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.