Occurrence of parent and substituted polycyclic aromatic hydrocarbons in typical wastewater treatment plants and effluent receiving rivers of Beijing, and risk assessment

Sixteen polycyclic aromatic hydrocarbons (PAHs) and some typical substituted polycyclic aromatic hydrocarbons (SPAHs) were investigated in wastewater treatment plants (WWTPs) and effluent effluent-receiving rivers in order to indentify the elimination of these compounds in WWTPs, as well as the potantial potential risk in the effluent-receiving rivers. The concentrations of ΣPAHs in the total phase (combined dissolved and adsorbed phases) in influent were between 944.1 and 1246.5 ng·L−1, and ΣSPAHs, including methyl PAHs (MPAHs) and oxygenated PAHs (OPAHs), between 684.9 and 844.9 ng·L−1. Regarding the SPAHs, the concentrations of ΣOPAHs (312.3 ng·L−1) were higher than those of ΣMPAHs (271.8 ng·L−1). The total removal efficiencies of PAHs in the biological treatment processes were between 59% and 68%, and those of SPAHs were a little lower (58–65%). The removal efficiency in the adsorbed phase was higher than in the dissolved phase. The concentrations of PAHs and SPAHs in the effluent were a little higher than in the receiving river. According to a PAH risk assessment of the effluent, 7 carcinogenic PAHs accounted for a relatively high proportion. Benzo[a]pyrene (BaP) and Dibenz[a,h]anthracene (DBA) were major contributors to the TEQs in the effluent of WWTPs, which should be taken into consideration.