Simultaneous control of organic chloramines and emerging contaminants in swimming pool water using far-UVC...

Organic chloramines (OCs) formed during chlorination of amino acids in swimming pool water, alongside emerging contaminants such as personal care products, pose health risks to swimmers. This study proposes a novel approach for simultaneous control of OCs and trace contaminants using far-UVC irradiation. Results demonstrate enhanced photodecay of OCs, radical production, and contaminant degradation when replacing conventional low-pressure mercury UV lamps (UV₂₅₄) with krypton chloride excimer lamps (UV₂₂₂). The UV fluence-based photodecay rate constants of six OCs are 1.00-1.83-fold higher under UV₂₂₂ (7.44 × 10^-4 to 3.28 × 10^-3 cm² mJ^-1) than under UV₂₅₄ (3.78 × 10^-4 to 2.34 × 10^-3 cm² mJ^-1). This enhancement primarily results from higher apparent quantum yields (1.78-5.51-fold increase), rather than molar absorption coefficients. Furthermore, steady-state concentrations of hydroxyl radicals (HO^•) and chlorine radicals (Cl^•)-normalized to incident fluence rates-are 1.00-1.86-fold and 2.35-5.32-fold higher under UV₂₂₂ than under UV₂₅₄, respectively. In actual swimming pool water, UV₂₂₂ rapidly degrades N,N‑diethyl-meta-toluamide (DEET) through synergistic radical pathways, whereas UV₂₅₄ exhibits negligible degradation. These findings advance the photochemistry of OCs and establish far-UVC as a promising technology for simultaneous control of OCs and trace contaminants in chlorinated swimming pools.