Micro-nano bubble ozonation for effective treatment of ibuprofen-laden wastewater and enhanced anaerobic digestion performance

The pharmaceutical industry plays a crucial role in driving global economic growth but also poses substantial environmental challenges, particularly in the efficient treatment of production wastewater. This study investigates the efficacy of micro-nano bubble (MNB) ozonation for treating high-strength ibuprofen (IBU)-laden wastewater (49.9 ± 2.3 mg/L) and mitigating its inhibitory effects on the anaerobic digestion (AD) of intralipid (IL)-laden wastewater. Our findings demonstrated that MNB ozonation achieved a 99.0 % removal efficiency of IBU within 70 min, significantly surpassing the 69.8 % efficiency observed with conventional ozonation under optimal conditions. Both conventional and MNB ozonation primarily transformed IBU through oxidation processes, including hydroxylation and the conversion of C–H bonds to C = O groups, along with carbon cleavage. However, MNB ozonation markedly reduced the toxicity of IBU-laden wastewater by further transforming toxic by-products, particularly under mildly alkaline conditions (pH 7.2 and 9.0). This reduction in toxicity led to a significant improvement in subsequent AD performance; specifically, a 70-min MNB ozonation pretreatment enhanced methane production by 48.1 %, increased chemical oxygen demand removal by 35.6 %, and reduced fatty acid accumulation compared to the control without pretreatment. Additionally, the effluent from MNB ozonation positively impacted the microbial community, particularly by enriching syntrophic bacteria and methanogens. Overall, these findings offered new insights into the behavior and toxicity of IBU oxidation by-products in both conventional and MNB ozonation processes. Furthermore, this study proposed a novel strategy for the combined treatment of IBU- and IL-laden wastewaters, establishing a robust foundation for advancing MNB ozonation technology in engineered pharmaceutical wastewater treatment.