City Of Fort Collins Water Reclamation And Biosolids Facility

1. INTRODUCTION

The Drake Water Reclamation Facility (DWRF) serves as the primary wastewater treatment hub for the City of Fort Collins, Colorado, a regional leader in sustainable resource management. Working in tandem with the smaller Mulberry Water Reclamation Facility, DWRF treats an average of 11 million gallons daily (MGD), serving a population of approximately 170,000 residents. The facility is distinguished not only by its advanced treatment capabilities required to discharge into the sensitive Cache la Poudre River but also by its integrated approach to resource recovery.

DWRF acts as the central solids handling facility for the city, processing sludge from both reclamation plants into Class B biosolids. These biosolids are beneficially reused at the city-owned Meadow Springs Ranch, a massive 26,000-acre site that exemplifies circular economy principles. With a design capacity of 23 MGD and a robust ISO 14001 certified Environmental Management System, the facility continues to set benchmarks in energy neutrality, biological nutrient removal (BNR), and regulatory compliance within the Rocky Mountain West.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The Fort Collins wastewater system serves a rapidly growing municipality in Northern Colorado. The service area encompasses approximately 58 square miles, handling domestic, commercial, and industrial flows (primarily breweries and high-tech manufacturing). The collection system comprises over 450 miles of sanitary sewer lines. DWRF handles the majority of the city’s flow, while the Mulberry Water Reclamation Facility (MWRF) handles flows from the eastern basin.

B. Operational Capacity

The Drake facility has a rated hydraulic design capacity of 23.0 MGD, with organic loading capacities designed to accommodate high-strength waste events typical of brewery-heavy industrial bases. Current average daily flows hover between 10-12 MGD, providing significant redundancy and capacity for future growth. The facility manages peak wet weather flows through equalization basins and robust hydraulic throughput design.

C. Discharge & Compliance

Treated effluent is discharged into the Cache la Poudre River, a tributary of the South Platte River. As a designated “Wild and Scenic River” in upper reaches, the Poudre has strict water quality standards. The facility operates under a Colorado Department of Public Health and Environment (CDPHE) permit (NPDES delegated), with stringent limits on ammonia, inorganic nitrogen, phosphorus, and E. coli. The facility consistently achieves 100% compliance, frequently earning Platinum Awards from the National Association of Clean Water Agencies (NACWA).

3. TREATMENT PROCESS

The DWRF utilizes an advanced secondary treatment process with biological nutrient removal (BNR) and UV disinfection. The treatment train is designed to meet Regulation 85 nutrient limits.

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it passes through mechanical bar screens (6mm spacing) to remove rags and large debris. This is followed by vortex grit removal systems that separate heavy inorganic solids (sand, gravel) to protect downstream pumps. The headworks is fully enclosed with foul air routed to biological odor control towers.

B. PRIMARY TREATMENT

Flow enters rectangular primary clarifiers where settleable solids drop to the bottom as primary sludge, and fats, oils, and grease (FOG) are skimmed from the surface. The primary sludge is pumped directly to the anaerobic digesters. Primary treatment removes approximately 30-40% of BOD and 50-60% of TSS, reducing the organic load on the biological stage.

C. SECONDARY TREATMENT (BNR)

The core of the DWRF is its Activated Sludge system, configured for Biological Nutrient Removal (BNR). The aeration basins utilize a multi-stage configuration:

• Anaerobic Zone: Promotes the growth of Phosphorus Accumulating Organisms (PAOs) for biological phosphorus removal.
• Anoxic Zone: Facilitates denitrification, converting nitrate to nitrogen gas.
• Aerobic Zone: Equipped with fine-bubble diffusers, this zone achieves carbon oxidation (BOD removal) and nitrification (ammonia conversion to nitrate).

Secondary clarification follows in circular clarifiers, where activated sludge settles. Return Activated Sludge (RAS) is recycled to the anoxic/anaerobic zones, while Waste Activated Sludge (WAS) is thickened via Dissolved Air Flotation (DAF) before digestion.

D. DISINFECTION

To protect the aquatic life in the Poudre River, DWRF utilizes Ultraviolet (UV) light disinfection rather than chlorination. This eliminates the need for dechlorination chemicals and prevents the formation of disinfection byproducts. The UV system is designed with multiple banks to handle peak flows and varying transmissivity.

E. SOLIDS HANDLING & BIOSOLIDS

DWRF serves as the regional solids processing hub.

• Thickening: WAS is thickened using DAF units; Primary sludge is gravity thickened.
• Anaerobic Digestion: Thickened sludge is stabilized in mesophilic anaerobic digesters (98°F). This process destroys pathogens (meeting Class B standards) and reduces volatile solids by over 50%.
• Dewatering: Digested sludge is dewatered using high-solids centrifuges, achieving a cake solid concentration suitable for transport.
• Disposal/Reuse: The biosolids are transported to Meadow Springs Ranch, a 26,000-acre city-owned property. Here, biosolids are land-applied as fertilizer for rangeland restoration and dryland farming, completing the nutrient cycle.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The DWRF site includes the Pollution Control Lab, a state-certified laboratory that performs compliance testing for wastewater, stormwater, and industrial pretreatment. The site layout is optimized for operations, with distinct zones for liquid treatment and solids handling.

B. Energy Systems & Co-Generation

Fort Collins Utilities prioritizes energy recovery. The anaerobic digesters produce methane-rich biogas, which is captured and scrubbed. This gas fuels two 350-kW Combined Heat and Power (CHP) engine generators. These units produce electricity to power facility equipment and recover heat to maintain digester temperatures. This system offsets a significant portion of the plant’s grid energy consumption.

C. Meadow Springs Ranch

A unique infrastructure asset, Meadow Springs Ranch is located 25 miles north of the city near the Wyoming border. It serves a dual purpose: a sustainable application site for biosolids and a working cattle ranch. This strategic asset secures the city’s long-term solids management capability without reliance on private landfills.

5. RECENT UPGRADES & MAJOR PROJECTS

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The DWRF operates under NPDES Permit CO0024473. Key effluent parameters include:

• BOD5: 30 mg/L (30-day avg) – Plant typically achieves < 5 mg/L.
• TSS: 30 mg/L (30-day avg) – Plant typically achieves < 5 mg/L.
• E. coli: Stringent limits to support recreational use of the Poudre River.
• Nutrients: Subject to Regulation 85 requirements for Total Inorganic Nitrogen (TIN) and Total Phosphorus (TP).

B. Environmental Stewardship

The facility maintains an ISO 14001 certified Environmental Management System (EMS), a rare distinction for municipal utilities. This framework ensures continuous improvement in environmental performance beyond mere compliance, focusing on carbon footprint reduction and chemical use minimization.

7. CHALLENGES & FUTURE PLANNING

A. Evolving Nutrient Regulations

The primary engineering challenge facing DWRF is the tightening of nutrient limits in Colorado. While current BNR processes are effective, future limits (Regulation 31) may require tertiary filtration upgrades or advanced membrane technologies to meet ultra-low phosphorus standards.

B. Emerging Contaminants

Fort Collins is proactively researching PFAS (Per- and Polyfluoroalkyl Substances) presence in wastewater and biosolids. As a university town (Colorado State University) with high-tech industry, the facility must monitor for complex industrial constituents.

C. Capital Improvement Planning

The utility’s master plan includes provisions for the eventual expansion of the Mulberry facility to offload Drake as the eastern sewershed grows. Asset management strategies prioritize the rehabilitation of the solids handling train, including potential upgrades to digester gas conditioning systems to possibly produce Renewable Natural Gas (RNG) for vehicle fuel in the future.

8. TECHNICAL SPECIFICATIONS SUMMARY

9. FAQ SECTION