Occurrence and environmental impact of pharmaceutical residues from conventional and natural wastewater treatment plants in Gran Canaria (Spain).

The presence and fate of pharmaceutical residues in environmental samples are of great interest. There is a vast number of studies published regarding their input, presence, effects and risks in ecosystems. Moreover, it has been demonstrated that the primary source of input of these contaminants in the environment is from Wastewater Treatment Plants (WWTPs). It is therefore essential to evaluate the efficiency of commonly used treatments and the necessity of applying novel purification processes in order to eliminate or reduce the concentration of pharmaceuticals from wastewater or from the effluent of WWTPs. The aim of this work was to quantify twenty-three pharmaceutical compounds in the aqueous phase at different stages of a conventional and a natural WWTP situated in Gran Canaria (Spain). The results indicate concentration levels in the range of 0.004±0.001 to 59.2±11.7μgL-1 and 0.018±0.001 to 148±14.7μgL-1 from conventional and natural WWTPs, respectively. Better efficiency was, however, offered by the conventional WWTP with a removal median of 99.7%. In addition, the impact on different aquatic organisms (algae, daphnids and fish) was assessed in terms of risk quotients. The results reveal a possible highly harmful effect towards organisms by gemfibrozil, ibuprofen and ofloxacin.