Racine Wastewater Treatment Plant

TARGET AUDIENCE

• Municipal consulting engineers evaluating wet-weather flow management
• Wastewater treatment plant operators and managers
• Environmental regulators (WDNR/EPA)
• Process engineers interested in phosphorus removal and UV disinfection
• Municipal decision-makers planning regional service agreements

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1. INTRODUCTION

The Racine Wastewater Treatment Plant (WWTP) serves as the primary environmental safeguard for the “Belle City of the Lakes” and surrounding municipalities, treating an average of 36 million gallons daily (MGD) before discharging to Lake Michigan. Managed by the Racine Water and Wastewater Utilities, this facility is critical not only for regional sanitation but also for the protection of Lake Michigan’s nearshore waters, which support a vibrant recreational economy and serve as the source of drinking water for the region.

Originally commissioned in 1938 and significantly expanded in the 1970s and 2000s, the plant faces the unique hydraulic challenges of a service area that includes historic combined sewer systems. With a peak hydraulic capacity exceeding 100 MGD to manage wet-weather events, the facility utilizes conventional activated sludge treatment augmented by robust solids handling and ultraviolet (UV) disinfection. Recent capital investments have focused on optimizing energy efficiency through biogas utilization and ensuring compliance with Wisconsin’s increasingly stringent phosphorus regulations.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The Racine WWTP operates as a regional facility, accepting wastewater from a diverse 60-square-mile service area. While the City of Racine constitutes the core urban density, the utility provides wholesale treatment services to neighboring communities through intergovernmental agreements. The service area includes the rapidly growing Villages of Mount Pleasant and Caledonia, as well as Sturtevant, Elmwood Park, North Bay, and Wind Point. The collection system is a mix of older combined sewers (in the historic city center) and separated sanitary sewers in the suburban periphery, necessitating complex flow equalization strategies.

B. Operational Capacity

The plant is designed for an average daily flow of 36 MGD, with current average flows hovering between 20 and 25 MGD during dry weather. However, the facility’s engineering is defined by its wet-weather capabilities. Due to inflow and infiltration (I/I) and the combined sewer network, the plant must handle peak hourly flows of up to 108 MGD. The facility utilizes onsite storage and high-rate treatment protocols to manage these surges, maintaining treatment integrity during storm events to minimize Combined Sewer Overflows (CSOs).

C. Discharge & Compliance

Treated effluent is discharged directly into Lake Michigan via a submerged outfall extending approximately 3,000 feet offshore. Operating under a Wisconsin Pollutant Discharge Elimination System (WPDES) permit, the facility adheres to strict limitations on BOD, TSS, Ammonia, and Phosphorus. The plant has consistently been recognized for its operational excellence, frequently achieving Gold Awards from the National Association of Clean Water Agencies (NACWA) for perfect permit compliance.

3. TREATMENT PROCESS

The Racine WWTP utilizes a conventional activated sludge process train designed for flexibility and robustness against hydraulic shock loads.

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A. PRELIMINARY TREATMENT

Raw wastewater enters the facility through large interceptors where it undergoes preliminary treatment to protect downstream equipment.

• Screening: Mechanically cleaned bar screens remove rags, plastics, and large debris. Screenings are washed, compacted, and disposed of at a sanitary landfill.
• Grit Removal: Following screening, flow enters aerated grit chambers. The velocity is controlled to allow heavy inorganic materials (sand, gravel, coffee grounds) to settle while keeping organic solids in suspension. Settled grit is pumped out, dewatered, and landfilled.

B. PRIMARY TREATMENT

The facility employs rectangular primary clarifiers. Here, the flow velocity is significantly reduced, allowing settleable solids to drop to the bottom as primary sludge, while grease and floatables are skimmed from the surface. The primary treatment stage typically removes 50-60% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD). Primary sludge is pumped directly to the anaerobic digesters.

C. SECONDARY TREATMENT

The biological heart of the plant is the activated sludge system.

• Aeration Basins: Clarified effluent mixes with Return Activated Sludge (RAS) in large aeration tanks. The facility uses a plug-flow configuration where compressed air is diffused through the liquid, providing oxygen for microorganisms to metabolize dissolved organic matter and ammonia.
• Process Control: Operators maintain specific Mixed Liquor Suspended Solids (MLSS) concentrations and Dissolved Oxygen (DO) levels to optimize BOD removal and nitrification (conversion of ammonia to nitrate).
• Secondary Clarification: The mixed liquor flows to circular secondary clarifiers. The biological floc settles to the bottom, leaving clear supernatant at the top. A portion of the settled solids is returned to the aeration tanks (RAS), while the excess biological growth is removed as Waste Activated Sludge (WAS).

D. TERTIARY & DISINFECTION

While the plant does not employ membrane filtration, it utilizes chemical precipitation for phosphorus removal to meet Lake Michigan discharge limits.

• Phosphorus Removal: Ferric chloride or alum is added to precipitate soluble phosphorus, which is then removed with the waste sludge.
• Disinfection: The facility utilizes a high-intensity Ultraviolet (UV) light disinfection system. This replaced the previous chlorination/dechlorination system, eliminating the safety risks associated with storing chlorine gas and preventing chlorinated byproducts from entering Lake Michigan. The UV system alters the DNA of pathogens, rendering them unable to reproduce.

E. SOLIDS HANDLING

Racine WWTP operates a sophisticated solids processing facility.

• Thickening: WAS is thickened using dissolved air flotation (DAF) or gravity belt thickeners to reduce water volume before digestion.
• Anaerobic Digestion: Primary sludge and thickened WAS are blended and fed into anaerobic digesters. The system operates in the mesophilic temperature range (~98°F). The digestion process reduces volatile solids by 40-50% and produces methane-rich biogas.
• Dewatering: Digested sludge is dewatered using Belt Filter Presses, producing a cake with 18-25% solids content.
• Biosolids Disposal: The dewatered Class B biosolids are transported for agricultural land application, recycling nutrients back to the soil in accordance with WDNR regulations.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The plant occupies a constrained urban footprint along the Lake Michigan shoreline, requiring efficient use of vertical space and compact process layouts. The site includes administrative offices, a fully equipped analytical laboratory for process control and compliance testing, and heavy vehicle maintenance bays.

B. Energy Systems

Energy efficiency is a cornerstone of the facility’s operations. The anaerobic digesters produce significant volumes of biogas. This gas is captured and utilized in Cogeneration (CHP) engine generators. These engines produce electricity to power plant equipment and heat to maintain digester temperatures and warm buildings during Wisconsin winters. This waste-to-energy loop significantly reduces the facility’s reliance on grid power and natural gas.

C. Odor Control

Given its proximity to residential areas and the downtown district, odor control is critical. The facility employs chemical scrubbers and biofilters at key emission points, including the headworks and sludge processing buildings, to neutralize hydrogen sulfide and other odorous compounds before venting to the atmosphere.

5. RECENT UPGRADES & MAJOR PROJECTS

Major Infrastructure Improvements (2015-2023)

Primary Battery Upgrade & HVAC Replacement

• Scope: Rehabilitation of aging primary clarifiers, replacement of flight and chain mechanisms, and complete overhaul of the HVAC systems in process buildings to mitigate corrosion.
• Driver: Asset management and life-cycle extension of 1970s-era infrastructure.
• Status: Completed.

Digester Mixing and Heating Improvements

• Scope: Replacement of draft tube mixers with linear motion mixers or pump mixing systems, and upgrade of heat exchangers.
• Technical Highlights: Improved volatile solids reduction and increased biogas production efficiency.
• Funding: Clean Water Fund (State Revolving Fund) loans.

UV Disinfection System Modernization

• Scope: Replacement of first-generation UV banks with more energy-efficient, low-pressure high-output (LPHO) lamp technology.
• Results: Reduced electrical consumption for disinfection by over 20% while maintaining compliance with E. coli limits.

Current & Upcoming Projects (2024-2027)

The utility is currently engaged in a comprehensive Facility Master Plan implementation. Upcoming projects focus heavily on electrical distribution upgrades, replacement of main influent pumps to ensure wet-weather reliability, and advanced phosphorus removal technologies to meet potentially tighter future limits under the Wisconsin River TMDL and Lake Michigan standards.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The facility operates under WPDES Permit WI-0022888. Key effluent limits include:

• BOD5: Monthly average limit of 30 mg/L (typically achieves <10 mg/L)
• TSS: Monthly average limit of 30 mg/L (typically achieves <10 mg/L)
• Phosphorus: 1.0 mg/L monthly average (with provisions for lower targets)
• Fecal Coliform: 400 colonies/100 ml (May-September)

B. Compliance History

The Racine WWTP maintains an exemplary compliance record. The facility has received the NACWA Peak Performance Gold Award multiple times, signifying calendar years with zero NPDES permit violations. This reliability is vital for the protection of North Beach, a certified “Blue Wave” beach located just north of the discharge point.

7. OPERATIONAL EXCELLENCE

A. Staffing

The facility is staffed by a team of approximately 30-40 professionals, including WDNR-certified operators, industrial mechanics, electricians, lab analysts, and administrative support. Operators maintain Advanced Wastewater certifications, with ongoing training supported by the Wisconsin Wastewater Operators’ Association (WWOA).

B. Laboratory Capabilities

Racine maintains a state-certified laboratory on-site. This allows for rapid turnaround of process control samples (ammonia, microscopic examination of sludge) and ensures official reporting data is generated with high precision. The lab also assists neighboring smaller utilities with analytical services.

8. CHALLENGES & FUTURE PLANNING

A. Combined Sewer Overflows (CSOs)

Like many older Great Lakes cities, Racine utilizes a partial Combined Sewer System. While significant investments have been made in storage and separation, extreme precipitation events attributed to climate change pose a risk of CSOs. The utility continues to invest in “gray” and “green” infrastructure to maximize capture and treatment of wet weather flows.

B. Aging Infrastructure

With major process trains dating to the 1970s, the facility faces the challenge of replacing large-scale concrete and mechanical assets without interrupting service. The Capital Improvement Plan (CIP) aggressively targets the rehabilitation of these assets, specifically electrical switchgear and clarifier mechanisms.

C. Nutrient Regulations

Wisconsin has some of the strictest phosphorus regulations in the United States. While the plant currently meets limits via chemical precipitation, future regulations may require the adoption of tertiary filtration or other advanced technologies to achieve ultra-low phosphorus levels.

9. COMMUNITY & REGIONAL IMPACT

The Racine WWTP is a silent engine of the regional economy. By ensuring high-quality effluent enters Lake Michigan, the plant directly supports the local tourism industry, specifically the usage of North Beach, which has been nationally recognized for water quality and safety. Furthermore, the regional treatment model provides cost-effective sanitation for the rapidly expanding Foxconn development corridor in Mount Pleasant, facilitating industrial and commercial growth without the need for redundant satellite treatment plants.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The Racine wastewater system relies on a network of major lift stations to convey flow to the central plant. Key facilities include the Chicory Road and Main Street lift stations. Additionally, the utility coordinates with the Racine Water Utility (Drinking Water), located nearby, to manage the complete water cycle. The drinking water plant draws from Lake Michigan, emphasizing the “One Water” cycle where WWTP effluent quality impacts the regional source water.

12. FAQ SECTION

Technical Questions

1. What is the hydraulic retention time (HRT) of the aeration basins?
Depending on flow conditions, the HRT typically ranges from 4 to 8 hours, allowing sufficient contact time for biological degradation of organics.

2. Does the Racine WWTP accept high-strength industrial waste?
Yes, the facility has a Pretreatment Program that monitors and regulates industrial dischargers. The plant accepts hauled waste and high-strength waste compatible with its biological process, particularly for boosting biogas production in digesters.

3. How does the plant manage peak wet-weather flows?
The plant utilizes flow equalization and high-rate treatment strategies. When flows exceed biological treatment capacity, primary treated effluent may be blended with fully treated effluent (in accordance with permit allowances during extreme events) and disinfected to prevent washout of the biological mass.

4. Is there tertiary filtration at the plant?
Currently, the plant relies on chemical precipitation and settling for phosphorus removal and does not utilize sand or cloth media filtration. However, space is reserved in the master plan should regulations require it.

General Interest Questions

5. Does the plant smell?
While wastewater treatment involves odorous compounds, the Racine WWTP employs advanced chemical scrubbers and biofilters to scrub air from process areas, minimizing off-site odors.

6. Can I tour the facility?
The Racine Water and Wastewater Utilities occasionally offer tours for educational groups, schools, and professional organizations. Interested parties should contact the utility administration directly to inquire about availability.

7. What happens to the “sludge”?
The solids are treated (digested) to reduce pathogens and volume. The resulting “biosolids” are a nutrient-rich fertilizer that is applied to local agricultural fields, recycling nitrogen and phosphorus back to the earth.