SRP485850 PRJNA1068586 Waste activated sludge metagenome We studied the effects of humic substances combined with ofloxacin on microbial communities and functional genes during anaerobic digestion of waste activated sludge. We found that the coexistence of HS and OFL significantly affected the community abundance of hydrolytic, acidifying, and methanogenic microorganisms. At the same time, the coexistence of HS and OFL significantly changed the expression of genes related to hydrolysis, acidification and methanogenesis.