City Of Omaha Missouri River Wastewater Treatment Plant

FACILITY BASIC INFORMATION

• Plant Name: Missouri River Water Resource Recovery Facility (formerly Missouri River WWTP)
• Location: 5600 South 10th Street, Omaha, Douglas County, Nebraska
• Operating Authority: City of Omaha Public Works Department
• Design Capacity (Biological): 62 MGD (Average Daily)
• Peak Wet Weather Capacity (Total): ~360 MGD (Combined Secondary + High Rate Treatment)
• Population Served: Approx. 400,000 (East Omaha and Downtown)
• Service Area: Eastern Omaha (Combined Sewer Service Area)
• Receiving Water Body: Missouri River
• NPDES Permit Number: NE0040649
• Year Commissioned: 1964 (Major expansions in 1990s, 2010s, 2020s)

1. INTRODUCTION

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The Missouri River Water Resource Recovery Facility (MRWRRF) is the cornerstone of wastewater infrastructure for the City of Omaha, Nebraska. Serving the older, eastern portion of the metropolitan area—which consists primarily of combined sewer systems—the facility plays a dual role: providing consistent biological treatment for municipal sewage and managing massive hydraulic loads during storm events to prevent Combined Sewer Overflows (CSOs).

Operated by the City of Omaha Public Works Department, the plant has recently undergone a transformation under the federally mandated “Clean Solutions! Omaha” (CSO) program. With the commissioning of a massive High Rate Treatment (HRT) facility, the MRWRRF can now treat peak flows exceeding 300 MGD, significantly reducing untreated discharges into the Missouri River. This facility represents a convergence of traditional activated sludge processing and cutting-edge ballasted flocculation technology, making it a case study in modern wet-weather flow management.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The MRWRRF services the eastern watershed of Omaha, covering approximately 40 square miles. This area includes the historic downtown, commercial districts, and older residential neighborhoods. Unlike the Papillion Creek WRRF to the west (which serves separate sanitary sewers), the Missouri River plant’s collection system is largely a Combined Sewer System (CSS). Consequently, the facility must handle extreme variations in flow, shifting from a dry-weather average of 25–30 MGD to hydraulic peaks hundreds of times higher during heavy Midwestern storms.

B. Operational Capacity

The facility operates with a tiered capacity structure designed to maximize treatment quality while managing volume:

• Average Dry Weather Flow: 25-30 MGD
• Biological Secondary Treatment Capacity: Rated for approx. 62 MGD average, with peaks up to 100-120 MGD.
• High Rate Treatment (HRT) Capacity: An additional wet-weather train capable of treating excess flows (up to 240 MGD) via physical-chemical processes.

C. Discharge & Compliance

Treated effluent is discharged directly into the Missouri River. The facility operates under a National Pollutant Discharge Elimination System (NPDES) permit issued by the Nebraska Department of Environment and Energy (NDEE). Strict compliance is required for E. coli (during the recreation season of May-September), Ammonia-Nitrogen, and Total Suspended Solids (TSS). The plant is a critical component in the regional effort to reduce nutrient loading to the Mississippi River Basin and the Gulf of Mexico.

3. TREATMENT PROCESS

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The MRWRRF utilizes a split-stream treatment approach during wet weather, while maintaining a conventional Activated Sludge process for base flows.

A. PRELIMINARY TREATMENT

Raw wastewater enters the facility via the South Interceptor and major force mains. The headworks is designed for robust debris removal to protect downstream pumps.

• Screening: Mechanically cleaned bar screens remove large debris, rags, and timber.
• Grit Removal: Aerated grit chambers settle out sand, gravel, and heavy inorganic solids. The grit is washed and dewatered before landfill disposal.
• Flow Splitting: During storm events, flow exceeding the biological capacity is diverted post-screening to the High Rate Treatment (HRT) facility.

B. PRIMARY TREATMENT (Biological Train)

Flow directed to the biological train enters primary clarifiers. These large rectangular basins slow the velocity of the wastewater, allowing settleable solids to drop to the bottom (primary sludge) and grease/oils to float to the top for removal. Primary treatment typically removes 30-40% of BOD and 50-60% of TSS.

C. SECONDARY TREATMENT

The facility utilizes a High Purity Oxygen (HPO) Activated Sludge system, a legacy technology often chosen for plants with limited footprints and high organic loading.

• Reactors: Covered aeration basins where high-purity oxygen (generated on-site via Cryogenic Air Separation or VSA) is injected. The high partial pressure of oxygen accelerates biological metabolism.
• Clarification: Mixed liquor flows to secondary clarifiers where biological floc settles.
• RAS/WAS: Return Activated Sludge is pumped back to the reactors; Waste Activated Sludge is thickened and sent to digesters.

D. WET WEATHER HIGH RATE TREATMENT (HRT)

Commissioned to address CSO mandates, the HRT facility utilizes Ballasted Flocculation technology (specifically Veolia ACTIFLO® systems).

• Coagulation/Flocculation: Polymer and microsand are injected into the stormwater/wastewater mix.
• Settling: The sand acts as a weight, causing floc to settle extremely rapidly in lamella clarifiers.
• Recovery: Hydrocyclones separate the sludge from the sand; the sand is recycled back into the process.
• Performance: This system allows the plant to treat massive spikes in flow (up to 240 MGD) to near-secondary standards for TSS and bacteria without washing out the biological mass in the main plant.

E. DISINFECTION

The facility employs chlorination for disinfection, utilizing sodium hypochlorite. After a dedicated contact time to ensure pathogen kill (specifically targeting E. coli), the effluent is dechlorinated using sodium bisulfite to prevent toxicity to aquatic life in the Missouri River.

F. SOLIDS HANDLING

Omaha acts as a regional solids processing hub.

• Thickening: Gravity belt thickeners concentrate WAS.
• Digestion: Anaerobic digesters stabilize the sludge, reducing volume and pathogens while producing biogas.
• Conditioning: Digested sludge is dewatered using high-performance centrifuges.
• Beneficial Use: The City produces “Oma-Gro,” a compost product, though process specifics have evolved. Biogas is captured, conditioned, and utilized for plant heating or processed into Renewable Natural Gas (RNG).

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site is constrained by the Missouri River to the East, railroad tracks to the West, and industrial zoning to the North/South. This spatial constraint drove the selection of compact technologies like HPO and Ballasted Flocculation. The campus includes the main Operations Building, the Cryogenic Oxygen facility, the new HRT building, and the massive digester complex.

B. Energy Systems

The MRWRRF is a significant energy consumer, primarily due to the oxygen generation systems and large influent pumps. However, the facility has moved toward sustainability through a Biogas Conditioning System. Methane produced in the anaerobic digesters is scrubbed of impurities (siloxanes, H2S) and used to offset natural gas demand or injected into the pipeline, turning a waste product into a revenue stream.

C. Flood Protection

Situated in the floodplain, the facility is protected by a levee system. Following the historic 2011 and 2019 Missouri River floods, the City has invested heavily in hardening infrastructure, raising critical electrical gear, and ensuring perimeter floodwall integrity.

5. RECENT UPGRADES & MAJOR PROJECTS

The City of Omaha is currently executing “Clean Solutions! Omaha,” a $2 billion Long Term Control Plan (LTCP) to reduce CSOs. The MRWRRF is the centerpiece of this initiative.

Missouri River WWTP High Rate Treatment (HRT) Facility

• Timeline: Completed approx. 2017-2018
• Budget: ~$110 Million
• Scope: Construction of a ballasted flocculation facility to treat wet weather flows.
• Technical Highlight: One of the largest Actiflo® installations in the Midwest. It allows the plant to process total flows approaching 400 MGD during storm events, treating water that previously would have overflowed directly to the river.
• Outcome: Massive reduction in untreated CSO volume, meeting NDEE compliance schedules.

Headworks and Grit Removal Improvements

• Timeline: 2015-2017
• Budget: ~$35 Million
• Scope: Replacement of aging coarse screens and grit removal systems to handle increased hydraulic throughput required by the new HRT facility.
• Outcome: Improved protection of downstream pumps and the new HRT basins.

Digester Gas Conditioning & CHP Projects

• Timeline: Ongoing optimization (2020-Present)
• Scope: Upgrading gas scrubbing systems to convert digester gas to Renewable Natural Gas (RNG) quality for pipeline injection.
• Drivers: Energy credits (RINs) and sustainability goals.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The facility operates under NPDES Permit NE0040649. The permit acknowledges the dual nature of the plant (biological vs. wet weather). While the biological train must meet strict secondary treatment standards (30 mg/L BOD/TSS), the HRT train operates under specific wet-weather bypass provisions that mandate high-efficiency solids removal and disinfection.

B. Compliance History

The City of Omaha has been working under a Consent Decree with the EPA and DOJ regarding CSOs. The construction of the MRWRRF HRT facility was a required milestone in this decree. Since its commissioning, the facility has successfully met the capture and treatment targets set forth in the Long Term Control Plan.

7. OPERATIONAL EXCELLENCE

A. Staffing

The facility is staffed 24/7/365 by a team of certified wastewater operators (Nebraska Class IV, III, II, I), maintenance mechanics, electricians, and laboratory technicians. The City of Omaha Public Works Quality Control Division oversees the laboratory analysis.

B. Process Control

A plant-wide SCADA system integrates the traditional biological plant with the intermittent HRT facility. Operators must make rapid decisions during storm events to divert flow to the HRT train as the biological plant reaches hydraulic capacity. This dynamic operation requires advanced training in wet-weather protocols.

8. CHALLENGES & FUTURE PLANNING

A. Nutrient Management

Like many dischargers to the Missouri/Mississippi basin, Omaha is facing increasing pressure regarding nutrient loads (Nitrogen and Phosphorus). While not currently under a strict numeric nutrient limit, the facility monitors these parameters. Future regulatory cycles will likely require capital improvements for Biological Nutrient Removal (BNR).

B. Aging Infrastructure

While the HRT facility is new, the core biological plant dates back to the 1960s. Concrete degradation in primary clarifiers and the maintenance of the oxygen generation system (cryogenic plants are maintenance-intensive) remain ongoing operational challenges.

C. Climate Resilience

The Missouri River has seen record flood levels twice in the last decade. Ensuring the plant remains operational when river levels are high—which necessitates pumping effluent against high head pressure—is a critical focus of the City’s asset management plan.

9. TECHNICAL SPECIFICATIONS SUMMARY

10. RELATED FACILITIES

Papillion Creek Water Resource Recovery Facility: Omaha’s second major treatment plant, serving the western, suburban watersheds (separate sanitary sewers). Solids from Papillion Creek are often transferred to the Missouri River plant or the associated solids processing facility.

Lift Stations: Over 70 lift stations throughout the metro area convey wastewater to these two central plants.

11. FAQ SECTION

Technical Questions

Q: Does the Missouri River plant use biological nutrient removal (BNR)?
A: Currently, the plant is designed primarily for BOD and TSS removal with ammonia toxicity control. Full biological nutrient removal (Nitrogen/Phosphorus) is not the primary design driver yet, but is being monitored for future permits.

Q: What happens to the biogas produced at the plant?
A: The City has invested in cleaning the gas for use as Renewable Natural Gas (RNG) or for heating plant processes, moving away from simple flaring.

Q: What is the peak hydraulic capacity?
A: By combining the biological train (~120 MGD peak) and the HRT train (~240 MGD), the plant can process over 350 MGD during extreme events.

Public Interest Questions

Q: Why is the plant located right on the river?
A: Wastewater systems rely on gravity. The river is the lowest point in the geographic basin, allowing sewage to flow downhill to the plant, reducing pumping costs.

Q: Does the plant smell?
A: While wastewater treatment inherently involves odors, the City utilizes odor control scrubbers, particularly at the headworks and solids handling areas, to minimize impact on neighboring areas.