Priority list of emerging contaminants in domestic wastewater treatment plants and their removal by different secondary treatment methods

• 84 emerging contaminants monitored across nine WWTPs in Japan. • Primary effluents were highly affected by the matrix effect. • 13 emerging contaminants prioritized for monitoring studies in water systems. • 3 biological treatment methods were compared for removal of emerging contaminants. • Bromobutide, a prioritized contaminant, has low removal. In this study, the contributions of wastewater treatment plants (WWTPs) to emerging contaminants in the environment were monitored. Samples were collected at nine WWTPs with sampling on three separate days at each WWTP. The WWTPs used the different secondary treatment methods as follows: conventional activated sludge (WWTPs 1, 2, and 9), aerobic contact oxidation (WWTPs 5 and 6), and oxidation ditch (WWTPs 3, 4, 7 and 8). A significant matrix effect was observed in primary effluent samples but not in secondary and final effluent samples. The matrix effect was more pronounced during sample preparation using solid-phase extraction. Triethylene glycol dimethyl ether and glycidyl methacrylate had high removal rates (> 50 %) with all three treatment methods. By contrast, tebuconazole and bromobutide had low removal rates or were not removed by any of the treatment methods. Thirteen compounds in various chemical classes were prioritized on the basis of their concentrations in the final effluent relative to their predicted no-effect concentrations. These compounds were surfactants (diethanolamine and N -methyldidecylamine), an industrial solvent (dicyclohexylamine), herbicides (2,4-dicholorophenoxyacetic acid, bromobutide, and butachlor/pretilachlor), an antiseptic (triclosan [and its chlorinated adducts]), industrial chemicals (hexamethylene diacrylate, pyridine, and decanoic acid), plasticizers (tributyl phosphate and tricresyl phosphate), and a corrosion inhibitor ( N,N -dimethyldodecylamine). Our results imply that WWTPs are sources of these compounds in the environment. These compounds could threaten ecosystems in receiving waterbodies and future studies should monitor release of these emerging contaminants from WWTPs. Funding: This work was supported by the Environment Research and Technology Development Fund JPMEERF20215G01 of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan and by KAKENHI Grand-in-Aid for Scientific Research (A) 21H04940.