The Long Island Sound Study (LISS), a partnership between the United States Environmental Protection Agency, New York, and Connecticut, was formed by Congress to address water quality concerns related to eutrophication and hypoxia. Nitrogen was identified as the causal agent for the observed water quality problems, and a set of phased Nitrogen removal targets were implemented to reduce discharges to the Sound by more than 50 % over a 15-year period of time. Over the course of those 15 years, the nitrogen reductions will ‘step-down’ so that a phased adaptive management approach is taken to achieve the long-term nitrogen removal goals, with a 23% reduction from 1990 levels after 5 years (16 mg/L TN based on 2005 flow), a 44% reduction after 10 years (12 mg/L TN based on 2005 flow) and the full 50% reduction in 15 years (8.5 mg/L TN based on 2005 flow).
The New York City Department of Environmental Protection (NYCDEP) has four wastewater pollution control plants (WPCPs) that discharge to the Upper East River, and ultimately, Long Island Sound: Hunts Point, Tallman Island, Bowery Bay, and Wards Island, with a combined secondary treatment capacity of over 700 mgd. Step-Feed Biological Nutrient Removal (BNR) was identified as the most feasible technology for implementation at the large scale WPCPs to achieve the necessary Nitrogen removal. To assist in the development of BNR designs and the management of these simultaneous upgrades, the Department formed the Advanced Wastewater Treatment (AWT) Team, to provide design and program management expertise. The AWT Team has assisted NYCDEP in meeting Consent Order milestones, development of BNR facility plans, production of site specific BNR design guidelines, review of BNR design drawings and specifications, and the development of programmatic guidance for design engineers at each of the four WPCPs.