The introduction of pharmaceutical residues into aquatic environment has threatened the livelihood of aquatic organisms worldwide. The entrance of these residues into the environment originates from sewage effluents discharged from domestic wastewater treatment plants. Up to date, their presence in the sewage effluent is not monitored in Malaysia. Therefore, this study aims to identify the presence of pharmaceutical residues in the effluent domestic sewage treatment plants employed in Johor Bahru, Malaysia. Briefly, ten pharmaceutical compounds, including acetaminophen, sulfathiazole, sulfamethazine, sulfamethoxazole, clarithromycin, trimethoprim, lincomycin, carbamazepine, naproxen and ibuprofen, were selected based on their worldwide consumption. Sewage samples from five different types of sewage treatment system were collected. The samples were filtered prior to solid-phase extraction. Finally, the extracted samples were analysed with LC-MS/MS. The analyses showed that only sulfathiazole was not present in all effluent samples. Acetaminophen recorded the highest concentration of 9299 ng/L in an Imhoff Tank. Meanwhile, the lowest concentration of pharmaceutical residue detected was sulfamethazine, i.e. 0.843 ng/L, in a sequencing batch reactor. Overall, six out from ten pharmaceutical residues were found in all sewage samples denoting the inefficiency of current biological treatment systems in removing trace pharmaceutical compounds from sewage
