Occurrence, transport, and ecological risk assessment of typical organophosphate flame retardants (OPFRs) in wastewater treatment plants (WWTPs): A case study in Suzhou, Eastern China

Organophosphate flame retardants (OPFRs), a family of emerging contaminants, are widely utilized in the chemical, electrical, and electronic industries. Municipal wastewater treatment plants (WWTPs) act as significant receptors for OPFR runoff. This study examined the occurrence, removal behavior, and potential risks of 10 specific OPFRs in nine representative WWTPs in Suzhou, China. Results indicated that the average concentrations of OPFR in the raw wastewater and residual sludge were 630.38 f 243.25 ng center dot L- 1 and 1408.46 f 1141.46 ng center dot g-1, respectively. The proportion of chloro-OPFRs was notably higher compared to previous studies. The concentration of OPFRs in the aqueous phase exhibited a significant correlation with total organic carbon content, while the concentration of OPFRs in the sludge was associated with both sludge retention time (SRT) and content of mixed liquid suspended solids. The oxidation ditch (OD) process, characterized by a longer SRT, demonstrated an overall removal efficiency of 63.13 % f 8.92 % for OPFRs, which was significantly higher than that in the anaerobic/anoxic/oxic (A/A/O, 23.03 % f 28.73 %) and anoxic/oxic (A/O, -46.39 % f 51.10 %) processes. Ecotoxicity risk assessment revealed that the effluent from Suzhou's WWTPs poses a medium risk to aquatic organisms mainly due to the presence of chlorinated OPFRs. These findings highlight the necessity of enhanced tertiary treatment and provide evidences to support rational production, use, and regulation of OPFRs in developed regions.