Inactivation of the waterborne pathogen Cryptosporidium parvum by photo-Fenton process under natural solar conditions

Cryptosporidium is an important genus of emerging enteropathogens responsible for waterborne outbreaks worldwide. This parasite has a robust infective form (oocyst), which is highly resistant to the environmental conditions and to the conventional disinfection treatments of water. This work evaluates for the first time the photo-Fenton process against Cryptosporidium parvum. For that, a factorial design was used to study the combined effects of the Fe²⁺/H₂O₂ concentration (5/10, 10/20 and 20/50 mg L⁻¹), pH (3, 5.5 and 8) and exposure time (2, 4 and 6 h) on the oocyst survival in distilled water under natural sunlight. The oocyst viability was determined by inclusion/exclusion of the fluorogenic vital dye propidium iodide. The variables Fe²⁺/H₂O₂ concentration and exposure time showed statistically significant effects on the oocyst viability, as did the interaction of pH with Fe²⁺/H₂O₂ concentration. The maximum oocyst inactivation rates corresponded to the combination of the highest concentration of Fe²⁺/H₂O₂ (20/50 mg L⁻¹), the lowest pH value (3) and longest exposure times (4 and 6 h) (3.68 ± 1.38% and 6.39 ± 2.65%, respectively, vs 91.67 ± 3.63%, initial oocyst viability). Although further studies are needed to evaluate the influence of the water matrix and optimize the photo-Fenton process, the results obtained demonstrate the efficacy of this advanced oxidation process against E oocysts. The inactivation of this enteropathogen would probably ensure elimination of other less resistant infectious agents, providing an appropriate protection for the environment and, consequently, for human and animal health.