This research characterizes the proteins in domestic wastewater treatment plant effluents in order to understand the organic fraction of effluent nitrogen. Domestic wastewater treatment plants have been identified as a major source of excess nitrogen that leads to eutrophication in marine environments in general, and the Long Island Sound, in particular. Initiatives to reduce the nitrogen load into Long Island Sound are underway. In Connecticut, regulators have instituted a cap and trade program for nitrogen releases from wastewater treatment plants, and in western Massachusetts new NPDES permits are requiring facilities that release into receiving waters that flow into the sound to monitor and report influent and effluent nitrogen concentrations. The total nitrogen released by wastewater treatment facilities can be successfully reduced through the addition of a nitrification/ denitrification process that removes inorganic nitrogen; however, the process does not remove most of the organic nitrogen. While proteins comprise a significant fraction of wastewater effluent organic carbon and nitrogen, they have not been extensively characterized, and little is known about their fate in the environment.