Evaluation of a concrete cascade solar still

Efficacy of a solar still in destroying virus and indicator bacteria in water for human consumption

“…Thus, in cases where contamination of distilled water was found, it is important to know at what hour of the day these contaminations occurred, or, in cases where the determination of coliform was made in one single daily sample, what was the operating time schedule of the equipment. However, the authors reporting contamination do not present this data (Balladin et al, 1999;Hanson et al, 2004).…”

“…Other studies report the removal of 100% of total and fecal coliform; however, this did not occur in all samples tested by the authors. Balladin et al (1999) found contamination by total coliform bacteria in all their treated water samples and claimed that this was probably due to airborne bacteria. Hanson et al (2004) found contamination in 8% of their treated samples, in this case by fecal coliforms, and claimed that this may have occurred due to the formation of turbulence at the time of adding the raw water to the equipment, which caused tiny bubbles to project contaminated water onto the internal surface of the cover.…”

Vapor-induced transfer of bacteria in the absence of mechanical disturbances

“…However, these studies, as well as the present study, only tested inactivation under favorable sunny weather conditions. Differences in weather conditions, along with other factors like variations in latitude and season, could explain why some studies reported less than complete bacterial inactivation [16,17,20] while others reported total bacterial elimination under sunlight.…”

“…resulting from these stills. In this context, contradictory results have been shown to exist in that some studies indicated that the distillate produced by a solar still was totally disinfected and fit for direct consumption [10][11][12][13][14][15] while others have reported bacteriological contamination to exist in the distillate [16][17][18][19][20]. Some of these studies have attributed contamination to the possibility that salinity and growth of algae and other micro-flora in the water to have affected the disinfection process in solar stills and sheltered microbial contaminants from UV radiation [18].…”

“…Others have hypothesized that bubbles, created by the turbulence of adding water to the basin, could have burst and formed droplets on the glass cover which contaminated the distillate [17]. Balladin et al attributed their distillate bacterial findings to airborne microorganism contamination and low chloride concentration [16]; Malaeb on the other hand suspected cross contamination [19]. These inconsistent results deem to shed doubts as to the health safety of distillates resulting from solar stills.…”