Antibiotics in Digested Slurry Treated with Anaerobic Lagoon and Advanced Treatment: Occurrence and Ecological Risk Assessment

Antibiotics as emerging contaminants have received much attention in recent years. Anaerobic digestion of animal manure contained antibiotics serves as an important reservoir of antibiotics in intensive farms. However, it is still lack of research report on antibiotics in duck farms in China, especially treated by anaerobic lagoon (CAL) process. This study analyzed residual concentrations of 15 common veterinary antibiotics in digested slurry (DS) collected from CAL and advanced treatments in an intensive duck farm in Jiangsu Province, China. The CAL treatment could effectively remove the target antibiotics, and the removal rates of tetracyclines (TCs), sulfonamides (SAs), and quinolones (QLs) ranged 93.8–100%, 51.5–98.9%, and 70.3–91.3%, respectively. The maximum residual concentrations of TCs, SAs, and QLs were 2.36, 4.02, and 29.30 µg/L, respectively, in DS samples. Advanced treatments including sedimentation tank, aeration tank, and ozonation could completely eliminate on most of target antibiotics, except for sulfamonomethoxine, sulfapyridine, and norfloxacin. The results of the ecological risk assessment indicated that residual antibiotics in DS samples can cause hazards to microorganisms and plants in the soil environment. The associated advanced treatment of DS samples still indicated potential ecological risk to aquatic environment, especially for ciprofloxacin. The residual antibiotics in DS samples collected from CAL and associated advanced treatments in an intensive duck farm increase their potential risks to the soil and aquatic ecosystems. The findings provide more information for investigating antibiotic residues in intensive farming, as well as insights into the far-reaching ecological risks of using the DS obtained from CAL treatments. Graphical Abstract