Pilot-scale hydrodynamic cavitation-enhanced ozonation for efficient removal of persistent pharmaceuticals from aqueous matrices: Experimental and numerical simulation studies

Hydrodynamic cavitation (HC)-based advanced oxidation processes (AOPs) are a promising method for removing persistent organic micropollutants (OMPs) from wastewater. HC induces bubble formation through rapid pressure fluctuations, and the subsequent bubble collapse generates a plethora of physicochemical phenomena and extreme conditions that promote the formation of highly reactive hydroxyl radicals (•OH). •OH radicals are highly effective at degrading a wide range of OMPs due to their high oxidation potential (2.8 V) and non-selective reactivity. This study investigated the treatment of real wastewater treatment plant effluent containing 1H-Benzotriazole, Metformin, Venlafaxine, and Metoprolol using a continuous pilot-scale HC system combination of ozone (O 3 ) with side injection concept. Dissolved O 3 was combined with the HC to enhance •OH production, further improving pollutant degradation. Cavitation was generated using a nozzle-type 200 µm orifice, operating at optimized nozzle pressure ( P n ) of 30 bar and a cavitation number ( C v ) of 0.03. Treatments were conducted with dissolved O 3 concentrations of 1 mg/L and 7 mg/L, with wastewater passed through the HC system in up to two passes. Experimental results demonstrated that the combination of HC and O 3 effectively degraded the studied OMPs in wastewater, and their degradation followed first-order kinetics ( k = 0.30 min –1 to 0.47 min –1 ). The removal was observed in the following order: Metoprolol > Venlafaxine > 1H-Benzotriazole > Metformin at O 3 dose of 7 mg/L. Process optimization was performed using high-speed imaging and computational fluid dynamics (CFD) simulations by enhancing flow characteristics and operational parameters. This study highlights the potential of HC + O 3 as a scalable and efficient wastewater treatment process.