Inactivation of fecal bacteria in drinking water by solar heating

The Journal of communicable diseases

Over 30% of the population in developing countries is in need of access to safe drinking water. The 875 million cases of diarrhea and 4.6 million deaths that occur each year due to a lack of a safe water supply occur primarily in these countries. It is estimated that these countries will need over $150 billion to establish full drinking water supply system coverage, a sum that they may not be able to raise within the near future. Conventional methods of drinking water disinfection, such as chemical treatment, heat pasteurization, and filtration, require facilities, materials, and fuel that may not be readily available or feasible to attain. An alternative treatment option is to utilize solar energy, which has been shown to inactivate pathogens through pasteurization and radiation effects.

Journal of Physics: …, 2008

Solar Disinfection (SODIS) is a low cost water treatment method currently used in communities that do not have year round access to safe water. However, there is still reluctance in widespread adoption of this treatment method due to a number of limitations. An important limitation is the lack of SODIS inactivation studies on some waterborne pathogens in the developing world. SODIS inactivation of enteropathogenic E. coli (EPEC), a major cause of infantile diarrhoea is reported for the first time under simulated sunlight conditions and following a natural temperature profile. EPEC was exposed to simulated sunlight (885Wm-2) for periods up to a cumulative time of 4 hours. Inactivation was determined by a log reduction in growth of the organisms. The temperature (o C) of the water was taken at every time point. After 4 hours exposure EPEC was completely inactivated (7 log reduction) by SODIS. Imposing a realistic water temperature profile (min-max) concomitant with irradiation produces a greater kill of EPEC. Maintaining simulated sunlight experiments at a high fixed temperature may result in over-estimation of inactivation. Following a natural water temperature profile will result in more reliable inactivation comparable with those that might be obtained under natural sunlight conditions.

Journal of Applied Microbiology, 1998

Journal of Medical Microbiology, 1999

Polish Journal of Environmental Studies, 2012

Our research investigated the potential use of solar radiation in water disinfection. Contaminated water was exposed to solar radiation under controlled conditions to deactivate and destroy pathogenic microorganisms. The experiment was directed toward examining the effective radiation time required for total coliform inactivation in the wastewater. The experiments were carried out between March and July 2009 with temperature ranges between 30-25oC and solar radiation intensity of 2073.9-2775.2 Jul/cm 2 . The impact of three parameters under direct exposure to the sun was studied: depth (10, 20, 30 cm), turbidity (135, 160, 200 NTU), and container color (white and black). Comparison between solar disinfection and chlorination also was conducted. The maximum removal of total coliform was found to be 92.95% at 10 cm depth for sunny conditions, at 110 NTU, and white container. It was found that the optimum contact time in the chlorination experiment was 240 min, which gives a disinfecti...

Journal of Environmental Health Science and Engineering, 2014

Disinfection of contaminated water using solar radiation (SODIS) is known to inactivate bacteria. Its inactivation efficiency depends on local conditions where the disinfection is made. This study was aiming to test the efficiency of solar disinfection using different water parameters as low-cost household water treatment technology. Inactivation of microbes was tested using fecal coliform as test organism. The SODIS experiment was carried out at turbidity 2NTU, pH 7, and various water temperature (38.1°C, 41.8°C, 45.6°Cand 51.1°C) and solar intensities, using clear and black plastic bottles filled to different depths. The results show that the rate of microbial inactivation in relation to depth of water, turbidity, container type, intensity of light and color of container was statistically significant (p < 0.05). However, bottle placement, exposure and water pH were unrelated to microbial inactivation. Bacterial re-growth was not observed after solar disinfection. By adjusting the parameters, complete and irreversible fecal coliform inactivation was achieved within an exposure time of less than four hours in the areas where the solar irradiance is about 3.99 kW/m 2 and above. Our results indicate that application of SODIS could play a significant role in the provision of safe water in rural communities of developing countries where there is ample sunshine, specifically in sub-Saharan African countries.

the Lancet, 1996

Journal of Applied Microbiology, 2006

To determine the efficacy of solar disinfection (SODIS) for enteric pathogens and to test applicability of the reciprocity law. Methods and Results: Resistance to sunlight at 37°C based on F 99 values was in the following order: Salmonella Typhimurium > Escherichia coli > Shigella flexneri > Vibrio cholerae. While F 90 values of Salm. Typhimurium and E. coli were similar, F 99 values differed by 60% due to different inactivation curve shapes. Efficacy seemed not to be dependent on fluence rate for E. coli stationary cells. Sensitivity to mild heat was observed above a temperature of 45°C for E. coli, Salm. Typhimurium and Sh. flexneri, while V. cholerae was already susceptible above 40°C. Conclusions: Salmonella Typhimurium was the most resistant and V. cholerae the least resistant enteric strain. The reciprocity law is applicable for stationary E. coli cells irradiated with sunlight or artificial sunlight. Significance and Impact of the Study: Escherichia coli might not be the appropriate indicator bacterium to test the efficacy of SODIS on enteric bacteria and the physiological response to SODIS might be different among enteric bacteria. The applicability of the reciprocity law indicates that fluence rate plays a secondary role in SODIS efficacy. Stating inactivation efficacy with T 90 or F 90 values without showing original data is inadequate for SODIS studies.

Applied and Environmental Microbiology, 2008

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 numbe...

Solar Energy, 2014

The bacterial inactivation efficacy of a solar water disinfection (SODIS) reactor consisting of a 25 L 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 10 5 and 10 7 CFU/100 ml. This spiked water was exposed to natural sunlight. Satisfactory bacterial inactivation (log 10 reduction values >6 units or inactivation to below the limit of detection (<1 CFU/100 ml)) 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.