Disinfection reactions are always altered when real water is compared to distilled water. The impact on disinfection in the case of the H2O2 and solar treatment could be expected to be mainly due to the ion charges, pH and turbidity of the water. Experiments with local well water were the closest approach to solar H2O2-enhanced disinfection in local greenhouses. Therefore, water with the physicochemical characteristics in Table 1 was used in bottle reactor experiments. The bottle reactors in Fig. 5 were exposed to sunlight with initial H2O2 concentrations of 0, 5, 10 and 50 mg/L. The temperature was from 25 to 39.3 °C, constantly increasing throughout the experiment. The control bottles stirred in darkness at similar temperatures did not show any Fusarium inactivation which excludes the possibility that fungal spore inactivation was due to heating. The average UV irradiance on this winter day was 22 W/m2. The fungal concentration decreased in the blank experiment 0.4 log. With the addition of 5 mg/L H2O2, fungal spore reduction was 0.8 log and with 10 mg/L H2O2 the spore concentration reached the detection limit (3 log-reduction). In this case, the blank experiment for solar-only disinfection was apparently less affected than the H2O2 and sunlight disinfection experiment, probably due to well water properties. In the distilled water experiment in Fig. 3, with an average UV irradiance of 30.4 W/m2, the reduction of the blank was 0.7 log compared to the 0.4 log reduction in well water with 22 W/m2. The lower irradiance cannot be expected to affect fungal viability linearly ( Sichel et al., 2007c), but provides a reasonable explanation for less inactivation in well water. In the hydrogen peroxide experiments at H2O2 concentrations of 5 mg/L, fungal CFU-reduction in well water was only 0.8 log, whereas in distilled water, the detection limit (2.7 log decrease) was already reached at that concentration. Additional measurements in the experiments of Fig. 3 and Fig. 5 with Merck-test strips showed on the one hand that a) in all reactions, even the 5 mg/L reaction H2O2 remained detectable until the end of the reaction and that in the blank experiments no detectable H2O2 was generated by the fungi or the water matrix.