We propose a simple estimation method of the effective irradiance of UV-LED light for the inactivation of bacteria suspended in an aqueous solution. Time courses of the survival ratio of Staphylococcus aureus depended on the turbidity of the suspension. Therefore, the effective irradiance value was calculated by averaging the integrated light transmitted value of the solution from the surface to the bottom of the solution layer based on the apparent absorption. As the results, fitting parameters of a multi-target model for the fluence-response curves were in good agreement even if the turbidity of the target solution is significantly different. In addition, the parameters may be one of the useful indexes for the evaluation of the effect on microbial inactivation.

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