A new bioassay technique for ultraviolet (UV) disinfection is presente
d which permits application to full-scale systems. The technique invol
ves comparison of batch dose-response behavior and full-scale, continu
ous-flow disinfection efficacy using indigenous indicator organisms pr
esent in secondary or tertiary wastewater effluent. This approach allo
ws the bioassay to be applied to UV systems of all sizes, thereby elim
inating the need for extrapolation of pilot-scale bioassays to full-sc
ale systems. By comparing the results of the bioassay with dose estima
tes from numerical modelling, a semi-quantitative assessment of full-s
cale system hydrodynamic efficiency is developed relative to two ideal
ized reactor models. This approach has merit in terms of evaluating fu
ll-scale disinfection system design and identification of hydrodynamic
shortcomings.