Ultraviolet irradiation of fluids for the purposes of disinfection, sterilization and modification of a target organic compound found within the fluids. The target compound in the fluids can have an absorption spectra with an ultraviolet wavelength ranging from 230 nm to 360 nm. The absorption spectra includes a first and second set of wavelengths corresponding to absorption peaks and absorption valleys in the absorption spectra, respectively. A-set of ultraviolet radiation sources irradiate the fluids. The set of ultraviolet radiation sources operate at a set of peak wavelengths ranging from 230 nm to 360 nm with a peak full width at half maximum that is less than 20 nm. The set of peak wavelengths are proximate to at least one wavelength in the second set of wavelengths corresponding to the absorption valleys in the absorption spectra with a variation of a full width half maximum of the absorption valley.