Loading and removal of PAHs in a wastewater treatment plant in a separated sewer system

The loading and removal of polycyclic aromatic hydrocarbons (PAHs) were measured and estimated in a wastewater treatment plant in a separated sewer system in a suburban area of Japan. The influent 16 PAHs concentration was 219 +/- 210 ng L-1, whereas the effluent concentration was 43.5 +/- 42.5 ng L-1 (mean sd). No clear diurnal or weekly fluctuation was observed. However, evaluation of long-term changes revealed PAH fluctuations continuing for more than 1 week. Half of the PAHs (63%) were biologically or chemically transformed, or vaporized in the treatment plant, while the remainder were discharged with effluent (28%) and excess sludge (9%). Measurement of the per capita loading of the treatment plant revealed values of 142 +/- 53 and 28 +/- 11 mu g person(-1) day(-1) (mean +/- 95% confidence interval) for influent and effluent, respectively. Isomer ratio analysis revealed that the PAHs originated from a mixture of petroleum, petroleum combustion, and burning of biomass residues. (C) 2015 Elsevier Ltd. All rights reserved.