Enhanced removal of sulfamethoxazole in a layered intimately coupled photocatalysis and biodegradation system encapsulated in calcium alginate

The high consumption of antibiotics has raised increasing concerns due to their adverse effects on ecosystems and human health. Intimately coupled photocatalysis and biodegradation (ICPB) technology attracts growing focuses for its performance in antibiotic removal. However, microbial detachment under irradiation and difficulty in photocatalyst recovery hinder the practical application of the ICPB. In this study, the removal performance of sulfamethoxazole (SMX) was investigated by a visible light-driven ICPB system in a layered reactor, using calcium alginate (CA) to encapsulate ZnO/g-C 3 N 4 as photocatalytic microspheres. The results indicated that CA could not only immobilize the photocatalyst for recovering, but also had a strong adhesive ability to prevent microorganisms detaching from biofilm carriers, thus achieving higher SMX removal efficiency in the ICPB-CA system (51.9%) than the ICPB system without CA (31.7%). Layered reactor facilitated an extremely enhanced SMX removal by the ICPB system (86.6%) compared to the non-layered ICPB system, due to the alleviation in shading effects of microorganisms on the photocatalysts through a physical separation. Combing the smaller molecules and less biotoxicities of degradation products compared to SMX, it was inferred that ICPB had the potential in elimination of antimicrobial activities of antibiotics during wastewater treatment. The findings imply the feasible application of ICPB by adopting CA encapsulation in the layered system during treatment of antibiotics in wastewater.