Nontarget Screening of Disinfection Byproducts in Treated Municipal Wastewater using Passive Sampling, GC×GC- TOFMS, and Advanced Data Analysis Tools

Abstract

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilizes polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), non-negative matrix factorization (NMF) spectral deconvolution for nontarget screening of DBPs in treated wastewater. PDMS samplers were deployed before and after the chlorination unit at a coastal treatment plant, and their extracts were analyzed using GC×GC-TOFMS. A multi-tiered stepwise screening procedure successfully screened out thousands of peaks, resulting in a final list of 22 candidate DBPs. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of 7 additional DBPs. Brominated DBPs were prevalent, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of the tentatively identified DBPs were evaluated using EPI SuiteTM and CompTox Chemicals Dashboard. The assessment of DBP toxicity unveiled significant toxicity levels to aquatic organisms and the potential for developmental toxicity, mutagenicity, and endocrine disruption in certain DBPs. Furthermore, specific DBPs were found to be active in numerous bioassays within the CompTox databases, highlighting their roles in diverse molecular initiating events that contribute to adverse outcome pathways. Additionally, 11 DBPs exhibited recalcitrance to biodegradation and high persistence in the environment. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks.