Emerging concerns of VOCs and SVOCs in coking wastewater treatment processes: Distribution profile, emission characteristics, and health risk assessment Academic Article in Scopus uri icon

abstract

  • © 2020 Elsevier LtdIn this study, the distribution profiles, emission characteristics, and health risks associated with 43 volatile and semi-volatile organic compounds, including 15 phenols, 18 polycyclic aromatic hydrocarbons (PAHs), 6 BTEX, and 4 other compounds, were determined in the wastewater treatment plant (WWTP) of a coking factory (plant C) and the succeeding final WWTP (central WWTP). Total phenols with a concentration of 361,000 ¿g L¿1 were the predominant compounds in the influent wastewater of plant C, whereas PAHs were the major compounds in the final effluents of both coking WWTPs (84.4 ¿g L¿1 and 30.7 ¿g L¿1, respectively). The biological treatment process in plant C removed the majority of volatile organic pollutants (94.1%¿99.9%). A mass balance analysis for plant C showed that biodegradation was the main removal pathway for all the target compounds (56.6%¿99.9%) except BTEX, chlorinated phenols, and high molecular weight (MW) PAHs. Chlorinated phenols and high MW PAHs were mainly removed via sorption to activated sludge (51.8%¿73.2% and 60.2%¿75.9%, respectively). Air stripping and volatilization were the dominant mechanisms for removing the BTEX compounds (59.8%¿73.8%). The total emission rates of the detected volatile pollutants from plant C and the central WWTP were 1,640 g d¿1 and 784 g d¿1, respectively. Benzene from the equalization basins of plant C and the central WWTP corresponded to the highest inhalation carcinogenic risks (1.4 × 10¿3 and 3.2 × 10¿4, respectively), which exceeded the acceptable level for human health (1 × 10¿6) recommended by the United States Environmental Protection Agency. The results showed that BaP exhibited the highest inhalation non-cancer risk, with a hazard index ratio of 70 and 30 for plant C and the central WWTP, respectively. Moreover, the excess sludge generated during wastewater treatment should also be carefully handled because it adsorbed abundant PAHs and chlorinated phenols at coking plant C (58,000 ¿g g¿1 and 3,500 ¿g g¿1) and the central WWTP (622 ¿g g¿1 and 54 ¿g g¿1).

publication date

  • October 1, 2020