Eliminating partial-transformation products and mitigating residual toxicity of amoxicillin through intimately coupled photocatalysis and biodegradation

Intimately coupled photocatalysis and biodegradation (ICPB) is a promising technology for treating wastewater containing antibiotics. While past work has documented the benefits of ICPB for removing and mineralizing antibiotics, its impacts on mitigating biotoxicity from products has not been studied. We fabricated an ICPB carrier by coating Ag-doped TiO₂ on the outer skeleton of sponge carriers and allowing biofilm to grow in the internal macro-pores. We used amoxicillin (C₁₆H₁₉N₃O₅S) as the model antibiotic. The amoxicillin-removal rate contents with ICPB was greater by 40% vs. photocatalysis and 65% vs. biodegradation, based on the first-order kinetic simulation. While mineralization of amoxicillin was minimal for photocatalysis or biodegradation alone, it was ∼35% with ICPB. Photocatalysis alone led to accumulation of C₁₄H₂₁N₃O₂S; biodegradation alone resulted in accumulation of C₁₄H₂₁N₃O₃, C₁₆H₁₈N₂O₄S, and C₁₅H₂₁N₃O₃; but they were negligible after ICPB. As a result, ICPB reduced toxicity impacts measured by Staphylococcus aureas growth, Daphnia magna mobility, and teratogenicity to Zebrafish embryos. In contrast, photocatalysis alone increased each of the toxicity effects. In sum, ICPB gave greater removal and mineralization of amoxicillin, and it mitigated biotoxicity from treatment products.