Ozonation Treatment Increases Chlorophenylacetonitrile Formation in Downstream Chlorination or Chloramination

Chlorophenylacetonitriles (CPANs) are an emerging group of aromatic nitrogenous disinfection byproducts (DBPs). However, their dominant precursors and formation pathways remain unclear, which hinders the further development of effective control strategies. For the first time, CPAN precursors were screened by conducting formation potential (FP) tests on real water samples from six drinking water treatment plants (DWTPs). The average overall removal of CPAN precursors across all six DWTPs was only 10%. Moreover, ozonation increased CPAN precursors by 140% on average. Fluorescence spectroscopy showed a dramatic reduction in aromatic proteins, tyrosine-like proteins, and tryptophan-like proteins following ozonation. Low-apparent-molecular-weight (AMW) (