Abstract
For the purpose of elucidating the behavior of nonionic surfactant nonylphenol polyethoxylates (NPnEOs) in sewage treatment plants (STPs) in Japan, investigations on the distribution of NPnEOs and their metabolites and halogenated compounds (collectively referred to“NPE-c”) in 40 domestic STPs were made. As a result, it was clarified that influx of NPnEOs was found into all 40 STPs and also that metabolites and halogenated compounds produced during the treatment process were discharged into water environment. Also, it was made evident that NPnEOs were removed on an average of 70% as NPE-c by going through the treatment processes and that the majority of the removal was accomplished in the biological treatment processes. Further, higher removal efficiency was observed in the AO/A2O processes than in the conventional activated sludge processes as a whole. Also, STPs employing an advanced treatment method such as chemical oxidation or rapid filtration showed an especially high removal efficiency.
