Encapsulated Hydrogels Enhance Sulfamethoxazole Removal via Structure-Driven Microbial Metabolisms

The widespread occurrence of antibiotics in aquatic environments poses serious ecological and public health risks, necessitating advanced treatment strategies. Biohydrogels present a versatile platform for enhancing the removal of sulfamethoxazole (SMX) by combining adsorption with microbial degradation. In this study, polyvinyl alcohol-sodium alginate (PVA-SA) hydrogels were used to immobilize anaerobic sludge, forming two hydrogel systems (gel7.5 and gel9) with distinct physical structures. Both systems achieved significantly higher SMX removal efficiencies (90.2 and 87.7%) compared with the control (67.7%). Metagenomic analysis revealed differential enrichment of key SMX-degrading genera, with Lentimicrobium dominant in gel7.5 and Pseudomonas and Acinetobacter enriched in gel9. Functional gene profiling further indicated that gel7.5 and gel9 favored distinct monooxygenase pathways for SMX transformation. These results demonstrate that the hydrogel composition shapes microbial community function and biodegradation mechanisms, offering an effective and adaptable solution for treating antibiotic-contaminated wastewater while mitigating the risk of resistance gene dissemination.