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 TiO2 and 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.