Unveiling the Occurrence and Potential Ecological Risks of Organophosphate Esters in Municipal Wastewater Treatment Plants across China

Organophosphate esters (OPEs) discharged from wastewater treatment plants (WWTPs) have attracted increasing concerns because of their potential risks to aquatic ecosystems. The identification of the structures of OPEs is a prerequisite for subsequent assessment of their environmental impacts, which could hardly be accomplished using traditional target analytical methods. In this study, we describe the use of suspect and nontarget screening techniques for identification of organophosphate triesters and diesters (tri-OPEs and di-OPEs) in the influent and effluent samples acquired from 25 municipal WWTPs across China. There are totally 33 different OPE molecules identified, 11 of which are detected in wastewater for the first time and 4 are new to the public. In all tested samples, di-OPEs account for a significant portion (53% on average) of the total OPEs (ng/L-μg/L). More importantly, most of the OPEs could not be eliminated after treatment in these WWTPs, while some of the di-OPEs even accumulate. The research priority of OPEs in the effluent based on ecological risk was also analyzed, and the results reflected a previously unrecognized exposure risk of emerging OPEs for aquatic living organisms. These findings present a holistic understanding of the environmental relevance of OPEs in WWTPs on a country scale, which will hopefully provide guidance for the upgrade of treatment protocols in WWTPs and even for the modification of governmental regulations in the future.