Rapid sulfate radical-driven inactivation of Pseudocohnilembus persalinus by an ozone/potassium peroxymonosulfate advanced oxidation process

• The O₃/PMS process achieves rapid inactivation of Pseudocohnilembus persalinus within 60 s, significantly outperforming O₃ alone. • Sulfate radicals (SO₄•⁻) are identified as the dominant reactive species driving the oxidation process. • Multi-ROS synergy induces membrane disruption, metabolic disorder, and DNA damage in protozoan cells. • The O₃/PMS system shows strong potential for controlling protozoan hazards in aquaculture water. Pseudocohnilembus persalinus, an opportunistic scuticociliate, poses a significant biological hazard in intensive marine aquaculture, causing scuticociliatosis, rapid transmission, and substantial economic losses under high-density farming conditions. Developing rapid and efficient control strategies is therefore critical. Here, the inactivation performance and mechanisms of an ozone/potassium peroxymonosulfate (O₃/PMS) advanced oxidation process were investigated. Complete inactivation was achieved within 60 s using 2 mmol·L⁻¹ PMS with O₃ aeration (10 g·h⁻¹), compared to 140 s for O₃ alone. Under mildly acidic conditions (pH 5.0–6.0), complete inactivation occurred within 20 s. Mechanistic analyses showed that O₃/PMS induced severe structural damage, including ciliary detachment, membrane disruption, and intracellular leakage. Electron paramagnetic resonance confirmed sulfate radicals (SO₄•⁻) as the dominant reactive species. Cell viability decreased by >80% within 60 s, accompanied by DNA fragmentation. Transcriptomic results revealed significant perturbations in oxidative stress response, cytoskeletal repair, and metabolic pathways. These findings demonstrate that SO₄•⁻-dominated oxidation enables rapid and effective control of protozoan hazards in aquaculture systems.