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

Abstract

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 C. parvum 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.