The upscaled experiment with well water in CPC reactors was the closest to real disinfection conditions in local greenhouses. Both solar-only and solar H2O2 combined disinfection were less effective under low irradiance. Nevertheless, in the 14-L CPC solar reactor experiment with natural well water, strongly enhanced disinfection was still achieved with the synergic solar H2O2 treatment (Fig. 6). Solar irradiance of 17.1 W/m2 reduced the fungal concentration in the blank solar disinfection experiment 0.4 log compared to a 0.8 log reduction in the distilled water CPC blank experiment (Irradiance = 23 W/m2). In the experiment with 50 mg/L H2O2, Fusarium concentrations were reduced 1.5 logs, from 0.3 × 103 CFU/mL to almost the detection limit, noticeably less than the total reduction in the distilled water experiment (2.6 logs). H2O2 consumption was also significantly reduced (8.5 mg/L) during the reaction from 51.5 mg/L to 43 mg/L. The dark H2O2 consumption was 1.3 mg/L over the experiment.