Solar Disinfection of Water (SODIS)

Household water treatment (HWT) including solar water disinfection (SODIS) is being  promoted as a simple and low cost intervention to reduce waterborne diseases amongst poor communities in developing countries (1, 2).

The exposure of water-filled transparent plastic bottles to sunlight for approximately 6 hours (or for 2 consecutive days when the sky is cloudy) produces safe drinking water. A combination of UV-A rays and the temperature of the water inside the bottles kills or incapacitates waterborne pathogens that can cause diseases such as diarrhea (3). Any plastic bottle is suitable for this technique provided that the bottles are transparent, clean, and label is removed (3). Muddy or turbid water however requires filtration through a piece of cloth or other filtering material prior to solar treatment.

Evidence from laboratory based studies: 
Laboratory based studies have shown that SODIS has been effective against various pathogenic microorganisms including protozoan parasites (Cryptosporidium parvum, Giardia muris, Acanthamoeba polyphaga cysts), bacteria (E.coli, Salmonella typhimurium, Shigella flexneri, Vibrio cholera) and viruses (poliovirus) (4-6). Various combination of intensity of solar radiation, water turbidity and duration of exposure/ time are shown to be effective against microorganisms (5-9).

Evidence from Human Studies:
Community based studies also shows that significantly lower incidence in diarrhea occurs in SODIS users as compared to SODIS nonusers (10, 11).
It was therefore concluded that SODIS is an appropriate intervention for use in developing countries during diarrhea epidemics.

References:

1.            Sobsey MD, Tauber CES, Casanova LM, Brown JM, Elliott MA. Point of Use Household
Drinking Water Filtration: Ä Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World. Environmental science and technology 2008.

2.            Sobsey MD. Managing water in the home: accelerated health gains from improved water supply. World Health Organization. 2002.

3.            McGuigan KG, Joyce TM, Conroy RM. Solar disinfection: Use of sunlight to decontaminate drinking water in developing countries. Journal of Medical Microbiology. 1999;48(9):785.

4.            Heaselgrave W, Patel N, Kilvington S, Kehoe SC, McGuigan KG. Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water–a laboratory study using simulated sunlight. Letters in applied microbiology. 2006;43(2):125-30.

5.            Berney M, Weilenmann HU, Simonetti A, Egli T. Efficacy of solar disinfection of Escherichia coli, Shigella flexneri, Salmonella typhimurium and Vibrio cholerae. Journal of applied microbiology. 2006;101(4):828-36.

6.            Gómez-Couso H, Fontán-Sainz M, McGuigan KG, Ares-Mazás E. Effect of the radiation intensity, water turbidity and exposure time on the survival of Cryptosporidium during simulated solar disinfection of drinking water. Acta tropica. 2009.

7.            Ubomba-Jaswa E, Navntoft C, Polo-López MI, Fernandez-Ibáñez P, McGuigan KG. Solar disinfection of drinking water (SODIS): an investigation of the effect of UV-A dose on inactivation efficiency. Photochemical & Photobiological Sciences. 2009;8(5):587-95.

8.            Boyle M, Sichel C, Fernandez-Ibanez P, Arias-Quiroz GB, Iriarte-Puna M, Mercado A, et al. Bactericidal effect of solar water disinfection under real sunlight conditions. Applied and environmental microbiology. 2008;74(10):2997.

9.            McGuigan KG, Méndez-Hermida F, Castro-Hermida JA, Ares-Mazas E, Kehoe SC, Boyle M, et al. Batch solar disinfection inactivates oocysts of Cryptosporidium parvum and cysts of Giardia muris in drinking water. Journal of applied microbiology. 2006;101(2):453-63.

10.          Altherr AM, Mosler HJ, Tobias R, Butera F. Attitudinal and relational factors predicting the use of solar water disinfection: A field study in Nicaragua. Health Education & Behavior. 2006.

11.          Graf J, Meierhofer R, Wegelin M, Mosler HJ. Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs. International Journal of Environmental Health Research. 2008;18(5):335-55.