Laboratory Investigation of Mineralization of Refractory Nitrogen from Sewage Treatment Plants.

Laboratory studies were conducted and modeled to evaluate whether refractory organic nitrogen in tertiary-treated wastewater effluent could become bioavailable by conversion to mineral forms. Multiday incubations of effluent collected from the Branford and New Haven, Connecticut, waste water treatment plants (WWTP) revealed low but steady conversion of organic nitrogen to nitrate (NO3-). In Branford, the principal form of organic nitrogen was dissolved, and in New Haven it was particulate. Modeling suggested that in both the cases conversion to NO3- from organic forms occurred at several per cent per day, and appeared to happen via the intermediary NH4+. The results suggest that organic nitrogen may be an important source of bioavailable N, contributing to the problem of hypoxia in Long Island Sound and other estuaries.