Abstract
UV-C at 254 nm and vacuum UV (VUV) at 185 nm are the two major emission lines of a low-pressure mercury lamp. Upon absorption of VUV photons, water molecules and selected inorganic anions generate hydroxyl (HO.) and other redox radicals, both capable of degrading organic micropollutants (OMPs), thereby offering the opportunity to reduce H2O2 and energy consumption in UV-based advanced oxidation process (AOP). To be successfully scaled-up, the dual-wavelength VUV+UV/H2O2 AOP requires laboratory-scale experiments to establish design criteria. The figures of merit typically used for reporting and interpreting quasi-collimated beam results for UV-based AOPs (time, dose, absorbed energy and EEO) are insufficient and inaccurate when employed for dual-wavelength AOP such as the VUV+UV/H2O2 AOP, and do not support system scale-up. In this study, we introduce a novel figure of merit, useful absorbed energy (uAE), defined as fraction of absorbed energy that results in the generation of oxidative radicals. Here, results of quasi-collimated beam VUV+UV/H2O2 AOP experiments on four different water matrices are used to introduce 2D plots that employ both uAEUV and uAEVUV as a novel method to represent laboratory-scale experiments of VUV+UV/H2O2 AOP and demonstrate how the 2D plots sufficiently support scale-up of the AOP.