Optimization and performance evaluation of a hybrid ultrasound–photocatalysis–ozonation system for pharmaceutical wastewater treatment

Pharmaceutical wastewater contains persistent organic pollutants that are difficult to remove using conventional treatment methods and may threaten aquatic ecosystems and public health. This study aimed to optimize an integrated advanced oxidation process combining ultrasound, photocatalysis, and ozonation for pharmaceutical wastewater treatment using Response Surface Methodology (RSM). A Central Composite Design (CCD) consisting of 20 experimental runs was applied to evaluate the effects of ultrasound, photocatalysis, and ozone dosage on Total Organic Carbon (TOC) removal and Inorganic Carbon (IC) formation. The integrated system showed strong synergistic effects among the three processes. Ozonation was identified as the dominant factor influencing TOC degradation, while IC formation was significantly affected by the interactions between ultrasound and ozonation and between photocatalysis and ozonation. The quadratic model for IC showed good statistical significance (p < 0.05), indicating reliable prediction of mineralization performance. The optimum operating conditions were obtained at 46.88 min of ultrasound, 39.84 min of photocatalysis, and 9.5 min of ozonation, with a desirability value of 0.519. The results confirm that the integrated process effectively enhanced both the degradation and mineralization of pharmaceutical pollutants. The novelty of this study lies in the comprehensive optimization and trade-off evaluation between TOC degradation and IC formation in a hybrid ultrasound–photocatalysis–ozonation system for pharmaceutical wastewater treatment.