Abstract
Water contamination with the enteroprotozoan parasite Cryptosporidium is a current challenge worldwide. Solar water disinfection (SODIS) has been proved as a potential alternative for its inactivation, especially at household level in low-income environments. This work presents the first comprehensive kinetic model for the inactivation of Cryptosporidium parvum oocysts by sunlight that, based on the mechanism of the process, is able to describe not only the individual thermal and spectral actions but also their synergy. Model predictions are capable of estimating the required solar exposure to achieve the desired level of disinfection under variable solar spectral irradiance and environmental temperature conditions for different locations worldwide. The thermal contribution can be successfully described by a modified Arrhenius equation while photoinactivation is based on a series-event mechanistic model. The wavelength-dependent spectral effect is modeled by means of the estimation of the C. parvum extinction coefficients and the determination of the quantum yield of the inactivation process. Model predictions show a 3.7% error with respect to experimental results carried out under a wide range of temperature (30 to 45 °C) and UV irradiance (0 to 50 W·m−2). Furthermore, the model was validated in three scenarios in which the spectral distribution radiation was modified using different plastic materials common in SODIS devices, ensuring accurate forecasting of inactivation rates for real conditions.
Highlights
Water contamination with the enteropathogen Cryptosporidium is a universal challenge (Efstratiou et al, 2017; Hamilton et al, 2018; Hofstra and Vermeulen, 2016; Karanis et al, 2007)
The experimental results were fitted to a firstorder kinetic model (Eq (1)), and the values of the kinetic constant were used to calculate the provisional values of the thermal kinetic parameters
The use of quantum yields reported in the literature should be carefully selected and the calculation for each specific device is always recommended
Summary
Water contamination with the enteropathogen Cryptosporidium is a universal challenge (Efstratiou et al, 2017; Hamilton et al, 2018; Hofstra and Vermeulen, 2016; Karanis et al, 2007). Based on WHO reports (WHO, 2015), there were approximately 64 million of estimated cases of illness caused by Cryptosporidium and 35% of them were related to contact with contaminated water sources. Prevalence rates range from 0.3 to 54.2%, mainly related to recreational or drinking water (Abeywardena et al, 2015), and reported because of the existence of surveillance systems for routine detection of Cryptosporidium (Cacciò and Putignani, 2014). The prevalence is assumed to be higher in developing countries (Putignani and Menichella, 2010) In these regions, Cryptosporidium is one of the top three pathogens causing diarrheal disease in children under two years old, and it is responsible for 30–50% of childhood mortality (Kotloff et al, 2013) estimated in 455,000 deaths in Sub-Saharan region (Sow et al, 2016)
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