City Of Reno Truckee Meadows Water Reclamation Facility

1. INTRODUCTION

The Truckee Meadows Water Reclamation Facility (TMWRF) serves as the primary wastewater treatment hub for the high-desert metropolitan region of Northern Nevada. Jointly owned by the Cities of Reno and Sparks and Washoe County, and operated by the City of Reno, this advanced tertiary treatment facility is critical to the ecological health of the Truckee River basin.

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Discharging into the Truckee River—a closed basin system that terminates in the culturally and ecologically sensitive Pyramid Lake—TMWRF operates under some of the most stringent nutrient discharge limits in the United States. The facility treats an average of 28 million gallons daily (MGD) utilizing a complex Biological Nutrient Removal (BNR) process designed to protect the endangered Cui-ui sucker fish and the threatened Lahontan Cutthroat Trout. As a regional model of sustainable water resource management, TMWRF combines legacy infrastructure with cutting-edge process controls to manage the delicate balance between rapid urban growth and environmental stewardship.

2. FACILITY OVERVIEW

A. Service Area & Coverage

TMWRF provides regional wastewater treatment for the Truckee Meadows hydrographic basin. The collection system spans a diverse topography, requiring extensive pumping and gravity conveyance from the foothills of the Sierra Nevada to the valley floor. The facility serves a mixed demographic including the dense urban cores of Reno and Sparks, rapidly expanding suburban developments, and significant industrial zones. The service area supports a population exceeding 450,000, with varying seasonal loads driven by the region’s tourism and event economy.

B. Operational Capacity

The facility has a rated hydraulic design capacity of approximately 44 MGD, though treatment process limitations regarding nutrient loading typically cap effective capacity closer to 40 MGD. Historically, flows have fluctuated with regional drought conditions and conservation efforts, currently averaging between 28 and 30 MGD. However, peak wet weather flows can surge significantly, testing the facility’s hydraulic throughput. As the region experiences a logistics and manufacturing boom, industrial loading has become a critical factor in capacity planning.

C. Discharge & Compliance

The plant discharges treated effluent via an outfall into the Truckee River. Because the river terminates in Pyramid Lake (a terminal sink with no outlet), salts and nutrients accumulate over time. Consequently, TMWRF operates under an NPDES permit with exceptionally strict Waste Load Allocations (WLAs) for Total Nitrogen (TN) and Total Phosphorus (TP). The facility is renowned for its ability to consistently meet these rigorous standards, often achieving effluent quality that rivals drinking water standards for certain parameters, effectively mitigating eutrophication risks in the downstream ecosystem.

3. TREATMENT PROCESS

TMWRF utilizes a sophisticated multi-stage treatment train designed specifically for high-efficiency nutrient removal. The process flow moves from preliminary screening through biological treatment, filtration, and disinfection.

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it passes through mechanically cleaned bar screens to remove large debris, rags, and plastics. Following screening, the flow enters aerated grit chambers where velocity is reduced to allow inorganic solids (sand, gravel, eggshells) to settle while keeping organic material in suspension. The removed grit is classified, dewatered, and hauled to a landfill. Odor control at the headworks is critical due to the proximity of commercial zones, utilizing chemical scrubbers to treat foul air.

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B. PRIMARY TREATMENT

Wastewater flows into large rectangular primary sedimentation tanks. Here, flow velocity is minimized to facilitate the gravity settling of heavy organic solids (primary sludge) and the flotation of oils and grease (scum). Scrapers collect the sludge from the bottom and scum from the surface. The primary clarifiers achieve approximately 30-40% BOD removal and 50-60% TSS removal, significantly reducing the load on the downstream biological processes. Primary sludge is pumped directly to the thickening and digestion complex.

C. SECONDARY TREATMENT (Biological Nutrient Removal)

The core of TMWRF is its activated sludge system, configured for Biological Nutrient Removal (BNR). The facility employs a modified Bardenpho/Phoredox process designed to remove carbon, nitrogen, and phosphorus biologically.

• Anaerobic Zones: Promote the growth of Phosphorus Accumulating Organisms (PAOs) to facilitate biological phosphorus removal.
• Anoxic Zones: Facilitate denitrification, where bacteria convert nitrate to nitrogen gas using internal recycle streams.
• Aerobic Zones: Provide oxygen for nitrification (ammonia to nitrate conversion) and BOD oxidation.

Following the aeration basins, the mixed liquor flows to secondary clarifiers where biological floc settles out. A portion is returned as Return Activated Sludge (RAS) to the front of the biological process, while excess biomass is removed as Waste Activated Sludge (WAS). Historically, TMWRF has also utilized nitrifying biotowers (trickling filters) to polish ammonia during peak loading or cold weather conditions, providing process redundancy.

D. TERTIARY TREATMENT

To meet the strict Total Phosphorus limit (often < 0.4 mg/L) and low turbidity requirements, secondary effluent undergoes tertiary filtration. The facility utilizes dual-media gravity filters (sand and anthracite). Alum and polymer are added prior to filtration to flocculate remaining particulate phosphorus and suspended solids, ensuring they are trapped in the filter media. The filters are periodically backwashed, with the backwash water returned to the head of the plant.

E. DISINFECTION

Disinfection is achieved using chlorination. Chlorine gas is dissolved in carrier water and injected into the chlorine contact basins to ensure adequate pathogen inactivation (CT value). Following the required contact time, the effluent is dechlorinated using Sulfur Dioxide (SO2) to protect aquatic life in the Truckee River, which is highly sensitive to chlorine residuals.

F. SOLIDS HANDLING

Solids handling is a major operational component:

• Thickening: Primary sludge and WAS are thickened (using gravity thickeners or DAF/rotary drum thickeners) to reduce hydraulic volume.
• Digestion: The thickened sludge is stabilized in anaerobic digesters. These mesophilic digesters reduce volatile solids, destroy pathogens, and produce methane gas.
• Dewatering: Digested sludge is pumped to the dewatering building, which utilizes high-performance centrifuges to separate water from the biosolids, producing a “cake” with 20-25% solids content.
• Disposal: The dewatered biosolids are trucked to the regional landfill for use as daily cover or disposal.

G. PROCESS CONTROL

The facility operates via a centralized SCADA system, monitoring thousands of I/O points. Online analyzers for Ammonia, Nitrate, Orthophosphate, and Dissolved Oxygen allow operators to fine-tune aeration and chemical dosing in real-time to maintain compliance with the tight nutrient limits.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

Spanning over 150 acres, the TMWRF site is a dense industrial complex. It houses the Administration Building, a state-certified environmental laboratory, extensive maintenance shops, and the process structures. The layout is designed to allow for gravity flow through much of the liquid train, reducing pumping requirements.

B. Energy Systems & Cogeneration

TMWRF is a significant energy consumer but offsets a large portion of its demand through on-site power generation. The facility utilizes Cogeneration (Combined Heat and Power – CHP) engines fueled by the methane biogas produced in the anaerobic digesters. This system generates electricity to run plant equipment and captures waste heat to warm the digesters, creating a sustainable energy loop. The cogeneration system is a cornerstone of the facility’s energy management strategy.

C. Odor Control

Located in the eastern Truckee Meadows valley, air dispersion can be limited during temperature inversions. TMWRF employs comprehensive odor control, including chemical scrubbers (wet scrubbers) and biofilters at key generation points like the headworks, primary clarifiers, and solids handling building to mitigate nuisance odors for the surrounding community.

5. RECENT UPGRADES & MAJOR PROJECTS

Recent Major Project: Dewatering Building Improvements

Timeline: 2018–2021
Approximate Cost: $25+ Million
Scope: The facility undertook a significant overhaul of its solids dewatering capabilities. The project involved replacing aging belt filter presses with modern high-speed centrifuges. This upgrade increased solids capture, produced a drier cake (reducing hauling costs), and improved the reliability of the solids handling train. The project also included HVAC improvements and odor control upgrades for the dewatering complex.

Current Initiative: OneWater Nevada (Advanced Water Purification)

Status: Pilot/Demonstration Phase moving to Implementation
Partners: University of Nevada, Reno; TMWA; City of Reno; City of Sparks; Washoe County.
Scope: TMWRF is the source water provider for the OneWater Nevada initiative. This project has successfully demonstrated the feasibility of Category A+ Reclaimed Water. While not a direct plant expansion, this involves the study and design of Advanced Water Purification (AWP) technologies (Ozone, BAC, GAC, UV) to treat TMWRF effluent to drinking water standards for groundwater recharge. This is a critical future-proofing strategy for the region’s water resilience.

Ongoing: Interceptor Rehabilitation

To support the plant, the Cities have invested millions in rehabbing the major gravity interceptors leading to TMWRF, utilizing CIPP (Cured-In-Place Pipe) lining to extend asset life and reduce inflow and infiltration (I/I) that dilutes influent and hydraulically stresses the plant.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Operating under NPDES Permit NV0020150, TMWRF faces some of the nation’s most complex permitting conditions due to the Truckee River’s TMDL (Total Maximum Daily Load).
Key Parameters:

• Total Nitrogen (TN): Seasonal limits apply, often requiring effluent concentrations < 2-4 mg/L depending on river flow and season.
• Total Phosphorus (TP): Extremely strict limits, typically around 0.2 – 0.4 mg/L depending on TMDL allocations.
• Total Dissolved Solids (TDS): Monitored closely due to the terminal nature of Pyramid Lake.
• Temperature: Thermal loading is regulated to protect cold-water fish species (Trout).

B. Compliance History

TMWRF maintains an exemplary compliance record, frequently earning Platinum and Gold Awards from the National Association of Clean Water Agencies (NACWA) for Peak Performance. Violations are rare and typically minor, reflecting the robust redundancy built into the treatment train and the high caliber of the operations staff.

7. CHALLENGES & FUTURE PLANNING

A. Aging Infrastructure

Commissioned in the 1960s with major expansions in the 80s and 90s, much of the concrete and mechanical infrastructure is reaching the end of its useful life. The facility faces the “replacement era” challenge, requiring significant capital investment to rehab basins, replace electrical gear, and upgrade SCADA systems without interrupting 24/7 service.

B. Effluent Management & Water Rights

In the arid West, effluent is a resource. Balancing the requirement to return flow to the Truckee River (to satisfy downstream water rights and environmental flows) against the desire to reuse water for irrigation or industrial parks (purple pipe) is a complex legal and operational challenge managed by the Joint Coordinating Committee.

C. Future Planning

The facility operates under a 20-year Master Plan. Future phases focus on process intensification—getting more treatment capacity out of the existing footprint through technology (such as potential future MBR retrofits or densified sludge processes) rather than just building new concrete basins.

8. TECHNICAL SPECIFICATIONS SUMMARY

9. FAQ SECTION

Technical Questions

1. Does TMWRF use chemical phosphorus removal?
While the plant utilizes biological phosphorus removal (Bio-P) as the primary mechanism, it has provisions for chemical polishing (Alum or Ferric) prior to tertiary filtration to ensure the strict Total Phosphorus limits are consistently met.

2. What is the sludge retention time (SRT) for the biological process?
The SRT varies by season to maintain nitrification. Typically, it ranges from 10 to 15 days, with longer retention times required in winter months to sustain nitrifying bacteria activity in colder water temperatures.

3. How does the plant handle high TDS/Salinity?
TMWRF does not remove salts (TDS). The region relies on source control (limiting industrial brine discharges and water softener restrictions) to manage salinity loading to the Truckee River.

General Public Questions

4. Is the discharged water safe for the river?
Yes. The treated water meets stringent environmental standards and supports a healthy ecosystem for trout and other wildlife immediately downstream of the outfall.

5. Can I tour the facility?
Yes, TMWRF offers tours for schools, professional groups, and the public. These must be scheduled in advance through the City of Reno Utility Services Department.

6. Does the plant smell?
Wastewater treatment inherently generates odors, but TMWRF employs extensive scrubbing technology. Occasional odors may be detectable during process upsets or weather inversions, but they are generally contained within the industrial buffer zone.