The fate of wastewater-derived dissolved organic nitrogen in the aquatic environment

Dissolved organic nitrogen (DON) accounts for approximately two thirds of the nitrogen in the effluent from wastewater treatment plants equipped with nitrogen removal systems. Wastewater-derived DON consists of a variety of compounds such as amino acids, dimethylamine and consumer products, such as the synthetic chelating agent EDTA. Wastewater-derived DON is a water quality concern because it has the potential to stimulate algal growth in nitrogen-limited systems and to act as a precursor for the carcinogenic disinfection byproduct N-nitrosodimethylamine (NDMA).; To determine the fate of wastewater-derived DON in the environment, three different approaches were employed. In the first stage of the research, DON was characterized by measuring the concentration of specific organic nitrogen-containing compounds which accounted for less than 25% of the DON. The remaining DON was characterized through ultrafilters and solid phase resins (SPE). Most the wastewater-derived DON consisted of hydrophilic, low molecular weight compounds that could pass through a 1 kDa ultrafilter.; In the second phase of the research, the potential of wastewater-derived DON to cause cultural eutrophication was assessed with algal uptake experiments in the absence and presence of bacteria. Wastewater-derived DON did not stimulate algal growth in the absence of bacteria. In the presence of bacteria, approximately half of the wastewater-derived DON was eventually bioavailable for algal growth.; Finally, the fate of nitrogen-containing wastewater-derived NDMA precursors was evaluated in incubation experiments with aerobic bacteria. The NDMA precursors were stable for as long as 30 days. The stability of NDMA precursors is important for systems where wastewater effluent is discharged into a river, which is used as a drinking water source downstream, because the NDMA precursors may lead to the formation of NDMA when the water is subjected to chloramination. (Abstract shortened by UMI.)...