Behaviour of nonylphenol ethoxylates in sewage treatment plants in Japan – biotransformation and ecotoxicity

Abstract

Behavior of nonylphenol polyethoxylates (NPnEOs, n; number of ethoxy units) in 40 full-scale sewage treatment plants (STPs) in Japan was studied. Primary effluent (PE), secondary effluent (SE) and final effluent (FE) samples were collected from the STPs, and NPnEOs, their metabolic intermediates and related halogenated derivatives were quantitatively analyzed. Parent NPnEOs (n=4–18) were detected at concentrations between 5.1 and 1035 μg/l with the average value of 296 μg/l in the PEs from all the STPs, indicating widespread pollution of NPnEOs in Japan. The analyses of SEs revealed that normal biological treatment can relatively efficiently remove NPnEOs, however, the biotransformation led to the formation of biologically-refractory metabolites like nonylphenol (NP), NPnEOs with shorter ethoxy chains (n=1–3; NP1-3EO) and nonylphenol carboxylic acids (NP1-3EC). Halogenated (chlorinated or brominated) NPnEOs and/or NPnECs (n=1–2), which are considered to be produced as by-products during the disinfection processes using chlorination, were also found in SEs and/or FEs from 25 STPs. The ecotoxicity assays showed that the metabolic intermediates of NPnEOs possess higher acute toxicity against Daphnia magna and estrogenic activity than the parent surfactant NPnEOs.