Occurrence, distribution and removal of polycyclic aromatic hydrocarbons in a typical process for textile wastewater treatment of the Pearl River Delta Region, South China

This investigation aimed at revealing the occurrence, distribution and removal of polycyclic aromatic hydrocarbons (PAHs) in a typical process for textile wastewater treatment of the Pearl River Delta Region, South China. The results demonstrated that 16 PAHs were all measured in the dissolved and adsorbed state excepting acenaphthylene in suspended solids. In the influent, the total PAHs ranged from 1210.18 to 1304.93 ng/L in the dissolved state, and the PAHs with 2 and 3 rings were the predominant, accounting for 83.78 +/- 3.66%, while, in the adsorbed state, it ranged from 2152.54 to 2554.18 ng/g, and the PAHs with 3 and 4 rings were the most abundant, accounting for 89.41 +/- 5.31%. The removal efficiencies of dissolved individual PAHs ranged from 81.38% to 100% in the whole treatment process, in which, PAHs with low molecular weight achieved higher removal efficiency in the anaerobic digestion step, and PAHs with high molecular weight (HMW) were easier to be removed in the sedimentation step. Such results verified that the number of benzene ring in PAHs was closely related to their occurrence, distribution and removal, and a risk assessment indicated that the HMW PAHs accumulated in the sedimentation tank might increase the environmental risk of excess sludge.