Indexed on: 27 Oct '17Published on: 27 Oct '17Published in: Environmental technology
A long term investigation, which covered 10 sampling campaigns over three years, was performed to evaluate the occurrence, removal and risk of ten pharmaceuticals in two full-scale sewage treatment plants (STPs) in Guangdong, South China. Target pharmaceuticals except for clofibrate and ibuprofen were detected in every sample, with mean concentrations of 12.5-685.6 ng/L and 7.9-130.3 ng/L in the influent and effluent, respectively. Salicylic acid was the most abundant compound in both the influents and effluents in the two STPs. For most pharmaceuticals, the seasonal variation in the influent showed the highest concentrations in January and lowest concentrations in July due to their consumption and rainfall. No significant differences by season were observed in various treatment process sections and the effluents. The overall removal rates varied strongly between individual pharmaceuticals and even for the same type of pharmaceutical at different sampling times. Ibuprofen and fenoprofen presented high removal rates (> 90%) and some of the targets like gemfibrozil, mefenamic acid, tolfenamic acid and diclofenac were detectable with significantly higher mass loads in effluents than in influents. Studies of the five efficiently eliminated pharmaceuticals show that the primary treatment and secondary treatment contributed to most pharmaceutical removal, the anoxic tank made a negligible contribution to their elimination. According to the results produced from the calculation of the risk quotient, only diclofenac might pose a risk to the aquatic environment.