Occurrence and removal efficiency of six polycyclic aromatic hydrocarbons in different wastewater treatment plants

Occurrence and removal efficiency of six polycyclic aromatic hydrocarbons (PAHs) (fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene) in wastewater were monitored at different treatment processes in three wastewater treatment plants (WWTPs) by using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Chromatographic separation was performed on a Waters Acquity UPLC BEHC18 column (1.7 μm, 2.1 mm × 50 mm). A 0.2 μm precolumn filter was used to protect the analytical column. The result indicated that (1) the total concentrations of six PAHs were 427, 318, and 220 ng L(-1) in the influent of three wastewater treatment plants, respectively. Among six PAHs, the content of fluoranthene was the highest, accounting for 62-66% of total PAHs. (2) Throughout the wastewater treatment process, different treatment units exhibited different removal efficiencies for six PAHs. Biological treatment stage and aerated grit chamber appeared to be necessary for effective removal of six PAHs. The removal efficiencies of six PAHs were 73-83% at biological treatment units, and 24-56% at the aerated grit stage, respectively. The final sedimentation and disinfection for PAH removal was minor.