Evaluation of Solar Disinfection of E. coli Under Sub-Saharan Field Conditions Using a 25 Litre Borosilicate Glass Batch Reactor Fitted with a Compound Parabolic Collector.

The bacterial inactivation efficacy of a solar water disinfection (SODIS) reactor consisting of a 25L borosilicate glass tube fitted with a compound parabolic collector (BGTR-CPC) was assessed under equatorial weather conditions in Uganda. The SODIS BGTR-CPC was tested over a 17-month period in Sub-Saharan conditions in Kampala, Uganda. The BGTR-CPC was filled with natural water from a nearby protected well. A wild strain of Escherichia coli isolated from local natural water was added to the reactor to give a starting population of between 105 and 107 CFU/100ml. This spiked water was exposed to natural sunlight. Satisfactory bacterial inactivation (log10 reduction values >6 units or inactivation to below the limit of detection (/100ml.)) was observed for 11 of 13 experiments. Rainfall and overcast/cloudy conditions were factors on both of the occasions when incomplete inactivation was observed. In conclusion, the use of CPC SODIS technology is suitable for treating drinking water both at household level and institutional level in Sub-Saharan and other similar tropical climates if careful consideration of the cloud cover and rainfall is taken into account.