Addition of hydrogen peroxide to natural ferruginous water improves the efficacy of SODIS method against the waterborne pathogen Cryptosporidium

The enhancement of SODIS method against the waterborne pathogen Cryptosporidium by incorporating H₂O₂ in natural ferruginous water (NFW) was evaluated. Polyethylene terephthalate bottles containing distilled water or different NFW with added different concentrations of H₂O₂ (0–100 mg L⁻¹) were spiked with Cryptosporidium parvum oocysts and exposed to simulated and natural solar radiation. Oocyst viability was evaluated by induced excystation and inclusion/exclusion of the vital dye propidium iodide (PI). The experiments performed under sunlight showed better C. parvum inactivation rates than those under simulated solar radiation. Oocyst viability rates of 2.26±1.91% and 16.52±3.83% were determined by induced excystation and inclusion/exclusion of PI, respectively, after exposure to natural sunlight during 6 h in NFW with 100 mg L⁻¹ of H₂O₂. This study proves the enhancement in the effectiveness of conventional SODIS by the addition of H₂O₂ to natural ferruginous waters, speeding up the C. parvum oocyst inactivation. Since surface waters in countries where the SODIS method can be used often contain dissolved iron salts, the addition of small amounts of H₂O₂ will increase the microbiological quality of drinking waters and consequently would decrease the risk of diarrhoeal diseases in the population, having a positive impact in terms of development and poverty reduction.