Occurrence of antibiotics in typical pig farming and its wastewater treatment in Thailand

This study investigated antibiotics in pig feed and drinking water and their excretion together with manure and wastewater at a typical pig farm in Thailand. Among the 21 antibiotics analyzed, tetracyclines, macrolides, β-lactams, aminoglycosides, quinolones, sulfonamides, pleuromutilin, and florfenicol classes, were found as active ingredients in feed and drinking water and excreted together with pig wastes. Among them, doxycycline, tilmicosin, and amoxicillin were detected higher concentrations in wastewater (12.9–459.1 μg L-1), sediment (0.074–0.62 mg kg-1), and pig manure (0.45–4.1 mg kg-1). During wastewater treatment, those major antibiotics were remaining in pond water and settled sludge up to 79.5 μg L-1 and 24.2 mg kg-1, respectively. The normalized excretion mass of total antibiotics was determined as 11.2 mg head-1 day-1, contributed mainly from doxycycline (5.9 mg head-1 day-1), tilmicosin (2.8 mg head-1 day-1), and amoxicillin (2.2 mg head-1 day-1). Based on total pig production in Thailand, the excreted mass of antibiotics was estimated at 79.3 tons year-1.