Changes in Dissolved Organic Matter Composition and Disinfection Byproduct Precursors in Advanced Drinking Water Treatment Processes

Molecular changes in dissolved organic matter (DOM) from treatment processes at two drinking water treatment plants in Japan were investigated using unknown screening analysis by Orbitrap mass spectrometry. DOM formulas with carbon, hydrogen and oxygen (CHO–DOM) were the most abundant class in water samples, and over half of them were commonly found at both plants. Among the treatment processes, ozonation induced the most drastic changes to DOM. Mass peak intensities of less saturated CHO–DOM (positive (oxygen subtracted double bond equivalent per carbon (DBE–O)/C)) decreased by ozonation, while more saturated oxidation byproducts (negative (DBE–O)/C) increased and new oxidation byproducts (OBPs) were detected. By Kendrick mass analysis, ozone reactions preferred less saturated CHO–DOM in the same alkylation families and produced more saturated alkylation families of OBPs. Following ozonation, biological activated carbon filtration effectively removed