An apparatus for the treatment of a liquid that includes a chamber having at least one inner surface, the chamber adapted for passage of a fluid therethrough. The chamber is at least 80 percent enclosed. The apparatus also includes an optional ultraviolet-transmissive tube disposed within the chamber and also adapted for the passage of the liquid therethrough. The apparatus further includes an ultraviolet lamp disposed within the chamber and, optionally, within the ultraviolet-transmissive tube. A reflective material is interposed between the chamber and the transmissive tube. The reflective material is adapted so as to reflect at least a portion of light emitted by the ultraviolet lamp, wherein the reflective material is at least 80 percent reflective.