(a) An ultraviolet light (UV) system must be sized based upon the results of an independent bioassay that meets the following minimum criteria.(1) The lamp and ballast in a bioassay test system must have the same spectral characteristics and 254 nanometers (nm) wavelength output as the full-scale system.(2) Spacing of the lamps in a bioassay test unit must be the same as in the full-scale system.(3) The arrangement of the lamps must mirror the full-scale system.(4) The maximum scale-up factor is 10.(5) Scale down is prohibited.(6) The minimum number of lamps in a bioassay is four lamps per reactor.(b) If a variable output lamp is used, detailed documentation from the lamp manufacturer must be provided to document 254 nm ultraviolet output, operational wattage versus lamp input power (voltage and current), along with data demonstrating power requirements to the lamp and ballast to achieve the stated output.