In the past, relatively minor attention has been focused on DON despite observations that both low and high molecular weight molecules containing organic nitrogen (e.g., simple amino acids, peptides, algal-derived humic substances) have been implicated as precursors of DBPs such as trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), nitromethanes, and nitrosamines like nitrosodimethylamine (NDMA). Nitrogenous organic matter has also been implicated as membrane foulant material. Dissolved organic carbon (DOC) is usually used as the surrogate for natural organic matter (NOM); NOM contains various ratios of carbon, oxygen, hydrogen, nitrogen, sulfur, and trace metals. While information exists on NOM removal through DOC measurements, it is unclear if DON is distributed equally among different molecular weight fractions. The project involved three phases. First, several pretreatment processes were evaluated to selectively remove inorganic nitrogen from samples, thus allowing more accurate and a potentially direct quantification of DON. Second, a survey of 28 water treatment plants was conducted during two different seasons to assess DON and related organic matter occurrence. Additional sampling of reclaimed wastewater systems was also conducted. Third, laboratory experiments were conducted with alum and cationic polymer coagulants, activated carbon, or disinfectants (free chlorine or monochloramine) to assess the ability to remove DON and understand its reactions with disinfectants.