What means "dose" in UV-disinfection with medium pressure lamps?

The "dose" in UV-disinfection plants for water, which are equipped with (ne arly monochromatic) low pressure mercury lamps is already well defined as R eduction Equivalent Fluence (REF). For plants with medium pressure mercury lamps, which emit polychromatic UV-radiation, several definitions of "dose" are possible. We measured the spectral sensitivity of spores of Bacillus s ubtilis ATCC 6633 and compared results gained by calculations using these s pectral functions with results from irradiation with a medium pressure lamp . The measurements and calculations showed good agreement.