Speeding up the solar water disinfection process (SODIS) against Cryptosporidium parvum by using 2.5 l static solar reactors fitted with compound parabolic concentrators (CPCs)

Abstract

Water samples of 0, 5, and 100 nephelometric turbidity units (NTU) spiked with Cryptosporidium parvum oocysts were exposed to natural sunlight in 2.5l static borosilicate solar reactors fitted with two different compound parabolic concentrators (CPCs), CPC1 and CPC1.89, with concentration factors of the solar radiation of 1 and 1.89, respectively. The global oocyst viability was calculated by the evaluation of the inclusion/exclusion of the fluorogenic vital dye propidium iodide and the spontaneous excystation. Thus, the initial global oocyst viability of the C. parvum isolate used was 95.3±1.6%. Using the solar reactors fitted with CPC1, the global viability of oocysts after 12h of exposure was zero in the most turbid water samples (100NTU) and almost zero in the other water samples (0.3±0.0% for 0NTU and 0.5±0.2% for 5NTU). Employing the solar reactors fitted with CPC1.89, after 10h exposure, the global oocyst viability was zero in the non-turbid water samples (0NTU), and it was almost zero in the 5NTU water samples after 8h of exposure (0.5±0.5%). In the most turbid water samples (100NTU), the global viability was 1.9±0.6% after 10 and 12h of exposure. In conclusion, the use of these 2.5l static solar reactors fitted with CPCs significantly improved the efficacy of the SODIS technique as these systems shorten the exposure times to solar radiation, and also minimize the negative effects of turbidity. This technology therefore represents a good alternative method for improving the microbiological quality of household drinking water in developing countries.