Journal of Water Supply: Research and Technology—AQUA Vol 56 No 4 pp 245–256 © IWA Publishing 2007 doi:10.2166/aqua.2007.058

Effect of solar water disinfection (SODIS) on model microorganisms under improved and field SODIS conditions

Simon Dejung, Martin Wegelin, Ivan Fuentes, Gabriela Almanza, Ruth Jarro, Lizeth Navarro, Gina Arias, Evelin Urquieta, Abraham Torrico, Wilma Fenandez, Mercedes Iriarte, Christof Birrer and Werner A. Stahel

SODIS is a solar water disinfection process which works by exposing untreated water to the sun in plastic bottles. Field experiments were carried out in Cochabamba, Bolivia, to obtain standard UV-A (320–405 nm) dose values required to inactivate non-spore forming bacteria, spores of Bacillus subtilis, and wild type coliphages. Inactivation kinetics for non-spore forming bacteria are similar under SODIS conditions, exhibiting dose values ranging between 15 and 30 Wh m^-2 for 1 log₁₀ (90%) inactivation, 45 to 90 Wh m^-2 for 3 log₁₀ (99.9%), and 90 to 180 Wh m^-2 for 6 log₁₀ (99.9999%) inactivation. Pseudomonas aeruginosa was found to be the most resistant and Salmonella typhi, the most sensitive of the non-sporulating organisms studied here. Phages and spores serve as model organisms for viruses and parasite cysts. A UV-A dose of 85 to 210 Wh m^-2 accumulated during one to two days was enough to inactivate 1 log₁₀ (90%) of these strong biological structures. The process of SODIS depended mainly on the radiation dose [Wh m^-2] an organism was exposed to. An irradiation intensity exceeding some 12 Wm^-2 did not increase the inactivation constant. A synergistic effect of water temperatures below 50°C was not observed. Data plotting from various experiments on a single graph proved to be a reliable alternative method for analysis. Inactivation rates determined by this method were revealed to be within the same range as individual analysis.

Keywords: home-based; low-budget water purification method; solar water disinfection

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