Impact of water disinfection processes on polycyclic aromatic hydrocarbons (PAHs): Comparison of ozonation, chlorination, and combined treatment

The effects of commonly used water disinfection techniques-namely chlorination, ozonation, and ozone-chlorine combination-on polycyclic aromatic hydrocarbons (PAHs) under various conditions were evaluated. Artificial raw water samples containing different concentrations of Benzo(a)pyrene, Benzo(b)fluoranthene, Benzo(k)fluoranthene, Benzo(g,h,i)perylene, and Indeno(1,2,3-c,d)pyrene were subjected to different disinfection processes, including 5-minute and 8-minute ozonation, 1 mg/L and 2 mg/L chlorination with varying doses and contact times, and ozone treatment followed by chlorination, resulting in a total of eight disinfection scenarios. High-performance liquid chromatography with fluorescence detection (HPLC-FLD) was used to analyze PAH compounds. The results indicated that the degradation of PAHs depended on the disinfection technique, compound type, and concentration. Ozonation led to the complete degradation of all PAH compounds (99-100% removal), while chlorination exhibited the highest degradation rate (average of 78%) for Benzo(a)pyrene. However, Benzo(b)fluoranthene was not affected by chlorine. The other PAH compounds showed degradation rates ranging from 15.8% to 30.3% during 2 mg/L chlorination. Furthermore, the disinfection efficacy of the methods was assessed, and it was found that all tested treatments eliminated Escherichia coli.