Metropolitan St Louis Sewer District Bissell Point Wastewater Treatment Plant

1. INTRODUCTION

The Bissell Point Wastewater Treatment Plant serves as the flagship facility for the Metropolitan St. Louis Sewer District (MSD), standing as one of the largest and most complex wastewater treatment facilities in the Midwest. Situated on the western bank of the Mississippi River, this critical infrastructure asset treats an average of 145 million gallons daily (MGD) from the northern watershed of the St. Louis metropolitan area. Beyond its liquid train, Bissell Point functions as the centralized solids processing hub for the district, receiving sludge from the Lemay WWTP via an inter-plant pipeline.

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Operated under the “MSD Project Clear” initiative, the facility is currently executing a multi-billion dollar capital improvement strategy driven by a federal consent decree. The plant distinguishes itself engineering-wise through its massive Trickling Filter/Solids Contact (TF/SC) secondary treatment configuration and its recently modernized Fluidized Bed Incineration (FBI) complex, which represents the state-of-the-art in thermal hydrolysis and biosolids volume reduction.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The Bissell Point service area encompasses approximately 54,000 acres covering the City of St. Louis (north of Mill Creek Valley) and a vast portion of St. Louis County. The collection system feeding the plant is a mixture of modern separated sanitary sewers and legacy combined sewers (CSS). The combined nature of the older collection system presents significant hydraulic challenges, requiring the plant to handle massive flow variances during wet weather events to mitigate Combined Sewer Overflows (CSOs).

B. Operational Capacity

While the plant’s average daily flow hovers around 145 MGD, its hydraulic engineering is designed for extreme resilience. The secondary treatment process is rated for 210 MGD, but peak hydraulic capacity through the headworks and primary treatment exceeds 400 MGD. Historically, the plant has managed peak instantaneous flows during storm events that test the limits of its pumping infrastructure, necessitating the robust wet-weather bypass and storage strategies currently being enhanced under the consent decree.

C. Discharge & Compliance

Treated effluent is discharged directly into the Mississippi River. Given the high dilution factor of the receiving water, the plant operates under specific NPDES parameters that focus heavily on Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD), and increasingly, bacteria limits during recreation seasons. The facility’s outfall structure is designed to ensure rapid mixing within the river’s main channel.

3. TREATMENT PROCESS

The Bissell Point WWTP utilizes a Trickling Filter/Solids Contact (TF/SC) process. This hybrid configuration is favored for its ability to handle shock loads and treat high-strength industrial wastewater, which makes up a significant portion of the influent due to the heavy industrial base in North St. Louis.

A. Preliminary Treatment

Raw wastewater enters the facility via the massive North Bissell and South Bissell pump stations. The headworks features:

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• Coarse Screening: Mechanically cleaned bar screens remove large debris, rags, and timber.
• Grit Removal: Aerated grit chambers reduce the velocity of the flow, allowing inorganic solids (sand, gravel, cinders) to settle while keeping organic material in suspension.
• Fine Screening: Recent upgrades have introduced finer screening to protect downstream pumps and the biosolids train.

B. Primary Treatment

Flow proceeds to a battery of circular primary clarifiers. These units utilize gravity sedimentation to remove approximately 60-70% of TSS and 30-40% of BOD. Primary sludge is pumped directly to the solids handling complex, while primary effluent flows to the secondary treatment stage.

C. Secondary Treatment (TF/SC Process)

The core of the biological treatment at Bissell Point is the coupled Trickling Filter and Solids Contact system:

• Trickling Filters: Primary effluent is distributed over rock or plastic media beds. A biofilm of microorganisms (zoogleal film) forms on the media, metabolizing organic matter. This stage is highly energy-efficient as it relies on passive aeration via natural draft ventilation.
• Solids Contact Basins: Effluent from the trickling filters enters aerated solids contact basins. Here, the process mimics activated sludge for a short retention time, flocculating fine solids that sloughed off the trickling filters and polishing the effluent BOD.
• Secondary Clarifiers: The mixed liquor settles in circular secondary clarifiers. The clear supernatant overflows to disinfection, while settled solids are either returned (RAS) or wasted (WAS) to thickening.

D. Disinfection

Disinfection is achieved through Chlorination using sodium hypochlorite, followed by Dechlorination using sodium bisulfite prior to discharge. This ensures compliance with E. coli limits during the recreational season (April 1 to October 31) while preventing chlorine toxicity in the Mississippi River biome.

E. Solids Handling & Incineration (Facility Highlight)

Bissell Point is the regional solids processing center. It processes sludge generated on-site and sludge pumped 11 miles from the Lemay WWTP.

• Thickening: Gravity Belt Thickeners (GBTs) increase solids concentration.
• Dewatering: High-solids centrifuges further reduce moisture content to prepare the “cake” for thermal processing.
• Thermal Oxidation: The facility recently replaced aging Multiple Hearth Incinerators (MHIs) with modern Fluidized Bed Incinerators (FBIs). The FBI technology utilizes a sand bed suspended by high-velocity air, ensuring uniform combustion, higher energy efficiency, and autogenous burning (reducing natural gas usage).
• Emissions Control: The system is equipped with advanced wet scrubbers, wet electrostatic precipitators (WESPs), and mercury control modules to meet strict MACT (Maximum Achievable Control Technology) standards.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans an industrial footprint in North St. Louis, dominated by the distinct architecture of the incinerator building and the expansive field of trickling filters. The facility includes extensive maintenance shops, a fully accredited laboratory for process control and compliance testing, and administration buildings.

B. Energy Recovery

The transition to Fluidized Bed Incineration included the installation of Waste Heat Recovery Boilers. These systems capture thermal energy from the incineration exhaust to generate steam, which is used for building heat and process heating requirements, significantly lowering the plant’s external energy demand.

C. Odor Control

Given its urban location and role as a sludge hub, odor control is paramount. The plant utilizes negative pressure containment in solids handling areas, piping foul air to chemical scrubbers and activated carbon adsorption units before release.

5. RECENT UPGRADES & MAJOR PROJECTS

Under the “Project Clear” consent decree, Bissell Point has seen significant investment.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

Bissell Point operates under a Missouri Department of Natural Resources (MDNR) NPDES permit. The facility is a focal point of the negotiated Consent Decree between MSD, the EPA, and the Missouri Coalition for the Environment.

• Effluent Standards: The plant consistently meets BOD5 and TSS removal rates exceeding 85% monthly averages.
• Air Quality: The new incineration complex operates under a Title V Air Permit, with Continuous Emissions Monitoring Systems (CEMS) tracking NOx, SOx, CO, and THC in real-time.
• Biosolids: The ash resulting from incineration is inert and is disposed of in landfills, significantly reducing the volume of waste compared to land application of wet cake.

10. TECHNICAL SPECIFICATIONS SUMMARY

12. FAQ

Technical Questions

Q: Why does Bissell Point use incineration instead of land application?
A: Due to the high density of the service area and the industrial nature of the influent (which can introduce metals), as well as limited available land for application, thermal reduction reduces volume by over 90% and destroys pathogens and organics effectively.

Q: Is the plant capable of nutrient removal?
A: The current NPDES permit focuses on carbonaceous removal (BOD/TSS). While the TF/SC process provides some nitrification, strict Total Nitrogen or Phosphorus limits have not yet been mandated for the main stem of the Mississippi River in this reach, though the facility monitors these parameters for future planning.

Q: How is the Lemay WWTP sludge transported to Bissell Point?
A: Sludge is transported via an 11-mile pressurized inter-plant sludge pipeline that runs along the riverfront, consolidating solids handling at a single location for efficiency.

General Questions

Q: What is “Project Clear”?
A: Project Clear is MSD’s multi-billion dollar initiative to improve water quality and alleviate many of the wastewater concerns in the St. Louis region, including removing CSOs and upgrading treatment plants like Bissell Point.

Q: Does the plant smell?
A: While wastewater treatment naturally generates odors, Bissell Point employs advanced negative pressure systems and chemical scrubbers to capture and treat foul air, particularly from the sludge processing buildings, to minimize impact on the surrounding community.