Aerobic degradation of antimicrobial compounds in digested swine manure , A laboratory study of benefits, potential and microbial impact of moving biomass carriers

Agricultural use of nutrient-rich manure improves crop yield, biodiversity, soil structure, and water and nutrient availability. Manure from industrial pig farming often contains high levels of antibiotics as only 10-30% of the antibiotics are metabolized by the animal, thus soil application of manure is contributing to the spread of antibiotics and antibiotic-resistant genes. As anaerobic digestion fails to completely remove the antibiotics and antibiotic-resistant genes from manure, this study investigates aerobic moving bed biofilm reactors (MBBRs) as a potential post-treatment solution. Eleven compounds where analysed in small batch MBBRs with pig manure and synthetic wastewater for three weeks. The aerobic MBBRs degraded the compounds with high efficiency. The antibiotic-resistant gene (ARG) abundance showed a positive relation to the antibiotic concentration supporting the idea that increased degradation of the antibiotics will reduce direct ARG spread to the environment. The overall abtibiotic resistance of the measured ARGs was dominated by sulfonamide resistant genes. The presence of biofilm carriers had no impact on the ARGs in the manure sludge in the reactors. We therefore propose to treat anaerobically digested manure by aerobic biofilm treatment for antibiotic removal.