Synergistic Ozonation-Photocatalysis Pretreatment and Rotating Biological Contactors for the Mineralization of Pharmaceutical Mixture: Design, Optimization, and Nanoscale Interfacial Analysis

Pharmaceutical residues may persist after conventional biological treatment, necessitating advanced oxidation before biological polishing. This study evaluated an integrated ozone–photocatalysis (O3/UV/TiO2) process followed by a rotating biological contactor (RBC) for a mixed pharmaceutical matrix. TiO2 immobilized on porous alumina ceramic foam was characterized using focused ion beam scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy, while biological compatibility was assessed using dehydrogenase activity and ATP bioluminescence. After 30 min of AOP treatment, pharmaceutical removal ranged from 38.2% to 99.6%, increasing to 45.5–99.8% after the complete AOP–RBC treatment, with carbamazepine remaining the most persistent compound. COD decreased from 172.3 ± 5.1 mg/L in the untreated mixture to 97.2 ± 2.0 mg/L after AOP, and 8.0 ± 0.6 mg/L after 24 h of RBC treatment. The BOD7/COD ratio increased from 0.19 to 0.29 after AOP and 0.45 after RBC treatment, indicating enhanced biodegradability. Residual ozone after pretreatment was 0.03 mg/L. Overall, sequential oxidation and biological treatment enhanced pharmaceutical and bulk organic matter removal, while persistent compounds and energy demand remain important considerations for further process optimization and scale-up.