Modeling Carbon Dosing Strategies for BNR Optimization in NYC
- S. Galst, I. Chu, R. Latimer, P. Pitt, M. Lynch - Hazen and Sawyer
- M. Motyl - CH2MHill
- S. Liu, M. Osit - New York City Department of Environmental Protection (NYCDEP)
The New York City Department of Environmental Protection (NYCDEP) is currently under Consent Judgment to upgrade to and operate eight of their 14 Wastewater Treatment Plants (WWTPs) in the Biological Nitrogen Removal (BNR) process. These upgrades are being implemented at four WWTPs discharging to the Upper East River and four WWTPs discharging to Jamaica Bay. The estimated capital cost for the BNR program is in excess of $1.5 Billion, and the upgrades will be implemented over a 30-year timeframe.
BNR Upgrades and Expected Nitrogen Reductions:
Faced with a future 2017 effluent total nitrogen discharge limit 64,000 lbN/d less than the original discharge of 108,375 lbN/d from 2009, the NYCDEP began implementing a series of BNR upgrades at four strategic East River WWTPs, including Bowery Bay (150 mgd), Hunts Point (200 mgd), Tallman Island (80 mgd), and Wards Island (275 mgd). Simultaneously, BNR upgrades are being implemented at several WWTPs located along Jamaica Bay, including 26th Ward (85 mgd) and Jamaica (100 mgd), and will be implemented in the future at Coney Island (110 mgd) and Rockaway (45 mgd). The future Jamaica Bay effluent TN discharge limits are performance based, and will be determined based on effluent quality over a year of BNR operations.
Construction of the BNR upgrades has been underway over the past decade, and the NYCDEP has reached a point where the upgrade construction is now complete at some of the BNR plants. Design of carbon facilities to further improve BNR operations to meet increasingly strict effluent TN limits is currently ongoing.
Modeling of Glycerol Addition Strategies:
Wastewater characterization and modeling of various carbon dosing strategies was conducted to support the design of storage and delivery facilities and development of control systems at each of NYC’s BNR plants slated for glycerol addition. The goal of this effort was to provide plant specific guidelines for glycerol usage and control set points, and to identify cost saving operation options for the NYCDEP.
Extensive special sampling was conducted at each plant during winter and summer conditions to characterize the seasonal denitrification potential of the plant’s primary effluent. Sampling for each season was conducted over a three week period per the WERF 2003 Methods for Wastewater Characterization in Activated Sludge Modeling. Primary effluent was also sampled diurnally to characterize typical weekday and weekend day diurnal loading patterns for each season. A wet weather day was sampled to provide wet weather model input.
Data analysis of special sampling results and plant flow culminated in the determination of plant specific primary effluent wastewater fractions for nutrients and chemical oxygen demand, COD, and hourly diurnal inputs for seven (7) -day dynamic Biowin simulations. Fractions and inputs were determined for winter and summer conditions at each plant. Where appropriate historic plant data supplemented results from special sampling.
Results of Glycerol Dosing Modeling:
Simulated effluent quality and carbon usage for each strategy was compared for a given plant and season. The results showed that the dynamic strategies produced moderate to significant glycerol (and thus cost) savings. Efficient use of carbon in strategies 3 (feed forward) and 5 (Manual look-up tables) produced glycerol savings of up to 15% when compared to the constant carbon strategy normally employed at wastewater treatment plants. The results provided insight into how NYC BNR plants may continue to does carbon efficiently in the event of probe failure.
The paper will show results for all plants modeled and provide cost saving information.
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