Presentation: 2025 ND EPSCoR Annual conference 

October 21, 2025, NDSU Memorial Union, Fargo, North Dakota

Far-UVC (222 nm) based advanced oxidation for the removal of organic micropollutants from wastewater recycling concentrate

The occurrence of persistent organic micropollutants (OMPs) such as carbamazepine (CBZ), N,N-diethyl-meta-toluamide (DEET), caffeine (CAF), and 1,4-dioxane (1,4-D) in water reuse systems poses risks to public and environmental health. They often accumulate in reverse osmosis (RO) concentrate and are difficult to remove. This research compared far-UVC (222 nm) and conventional low-pressure UV (254 nm) for their ability to degrade these compounds in RO concentrate with and without oxidants (H₂O₂, NH₂Cl, Cl₂ at 100 μM). Direct photolysis at 222 nm achieved 8–12 times greater decay than 254 nm. With H₂O₂ addition, degradation increased sharply, with CBZ (1.89 × 10⁻² cm²/mJ) and CAF (2.23 × 10⁻² cm²/mJ) showing ~20-fold higher rates, and DEET achieving 1.43 × 10⁻² cm²/mJ (~13-fold enhancement). CBZ removal was most efficient with UV 222/NH₂Cl (2.09 × 10⁻² cm²/mJ), while DEET and CAF were maximized under UV 222/H₂O₂. For 1,4-D, the UV 222/NH₂Cl system reached 1.89 × 10⁻³ cm²/mJ, a 13-fold increase over UV 254. Notably, far-UVC remained effective in RO concentrate, despite strong light screening from background organics and ions that suppress UV 254 performance. Overall, the results demonstrate that UV 222-based AOPs provide a sustainable approach for mitigating persistent OMPs in water reuse systems.