Systematic analysis of occurrence and variation tendency about 58 typical veterinary antibiotics during animal wastewater disposal processes in Tianjin, China.

Residue of veterinary antibiotics (VAs) in the animal breeding industry has become a problematic environmental issue. However, the residual levels of VAs as well as their variation tendency, degradation mechanisms and relationships with other parameters during animal wastewater disposal processes are still obscure. This study measured different samples during wastewater disposal processes from three farms, and systematically analyzed the residue, migration and removal of 58 kinds of typical VAs (6 classes) in Tianjin, China. The results showed that about 44 kinds of VAs were quantitatively detected. Tetracycline antibiotics (TCs) usually had higher residual concentrations than other classes of VAs in the raw wastewater; the highest residual concentration was 130.67 ± 5.90 μg/L which occurred for chlortetracycline (CTC). Pig farms generally had more VAs species and higher residual concentrations than dairy farms, and the proportion of different VAs was similar for dairy farms. The final removal rates of different VAs classes varied largely (negative to > 99.87%), and the highest removal rates usually occurred in biological processes for adsorption and biodegradation effects, and occasionally occurred in the final effluents. The correlation coefficients between VAs removal rates and chemical oxygen demand (COD) removal rates were much higher than those of total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH4-N) in pig farms, while opposite conclusion was obtained in dairy farms. Among different classes, TCs presented the highest daily mass loading of ND ~ 10,453.8 ± 471.7 mg/d in the influent and ND ~ 1141.6 ± 58.9 mg/d in the effluent in farm 1.