Metro Wastewater Reclamation District Robert W Hite Treatment Facility Denver

FACILITY BASIC INFORMATION

• Plant Name: Robert W. Hite Treatment Facility (RWHTF)
• Location: 6450 York Street, Denver, Denver/Adams County, Colorado
• Operating Authority: Metro Water Recovery (formerly Metro Wastewater Reclamation District)
• Design Capacity: 220 MGD (Secondary Treatment Capacity)
• Current Average Flow: ~130 MGD
• Population Served: ~2.2 million residents
• Service Area: 715 square miles (Denver and 60+ local governments/sanitation districts)
• Receiving Water Body: South Platte River (Segment 15)
• NPDES Permit Number: CO-0026638
• Year Commissioned: 1966 (Major expansions in 1970s, 1980s, and 2010s)

1. INTRODUCTION

The Robert W. Hite Treatment Facility (RWHTF) serves as the centralized wastewater treatment hub for the Denver metropolitan area and stands as the largest reclamation facility in the Rocky Mountain West. Operated by Metro Water Recovery, the facility provides critical sanitary services for approximately 2.2 million people—roughly 40% of Colorado’s population. Located at the confluence of the South Platte River and Sand Creek, the plant is a marvel of large-scale hydraulic engineering and biological process control.

With a rated secondary treatment capacity of 220 million gallons per day (MGD), the RWHTF is not merely a disposal site but a resource recovery center. In recent years, the facility has transitioned toward a “utility of the future” model, implementing cutting-edge technologies such as the MagPrex phosphorus recovery system and advanced cogeneration infrastructure. The plant plays a pivotal role in the hydrology of the South Platte River; during dry months, the facility’s high-quality effluent comprises nearly 85-90% of the river’s flow downstream of Denver, making its operational reliability essential for downstream agriculture and aquatic life.

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2. FACILITY OVERVIEW

A. Service Area & Coverage

The RWHTF serves a massive 715-square-mile service area encompassing metropolitan Denver, including parts of Adams, Arapahoe, Denver, Douglas, Jefferson, and Weld counties. Metro Water Recovery acts as a wholesale provider to approximately 60 local governments and sanitation districts. The collection system feeding the plant is extensive, relying on a gravity-fed network of large-diameter interceptors that converge at the lowest geographical point in the service area.

B. Operational Capacity

While the facility is rated for 220 MGD, current average daily flows hover around 130 MGD. The plant is designed to handle significant hydraulic peaks, with a wet weather peak flow capacity exceeding 400 MGD. Historically, flows have stabilized despite population growth, attributed largely to successful water conservation efforts in the Denver metro area and the diversion of flow to the newer Northern Treatment Plant (NTP) in Brighton. This strategic offloading allows the RWHTF to focus on process optimization and nutrient removal rather than solely hydraulic expansion.

C. Discharge & Compliance

Treated effluent is discharged into the South Platte River under CDPS Permit No. CO-0026638. The receiving water is classified as a sensitive warm-water fishery, imposing strict limits on ammonia, nitrates, and dissolved oxygen. The facility consistently operates in compliance with Colorado Regulation 85 (Nutrients), targeting stringent effluent phosphorus and nitrogen levels to prevent eutrophication in downstream reservoirs.

3. TREATMENT PROCESS

The RWHTF utilizes a complex arrangement of physical and biological processes, effectively split into two parallel treatment trains—the North Complex and the South Complex—before converging for disinfection.

A. Preliminary Treatment

Raw wastewater enters via major interceptors into the Headworks facility. The process begins with coarse screening using mechanically cleaned bar screens to remove large debris (rags, wood, plastics). Following screening, flow velocity is reduced in aerated grit chambers, allowing inorganic solids (sand, gravel, eggshells) to settle while organic matter remains suspended. The grit is washed, dewatered, and landfilled. The facility utilizes robust chemical scrubbers and biofilters at the headworks to mitigate odors, a critical necessity given the plant’s proximity to commercial zones.

B. Primary Treatment

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The flow is distributed to rectangular primary clarifiers. Here, gravity settling removes approximately 60-70% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD). Floating grease and scum are skimmed from the surface. The primary sludge is co-thickened and pumped directly to the anaerobic digesters. The facility has the capability for Chemically Enhanced Primary Treatment (CEPT) using ferric chloride during high-flow events or for odor control, though biological selection is preferred for nutrient management.

C. Secondary Treatment (Activated Sludge with BNR)

The heart of the RWHTF is its advanced activated sludge system, configured for Biological Nutrient Removal (BNR). The aeration basins are designed to create specific environmental zones:

• Anaerobic/Anoxic Zones: To facilitate biological phosphorus removal (Bio-P) and denitrification.
• Aerobic Zones: To achieve nitrification (converting ammonia to nitrate) and BOD oxidation.

Air is supplied via a network of centrifugal blowers delivering oxygen through fine-bubble membrane diffusers (recently upgraded from ceramic discs for energy efficiency). The mixed liquor flows to secondary clarifiers—a mix of circular and rectangular units depending on the complex—where the biomass settles. Return Activated Sludge (RAS) is recycled to the front of the aeration basins, while Waste Activated Sludge (WAS) is sent to solids handling.

D. Tertiary/Advanced Treatment

While the RWHTF does not utilize traditional sand filtration for the bulk flow, it employs an advanced nutrient recovery step on the centrate return stream. The facility utilizes the MagPrex technology. This system treats the nutrient-rich centrate (liquid separated from digested sludge) by adding magnesium chloride to precipitate struvite (magnesium ammonium phosphate). This process recovers phosphorus as a slow-release fertilizer and significantly reduces the nutrient load returned to the head of the plant, improving overall process stability.

E. Disinfection

Disinfection is achieved using liquid sodium hypochlorite (chlorination) to inactivate pathogens. To protect aquatic life in the South Platte River, the chlorinated effluent undergoes dechlorination using sodium bisulfite before final discharge. The plant includes complex cascade aeration structures at the outfall to ensure the effluent meets Dissolved Oxygen (DO) requirements before entering the river.

F. Solids Handling & Biosolids

Metro Water Recovery is a pioneer in biosolids management.

• Thickening: Dissolved Air Flotation (DAF) and centrifugation.
• Digestion: Mesophilic anaerobic digestion stabilizes the sludge, reducing pathogens and volatile solids. The facility operates a massive complex of 24 digesters.
• Dewatering: High-solids centrifuges dewater the digested sludge.
• Reuse: The resulting Class B biosolids, branded as METROGRO, are land-applied to dryland wheat farms and rangeland in eastern Colorado, recycling nutrients back to the soil. The facility also produces Class A biosolids on a smaller scale through composting.

G. Process Control

The entire facility is monitored via a centralized SCADA system. The plant utilizes real-time ammonia and nitrate analyzers to optimize aeration setpoints, reducing energy consumption while ensuring permit compliance.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans over 150 acres, comprising a dense industrial campus of clarifiers, gallery tunnels, maintenance shops, and the Administration Building. The facility includes a fully accredited environmental laboratory that processes over 150,000 analyses annually for process control and regulatory reporting.

B. Energy Systems

The RWHTF is a leader in energy recovery. The anaerobic digestion process produces roughly 2.5 to 3.0 million cubic feet of biogas daily. This gas fuels an on-site Cogeneration (CHP) Power Plant. The facility captures waste heat from the engines to heat the digesters and buildings. Recently, Metro Water Recovery partnered with Xcel Energy to inject renewable natural gas (RNG) into the pipeline, further monetizing the biogas resource.

C. Odor Control

Given the urban encroachment around the plant, odor control is a top priority. The facility utilizes dual-stage systems combining chemical scrubbers and activated carbon, alongside vast biofilters that use organic media to oxidize odorous compounds naturally. The “Good Neighbor” policy drives operational decisions regarding odor containment.

5. RECENT UPGRADES & MAJOR PROJECTS

Metro Water Recovery maintains an aggressive Capital Improvement Plan (CIP). Key recent and ongoing projects include:

PAR 1085 – Phosphorus Recovery (MagPrex) (2018-2020)

• Project Scope: Installation of a struvite recovery reactor system to treat centrate side-streams.
• Project Budget: ~$35 Million
• Technical Highlights: Implemented the MagPrex technology to sequester phosphorus. This prevents “nuisance struvite” from scaling pipes and pumps within the plant while producing a marketable fertilizer product.
• Results: Significant reduction in phosphorus feedback loops, improved dewaterability of biosolids, and reduced polymer consumption.

PAR 1232 – Aeration Improvements (2016-2021)

• Project Scope: Replacement of aging ceramic disc diffusers with high-efficiency membrane diffusers across the North and South secondary complexes.
• Project Budget: ~$25 Million
• Drivers: Energy efficiency and process control optimization.
• Results: The project reduced the facility’s aeration energy demand by nearly 20%, saving millions in annual electrical costs and reducing the carbon footprint.

South Secondary Improvements (Current/Ongoing)

• Scope: Rehabilitation of secondary clarifiers and mechanisms in the South Complex to extend asset life and ensure hydraulic reliability during peak flow events.
• Drivers: Aging infrastructure and asset management.

NTP Interceptor System

• Scope: While not inside the Hite fence line, the construction of the interceptors diverting flow to the Northern Treatment Plant was a massive capital undertaking that directly impacts Hite’s operation by offloading hydraulic capacity.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Operating under the Colorado Discharge Permit System (CDPS), the RWHTF faces some of the state’s strictest nutrient limits due to Regulation 85.
Key Targets:
— Ammonia (NH3-N): Seasonally variable, often < 2.0 mg/L
— Total Inorganic Nitrogen (TIN): Monitoring and voluntary reduction targets
— Total Phosphorus: < 1.0 mg/L (rolling annual median)

B. Compliance History

The facility maintains an exemplary compliance record, receiving multiple Peak Performance Awards from the National Association of Clean Water Agencies (NACWA). The plant has successfully navigated the transition to stricter nutrient limits without requiring massive concrete expansion, relying instead on process optimization and side-stream treatment innovations.

7. OPERATIONAL EXCELLENCE

A. Staffing

The facility is staffed by highly trained operators, holding Colorado Class A Wastewater certifications. The district employs over 400 specialized staff, including electricians, mechanics, instrumentation technicians, and microbiologists.

B. Innovation

Metro Water Recovery is frequently cited in academic journals and industry conferences (WEFTEC) for its research. The facility often serves as a test bed for new technologies, such as peracetic acid (PAA) disinfection pilots and advanced dewatering technologies.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

PFAS and Emerging Contaminants: Like all major WWTPs, RWHTF is monitoring the regulatory landscape regarding PFAS (forever chemicals). As a receiver of flow from diverse industrial sources, source control will be the primary strategy.
Temperature Regulations: New regulations regarding the temperature of the effluent entering the South Platte River may require cooling technologies in the future, a technically difficult and expensive challenge for a plant of this size.

B. Future Planning

The strategic vision involves further integration of the Northern Treatment Plant to balance regional growth. The RWHTF is moving toward energy neutrality, aiming to generate as much energy from biogas and solar as it consumes from the grid.

9. COMMUNITY & REGIONAL IMPACT

The RWHTF is an economic engine for the region. By providing reliable wastewater treatment, it enables residential and commercial development in the Denver metro area. The METROGRO farm program supports Colorado agriculture by providing a cost-effective, nutrient-rich soil amendment to local farmers. Furthermore, the high quality of the effluent sustains the urban stretch of the South Platte River, turning what was once an industrial drainage ditch into a recreational amenity for kayakers and anglers through downtown Denver.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

Northern Treatment Plant (NTP): Located in Brighton, CO, this 28.8 MGD facility was commissioned in 2016 to serve the growing northern service area. It operates as a satellite facility, treating flows that would otherwise travel to the Robert W. Hite facility, thereby preserving capacity at the main plant.

METROGRO Farm: A 52,000-acre agricultural site in eastern Colorado owned and/or managed by the district for the beneficial reuse of biosolids.

12. FAQ

Technical Questions

1. What is the hydraulic retention time (HRT) at RWHTF?
The HRT varies by flow, but typically ranges from 12 to 16 hours through the primary and secondary treatment trains.

2. How does the plant manage “nuisance struvite”?
RWHTF utilizes the MagPrex system to deliberately precipitate struvite in a controlled reactor, preventing it from scaling pipes and damaging pumps downstream.

3. Is the RWHTF regulated for temperature?
Yes, temperature standards for the South Platte River are a major compliance focus, particularly during low-flow months where the effluent dominates the river volume.

4. What is the solids retention time (SRT) in the digesters?
The anaerobic digesters typically operate with a retention time of 15 to 20 days to ensure pathogen reduction and volatile solids destruction.

Public Interest Questions

5. How many people does the plant serve?
The facility serves approximately 2.2 million people across the Denver Metro area.

6. Does the plant smell?
While wastewater treatment naturally generates odors, RWHTF employs extensive odor control technologies (scrubbers and biofilters) to capture and neutralize smells before they leave the property boundary.

7. What is METROGRO?
METROGRO is the brand name for the Class B biosolids fertilizer produced by the plant, which is used to improve soil health on farms in eastern Colorado.

8. Who runs the facility?
It is operated by Metro Water Recovery, a political subdivision of the State of Colorado formed in 1961.