Ecotoxicity evaluation and removal of sulfonamides and their acetylated metabolites during conventional wastewater treatment

► The removal of selected sulfonamides was studied in 22 wastewater treatment plants. ► Five different acetylated metabolites were detected in both water matrices and sewage sludge. ► Hydraulic retention times and removals of sulfonamides were not correlated. ► EC50 was calculated for N4-acetylsulfapyridine and sulfapyridine for the first time. ► N4-acetylsulfapyridine was more toxic than its parent drug, sulfapyridine.