Simultaneous determination and removal assessment of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in wastewater treatment plants, Zunyi, China

This study developed a liquid-liquid extraction method coupled with gas chromatography–mass spectrometry (GC-MS) for the simultaneous determination of 13 organochlorine pesticides (OCPs) and 9 polychlorinated biphenyls (PCBs) in wastewater. By optimizing the extraction solvent ratio ( n- hexane/dichloromethane 9:1, v/v) and adding 1 %(w/w) polyethylene glycol 4000 (PEG4000) as a phase-transfer catalyst, mean recoveries improved from 87.3 ± 6.4 % to 96.4 ± 4.8 %. The method was applied to analyze influent and effluent samples from 13 wastewater treatment plants (WWTPs) in Zunyi, Guizhou Province. Results showed that the average concentrations of Σ 13 OCPs and Σ 9 PCBs in the influent were 114.8 ± 30.1 ng/L and 23.1 ± 9.5 ng/L, respectively, while those in the effluent were 20.0 ± 5.5 ng/L and 4.2 ± 1.9 ng/L, respectively. The average removal efficiencies for OCPs and PCBs were 70.6 ± 21.0 % and 61.3 ± 27.8 %, respectively, with membrane bioreactor (MBR) processes demonstrating the highest and most stable removal performance. This work provides a reliable analytical approach and city-scale data to support monitoring of OCPs and PCBs and evaluation of WWTP removal performance. • n- Hexane/dichloromethane (9:1, v/v) + polyethylene glycol 4000 extracts organochlorine pesticides and polychlorinated biphenyls. • Zunyi wastewater treatment plants influent:organochlorine pesticides 114.8 ± 30.1 ng/L;polychlorinated biphenyls 23.1 ± 9.5 ng/L. • Average removal efficiencies: 70.6 ± 21.0 % for organochlorine pesticides and 61.3 ± 27.8 % for polychlorinated biphenyls. • Membrane bioreactor showed the highest and most stable removal of organochlorine pesticides and polychlorinated biphenyls.