The effect of UV radiation on viral inactivation was modelled using linear regression analysis to predict the UV fluences necessaryto achieve 90 (D90, corresponding to1-log) to 99.99% (D99.99, cor-responding to 4-log) reductions. In addition, measured infectivity data were compared to estimated infectivity using the qPCR-based approach developed by Pecson et al. (2011). The mathematicalapproach used in these experiments has been applied to sev-eral other viruses (e.g., Human Adenovirus, JC Polyomavirus and MS2 bacteriophage) to calculate estimated inactivation, which hasshown a good correlation with actual results (Calgua et al., 2014).The formula applied to estimate the infectivity of HEV from qRT-PCR data was as follows:log(Nt/N0)infectivity = c * log(Nt/N0)qRT-PCR,where c is a measure of the lesion rate in the targeted genomeregion relative to the inactivation rate of the virus. Basically, by analysing experimentally derived measurements of infectivity andqRT-PCR decay, we can calculate the value c. Then, as long as thesame genome region is used, we can estimate infectivity from qRT-PCR data with this parameter in future experiments.To analyse the efficiency of the FCS preparations, the water sam-ples were measured pre- and post-treatment in duplicate for eachcondition and for each virus. Log Reduction Values (LRVs) werecalculated using the following formula:LRV = log(pre-treatment)-log(post-treatment).Statistical analysis were performed to compare LRV between methods by ANOVA. All analyses were performed using the R software program (version 3.0.2).