"Cryptosporidium" en la desinfección solar del agua de bebida

Abstract

Using a 2×3 first-order full factorial design and under simulated solar radiation and a constant temperature of 30 °C, the influence that the water turbidity (5, 100, and 300 nephelometric turbidity units NTU), the intensity of radiation (200, 600, and 900 W/m2 of global radiation, equivalent to the intensity of solar radiation in equatorial areas described for total and partly cloudy and sunny days, respectively) and exposure time (4, 8, and 12 hours) have on the survival of C. parvum oocysts during solar disinfection processes of drinking water was evaluated. Using the technique of inclusion/exclusion of the fluorogenic vital dye propidium iodide (PI), it was observed that the potential viability of oocysts ranged from a minimum of 54.0% (5 NTU, 900 W/m2, and 12 hours) and a maximum of 91.7% (200 W/m2, 4 hours, regardless of the level of turbidity). Similarly, it was found that the lowest value of oocyst infectivity (30.8%) was obtained for conditions of 5 NTU of turbidity, 900 W/m2 of radiation and 12 hours of exposure time. It was shown that the three parameters, as well as the interactions intensity of radiation-exposure time and turbidity level-intensity of radiation are statistically significant factors that affect to the potential viability and infectivity of C. parvum oocysts. The empirical equations obtained with the different evaluated parameters showed that the largest coefficient with a negative sign corresponded to the intensity of radiation. Thus, it was observed that, independently of exposure time and the turbidity level, the lowest intensity of radiation evaluated (200 W/m2) did not exert statistical significant influence on oocyst survival. By contrast, the percentage of negative PI oocysts (potentially viable) and infectivity determined in the suckling mouse model tend to decrease when water samples were exposed to a radiation level 600 W/m2. At the highest intensity of radiation (900 W/m2) evaluated, statistically significant reductions in the potential oocyst viability and infectivity for both turbidity levels and for different exposure times tested were observed. The obtained equations are valid for predicting the potential viability and infectivity of oocysts of C. parvum in the range of tested conditions.