Colorado Wastewater Treatment Plants

Colorado Wastewater Treatment Plants

Introduction

Colorado sits at a unique geographical and regulatory intersection within the United States water sector. As a headwaters state, the effluent quality from Colorado’s wastewater treatment plants (WWTPs) dictates the water health for millions of downstream users in the Colorado, Platte, Arkansas, and Rio Grande river basins. Consequently, the state maintains some of the most rigorous nutrient and temperature regulations in the country.

The state’s infrastructure is currently bifurcated. The rapidly urbanizing Front Range (Denver, Colorado Springs, Fort Collins) is seeing massive consolidation and capacity expansion to handle population growth. Conversely, mountain and rural communities are grappling with aging infrastructure and the technical challenges of treating water at high altitudes with extreme seasonal load variations due to tourism. Currently, the Colorado Department of Public Health and Environment (CDPHE) oversees over 250 permitted domestic wastewater treatment facilities, ranging from massive regional reclamation districts to small lagoon systems.

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For consulting engineers and equipment vendors, Colorado represents a high-activity market driven primarily by Regulation 85 (Nutrient Management Control), water reuse initiatives (including recently approved Direct Potable Reuse regulations), and aging infrastructure replacement.

Recent Developments & Infrastructure Trends

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In the last 36 months, Colorado’s wastewater sector has shifted focus from simple capacity expansion to advanced resource recovery and complex nutrient removal. The implementation of Regulation 85 has forced nearly every mechanical plant in the state to evaluate or upgrade their Biological Nutrient Removal (BNR) capabilities to meet strict Total Inorganic Nitrogen (TIN) and Total Phosphorus (TP) limits.

Key Market Drivers:

  • Direct Potable Reuse (DPR): In late 2022/early 2023, Colorado became one of the first states to adopt formal regulations for Direct Potable Reuse. This is spurring new feasibility studies for “pipe-to-pipe” infrastructure projects in the drought-prone Front Range.

  • Biogas and Energy Recovery: Facilities like Metro Water Recovery and South Platte Renew are heavily investing in co-generation and Renewable Natural Gas (RNG) pipeline injection, leveraging federal RIN credits.

  • PFAS Mitigation: With the CDPHE intensifying testing requirements for Per- and Polyfluoroalkyl Substances, several municipalities are launching pilot studies for granular activated carbon (GAC) and ion exchange solutions.

  • Funding Influx: The state has seen a significant injection of funds via the State Revolving Fund (SRF) and the Bipartisan Infrastructure Law (IIJA), specifically targeting disadvantaged communities and emerging contaminants.

Top 20 Largest Treatment Plants in Colorado

The following list ranks the largest wastewater treatment facilities in Colorado based on rated Design Capacity (MGD). Data is compiled from CDPHE discharge permits, utility master plans, and Metro Water Recovery annual reports.

Rank Plant Name City/Location Design Capacity (MGD) Pop. Served Operating Authority
1 Robert W. Hite Treatment Facility Denver 220.0 2.2M Metro Water Recovery
2 Las Vegas Street WRF Colorado Springs 75.0 400k Colorado Springs Utilities
3 South Platte Renew (Pierson Park) Englewood 50.0 300k South Platte Renew
4 Northern Treatment Plant Brighton 28.8 Included in Metro Metro Water Recovery
5 Persigo Wastewater Treatment Plant Grand Junction 25.0 100k City of Grand Junction
6 Pueblo Water Reclamation Facility Pueblo 19.0 160k City of Pueblo
7 Drake Water Reclamation Facility Fort Collins 23.0 130k City of Fort Collins
8 Greeley WPCF Greeley 14.7 110k City of Greeley
9 Boulder WRF (75th Street) Boulder 25.0 108k City of Boulder
10 Longmont WWTP Longmont 17.0 98k City of Longmont
11 Big Dry Creek WWTF Westminster 12.0 110k City of Westminster
12 Boxelder Sanitation District Plant Fort Collins 10.6 70k Boxelder Sanitation District
13 Broomfield WWTF Broomfield 12.0 75k City & County of Broomfield
14 Plum Creek Water Reclamation Authority Castle Rock 10.6 75k PCWRA
15 Loveland WRF Loveland 10.0 78k City of Loveland
16 Centennial Water & Sanitation (Marcy Gulch) Highlands Ranch 9.5 100k Centennial WSD
17 Sand Creek Reuse Facility Aurora 10.0 N/A (Reuse) Aurora Water
18 Parker Water & Sanitation District (South) Parker 8.0 55k Parker WSD
19 Fountain Sanitation District Fountain 7.2 45k Fountain SD
20 Security Sanitation District Colorado Springs 6.5 40k Security SD

Profiles of the Top 5 Largest Facilities

1. Robert W. Hite Treatment Facility (RWHTF)

  • Location: Denver, Adams County

  • Design Capacity: 220 MGD (Peak capability significantly higher)

  • Current Average Flow: ~130 MGD

  • Operating Authority: Metro Water Recovery

  • Receiving Water: South Platte River

  • Service Area: Denver and 60+ local connectors including Arvada, Aurora, Lakewood, Wheat Ridge.

Treatment Process: The RWHTF is the largest facility in the Rocky Mountain West. It utilizes advanced secondary treatment with nitrification/denitrification (Bardenpho process) in parts of the plant. The facility employs gravity thickening, dissolved air flotation, and extensive anaerobic digestion.

Infrastructure Highlights:

  • Biosolids: Class B biosolids produced and land applied (METROGRO Farm).

  • Energy: A massive Cogeneration facility utilizes biogas to offset substantial grid energy needs.

  • Resource Recovery: Recently installed MagPrex technology for struvite recovery to reduce phosphorus recycling and maintenance costs.

2. Las Vegas Street Water Resource Recovery Facility

  • Location: Colorado Springs, El Paso County

  • Design Capacity: 75 MGD

  • Operating Authority: Colorado Springs Utilities (CSU)

  • Receiving Water: Fountain Creek

Treatment Process: The facility utilizes a rigorous biological nutrient removal process. Given its location on Fountain Creek (a tributary to the Arkansas River), effluent quality is critical for downstream agricultural users.

Recent Upgrades: CSU has invested heavily in “advanced technology” filtration to meet Reg 85 limits. The plant is currently undergoing modernization to replace aging clarifiers and solids handling equipment.

3. South Platte Renew (formerly Littleton/Englewood)

  • Location: Englewood, Arapahoe County

  • Design Capacity: 50 MGD

  • Operating Authority: South Platte Renew (Joint Authority)

  • Service Area: Littleton, Englewood, and 19 connector districts.

Treatment Process: A trickling filter/solids contact process (TF/SC) converted to allow for denitrification. This hybrid system offers stability against shock loads while meeting ammonia limits.

Innovation: South Platte Renew recently completed a massive Gas-to-Grid pipeline injection project, becoming a leader in renewable natural gas (RNG) production in the region.

4. Northern Treatment Plant (NTP)

  • Location: Brighton, Weld County

  • Design Capacity: 28.8 MGD

  • Operating Authority: Metro Water Recovery

Treatment Process: Commissioned in 2016, this is one of the most modern plants in the West. It uses a state-of-the-art multi-stage Activated Sludge process designed specifically for high-efficiency nutrient removal.

Significance: The NTP was built to offload capacity from the Robert W. Hite facility and serve the rapidly growing northern suburbs. It features advanced odor control and discharges to the South Platte River.

5. Persigo Wastewater Treatment Plant

  • Location: Grand Junction, Mesa County

  • Design Capacity: 25 MGD

  • Operating Authority: City of Grand Junction (Jointly owned with Mesa County)

  • Receiving Water: Colorado River

Treatment Process: As the largest plant on the Western Slope, Persigo utilizes oxidation ditches and UV disinfection. It is critical for protecting the water quality of the Colorado River before it flows into Utah.

Renewables: The plant injects refined biogas into the Xcel Energy pipeline, generating revenue and carbon credits for the city.

Regional Plant Listings (Tiers 6-20)

Large Municipal Plants (Rank 6-10)

  • Pueblo Water Reclamation Facility (19 MGD): Key discharger to the Arkansas River; utilizes activated sludge with significant nutrient removal upgrades planned.

  • Drake WRF – Fort Collins (23 MGD): Known for environmental stewardship; heavily invested in biological phosphorus removal and energy optimization.

  • Greeley WPCF (14.7 MGD): Serving the agricultural hub of Weld County; recently underwent significant headworks and odor control improvements.

  • Boulder WRF (25 MGD): Uses a modified Bardenpho process; famous for its Renewable Natural Gas (RNG) complex.

  • Longmont WWTP (17 MGD): Recently completed a Biogas Treatment Project to convert digester gas to Vehicle Fuel (RNG).

Significant Facilities (Rank 11-20)

  • Big Dry Creek (Westminster): 12 MGD capacity, heavy focus on water reuse for irrigation (golf courses/parks).

  • Boxelder Sanitation District: 10.6 MGD, serving rapid growth east of Fort Collins; recently expanded with new BNR basins.

  • Plum Creek (Castle Rock): 10.6 MGD, a regional authority known for advanced oxidation processes to handle reuse water standards.

  • Centennial (Marcy Gulch): 9.5 MGD, integral to the south metro water reuse strategy.

Plants with Approved Budgets & Expansion Projects

Colorado’s wastewater sector is seeing high capital velocity. The following projects represent confirmed capital allocations derived from municipal CIPs, bond issuances, and SRF Intended Use Plans.

A. Major Projects Under Construction (2024-2026)

Metro Water Recovery – Second Creek Interceptor & Transmission Improvements

  • Location: Denver Metro Area

  • Project Scope: Massive rehabilitation and capacity expansion of interceptors to route flows to the Northern Treatment Plant.

  • Total Budget: Est. >$100 Million (Multi-phase)

  • Drivers: Population growth in the northern sector (DIA airport area) and aging infrastructure.

  • Current Status: Various segments in active construction.

South Platte Renew – Biogas Conditioning & Pipeline Injection

  • Location: Englewood, CO

  • Project Scope: Installation of gas conditioning equipment to scrub biogas to pipeline-quality natural gas.

  • Budget: ~$15-20 Million

  • Key Contractors: Carollo Engineers (Design), J.R. Filanc (Construction).

  • Expected Benefits: Revenue generation via RIN credits; reduced greenhouse gas emissions.

  • Current Status: Commissioning/Operational phase.

Colorado Springs Utilities – Warren Water Resource Recovery Facility Upgrades

  • Location: Colorado Springs

  • Project Scope: Process modernization for Reg 85 compliance and capacity assurance.

  • Funding: Revenue Bonds.

  • Timeline: Construction ongoing through 2025.

  • Drivers: Nutrient removal compliance and asset management.

B. Projects in Design/Planning Phase (2025-2027)

  • Aurora Water – Wild Horse Reservoir (Related Infrastructure): While primarily a water supply project ($600M+), this involves significant pumping and potential reuse integration that will impact wastewater strategy.

  • Town of Erie – WRF Expansion: In planning to expand capacity from 3.5 MGD to 5+ MGD to accommodate one of the fastest-growing towns in the state. Budget est. $40M+.

  • Pueblo West Metro District – Plant Expansion: Design phase for increasing hydraulic capacity to handle new housing developments.

C. Summary Statistics: Colorado Market

  • Total Active Capital Investment: ~$650 Million (Active & Planned Major Projects)

  • Primary Project Drivers:
    1. Nutrient Removal Compliance (Reg 85) – 40%

    2. Capacity Expansion (Front Range Growth) – 35%

    3. Aging Infrastructure/Solids Handling – 25%

  • Key Funding Sources: Colorado Water Resources & Power Development Authority (CWRPDA) SRF Loans, Municipal Revenue Bonds, WIFIA.

Regulatory & Compliance Landscape

Colorado’s regulatory environment is among the strictest in the interior United States, driven by the need to protect headwaters.

  • Regulation 85 (Nutrients): The defining regulation for the decade. It sets effluent limits for Total Inorganic Nitrogen (TIN) and Total Phosphorus (TP). It applies to all domestic wastewater treatment works discharging to surface waters. Phase 2 implementation is tightening limits further, driving BNR retrofits.

  • Regulation 31 (Temperature): Strict temperature standards to protect aquatic life (trout/fisheries) are forcing plants to investigate thermal reduction strategies, including effluent cooling or riparian shading.

  • Regulation 84 & DPR: Colorado governs reclaimed water use under Reg 84. The recent adoption of Direct Potable Reuse (DPR) rules creates a new compliance pathway for utilities to treat wastewater to drinking water standards, opening a new market for advanced oxidation and membrane technologies.

  • PFAS/PFOA: The CDPHE is currently in a rigorous data-collection phase, requiring sampling from facilities. Future discharge limits are anticipated, which will require capital investment in GAC or Ion Exchange systems.

Resources for Engineers & Operators

Professionals working in the Colorado water sector should engage with the following organizations:

  • Rocky Mountain Water Environment Association (RMWEA): The primary member association for wastewater professionals in CO, NM, and WY. Hosts the annual Joint Conference.

  • CDPHE Water Quality Control Division: The regulatory body issuing discharge permits and operator certifications.

  • Colorado Certification Office (CCWP): Manages testing and licensure for Class D through Class A wastewater operators.

  • Colorado Water Resources & Power Development Authority: The financial vehicle for SRF loans.

Frequently Asked Questions

What is the largest wastewater treatment plant in Colorado?

The Robert W. Hite Treatment Facility (operated by Metro Water Recovery) in Denver is the largest, with a design capacity of 220 MGD, treating wastewater for approximately 2.2 million people.

What is Regulation 85 in Colorado?

Regulation 85 is the Nutrients Management Control Regulation. It establishes numerical effluent limitations for nitrogen and phosphorus to prevent algae blooms and protect downstream water quality. It is the primary driver for current treatment plant upgrades.

Are there opportunities for Direct Potable Reuse (DPR) in Colorado?

Yes. Colorado recently finalized regulations allowing for Direct Potable Reuse. Utilities like Aurora Water and Castle Rock Water are at the forefront of implementing advanced treatment trains to turn wastewater directly into drinking water.

How many wastewater treatment plants are in Colorado?

There are approximately 250 permitted domestic wastewater treatment facilities in the state, ranging from large mechanical plants to small stabilization lagoons.

What funding is available for wastewater projects in Colorado?

Major funding comes through the State Revolving Fund (SRF) managed by the CWRPDA, WIFIA loans from the EPA, and increasingly, federal grants via the IIJA (Bipartisan Infrastructure Law) for emerging contaminants.