The occurrence of sulfonamide antibiotics(SAs) was investigated in the six sewage treatment plants(STPs) of Beijing,China.Of the 13 objective antibiotics,sulfamethoxazole,sulfapyridine,sulfamerazine,sulfadiazine and sulfamethizol were detected in the influents with the average concentrations of 1.2 ± 0.45,0.29 ± 0.25,0.048 ± 0.012,0.35 ± 0.52 and 0.33 ± 0.21 μg·L-1,respectively,and those in the effluents were 1.4 ± 0.74,0.22 ± 0.19,0.021 ± 0.008,0.22 ± 0.21and 0.01± 0 μg·L-1,respectively.Sulfamethoxazole was the predominant compound detected,and was found in all wastewater samples with the other two compounds sulfapyridine and sulfamerazine.It should be noted that sulfadiazine was first reported in wastewaters,and the concentration levels of all detected compounds except for sulfamethizol(detected once in the effluent samples) in the influents were observed to be similar to those in the effluents.From the data in this study,it can be found that sulfamethoxazole,sulfapyridine,sulfamerazine and sulfadiazine could be partly removed in anoxic and aerobic treatment unit and vice versa in anaerobic process,which led to their low or even negative removal rates in the effluents.The increase on the concentrations of sulfamethoxazole and sulfapyridine in the effluents was found probably due to the biotransformation of their acetylated forms in anaerobic treatment unit.In addition,it was observed that the biodegradation of sulfamethoxazole and sulfapyridine could partly occur during the anoxic and aerobic process,while sulfamerazine was partly eliminated in the anaerobic and anoxic units.
