AWWA WQTC58855

Dissolved organic nitrogen (DON) has not received much attention by the drinking water community despite the potential role of DON on disinfection byproduct (DBP) formation and speciation, biostability of raw and finished water, and membrane fouling. The European Community directive has a maximum admissible concentration for org-N of 1 mg Kjeldhal-N/L (DON+NH₄ ⁺), but the US has no similar guidelines. Currently, there are no reports of DON fate during water treatment. Furthermore, some chemicals added during water treatment (e.g., polymers) contain organic nitrogen and their contribution to DON in finished water has largely been overlooked. As a first step in understanding the fate of DON during water treatment, this paper provides evidence that some forms of DON are removed during alum coagulation. Over the past two decades marine scientists, limnologists, and ecologists have studied DON, offering several techniques for measuring DON concentrations and understanding DON occurrence. DON is comprised of a broad spectrum of molecular weight compounds, including amino acids, amides, heterocyclic-N, and lesser amounts of uncharacterized nitriles and nitrosamines (Westerhoff et al. 2002). This paper summarizes DON concentrations and DOC/DON ratios in over 14,000 surface waters based upon an analysis of USGS-NAWQA datasets, which use a TKN method (ammonia + DON) with a TKN detection limit of 0.2 mgN/L. The median DON concentration was 0.34 mg-N/L, although approximately 30% of the samples had a TKN value of less than 0.2 mgN/L. Primary sources of DON in watersheds include: upstream wastewater discharges; infiltration and runoff of organic fertilizers from agricultural areas; excretion of algae products in eutrophic waters; urban runoff; and, forest litter. DON concentrations in surface waters are commonly higher than groundwater levels. Despite the information on DON sources, occurrence, and fate within watersheds, there has been no interpretation of DON occurrence as related to the management of drinking water supplies. Includes 8 references, tables, figures.