City Of Bridgeport East Side Wastewater Treatment Plant

The East Side Water Pollution Control Facility (WPCF) is a critical infrastructure asset serving the Greater Bridgeport region, Connecticut’s most populous municipality. Treating an average of 10 million gallons daily (MGD) for a population of approximately 80,000 residents across eastern Bridgeport, Trumbull, and Monroe, this facility plays a pivotal role in the ecological restoration of Long Island Sound. Operated by Inframark under contract with the Bridgeport Water Pollution Control Authority (WPCA), the plant distinguishes itself through a unique combination of advanced nutrient removal technologies and a state-of-the-art waste-to-energy complex.

Following a comprehensive multi-year upgrade program valued at over $40 million, the East Side WPCF has transitioned from a conventional secondary treatment plant into a resource recovery facility. The site features Integrated Fixed-Film Activated Sludge (IFAS) technology to meet stringent federal nitrogen limits and hosts a pioneering anaerobic co-digestion facility developed in partnership with Anaergia. This facility not only treats wastewater to high standards but also converts organic waste into renewable natural gas (RNG), setting a regional benchmark for circular economy principles in municipal utility management.

Facility Overview

A. Service Area & Coverage

The East Side WPCF serves a diverse, dense urban catchment area comprising the eastern districts of the City of Bridgeport, as well as suburban flows from the neighboring towns of Trumbull and Monroe. The collection system is a hybrid of separated sanitary sewers and aging combined sewers (CSO), typical of historic New England coastal cities. The service area includes a mix of high-density residential zones, commercial corridors along Stratford Avenue, and significant industrial parcels surrounding the harbor.

B. Operational Capacity

The plant is designed for an average daily flow of 10.0 MGD. However, hydraulic capacity is a critical operational parameter due to the combined sewer system. During wet weather events, the facility must manage peak flows significantly higher than average design:

• Design Average Flow: 10.0 MGD
• Peak Secondary Capacity: 24.0 MGD
• Peak Primary Capacity: 40.0 MGD

Flows exceeding secondary capacity are typically subjected to primary treatment and disinfection before discharge, consistent with the WPCA’s Combined Sewer Overflow (CSO) Long Term Control Plan.

C. Discharge & Compliance

Effluent is discharged into Bridgeport Harbor, an embayment of Long Island Sound (LIS). Due to the hypoxia (low oxygen) challenges in the LIS, the Connecticut Department of Energy and Environmental Protection (CT DEEP) enforces strict Total Nitrogen (TN) limits. The East Side WPCF operates under the General Permit for Nitrogen Discharges, necessitating high-efficiency denitrification processes to participate effectively in the state’s Nitrogen Credit Exchange program.

Treatment Process

The East Side WPCF utilizes a modified secondary treatment process optimized for nitrogen removal within a constrained urban footprint.

A. Preliminary Treatment

Raw influent enters the headworks where it passes through mechanical bar screens to remove large debris, rags, and plastics—a critical step given the combined sewer system’s propensity for conveying street litter. Following screening, flow enters aerated grit chambers where sand, gravel, and heavy particulates settle out. Grit removal safeguards downstream mechanical equipment, particularly the sensitive anaerobic digestion transfer pumps.

B. Primary Treatment

Wastewater flows into three rectangular primary settling tanks. Here, flow velocity is reduced to allow settlable organic solids to drop to the bottom as primary sludge, while fats, oils, and grease (FOG) are skimmed from the surface. The primary sludge is pumped directly to the solids handling train for gravity thickening. This stage typically removes 30-40% of BOD and 50-60% of TSS.

C. Secondary Treatment (IFAS System)

The core of the plant’s modernization is the Integrated Fixed-Film Activated Sludge (IFAS) system. Facing strict nitrogen limits but lacking the physical space to build additional aeration basins, engineers retrofitted the existing aeration tanks with free-floating plastic media carriers.

• Configuration: The aeration basins are divided into anoxic and aerobic zones.
• Mechanism: The suspended media provides a massive surface area for biofilm growth (specifically nitrifying bacteria), while the suspended activated sludge (MLSS) handles carbonaceous BOD removal. This hybrid approach significantly increases the biomass inventory without overloading the secondary clarifiers.
• Aeration: Fine-bubble diffusers provide oxygen to the aerobic zones and mixing energy to keep the IFAS media in suspension.
• Clarification: Mixed liquor flows to three secondary clarifiers where biological solids settle and are returned (RAS) to the head of the aeration tanks or wasted (WAS) to solids processing.

D. Disinfection

The facility utilizes Ultraviolet (UV) disinfection, having moved away from chlorine gas for safety and environmental reasons. The UV system inactivates pathogenic bacteria (E. coli, enterococci) by disrupting their DNA structure immediately prior to discharge. This eliminates the need for dechlorination chemicals and reduces toxicity risks to marine life in Bridgeport Harbor.

E. Solids Handling & Resource Recovery

The solids handling train is the site of the facility’s most advanced innovation, developed via a public-private partnership with Anaergia:

• Thickening: Primary sludge is gravity thickened; Waste Activated Sludge (WAS) is thickened via rotary drum thickeners (RDT).
• Co-Digestion: The facility features anaerobic digesters retrofitted to process both municipal sewage sludge and high-strength organic waste (food scraps) imported from the region.
• Recuperative Thickening: Advanced recuperative thickening loops maintain optimal solids density within the digesters, maximizing volatile solids reduction (VSR).
• Dewatering: Digested sludge is dewatered using high-solids centrifuges before final disposal.

Infrastructure & Facilities

A. Physical Plant

The site is located on Seaview Avenue in a heavily industrialized zone, bounded by the harbor and urban development. The compact footprint necessitated vertical construction and deep-tank retrofits rather than lateral expansion. The architecture is utilitarian, with recent additions (the receiving station and gas conditioning skid) featuring modern industrial design elements.

B. Energy Systems & Renewables

The East Side WPCF is a model for the “Net Zero” energy concept in wastewater treatment.

• Biogas Utilization: Methane generated in the digesters is captured, conditioned, and used to fuel Combined Heat and Power (CHP) cogeneration engines.
• Grid Injection: Excess renewable natural gas (RNG) is conditioned to pipeline quality and injected into the local natural gas grid, generating revenue and renewable energy credits (RINs).
• Heat Recovery: Waste heat from the CHP engines is recovered to maintain digester temperatures and heat buildings, reducing reliance on fossil fuels.

C. Odor Control

Given the importation of food waste and the proximity to residential neighborhoods, odor control is paramount. The facility utilizes a multi-stage system including chemical scrubbers and activated carbon filters to treat air from the headworks, sludge holding tanks, and the food waste receiving station.

Recent Upgrades & Major Projects

Phase 2 Facility Plan Improvements (Completed ~2021)

• Project Budget: ~$40 Million
• Funding Sources: CT Clean Water Fund (Grant/Loan mix)
• Scope:
  • Full retrofit of aeration basins to IFAS configuration.
  • Rehabilitation of secondary clarifiers.
  • Replacement of blower systems with high-efficiency turbo blowers.
  • Electrical distribution system upgrades.

• Design Engineer: Wright-Pierce
• Key Results: Successfully reduced Total Nitrogen discharge to meet the LIS General Permit requirements without expanding the plant footprint.

Anaergia Resource Recovery Project (Commissioned ~2019-2022)

• Project Type: Public-Private Partnership (P3)
• Scope: Construction of a food waste receiving station, digester upgrades, and gas conditioning infrastructure.
• Technical Highlight: Implementation of the Omnivore high-solids anaerobic digestion technology.
• Results: The plant now processes organic waste that would otherwise go to landfills/incinerators, converting it into renewable energy.

Regulatory Compliance & Environmental Performance

The East Side WPCF operates under NPDES Permit No. CT0100625, issued by the CT DEEP. The permit emphasizes protections for the Long Island Sound estuary.

Key Compliance Parameters:

• Total Nitrogen (TN): Subject to the CT General Permit for Nitrogen Discharges. The plant has historically purchased credits but recent upgrades aim to make the facility a net seller or neutral participant in the credit exchange.
• BOD5 & TSS: 30 mg/L monthly average (secondary treatment standard).
• Bacteria: Strict seasonal limits for Enterococci and Fecal Coliform to protect recreational use of the harbor.

Environmental Stewardship: By diverting food waste from incineration (the standard disposal method in CT) to anaerobic digestion, the facility significantly lowers the region’s carbon footprint while protecting local water quality.

Challenges & Future Planning

A. Combined Sewer Overflows (CSO)

Like many historic Northeast cities, Bridgeport’s primary challenge is managing wet weather flows. The WPCA is engaged in a multi-decade Long Term Control Plan (LTCP) to separate sewers where feasible and maximize capture at the plant. The East Side facility must maintain rapid response capabilities to handle sudden hydraulic spikes during storms.

B. Climate Resilience

Located directly on the waterfront, the East Side WPCF is vulnerable to storm surge and sea-level rise. Future capital planning includes hardening critical electrical infrastructure, raising sensitive equipment above projected flood elevations, and reinforcing perimeter barriers.

C. Aging Conveyance Infrastructure

While the plant has been upgraded, the network of pump stations and force mains feeding the plant requires continuous rehabilitation to prevent sanitary sewer overflows (SSOs) before wastewater reaches the treatment train.

Technical Specifications Summary

Frequently Asked Questions (FAQ)

Technical Questions

1. What is the IFAS system used at Bridgeport East Side?
The Integrated Fixed-Film Activated Sludge (IFAS) system uses free-floating plastic media carriers retained in the aeration basins by screens. This increases the biomass inventory (specifically nitrifiers) for better nitrogen removal without requiring larger tanks.

2. How does the facility handle food waste?
The facility has a dedicated receiving station where food waste slurry is accepted. It is then co-digested with municipal sludge in the anaerobic digesters, significantly boosting biogas production compared to sludge-only digestion.

3. Who operates the plant?
The plant is owned by the Bridgeport WPCA but operations and maintenance are outsourced to Inframark (formerly Severn Trent Services).

Public Interest Questions

4. Does the plant smell?
Wastewater treatment inherently produces odors, but the East Side WPCF employs chemical scrubbers and carbon filters to capture and neutralize odors, particularly from the headworks and food waste receiving areas.

5. Is the water discharged safe for the Sound?
Yes. The effluent is treated to strict state and federal standards, including the removal of harmful bacteria via UV light and the reduction of nitrogen to prevent algae blooms in Long Island Sound.

Disclaimer: This page is for informational purposes for engineering and industry professionals. Data is based on public permits, WPCA reports, and engineering documents available as of late 2023. For official regulatory inquiries, contact the Connecticut DEEP or the Bridgeport WPCA.