Utilization of UV/VUV irradiation for removal of human body fluids related pollutants in swimming pool water

Human body fluids related pollutants (BFPs) are primary precursors to disinfection by-products (DBPs) in swimming pool water (SPW). This study evaluated the degradation efficiency of ultraviolet/vacuum ultraviolet (UV/VUV) technology for the removal of three typical BFPs: urea, creatinine, and hippuric acid. The results showed that UV/VUV irradiation significantly enhanced the removal of these pollutants compared to UV alone. In addition, the observed rate constant (k_obs) of the UV/VUV system was 1.9-8.0 times higher than that of the UV/H₂O₂ system, accompanied by a substantial 89.6 % reduction in the electrical energy per order (EEO). Urea degradation primarily involved the cleavage of C-N and C-H bonds within the urea molecule induced by VUV photolysis, whereas the degradation of creatinine and hippuric acid was mainly driven by a series of reactions (including decarboxylation, demethylation, hydroxylation, and ring opening) initiated by •OH. pH variations within the range of 6.8-8.2 exerted minimal impact on pollutant removal. However, NO₃, humic acid, and cyanuric acid obviously inhibited the removal of BFPs. Employing UV/VUV system as a pretreatment step prior to chlorination disinfection led to a noteworthy reduction of 63.6 %-69.1 % of the adsorbable chlorine in actual SPW. Results of this study presented a green, chemical-free, and operationally simple method to mitigate DBPs formation in SPW.