City Of Bridgeport West Side Wastewater Treatment Plant

TARGET AUDIENCE

• Municipal consulting engineers evaluating biosolids-to-energy systems
• Wastewater treatment plant operators and contract management firms
• Environmental regulators (CT DEEP, EPA Region 1)
• Clean energy developers interested in co-digestion technologies
• Municipal planners focused on CSO Long Term Control Plans

1. INTRODUCTION

The City of Bridgeport West Side Wastewater Treatment Plant (West Side WWTP) serves as the primary sanitation infrastructure for the western district of Connecticut’s most populous city. As a critical component of the Bridgeport Water Pollution Control Authority (WPCA) system, this 30-MGD facility manages wastewater for a dense urban corridor and surrounding suburban communities. Situated in an industrial zone along Cedar Creek, the plant plays a pivotal role in the environmental health of Long Island Sound.

Historically a conventional activated sludge facility, the West Side WWTP has recently garnered national engineering attention due to its transformation into a green energy hub. Through a public-private partnership involving the construction of an advanced anaerobic digestion and resource recovery facility, the plant now co-digests sewage sludge with organic food waste to produce renewable natural gas (RNG). This facility represents a paradigm shift in municipal wastewater treatment, moving beyond simple compliance to active resource recovery and carbon footprint reduction.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The West Side WWTP services a highly urbanized sewershed encompassing the western half of Bridgeport, along with inter-municipal connections serving portions of the Town of Trumbull and the Town of Fairfield. The collection system is a mix of separated sanitary sewers and combined sewers (CSS), typical of older New England infrastructure. The service area is characterized by heavy industrial usage, dense residential zoning, and significant impervious surface area, leading to rapid hydraulic peaking during storm events.

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B. Operational Capacity

The facility is designed for an Average Daily Flow (ADF) of 30 MGD. However, due to the combined nature of the collection system, the plant must manage extreme hydraulic variability. During wet weather events, the facility is designed to process up to 90 MGD through primary treatment to mitigate Combined Sewer Overflows (CSOs). Historical average flows typically range between 20 and 24 MGD during dry weather. The plant is currently operating within its organic loading design limits, though hydraulic throughput is a constant operational focus due to infiltration and inflow (I/I).

C. Discharge & Compliance

Treated effluent is discharged via Outfall 001 into Cedar Creek, a tidal estuary that flows into Black Rock Harbor and ultimately Long Island Sound. The discharge is regulated under NPDES Permit CT0020524, issued by the Connecticut Department of Energy and Environmental Protection (CT DEEP). As a facility discharging into the Long Island Sound watershed, the plant is subject to stringent Nitrogen removal requirements under the Total Maximum Daily Load (TMDL) program to prevent hypoxia in the Sound.

3. TREATMENT PROCESS

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it undergoes rigorous physical screening to protect downstream equipment. The headworks utilizes mechanical bar screens to remove large debris, rags, and plastics. Following screening, flow velocity is reduced in aerated grit chambers, allowing inorganic sands and gravel to settle while keeping organics in suspension. The grit is mechanically removed, washed, and dewatered for landfill disposal. Significant odor control systems utilizing chemical scrubbers are employed at the headworks to mitigate nuisance odors for the surrounding community.

B. PRIMARY TREATMENT

Wastewater flows to rectangular primary settling tanks. These tanks utilize chain-and-flight mechanisms to scrape settled sludge to hoppers at the inlet end and skim floating grease and scum to the outlet end. The primary treatment stage is critical for reducing Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD) prior to the biological stage, reducing the energy load on the aeration system. During peak wet weather flows (above secondary capacity), excess flow may receive primary treatment and disinfection before blending or discharge, per wet weather permit protocols.

C. SECONDARY TREATMENT

The biological treatment utilizes a conventional activated sludge process modified for nutrient removal. The aeration basins are equipped with fine-bubble diffused aeration systems to maximize oxygen transfer efficiency. To meet CT DEEP nitrogen limits, the plant operates zones within the aeration tanks to facilitate nitrification (ammonia conversion to nitrate) and denitrification (nitrate conversion to nitrogen gas).

• Aeration Control: Automated dissolved oxygen (DO) control systems modulate blower output based on real-time demand.
• Clarification: Mixed liquor flows to circular secondary clarifiers where biological floc settles. Return Activated Sludge (RAS) is recycled to the aeration basins, while Waste Activated Sludge (WAS) is thickened and sent to the solids handling train.

D. DISINFECTION

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In a major safety and environmental upgrade completed in recent years, the West Side WWTP converted from gaseous chlorine disinfection to Ultraviolet (UV) disinfection. The effluent passes through open-channel UV banks where high-intensity light neutralizes pathogens (bacteria and viruses) by disrupting their DNA, preventing replication. This eliminates the need for dechlorination chemicals (sulfur dioxide/bisulfite) and removes the risks associated with storing hazardous chlorine gas on-site.

E. SOLIDS HANDLING & RESOURCE RECOVERY

The solids handling train is the facility’s most technologically advanced sector. The process includes:

• Thickening: Gravity belt thickeners reduce the water content of WAS.
• Anaerobic Digestion: The plant utilizes high-rate anaerobic digesters. In partnership with Anaergia, the facility has implemented a co-digestion strategy.
• Co-Digestion: The facility accepts external organic food waste, which is processed and introduced into the digesters alongside municipal sludge. This high-strength feedstock significantly boosts biogas production.
• Dewatering: Digested sludge is dewatered using high-performance centrifuges to produce a drier cake, reducing hauling costs.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site occupies an industrial footprint along the waterfront, necessitating compact process configurations. The site includes administrative offices, a SCADA control center, and a fully equipped laboratory for process control testing (pH, settleability, microscopy). Heavy maintenance is supported by on-site garages and machine shops.

B. Energy Systems & Biogas

The West Side WWTP is a model for the “Utility of the Future” energy concept.

• Biogas Utilization: The enhanced biogas production from food waste co-digestion is treated to remove siloxanes, hydrogen sulfide, and moisture.
• CHP System: The gas fuels Combined Heat and Power (CHP) engines, generating electricity to offset grid consumption and producing waste heat used to maintain optimal digester temperatures (mesophilic range).
• RNG Injection: Excess gas is conditioned to pipeline-quality Renewable Natural Gas (RNG) and injected into the local natural gas grid, creating a revenue stream and carbon-negative energy source.

5. RECENT UPGRADES & MAJOR PROJECTS

Bridgeport Bioenergy Facility (2019-2022)

• Project Scope: Construction of an organic waste receiving and pre-processing facility and upgrades to existing anaerobic digesters for co-digestion.
• Investment: Approx. $30-$40 million (Public-Private Partnership).
• Key Partner: Anaergia Inc.
• Technical Highlights:
  • Installation of Anaergia’s OREX extrusion press to separate organics from solid waste.
  • Retrofitting of digesters with new mixing and heating systems.
  • Installation of gas conditioning and CHP units.

• Results: The facility diverts thousands of tons of food waste from landfills annually and generates renewable energy, significantly reducing the plant’s net operational costs and carbon footprint.

West Side Plant Modernization (Ongoing)

• Project Scope: Comprehensive rehabilitation of aging civil and mechanical infrastructure.
• Funding: CT Clean Water Fund (State Revolving Fund) and local bonding.
• Components:
  • Rehabilitation of primary and secondary clarifier mechanisms.
  • Concrete repair on aeration basins.
  • Electrical distribution system upgrades to improve resiliency.
  • HVAC and odor control improvements.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The facility operates under NPDES Permit No. CT0020524. Critical parameters include:

• CBOD5: Average monthly limits typically <30 mg/L (with 85% removal efficiency required).
• TSS: Average monthly limits typically <30 mg/L.
• Nitrogen: The plant operates under the General Permit for Nitrogen Discharges (Long Island Sound TMDL), which assigns an annual mass loading limit (lbs/day) that decreases over time. The plant participates in the Nitrogen Credit Exchange program.
• Bacteria: Enterococci/Fecal Coliform limits apply seasonally (May-Sept).

B. Compliance History

Like many older urban systems, the primary compliance challenges have historically been related to wet weather flow management and nitrogen targets. The implementation of UV disinfection has stabilized bacteria compliance. The WPCA is currently executing a Long Term Control Plan (LTCP) to address CSOs, aiming to separate sewers where feasible and maximize capture at the treatment plant.

7. OPERATIONAL EXCELLENCE

A. Staffing & Management

The facility is operated by Inframark, a private contract operations firm, under the oversight of the Bridgeport WPCA. This model leverages private sector technical expertise and staffing flexibility. The plant is staffed 24/7/365, requiring CT DEEP certified operators (Class IV capability) due to the complexity of the treatment and solids handling systems.

B. Technology & Automation

The plant utilizes a robust SCADA (Supervisory Control and Data Acquisition) system that provides real-time monitoring of flows, tank levels, DO profiles, and energy generation. Operators can adjust return rates, wasting rates, and chemical dosages from the central control room or remote terminals.

8. CHALLENGES & FUTURE PLANNING

A. Aging Infrastructure

The structural integrity of concrete tanks and conveyance channels dating back to the mid-20th century requires constant maintenance. Corrosion in headworks and covered processes due to H2S is an ongoing management focus.

B. Nitrogen Reduction

As CT DEEP continues to lower the nitrogen limits for Long Island Sound, the West Side WWTP faces pressure to optimize denitrification. This is challenging within the existing footprint, as additional tankage is difficult to construct on the land-locked site. Future planning involves advanced process controls and potential side-stream treatment of nitrogen-rich centrate from the dewatering process.

C. Climate Resilience

Located at sea level on the coast, the plant is vulnerable to storm surge and sea-level rise. Resiliency planning involves hardening electrical substations (elevating critical gear) and ensuring outfall hydraulic capacity during high tide events.

9. COMMUNITY & REGIONAL IMPACT

The West Side WWTP is a cornerstone of Bridgeport’s “Eco-Technology Park,” a collection of businesses dedicated to sustainability and green energy. By converting waste to energy, the plant contributes to the local tax base and attracts green tech investment. Furthermore, the improvement in effluent quality has directly contributed to the ecological recovery of Black Rock Harbor, supporting local recreational boating and fishing industries.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The Bridgeport WPCA also operates the East Side Wastewater Treatment Plant (10 MGD Design), located on Seaview Avenue. The systems are hydraulically distinct but managed under the same authority. Additionally, the WPCA maintains numerous remote pump stations throughout the city that convey flow to the West Side facility, including critical lift stations in the Black Rock and Seaside Park areas.

12. FAQ SECTION

Technical Questions

1. What is the solids retention time (SRT) target for the facility?
While variable based on season, the plant generally targets an SRT sufficient to maintain nitrification (typically 8-12 days), though wet weather washouts can challenge this target.

2. How does the Anaergia system handle food waste contaminants?
The system utilizes an OREX press which separates organics from packaging and contaminants through high-pressure extrusion, creating a clean organic pulp for the digesters.

3. Is the plant capable of Phosphorus removal?
Currently, the primary nutrient focus for Long Island Sound is Nitrogen. However, the facility can implement chemical precipitation (Ferric Chloride or Alum) if Phosphorus limits are tightened in the future.

4. Does the plant accept hauled waste?
Yes, the facility is designed to accept hauled organic waste and fats, oils, and grease (FOG) to feed the co-digestion system.

Public Interest Questions

5. Does the plant smell?
While wastewater treatment inherently generates odors, the West Side WWTP utilizes advanced chemical scrubbers and carbon filters, particularly at the headworks and sludge processing areas, to minimize impact on neighbors.

6. Is the gas produced at the plant used in Bridgeport homes?
Yes, the Renewable Natural Gas (RNG) produced is injected into the gas utility grid, meaning it mixes with the natural gas supply used by local residents and businesses.

7. How clean is the water released into the Sound?
The effluent is treated to secondary standards, disinfected to kill bacteria, and monitored daily. It meets all state and federal standards for safe discharge into a marine environment.

8. Who do I call for a sewer backup in Bridgeport?
Residents should contact the Bridgeport WPCA Emergency Line (203-332-5550) available 24/7 for sewer emergencies.