Coking wastewater treatment plant as a source of polycyclic aromatic hydrocarbons (PAHs) to the atmosphere and health-risk assessment for workers

Abstract

PAHs were identified and some of them were determined in the air around a coking wastewater treatment plant (WWTP) using passive air samplers. Seventy seven PAHs were found in the emissions from the degreasing tanks, the aeration tanks and the secondary clarifiers. ∑PAH concentrations within the plant (373.3±27.3–12959.5±685.9ng/m3) were 3–41 times higher compared to the reference sites (315.7±50.2–363.4±77.5ng/m3). The identification of numerous PAHs and high concentrations of these selected ones in the air of the studied sites indicated that the coking WWTP was a new source of atmospheric PAHs. Variations in the PAH pattern were observed in air within the coking WWTP. For example, Flu and Pyr accounted for 35–46% of the total contents at the degreasing tanks, but less than 10% at the hydrolytic tanks. The calculation of the diagnostic ratios suggested that PAHs in the emissions had the source characters of coal combustion. Furthermore, highly elevated PAH concentrations were determined at the degreasing tanks compared to the other tanks (i.e., aeration tanks and secondary clarifiers) and likely associated with their high concentrations in the coking wastewater and increased volatilization at high water temperature. Health risk assessments were carried out by evaluating the inhalation PAH exposure data. The resultant inhalation exposure levels due to TEQBaP for workers ranged from 1.6±0.6 to 71.2±8.2ng/m3, and the estimated lung cancer risks were between 0.1×10−3±0.1×10−4 and 5.2×10−3±0.5×10−3, indicating PAHs in the air around the degreasing tanks and the aerobic tanks would have potential lung cancer risk for the operating workers.