An ultraviolet (UV) liquid disinfection system and method are described. The system includes a conduit to carry liquid to be disinfected, the conduit having an inlet to receive the liquid and an outlet to discharge the liquid; a UV source configured to illuminate the liquid within the conduit; a liquid salinity detector to measure a value indicative of the liquid salinity; and a controller coupled to the salinity detector and configured to receive from the liquid salinity detector the measured value and to determine a desired salinity-adjusted UV dose level based on the measured value and predetermined data correlating salinity levels to respective UV dose levels.