Hunts Point Wastewater Treatment Plant Bronx

FACILITY BASIC INFORMATION

• Official Name: Hunts Point Wastewater Resource Recovery Facility (WRRF)
• Location: Hunts Point, Bronx, New York
• Operating Authority: New York City Department of Environmental Protection (NYC DEP)
• Design Capacity (Dry Weather): 200 MGD
• Design Capacity (Wet Weather): 400 MGD
• Current Average Flow: ~110-130 MGD
• Population Served: ~690,000 residents
• Service Area: Northeast, East, and South Central Bronx (16,664 acres)
• Receiving Water Body: Upper East River
• SPDES Permit Number: NY0026191
• Year Commissioned: 1952 (Major expansion 1978, Upgrades 2000s-Present)

TARGET AUDIENCE

• Civil and environmental engineers analyzing urban wastewater infrastructure.

Read more4D-Printed Smart Materials For Water Treatment
• Plant operators studying biological nutrient removal (BNR) in space-constrained sites.
• Municipal planners reviewing sludge handling and anaerobic digestion technologies.
• Regulatory compliance officers focused on Long Island Sound nitrogen reduction.

1. INTRODUCTION

The Hunts Point Wastewater Resource Recovery Facility (WRRF) serves as a cornerstone of New York City’s wastewater infrastructure, managing sanitation for nearly 700,000 residents in the Bronx. Operated by the NYC Department of Environmental Protection (DEP), the facility is one of the 14 treatment plants comprising the city’s vast collection system. With a design dry weather flow capacity of 200 million gallons per day (MGD) and the ability to treat up to 400 MGD during wet weather events, Hunts Point plays a pivotal role in protecting the water quality of the Upper East River and Long Island Sound.

Distinguished by its iconic egg-shaped anaerobic digesters—landmarks visible from major regional highways—the facility represents a convergence of mid-20th-century design and modern advanced treatment technologies. Following substantial capital investment exceeding $1 billion over the last two decades, Hunts Point has transitioned into a model for biological nutrient removal (BNR) and carbon footprint reduction, utilizing step-feed BNR processes and robust biogas cogeneration systems to meet strict State Pollutant Discharge Elimination System (SPDES) requirements.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The Hunts Point WRRF services a 16,664-acre drainage basin covering the northeast, east, and south-central portions of the Bronx. The service area is a dense urban environment characterized by a mix of residential high-rises, commercial districts, and significant industrial zones, particularly the Hunts Point Food Distribution Center. The collection system is primarily a Combined Sewer System (CSS), meaning it conveys both sanitary sewage and stormwater runoff to the facility. This presents significant hydraulic challenges during precipitation events, requiring robust wet-weather flow management strategies to minimize Combined Sewer Overflows (CSOs).

B. Operational Capacity

The plant operates with a Design Dry Weather Flow (DDWF) of 200 MGD. However, due to the combined sewer network, the facility is designed to accept and treat 2xDDWF (400 MGD) through primary treatment, with secondary treatment capacity generally capped closer to the dry weather design to prevent biomass washout. Historical flow trends indicate an average daily flow ranging between 110 and 130 MGD, providing a capacity utilization of approximately 60-65% during dry periods. This headroom is critical for accommodating the rapid hydraulic surges typical of NYC storm events.

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C. Discharge & Compliance

Effluent is discharged into the Upper East River. This water body connects directly to the Long Island Sound, an estuary of national significance. Consequently, the facility is subject to rigorous nitrogen limits under the Long Island Sound Nitrogen Total Maximum Daily Load (TMDL). Compliance strategies focus heavily on maximizing nitrogen removal efficiency to prevent hypoxia in the Sound. The facility operates under SPDES Permit NY0026191, administered by the New York State Department of Environmental Conservation (NYSDEC).

3. TREATMENT PROCESS

A. PRELIMINARY TREATMENT

Raw sewage enters the plant via the Main Interceptor and travels to the screening building. Here, heavy-duty mechanical bar screens (climber type) remove large debris—rags, wood, and plastics—that could damage downstream pumps. Following screening, the flow enters aerated grit chambers where velocity is reduced to allow inorganic sands, gravel, and coffee grounds to settle while keeping lighter organic matter in suspension. The grit is mechanically removed, washed, and hauled off-site to landfills. Odor control at the headworks is a critical operational priority due to the facility’s proximity to residential neighborhoods and Hunts Point Riverside Park.

B. PRIMARY TREATMENT

The wastewater flows into rectangular primary settling tanks. These tanks reduce the flow velocity, allowing settleable solids to drop to the bottom as primary sludge and floatable grease and oil to rise to the surface for skimming. Hunts Point utilizes a series of collector flights to scrape sludge to hoppers for removal. Primary treatment typically achieves 50-60% removal of Total Suspended Solids (TSS) and 30-35% removal of Biochemical Oxygen Demand (BOD). In wet weather events exceeding secondary capacity, excess flow may receive primary treatment and disinfection before discharge.

C. SECONDARY TREATMENT (Step-Feed BNR)

The core of the treatment train is the Step-Feed Activated Sludge process, specifically modified for Biological Nutrient Removal (BNR). Unlike conventional plug-flow aeration, the primary effluent is introduced at multiple points along the length of the aeration pass. This configuration allows operators to manage Solids Retention Time (SRT) and create anoxic zones at the front of each pass where denitrification occurs.

• Aeration Basins: The facility utilizes four batteries of aeration tanks equipped with fine-bubble diffusers to maximize oxygen transfer efficiency.
• Carbon Addition: To drive the denitrification process (converting nitrate to nitrogen gas), the facility has a supplemental carbon addition system (using glycerol or methanol). This external carbon source is essential during periods when the influent wastewater lacks sufficient carbon to support biological denitrification.
• Secondary Clarifiers: Mixed liquor flows to rectangular final settling tanks where the biological floc settles. Return Activated Sludge (RAS) is pumped back to the aeration tanks, while Waste Activated Sludge (WAS) is sent to the thickening facility.

D. DISINFECTION

Effluent from the secondary clarifiers flows to the chlorine contact tanks. Hunts Point utilizes sodium hypochlorite for disinfection to inactivate pathogens. The dosage is flow-paced and tightly controlled to meet fecal coliform limits while minimizing residual chlorine in the discharge. Following sufficient contact time, the treated effluent flows by gravity to the East River outfall.

E. SOLIDS HANDLING

Hunts Point is a regional sludge hub. It processes solids generated on-site as well as sludge received via marine vessel from other NYC DEP plants.

• Thickening: Primary and secondary sludge is thickened using gravity thickeners and centrifuges to reduce water content before digestion.
• Anaerobic Digestion: The facility features four distinctive egg-shaped digesters, each approximately 140 feet tall with a capacity of 3 million gallons. These digesters operate at mesophilic temperatures (approx. 98°F). The egg shape offers superior mixing characteristics and minimizes grit accumulation compared to conventional cylindrical tanks.
• Dewatering: Digested sludge is pumped to a dedicated dewatering building equipped with high-performance solid-bowl centrifuges. Polymer is added to flocculate the solids, achieving a cake dryness suitable for transport.
• Disposal: The dewatered biosolids cake is transported off-site for beneficial reuse (land application or composting) or landfill disposal, depending on current contracts and regulatory requirements.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans approximately 45 acres in a densely developed industrial peninsula. The layout is compact, necessitating vertical construction (e.g., the egg digesters) to maximize capacity. Key structures include the Main Building, Screen House, Dewatering Building, and the distinctive shiny metal cladding of the digester complex.

B. Energy Systems

Hunts Point is a leader in energy recovery. The anaerobic digesters produce significant volumes of biogas (methane). This gas is captured, scrubbed to remove siloxanes and hydrogen sulfide, and utilized in on-site cogeneration engines. These engines generate electricity to power plant equipment and heat to maintain digester temperatures, significantly offsetting the facility’s purchase of grid electricity and natural gas. The plant also houses extensive emergency standby generators to ensure continuous operation during grid outages.

C. Odor Control

Given the proximity to the community, NYC DEP has installed extensive odor control systems. This includes covering primary settling tanks and sludge thickeners to capture foul air. The captured air is treated through a combination of wet chemical scrubbers (using bleach and caustic soda) and activated carbon adsorption units before being released to the atmosphere.

5. RECENT UPGRADES & MAJOR PROJECTS

Carbon Addition for Nitrogen Removal (2018-2020)

• Project Scope: Installation of chemical storage and feed systems for supplemental carbon (glycerol) to enhance denitrification in the aeration tanks.
• Project Budget: ~$25 Million
• Drivers: Compliance with the Long Island Sound Nitrogen TMDL and NYSDEC consent order.
• Technical Highlights: Automated dosing control linked to real-time nitrate sensors in the aeration basins.
• Results: Significant reduction in Total Nitrogen load discharged to the East River, contributing to improved dissolved oxygen levels in Long Island Sound.

Main Sewage Pumps & Bar Screen Replacement (2015-2019)

• Project Scope: Replacement of aging main influent pumps and the installation of new, robust climber-screen mechanisms at the headworks.
• Project Budget: ~$65 Million
• Drivers: Aging infrastructure (state of good repair) and improved screenings capture.
• Technical Highlights: High-efficiency motors and VFDs installed on main pumps to optimize energy usage during varying flow conditions.

Standby Power & Resiliency (Post-Sandy Initiatives)

• Project Scope: Installation of elevated emergency generators and hardening of electrical substations against storm surge.
• Timeline: Ongoing phased completion through 2024.
• Drivers: Climate change resilience following Superstorm Sandy.
• Goal: Ensure 100% operational capacity during grid failure events.

Upcoming: Phase III Reconstruction

NYC DEP is planning further modernization focused on the replacement of secondary settling tank mechanisms and concrete rehabilitation, anticipated to mobilize in the 2025-2027 capital cycle.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

NPDES/SPDES Permit: The facility operates under SPDES Permit NY0026191. Key parameters include:

• CBOD5: 25 mg/L (monthly average)
• TSS: 30 mg/L (monthly average)
• Settleable Solids: 0.1 ml/L
• Fecal Coliform: 200 MPN/100 mL (geometric mean)
• Total Nitrogen: Aggregate rolling limits assessed across the East River facility complex (Hunts Point, Bowery Bay, Wards Island, Tallman Island).

Performance: Hunts Point consistently achieves 85-95% removal of BOD and TSS. The facility has successfully met the stringent nitrogen reduction targets set forth by the Long Island Sound Nitrogen Reduction Strategy, reducing aggregate nitrogen discharges from NYC plants by over 60% compared to 1990 levels.

7. OPERATIONAL EXCELLENCE

The facility is staffed by over 80 personnel, including stationary engineers, sewage treatment workers, electricians, and laboratory technicians. Operators must hold NYSDEC Wastewater Treatment Plant Operator certifications (Grade 4A). The plant utilizes a distributed SCADA system for process monitoring, allowing real-time adjustments to RAS/WAS rates and dissolved oxygen setpoints. The on-site process control laboratory performs daily analysis of regulatory and process parameters, ensuring rapid response to changing influent conditions.

8. CHALLENGES & FUTURE PLANNING

A. Combined Sewer Overflows (CSO)

Like much of older NYC, the primary environmental challenge is managing wet weather flows. While the plant treats up to 2xDDWF, extreme rain events trigger CSOs in the collection system before flow reaches the plant. Future planning involves the construction of off-site retention tanks and green infrastructure in the Bronx to reduce peak inflows.

B. Aging Infrastructure vs. Modern Standards

Maintaining a facility commissioned in 1952 requires constant capital investment. The “State of Good Repair” is a primary driver for the NYC DEP Capital Improvement Plan, balancing the need for new nutrient removal technology with the necessity of replacing basic concrete and steel assets.

C. Community Relations & Odors

Hunts Point is an Environmental Justice community. Historically, the plant was a source of odor complaints. The DEP has invested heavily in odor control and established community advisory relationships to address local concerns, viewing odor control not just as a nuisance issue but as a quality-of-life imperative.

10. TECHNICAL SPECIFICATIONS SUMMARY

12. FAQ SECTION

1. What makes the Hunts Point digesters unique?
The facility features four “egg-shaped” digesters. This shape improves mixing efficiency, reduces “dead zones” where grit accumulates, and minimizes surface area for heat loss compared to traditional flat-bottom cylindrical tanks. They are a visual landmark in the Bronx.

2. How does Hunts Point reduce Nitrogen?
The plant uses a step-feed biological nutrient removal (BNR) process combined with supplemental carbon addition (glycerol). This creates anoxic zones within the aeration tanks where bacteria convert nitrates into harmless nitrogen gas.

3. What is the capacity of the Hunts Point plant?
The plant is designed to treat 200 million gallons per day (MGD) during dry weather and up to 400 MGD during wet weather events.

4. Does the facility generate its own energy?
Yes. The biogas (methane) produced during anaerobic digestion is captured and used in on-site cogeneration engines to produce heat and electricity, increasing the plant’s sustainability.

5. Where does the treated water go?
The treated effluent is discharged into the Upper East River, which flows into the Long Island Sound.

6. How are odors managed at the plant?
NYC DEP utilizes covers on primary tanks and thickeners, along with negative air pressure systems that route foul air through chemical scrubbers and activated carbon filters before release.

7. Is the plant affected by stormwater?
Yes. The Bronx utilizes a Combined Sewer System. During heavy rain, flow to the plant increases dramatically. If the flow exceeds the plant’s hydraulic capacity, a mix of stormwater and wastewater may be discharged as a Combined Sewer Overflow (CSO) at designated outfalls in the network, though the plant maximizes treatment up to 400 MGD to minimize this.

8. Can I tour the Hunts Point facility?
NYC DEP occasionally offers tours for educational groups, universities, and professional organizations. Requests must be made directly through the NYC DEP public affairs office. Visitor access is restricted due to safety and security protocols.