The influence of an upgrade on the reduction of organophosphate flame retardants in a wastewater treatment plant

Abstract

The appearance of an increased amount of organophosphate flame retardant (OPFRs) in natural water is related the treated effluents from wastewater treatment plants (WWTPs) and thus understanding the OPFRs concentration and reduction variation in WWTPs would provide valuable insight into OPFR management and reduction. In this study, we have analyzed OPFRs (10 kinds: tris(chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate (TDCP), tris(phenyl) phosphate (TPhP), tris(2-ethylhexyl) phosphate (TEHP), diphenylcresylphosphate (DCP), tris(methylphenyl) phosphate (TCP), tris(2-butoxyethyl) phosphate (TBEP), 2-ethylhexyl diphenyl phosphate (EHDP), and tris(butyl) phosphate (TBP)) in both water and sludge samples collected from different phases of a WWTP upgrading. The results show that TCPP and TCEP were mainly present in the aqueous phase, whereas TEHP dominated in the solid phase. The overall OPFR reduction efficiencies were above 40% through whole treatment processes by all the phases. More OPFRs reduction efficiency in primary sedimentation tanks was higher mainly because of bigger tank volume. The anaerobic zone in all cases could decrease OPFRs by over 13%. The removal of OPFRs in the oxic zone highly varied under the influence of the aeration pipe, water temperature, and aeration amount. Compared with chlorinated OPFRs, aryl and alkyl OPFRs were easier to reduce and less affected by the upgrading. Because OPFRs have been widely used in plastic materials such as pipes, WWTP upgrading – which usually requires more aeration and addition of reagents and instruments and the aim of which is normally to reduce more COD, N and P -- has introduced more OPFRs into the water within the WWTP.