TiO2-photocatalysis disinfection experiments were carried out with both E. coli in distilled water and natural water samples from the Cauca River (Cali, Colombia). The experiments performed with E. coli in distilled water showed no increase in cell concentration after the treated solution was left in the dark for 24 h. However, the experiments carried out with natural water samples showed drastic culturable cell concentration increase 24 h after stopping the irradiation. This shows the lack of residual effect of TiO2-photocatalysis.