Seasonal Occurrence and UV-Based Oxidative Removal of Odorants in Surface Water: Insights into Structure-Dependent Reactivity

Odorants present a persistent challenge in drinking water treatment due to their low odor threshold concentrations (OTCs) and their resistance to conventional processes. This study investigated the seasonal occurrence of eight odorants across 20 surface water sources in Shandong, China. It evaluated their degradation using UV photolysis and four UV-based advanced oxidation processes (UV-AOPs): UV/H2O2, UV/PMS, UV/Cl, and UV/TiO2. Total odorant concentrations ranged from 8 to 496 ng L−1 in the wet season and from 5 to 184 ng L−1 in the dry season, with 2-MIB as the dominant compound (detection frequency: 95%; contributions: 58.48% and 48.88%, respectively). Pearson correlation analysis revealed a seasonal shift in environmental drivers: total phosphorus (TP) and dissolved oxygen (DO) in the wet season versus NH3-N and CODMn in the dry season. Across all five processes, degradation efficiency followed a consistent, structure-dependent hierarchy, ranking as CTA >> 2,4,6-TCA ≈ IPMP > IPO > 2-MIB ≈ GSM, with CTA achieving 74.66–95.03% removal while 2-MIB and GSM remained largely refractory (≤29.70%). Process-specific selectivity was also observed: UV/H2O2 was most effective for IPO, IPMP, and GSM; UV/PMS excelled for CTA and 2,4,6-TCA; and UV/Cl showed a slight advantage for 2-MIB. These findings provide mechanistic insights into structure-dependent odorant oxidation and suggest that UV-AOP performance may vary according to target-compound characteristics. Further validation in real water matrices is required before practical application.