Beyond conventional advanced oxidation processes for reliable 2-methylisoborneol and geosmin: Overcoming matrix...

Taste and odor (T&O) compounds in drinking water pose a pervasive threat to water security due to their ultralow odor thresholds. Conventional ozone-based advanced oxidation processes (AOPs) often fail to eliminate recalcitrant odorants such as geosmin (GSM) and 2-methylisoborneol (2-MIB) in complex water matrices, largely because nonselective HO^• are rapidly scavenged by background constituents. Here we showed that dosing trace peroxymonosulfate (PMS) into ozonation overcame this limitation by harnessing a dual-radical (SO₄^•-/HO^•) synergy. At ultralow [PMS]/[O₃] molar ratios (0.032∼0.16), O₃/PMS achieved near-complete removal of 100 ng/L odorants within 10 min, meeting stringent sensory-based finished water targets (<10 ng/L) and outperforming ozonation alone and O₃/H₂O₂. Quantitative contribution analysis indicated that co-generated SO₄^•- crucially compensated for HO^• sensitivity, resulting in substantially smaller efficiency loss than O₃/H₂O₂ under challenging conditions, e.g., high-level bicarbonate and significant natural organic matter (NOM). In actual settled water, O₃/PMS further outperformed O₃/H₂O₂ by 4.7 % and 6.2 % in GSM and 2-MIB removal, respectively. Through thermodynamic and kinetic analyses (ΔG and ΔG‡) at molecular orbital level, hydrogen-atom abstraction at β‑carbon sites was confirmed to be the favored reaction pathway initiating 2-MIB and GSM degradation. Collectively, O₃/PMS offered a practical, matrix-tolerant upgrade to existing ozone infrastructure for reliable T&O control.