Occurrence and the potential ecological risk of veterinary antimicrobials in swine farm wastewaters in Japan: Seasonal changes, relation to purchased quantity and after termination of oxytetracycline usage

Abstract

This study provides the first comprehensive investigation of the residual concentrations of eight classes of antimicrobial agents (AMs, 20 compounds) in 13 swine wastewater treatment facilities in Japan. These facilities implemented the aerobic activated sludge (AS) or its alternative methods. The maximum concentrations before treatment were found at the level of 7100, 6900, 6000, 3600, 3400, and 1400 µg/L for tilmicosin, oxytetracycline (OTC), chlortetracycline, lincomycin , sulfamethoxazole, and trimethoprim, respectively. The highest detection rate (96.3%) in influents was noted for the morantel, which was a feed additive. The seasonal difference in residual concentration was much greater for tetracyclines (TCs) and macrolides (MLs) when their residual concentrations were high, especially in the cold season. There was a positive correlation between the purchased quantity of TCs and fluoroquinolones (FQs) and their residue levels detected in the effluents (p 99.8% and >92% in the influents and effluents, respectively. This data suggested that it is essential to reduce the amount used and introduce more efficient methods and operating conditions to constantly remove AMs during the treatment to reduce the risk of AM discharge from swine farms.

Keywords

• Antimicrobials
• Pig
• Aerobic wastewater treatment
• Activated sludge method
• Risk assessment