Duke University/University of North Carolina Study
"Impact of Chlorine and Monochloramine on Ultraviolet Light Disinfection"
"The absorption maximum of free-chlorine is somewhere around 290 nm which falls in the range of polychromatic UV light from medium-pressure UV lamp
output. The absorption maximum of monochloramine is approximately 246 nm, close to the low-pressure UV lamp output at 254 nm. Therefore, when decay
rates are based on delivered UV energy, monochromatic UV (254 nm irradiation) proves more effective than polychromatic UV light in the photochemical
degradation of monochloramine."
"Monochromatic UV light is more effective in degrading monochloramine, and polychromatic UV light is more
effective in degrading Free-Chlorine".