Tallman Island Wastewater Treatment Plant Queens

1. Introduction

The Tallman Island Wastewater Treatment Plant (TIWWTP) stands as a critical component of the New York City Department of Environmental Protection (NYC DEP) wastewater infrastructure portfolio. Located on a 31-acre promontory in College Point, Queens, the facility provides essential sanitation services for approximately 400,000 residents in Northeast Queens. Originally commissioned in 1939, Tallman Island has evolved from a primary treatment facility into a sophisticated secondary treatment plant with advanced Biological Nutrient Removal (BNR) capabilities.

With a design dry-weather capacity of 80 million gallons per day (MGD) and a wet-weather peak capacity of 160 MGD, the plant plays a pivotal role in protecting the water quality of the Upper East River and Long Island Sound. Following a massive, multi-year upgrade program totaling over $300 million completed in the mid-2010s, the facility now operates as a model of energy efficiency and nitrogen reduction, adhering to strict State Pollutant Discharge Elimination System (SPDES) requirements.

2. Facility Overview

A. Service Area & Coverage

The Tallman Island WWTP serves a drainage area of approximately 16,000 acres (25 square miles) in Northeast Queens. The service area is a mix of dense residential neighborhoods, commercial districts, and light industry. Specific neighborhoods served include:

• College Point
• Whitestone
• Flushing
• Bayside
• Douglaston
• Little Neck

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The collection system is primarily a combined sewer system (CSS), meaning it conveys both sanitary sewage and stormwater runoff. This configuration necessitates robust wet-weather management strategies to mitigate Combined Sewer Overflows (CSOs).

B. Operational Capacity

The facility is designed to handle significant hydraulic variations typical of combined systems:

• Design Dry Weather Flow: 80 MGD
• Design Wet Weather Flow: 160 MGD
• Current Average Daily Flow: ~55-60 MGD

Historically, flows have fluctuated based on rainfall intensity. The plant utilizes onsite storage and throttling mechanisms to manage peak flows, treating up to 2x dry weather flow through secondary treatment before bypassing excess diluted flow (chlorinated) during extreme storm events.

C. Discharge & Compliance

Treated effluent is discharged into the Upper East River/Long Island Sound via a submerged outfall. The facility operates under a SPDES permit issued by the New York State Department of Environmental Conservation (NYSDEC). Due to the sensitivity of the Long Island Sound to hypoxia (low oxygen), the plant is subject to rigorous Total Maximum Daily Loads (TMDL) for nitrogen, driving the implementation of BNR technology.

3. Treatment Process

The Tallman Island facility employs a modified activated sludge process optimized for nitrogen removal. The treatment train is designed to maximize removal efficiency within the constraints of the existing physical footprint.

A. Preliminary Treatment

Raw sewage enters the plant via the Main Interceptor. Preliminary treatment includes:

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• Screening: Mechanical bar screens remove large debris, rags, and plastics to protect downstream pumps.
• Grit Removal: Aerated grit chambers facilitate the settling of heavy inorganic materials (sand, gravel) while keeping lighter organic matter in suspension.
• Main Sewage Pumps: Following recent upgrades, the plant utilizes high-efficiency electric motors to lift wastewater to the primary settling tanks.

B. Primary Treatment

Wastewater flows into rectangular primary settling tanks. Here, gravity separation occurs:

• Solids Removal: Settleable solids form a primary sludge blanket at the bottom, which is scraped to hoppers and pumped to the thickening process.
• Scum Removal: Floatables (grease, oil) are skimmed from the surface.
• Efficiency: Typical removal rates are 60% for Total Suspended Solids (TSS) and 30-35% for Biochemical Oxygen Demand (BOD).

C. Secondary Treatment (BNR)

The core of Tallman Island’s process is the Step-Feed Biological Nutrient Removal (BNR) system. This configuration allows the plant to meet stringent nitrogen limits without expanding tank volume.

• Step-Feed Configuration: Primary effluent is introduced at multiple points along the aeration tank rather than just at the head. This creates alternating anoxic and aerobic zones.
• Nitrification/Denitrification:
  • Aerobic Zones: Ammonia is converted to nitrate (Nitrification).
  • Anoxic Zones: Nitrate is converted to nitrogen gas (Denitrification) using the carbon present in the incoming wastewater.

• Aeration: Fine-bubble diffusers provide oxygen, driven by high-efficiency turbo blowers.
• Secondary Clarification: Mixed liquor settles in rectangular final settling tanks. Return Activated Sludge (RAS) is recycled to the aeration tanks, while Waste Activated Sludge (WAS) is removed for processing.

D. Centrate Treatment

A unique feature at Tallman Island is its dedicated Centrate Treatment Facility. The liquid stream (centrate) resulting from sludge dewatering is extremely high in ammonia. Rather than returning this high-load stream directly to the headworks (which can upset the biological balance), it undergoes separate treatment to reduce nitrogen load before rejoining the main process stream.

E. Disinfection

Effluent enters chlorine contact tanks where sodium hypochlorite is added for disinfection to eliminate pathogenic bacteria (coliforms). Following the contact period, the effluent is dechlorinated (using sodium bisulfite) as required to prevent toxicity to marine life before discharge into the East River.

F. Solids Handling

Solids processing is comprehensive and energy-conscious:

• Thickening: Primary sludge is gravity thickened; WAS is thickened using centrifuges or gravity belt thickeners.
• Anaerobic Digestion: Thickened sludge is stabilized in anaerobic digesters heated to mesophilic temperatures (~98°F). This process reduces volatile solids and produces biogas (methane).
• Dewatering: Digested sludge is dewatered using high-solids centrifuges.
• Disposal: The resulting biosolids cake is hauled off-site for beneficial reuse (land application or composting) or landfilling, depending on current DEP contracts.

4. Infrastructure & Facilities

A. Physical Plant

The site covers approximately 31 acres. Notable structures include the Main Building (housing pumps and blowers), the Sludge Thickening Complex, the Digester Complex, and the administrative/laboratory wing. The architecture reflects the Art Deco style of the late 1930s public works era, which has been preserved during modernizations.

B. Energy Systems

Tallman Island has historically been a leader in energy innovation. Recently, the plant transitioned from direct-drive internal combustion engines (which powered pumps using digester gas) to an all-electric drive system for main sewage pumps and blowers. This shift improves reliability and reduces local air emissions. The plant utilizes digester gas in boilers to heat the digesters and facility buildings, offsetting natural gas consumption.

C. Odor Control

Given its proximity to residential areas and Powell’s Cove Park, odor control is paramount. The facility utilizes covered channels, chemical scrubbers, and carbon adsorption systems at the headworks, thickeners, and dewatering facilities to treat foul air before release.

5. Recent Upgrades & Major Projects

The NYC DEP has invested heavily in Tallman Island to ensure regulatory compliance and extend asset life.

Tallman Island WWTP Upgrade Program (2009–2016)

• Project Budget: ~$340 Million
• Drivers: Nitrogen reduction (TMDL compliance), “State of Good Repair,” Energy Efficiency.
• Key Contractors:
  • Construction Management: AECOM / Hazen and Sawyer
  • General Contractor: Silverite Construction / WDF Inc.

• Technical Scope:
  • Pumping Systems: Replaced five mixed-fuel internal combustion engines driving main sewage pumps with electric motors and variable frequency drives (VFDs).
  • Process Air: Installation of new single-stage turbo blowers to improve aeration efficiency.
  • BNR Enhancement: Upgrades to aeration tanks to facilitate step-feed BNR and optimize mixing.
  • Electrical Distribution: Complete overhaul of the plant’s electrical substation and distribution system to support new electric loads.

• Results: The project successfully reduced total nitrogen discharge by over 50% compared to historical baselines and significantly reduced the plant’s carbon footprint by eliminating old combustion engines.

Current/Ongoing Projects

Current CIP initiatives focus on Resiliency following Superstorm Sandy. While Tallman Island is elevated relative to other NYC plants, investments are being made in flood-proofing critical equipment, installing submersible pumps, and hardening power supply systems to withstand sea-level rise and storm surges.

6. Regulatory Compliance & Environmental Performance

A. Permit Requirements

The facility operates under SPDES Permit NY-0026239. Critical parameters include:

• TSS & BOD: 30 mg/L (Monthly Average) and 85% removal efficiency.
• Total Nitrogen: Subject to an aggregate limit across East River plants to meet the Long Island Sound TMDL.
• Settleable Solids: 0.1 ml/L.

B. Nitrogen Reduction Success

Tallman Island is part of the NYC DEP’s “Nitrogen Control Action Plan.” Through the implementation of step-feed BNR and separate centrate treatment, the facility contributes significantly to the recovery of the East River ecosystem. Dissolved oxygen levels in the receiving waters have shown consistent improvement over the last decade.

7. Operational Excellence

Staffing: The facility is staffed 24/7 by a team of approximately 50-60 personnel, including Senior Stationary Engineers (Electric), Sewage Treatment Workers, and laboratory technicians. Operators must hold NYSDEC certifications ranging from Grade 1 to Grade 4A.

SCADA Integration: The plant utilizes a Distributed Control System (DCS) for real-time monitoring of dissolved oxygen profiles, pump status, and flow rates, allowing operators to dynamically adjust return rates and aeration to optimize biological performance.

8. Challenges & Future Planning

A. Climate Resilience

Located on the waterfront, Tallman Island faces risks from climate change. Although portions of the site are elevated, protecting the low-lying pumping galleries and electrical switchgear from 100-year and 500-year storm events is a primary engineering challenge for the next decade.

B. Aging Infrastructure

While the mechanical systems were upgraded recently, the concrete structures (tanks and channels) date back to 1939 and 1964 expansions. Ongoing concrete rehabilitation is necessary to prevent corrosion and structural degradation.

C. Combined Sewer Overflows (CSO)

Managing wet weather flows remains a priority. Future planning involves optimizing the collection system to maximize flow to the plant without washing out the biological mass, alongside the construction of off-site retention tanks (like the Flushing Bay CSO Tank) to reduce untreated discharges.

9. Community & Regional Impact

The Tallman Island plant is integral to the health of the Upper East River and Long Island Sound, supporting recreational boating and fishing industries. The DEP maintains a Community Advisory Board to interface with local residents regarding construction impacts and odor complaints. The facility’s ability to operate quietly and without odor is critical for its relationship with the adjacent Powell’s Cove Park and residential developments.

10. Technical Specifications Summary

12. FAQ Section

Technical Questions

Q: What is the primary method of nitrogen removal at Tallman Island?
A: The plant utilizes Step-Feed Biological Nutrient Removal (BNR), which creates alternating anoxic and aerobic zones within the aeration tanks to promote nitrification and denitrification.

Q: How does the plant handle high-strength centrate return?
A: Tallman Island operates a dedicated Centrate Treatment system to treat ammonia-rich liquid from the dewatering process before it returns to the head of the plant, preventing shock loading.

Q: Does the facility generate its own power?
A: The plant recovers biogas (methane) from anaerobic digesters. This gas is primarily used in boilers for process and building heat. Historically, engines drove pumps directly, but the plant has transitioned to electric motors grid-powered for reliability.

Public Interest Questions

Q: Where does the treated water go?
A: Treated effluent is discharged into the Upper East River, which connects to the Long Island Sound.

Q: How does the plant prevent odors from affecting the neighborhood?
A: The DEP employs carbon filtration and chemical scrubbers at key odor-generation points (headworks and sludge processing) and maintains negative air pressure in processing buildings.