Sewage water, the influent of the secondary sedimentation tanks, the final effluent, sludge from biological pools, and dewatered excess sludge samples from eight wastewater treatment plants (WWPTs) in Suzhou, including those from seven A2/O processes and one oxidation ditch process, were collected in 2017 to study the pollution characteristics of organophosphorus flame retardants (OPFRs) in WWPTs. Accelerated solvent extraction (ASE) combined with a solid-phase extraction method was used to detect the concentration of 10 organic phosphorus flame retardant (OPFRs). The removal efficiency of OPFRs was compared and final daily emissions were estimated. The results showed seven kinds of OPFRs were detected in the influent, final effluent, and sludge. The total content of OPFRs in the influent ranged from 0.74 to 222.65 μg ·L-1 (average 65.56 μg ·L-1), while the content in the final effluent was between 0.46 and 175.41 μg ·L-1 (average 22.99 μg ·L-1). The concentration in the effluent of the secondary sedimentation tank was between 0.48 and 178.14 μg ·L-1 (average 43.14 μg ·L-1). The daily emission of OPFRs in final effluent was 36.69-2177.12 g ·d-1. The content in the dewatered excess sludge was between 89.32 and 596.24 μg ·g-1 dw (average 249.35 μg ·g-1 dw), the minimum daily emission was 3.57-7.15 kg ·d-1, and the maximum was 47.70-95.40 kg ·d-1. The oxidation ditch process has a good removal rate of OPFRs, at 92%, while the A2/O process removal rate covered a large range from 11%-99%. Three chlorinated OPFRs, TCEP, TCPP, and TDCPP, were the main components in the influent and final effluent, mainly because of the large consumption of OPFRs and also because the removal rate by the traditional wastewater treatment technology was low.
Keywords: A2/O; organophosphorus flame retardant (OPFRs); oxidation ditch; wastewater treatment plant.