You are here:
Solar Radiation Disinfection of Drinking Water at Temperate Latitudes: Inactivation rates for an optimized reactor configuration
Davies, C. M., D. J. Roser, A. J. Feitz, AND N. ASHBOLT. Solar Radiation Disinfection of Drinking Water at Temperate Latitudes: Inactivation rates for an optimized reactor configuration. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 43(3):643-652, (2009).
The experimental program was not designed to prove that sunlight has high disinfectant potential. Rather, the objective was to estimate how effective solar disinfection is away from the equator, how well a basic reactor can disinfect water, and the extent to which its performance might be constrained. The overall conclusion is that the solar disinfection of drinking water can be undertaken successfully at temperate latitudes, even in winter. A number of limitations to the experimental procedure were also recognised, and these form the basis of the recommendations listed below.
Solar radiation-driven inactivation of bacteria, virus and protozoan pathogen models was quantified in simulated drinking water at a temperate latitude (34°S). The water was seeded with Enterococcus faecalis, Clostridium sporogenes spores, and P22 bacteriophage, each at ca 1 x 10,sup>5 mL-1, and exposed to natural sunlight in 30-L reaction vessels. Water temperature ranged from 17 to 39 °C during the experiments lasting up to 6 h. Dark controls showed little inactivation and so it was concluded that the inactivation observed was primarily driven by non-thermal processes. The optimised reactor design achieved S90 values (cumulative exposure required for 90% reduction) for the test microorganisms in the range 0.63–1.82 MJm-2of Global Solar Exposure (GSX) without the need for TiO2 as a catalyst. High turbidity (840–920 NTU) only reduced the S90 value by <40%. Further, when all S90 means were compared this decrease was not statistically significant (prob. > 0.05). However, inactivation was significantly reduced for E. faecalis and P22 when the transmittance of UV wavelengths was attenuated by water with high colour (140 PtCo units) or a suboptimally transparent reactor lid (prob. < 0.05). S90 values were consistent with those measured by other researchers (ca 1–10 MJm-2) for a range of waters and microorganisms . Although temperatures required for SODIS type pasteurization were not produced, nonthermal inactivation alone appeared to offer a viable means for reliably disinfecting low colour source waters by greater than 4 orders of magnitude on sunny days at 34°S latitude.