Thermal Contribution to the Inactivation of Cryptosporidium in Plastic Bottles during Solar Water Disinfection Procedures

Abstract

Abstract. To determine the thermal contribution, independent of ultraviolet radiation, on the inactivation of Cryptosporidium parvum during solar water disinfection procedures (SODIS), oocysts were exposed for 4, 8, and 12 hours to temperatures recorded in polyethylene terephthalate bottles in previous SODIS studies carried out under field conditions. Inclusion/exclusion of the fluorogenic vital dye propidium iodide, spontaneous excystation, and infectivity studies were used to determine the inactivation of oocysts. There was a significant increase in the percentage of oocysts that took up propidium iodide and in the number of oocysts that excysted spontaneously. There was also a significant decrease in the intensity of infection elicited in suckling mice at the end of all exposure times. The results of the study demonstrate the importance of temperature in the inactivation of C. parvum oocysts during application of SODIS under natural conditions.

Solar water disinfection (SODIS): A review from bench-top to roof-top

“…In contrast, cysts of Giardia muris (acting as surrogate for G. lamblia) were rendered completely non-infective (<0.2% infectivity, 95% CI 0.0-7%) after only 4 h exposure when subjected to SODIS conditions of 40 • C water temperature and 870 W m −2 irradiance [72]. Ares-Mazas and co-workers have also demonstrated a similarly important effect of temperature on the inactivation of C. parvum oocysts during SODIS procedures, independent of UV radiation [73,74]. …”

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

“…Dye permeability and in vitro excystation were found to underestimate oocyst inactivation compared to animal infectivity tests (Swiss CD-1 suckling mice). 177 Another challenge is different sources of oocysts; because oocysts cannot be propagated in vitro, propagation through animals such as calves and mice is required. Also oocysts for experiments are usually puried from feces of infected animals; however, puried oocysts have been shown to lose infectivity within 24 weeks during storage at 4 C in autoclaved water.…”

Wastewater reuse in agriculture and health risk in Vietnam

“…As water is exposed to sunlight, its temperature increases and microorganisms can be thermally inactivated (See section on heat inactivation). There are some synergetic effects between optical and thermal effects of solar water treatment (Šolić and Krstulović 1992;Wegelin et al, 1994;McGuigan et al, 1998;Berney et al, 2006;Gómez-Couso et al, 2010;Theitler et al, 2012;Giannakis et al, 2014;Carratalà et al, 2015). Most methods of improving the efficiency of sunlight-based water treatment involve maximizing or concentrating sunlight interaction with water (Saitoh and El-Ghetany, 2002;Rijal and Fujioka, 2004;Mani et al, 2006), increasing temperature of the water (Sommer et al, 1997;Rijal and Fujioka, 2001;Rijal and Fujioka, 2004;Martín-Domínguez et al, 2005), or augmenting the concentration of sensitizers in solution by adding photoinducers, photocatalysts, or oxygenating the liquid matrix (Heaselgrave et al, 2006;Fisher et al, 2008;Harding and Schwab, 2012).…”