a generally tubular filter element arranged generally concentric inside the housing, through which liquid is fed from outside the filter to inside the filter, an elongated UV-generating element arranged inside the filter element, whose longitudinal direction generally corresponds to that of the filter element, material displaying catalytic properties and radiated by UV-light arranged on at least the inner surfaces of the filter element. The elongated UV-generating element extends a further distance than the generally tubular filter element, which extension is positioned adjacent the outlet, wherein the further distance ensures the flow of liquid, that has passed through the filter element, to flow a certain minimum distance along the elongated UV-generating element, thereby exposing the flow of liquid to UV-light.