Native Nitrate in Wastewater Enhances 222 nm UV Advanced Oxidation of Micropollutants

222 nm irradiation, emitted from krypton chloride excimer (KrCl*) lamps, of waters containing nitrate has previously been demonstrated to lead to de facto advanced oxidation, due to the high absorbance and hydroxyl radical quantum yield of nitrate at 222 nm. Because nitrate is widespread in environmental waters, including nitrified wastewaters and wastewater-impacted surface water, this raises the possibility of UV advanced oxidation, which harnesses in situ nitrate for radical generation when KrCl* lamps are used as the UV source. In turn, this process is effective directly in wastewater effluent without the addition of chemicals. In this study, we compare UV222 treatment, without the addition of an external radical promoter, to UV254 with 10 mg/L hydrogen peroxide (H 2 O 2 ) for the removal of 1,4-dioxane in three effluent waters containing nitrate at 2.1–8.9 mg-N/L. UV222 leads to 2.8–3.9 faster 1,4-dioxane degradation, on an incident fluence basis, resulting in an electrical consumption that is within 0.89–1.3 times that of UV254/H 2 O 2, despite low-pressure mercury vapor lamps having at least 3.5× higher electrical efficiency than KrCl* lamps. When the cost of hydrogen peroxide dosing and quenching is considered, UV222 treatment leads to a projected cost savings of 12.4–21.8% compared to UV254/H 2 O 2 . Furthermore, despite the low UV transmittance (UVT) of these effluent waters at 222 nm (