Effect of UV solar intensity and dose on the photocatalytic disinfection of bacteria and fungi

Solar disinfection modeling and post-irradiation response of Escherichia coli in wastewater

“…Increasing intensity continued to decrease the shoulder length, to a minimum of approximately 80 min, followed by acute log-linear decrease within the next 60 min after the shoulder is finished. In this case, the equilibrium set between the growth forces and the disinfecting action of light is imbalanced against E. coli very fast, indicating a possible minimum dose required for initiating the log-linear decay phase, as also suggested by Sichel et al [22] and Ubomba-Jaswa et al [5]. In total, increasing the intensity from 500 to 1600 W/m 2 has inflicted dramatic change to the necessary exposure time, with the initial 420 min being reduced to (approximately) 130 min, which equals to 70% less time necessary.…”

“…Marugan et al [20] have stated the modification of disinfection potentials when the chemistry of the matrix is altered and Salih [21] marked the importance of consideration of pollution load. Furthermore, Sichel et al [22] and Rincon and Pulgarin [23] discussed the idea of minimum dose for inactivation and the importance of irradiation conditions on photolysis and Malato et al [24] in their review mentioned the importance of light dispersion. These are factors that all co-exist in wastewater and affect the process more than drinking water.…”

Temperature-dependent change of light dose effects on E. coli inactivation during simulated solar treatment of secondary effluent

“…This practice has drawn interest among other disinfection methods in developing countries, because of its simplicity and high acceptance rates (Ubomba-Jaswa et al, 2009;McGuigan et al, 2012). Following its introduction, more sophisticated aspects were gradually studied, such as the responses of different microorganisms and solar light delivery methods (continuous-intermittent) (Rincon and Pulgarin, 2003;Sichel et al, 2007).…”

“…Rincon and Pulgarin (2004a) stated that for the same dose, the high irradiation/low time combination provided better results for solar treatment of water, indicating a non-linear dependence between light intensity and deactivation of bacteria. Sichel et al (2007) found that increasing the dose did not significantly improve disinfection in fungi, if the intensity was kept constant, while Bosshard et al (2009) and Berney et al (2006) directly challenged reciprocity law in SODIS; Bosshard et al (2009) found some deviations of Sh. flexneri and S. typhimurium from this law, while Berney et al (2006) verified the law for E. coli in temperatures between 40-52˚C.…”

Environmental considerations on solar disinfection of wastewater and the subsequent bacterial (re)growth

“…In most cases, areas with challenged water supplies are subjected to many sunny days per year (Blesa and Litter, 2007), but for instance, solar-UV power is a function of sky clarity and of the presence of clouds. The solar-only disinfection is affected by changes in irradiation intensity, and therefore, takes place (more efficiently) at higher irradiance values (Sichel et al, 2007). However, even in the sunniest areas in the world, the UV supply can be subjected to temporal variations; therefore, it is important to assess the implications light intermittence would cause to the removal efficiency of a solar wastewater application.…”