Bactericidal Effect of Solar Water Disinfection under Real Sunlight Conditions

Abstract

Batch solar disinfection (SODIS) inactivation kinetics are reported for suspensions in water of Campylobacter jejuni , Yersinia enterocolitica , enteropathogenic Escherichia coli , Staphylococcus epidermidis , and endospores of Bacillus subtilis , exposed to strong natural sunlight in Spain and Bolivia. The exposure time required for complete inactivation (at least 4-log-unit reduction and below the limit of detection, 17 CFU/ml) under conditions of strong natural sunlight (maximum global irradiance, ∼1,050 W m ⁻² ± 10 W m ⁻² ) was as follows: C. jejuni , 20 min; S. epidermidis , 45 min; enteropathogenic E. coli , 90 min; Y. enterocolitica , 150 min. Following incomplete inactivation of B. subtilis endospores after the first day, reexposure of these samples on the following day found that 4% (standard error, 3%) of the endospores remained viable after a cumulative exposure time of 16 h of strong natural sunlight. SODIS is shown to be effective against the vegetative cells of a number of emerging waterborne pathogens; however, bacterial species which are spore forming may survive this intervention process.