Effect of the water matrix and reactor configuration on Enterococcus sp. inactivation by UV-A activated PMS or H2O2

In this work, the influence of the matrix on the photolytic activation of peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) has been studied for the inactivation of Enterococcus sp. Additionally, two different reactor configurations (batch reactor and tubular reactor) have been evaluated that achieve complete disinfection within 120 min when using a tubular reactor. Three water matrices (distilled water, saline solution and simulated wastewater) have been studied, and experiments have been carried out using radical scavengers to determine the main reactive species involved in each process. The hydroxyl radical (OH) has been found to be the main responsible for the inactivation of bacteria in distilled water, while chlorinated species generated during treatments are responsible for disinfection in a saline matrix. The study of the influence of various inorganic ions (Br−, F−, PO43−, NO3−, NO2−) on treatments revealed an increase in the efficacy of the PMS/UV-A system in the presence of Br− due to the bromine generation. Furthermore, the effect of F− has been studied for the first time, determining that the presence of this compound does not have a significant influence on the H2O2/UV-A system while inhibiting PMS/UV-A treatment. Overall, the results suggest that H2O2-based treatments would be less dependent on matrix composition than those involving PMS, and the presence of nitrites is a contraindication to the application of either process.