There is provided a treatment device for disinfecting a fluid being configured as a conduit for conveying a flow of fluid to be treated, said device being toroidal-shaped with an inner concave parabolic surface, wherein the device is provided with apertures extending from the outer to the inner surface of the toroidal-shaped device; one or more UV LED(s) provided in the apertures thereby enabling emitted light to be transmitted through the apertures into the interior part of the device for disinfecting said fluid; a power source for powering the UV LEDs, wherein the inner surface is made from a light reflecting material, and the apertures are sealed in the ends extending into the interior part of the device by a UV-transparent material.