Evaluating synergy of dual-wavelength deep-UV radiation (222 + 282 nm) for synchronous water decontamination and disinfection

This study is the first to explore a potential synergy of deep dual-wavelength ultraviolet (DWUV) radiation of KrCl (222 nm) and XeBr (282 nm) excilamps towards synchronous elimination of bacteria (105 CFU/mL E. coli and E. faecalis) and pharmaceutical (20 μM bezafibrate) from model and real (natural) water matrices at unadjusted pH. A time-based synergistic effect of DWUV photolysis and DWUV+H2O2 process in terms of 5-log (total) inactivation was found under all experimental conditions with synergistic indices in the range of 1.3–3.9. In the absence of bezafibrate, no inhibition effect of natural water matrix was found for inactivating bacteria by DWUV radiation with and without H2O2. Adding bezafibrate inhibited inactivation in natural water with keeping a synergistic effect and low dose requirements for complete inactivation (below 6 mJ/cm2). Despite the absence of synergistic effect towards degradation of bezafibrate, its synchronous degradation is achievable at higher doses. Unlike inactivation, the pseudo-first-order rate constants showed that degradation was inhibited by water matrix and bacteria (to a lesser degree) in DWUV+H2O2 mode, but not under DWUV photolysis. However, the DWUV+H2O2 process was more efficient than direct photolysis and provided faster decontamination and disinfection. Results show that this advanced oxidation process is applicable for treating real water matrices and represent a promising strategy in controlling microbial pathogens and pharmaceuticals in water.