Mass flow of PAHs and fragrance substances in the sedimentation tanks of conventional domestic wastewater treatment plant–trace organic chemicals passing through sedimentation tank

This study examines the behavior of trace organic pollutants, specifically fragrances (OTNE, HHCB, AHTN), caffeine, and polycyclic aromatic hydrocarbons (PAHs), within a conventional wastewater treatment plant (WWTP). By systematically quantifying sedimentation ratios across treatment stages, our findings reveal an unexpectedly low sedimentation efficiency for these hydrophobic trace pollutants, particularly in the final sedimentation tank. This phenomenon is linked to the removal efficiencies of suspended solids (SS), highlighting a previously underexplored aspect of sedimentation processes. Additionally, the study investigates the partitioning behaviors of these compounds between solid and liquid phases and provides insights into the role of secondary sedimentation in pollutant management. These findings address a critical gap in the literature by coupling sedimentation ratios with SS removal efficiencies, offering a novel perspective on the limitations of conventional WWTPs in handling hydrophobic pollutants. The results provide a foundation for future research aimed at optimizing sedimentation mechanisms and exploring advanced treatment strategies to improve pollutant removal efficiency and environmental protection.