Addition of Hydrogen Peroxide to Groundwater with Natural Iron Induces Water Disinfection by Photo-Fenton at Circumneutral pH and other Photochemical Events.

Samples of natural groundwater (with low turbidity, neutral pH and 0.3 mg L iron concentration) inoculated with Escherichia coli K-12 were exposed to simulated solar light both in the presence and in the absence 10 mg L of H O Results demonstrated that the viability of E. coli (by DVC-FISH) was grounded to zero after 360 min of irradiation. This abatement could be caused by the oxidative stress induced by ·OH radicals or another photo-induced reactive oxygen species. Two 2 factorial experimental designs enabled the evaluation of the effects of chemical factors on the inactivation of E. coli. The first experimental design considered the pH, iron and H O , while the second evaluated the ions fluoride, carbonate and phosphate found in groundwater. pH was found to play a key role in the inactivation of E. coli. The best reduction in viability was obtained at the lower pH (6.75), while a nonsignificant effect was observed when iron or H O concentrations were raised. At higher concentrations, anions, such as carbonate and phosphate, negatively affected the E. coli abatement. However, a higher concentration of fluoride accelerated it. In all experiments, the pH was observed to rise to values higher than 8.0 units after 360 min of treatment.