Degradation of N-nitrosamines and 1,4-dioxane using vacuum ultraviolet irradiation (UV or UV).

Advanced oxidation processes (AOPs) play a vital role in attenuating contaminants of emerging concern (CECs) during potable water reuse. AOPs are conventionally performed by irradiating with a 254-nm low-pressure (LP) mercury-vapor (Hg) ultraviolet (UV) lamp along with chemical treatment. Compared with UV-C light treatment (200-280 nm), vacuum-UV (V-UV) light treatment (100-200 nm) is advantageous in terms of hydroxyl radical generation without the requirement for chemical treatment. This study assessed the potential of V-UV (172-nm Xe excimer or 185 + 254-nm LP-Hg) lamps on the destruction of two major CECs in potable water reuse, namely N-nitrosodimethylamine (NDMA) and 1,4-dioxane. Direct irradiation using UV or UV lamps achieved ≥94% removal of N-nitrosamines, including NDMA, at a UV dose of 900 mJ/cm. In contrast, the Xe excimer lamp (UV) was less effective for N-nitrosamine removal, achieving up to 82% removal of NDMA. The removal of 1,4-dioxane by V-UV lamps at a UV dose of 900 mJ/cm reached 51% (UV) and 28% (UV), both of which results were superior to that obtained using a conventional UV lamp (10%). The addition of hydrogen peroxide during UV or UV irradiation was found to enhance the removal of 1,4-dioxane, while UV irradiation without hydrogen peroxide addition still exhibited greater efficiencies than those UV lamps-based AOPs. Overall, this study demonstrated that the removal of both NDMA and 1,4-dioxane can be successfully achieved using either a UV lamp with hydrogen peroxide or a UV Xe excimer lamp without hydrogen peroxide.