Photocatalytic inactivation of the waterborne protozoan parasite Cryptosporidium parvum using TiO₂/H₂O₂ under simulated and natural solar conditions

This is the first study that evaluates the efficacy of the photocatalytic disinfection against the waterborne protozoan parasite Cryptosporidium using a combination of TiO₂ and H₂O₂ under simulated and natural solar conditions. Samples of distilled water containing 100 mg/L of TiO₂ and/or 50 mg/L of H₂O₂ were spiked with purified Cryptosporidium parvum oocysts and exposed to solar radiation for 5 h. The oocyst global viability was determined by inclusion/exclusion of the fluorogenic vital dye propidium iodide. A strong decrease in the oocyst global viability was observed in samples containing TiO₂ and TiO₂/H₂O₂ under simulated solar conditions (4.16 ± 2.35% and 3.82 ± 4.26%, respectively, vs 90.44 ± 5.87%, initial global viability). Similarly, a drastic reduction in the oocyst global viability was observed under real sunlight (2.29 ± 1.99% and 0.92 ± 0.71% in samples containing  TiO₂and  TiO₂/H₂O₂ , respectively, vs 99.45 ± 0.95%, initial global viability). These results prove the efficacy of the  TiO₂ photocatalytic disinfection against C. parvum, decreasing the time needed to reach the oocyst inactivation in comparison with exclusive solar disinfection. However, the addition of H₂O₂  at low concentrations (50 mg/L) did not enhance the TiO₂  photocatalytic process against Cryptosporidium.