Study of the Inactivation of Escherichia Coli Strain Vs. Native Bacteria During Uv Disinfection Treatment with a Flow-trough Reactor

The reuse of effluents from wastewater treatment plants is a reality in several countries due to water scarcity. To ensure its quality, tertiary disinfection treatments are needed. The present work aims to evaluate the efficacy of ultraviolet (UV) disinfection systems for the elimination of fecal bacteria in effluents from urban wastewater treatment plants. Kinetic modeling was used to study the influence on the inactivation of Escherichia coli considering different UV doses, origin of the bacteria (native or standardized lyophilized strain), and the response to post-treatment at 24 hours under light and dark conditions. In the adjustment of the experimental inactivation values with non-linear regression techniques, the linear mathematical model with tail was chosen as it showed better statistical fit. The evaluation showed that between the two E. coli variants tested, the native bacterium presented higher UV resistance and was also affected by reactivation to a lesser extent, with respect to the E. coli ATCC 8739 strain. In other words, although the inactivation dose for both bacteria was similar, the recovery of damage from photoreactivation effects was higher in the native species. Therefore, the necessary dose of inactivation was determined by UV technology, which was equal to 15 mJ cm-2 for a reduction of 5 log10 for both the E. coli strain and the native type, without considering reactivation processes, while the maximum percentage of photoreactivation detected was 6% achieved by native E. coli treated with 5.88 mJ cm-2.