Relationships between sulfachloropyridazine sodium, zinc, and sulfonamide resistance genes during the anaerobic digestion of swine manure

- Dissipation of sulfachloropyridazine-Na delayed by Zn during anaerobic digestion.
- Abundances of intI1 and intI2 decreased after anaerobic digestion for 52 days.
- Zn increased sul1 and sul2 abundances by 1.3-10.7 times after anaerobic digestion.
- Sulfachloropyridazine-Na and Zn changed the microbial community during digestion.

In this study, swine manure containing sulfachloropyridazine sodium (SCPS) and zinc was subjected to mesophilic (37 °C) anaerobic digestion (AD). The absolute abundances (AAs) of antibiotic resistance genes (ARGs) were evaluated, as well as intI1 and intI2, and the degradation of SCPS according to variation in the amount of bio-available zinc (bio-Zn). In digester that only contained SCPS, the concentrations of SCPS were lower than that digesters both contain SCPS and Zn. Compared with the control digester, the addition of SCPS increased the AAs of sul1, sul3, drfA1, and drfA7 by 1.3-13.1 times. However, compared with the digester with SCPS but no added Zn, the AAs of sul3, drfA1, and drfA7 were decreased by 21.4-70.3% in the presence of SCPS and Zn, whereas sul1 and sul2 increased 1.3-10.7 times. There were significant positive correlations (P < 0.05) between the concentrations of SCPS with several ARGs and bio-Zn.