City Of Dayton Water Reclamation Facility

FACILITY BASIC INFORMATION

• Plant Name: City of Dayton Water Reclamation Facility (DWRF)
• Location: 2800 Guthrie Road, Dayton, Montgomery County, Ohio
• Operating Authority: City of Dayton Department of Water
• Design Capacity: 72 MGD (Average Daily Flow), 200 MGD (Peak Hydraulic)
• Current Average Flow: ~48–55 MGD
• Population Served: ~400,000 residents
• Service Area: City of Dayton, Montgomery County, and portions of Greene and Miami Counties
• Receiving Water Body: Great Miami River
• NPDES Permit Number: 1PF00000*OD (Ohio EPA)
• Year Commissioned: 1927 (Major expansions in 1970s, 1980s, and 2010s)

TARGET AUDIENCE

• Municipal consulting engineers evaluating trickling filter/activated sludge hybrid systems

Read more10 Surprising Benefits of Upgrading Your Aeration Tank System
• Wastewater treatment plant operators and asset managers
• Energy managers interested in biogas reuse and RNG applications
• Environmental regulators (Ohio EPA, US EPA)
• Engineering firms pursuing Midwest infrastructure projects

1. INTRODUCTION

The City of Dayton Water Reclamation Facility (DWRF) serves as the cornerstone of wastewater management for the Greater Dayton region. As one of the largest advanced wastewater treatment plants in Ohio, DWRF is designed to treat an average daily flow of 72 million gallons per day (MGD) with a wet-weather peak hydraulic capacity reaching 200 MGD. Operated by the City of Dayton Department of Water, the facility protects the ecological health of the Great Miami River, a vital waterway for recreation and aquifer recharge.

Originally commissioned in the late 1920s, the plant has evolved from primary treatment to a sophisticated tertiary treatment facility. It is particularly renowned in the engineering community for its robust hybrid secondary treatment process—combining trickling filters with activated sludge—and its progressive stance on energy neutrality. Recent capital investments exceeding $50 million have modernized its solids handling capabilities, positioning DWRF as a regional leader in resource recovery and renewable natural gas (RNG) production.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The DWRF operates as a regional facility, accepting wastewater not only from the City of Dayton but also from approximately 20 surrounding jurisdictions through inter-jurisdictional agreements. The service area encompasses roughly 100 square miles, serving a population of approximately 400,000. The collection system feeding the plant is a mix of combined and separate sanitary sewers, necessitating robust wet-weather management strategies. Major customers include Montgomery County Environmental Services, which pumps significant volume to the Dayton facility.

B. Operational Capacity

The facility operates with a design average flow of 72 MGD. Historical data indicates a current average daily flow fluctuating between 48 and 55 MGD, providing the plant with a capacity utilization of approximately 70-75% during dry weather. However, the plant is engineered to handle significant peaking factors due to inflow and infiltration (I/I) in the aging collection system. The peak hydraulic capacity of 200 MGD is critical during Ohio’s intense spring storm events. The facility utilizes retention basins and flow equalization strategies to manage surges that exceed biological treatment capacity.

Read more4D-Printed Smart Materials For Water Treatment

C. Discharge & Compliance

Treated effluent is discharged into the Great Miami River via a submerged outfall. The discharge is regulated under the National Pollutant Discharge Elimination System (NPDES) permit #1PF00000 issued by the Ohio Environmental Protection Agency (Ohio EPA). The receiving water is sensitive to nutrient loading (phosphorus and nitrogen) and dissolved oxygen sags, dictating strict effluent limits. The facility consistently achieves high compliance rates, often performing well below permitted limits for BOD, TSS, and Ammonia-Nitrogen.

3. TREATMENT PROCESS

The DWRF utilizes a highly reliable “multi-barrier” approach to wastewater treatment, featuring a hybrid secondary process that combines the shock-loading resilience of trickling filters with the effluent quality of activated sludge. The liquid treatment train concludes with tertiary rapid sand filtration.

A. PRELIMINARY TREATMENT

Raw wastewater enters the headworks where it passes through mechanically cleaned bar screens (0.5-inch opening) to remove large debris, rags, and plastics. Following screening, flow enters aerated grit chambers where velocity is reduced to allow inorganic solids (sand, gravel, eggshells) to settle while keeping organic matter in suspension. The removed grit is washed and dewatered before landfill disposal. Odor control at the headworks utilizes chemical scrubbers to mitigate H2S emissions from the collection system.

B. PRIMARY TREATMENT

Flow proceeds to rectangular primary settling tanks. These tanks reduce flow velocity to allow settleable solids to drop to the bottom as primary sludge, while fats, oils, and grease (FOG) float to the surface for skimming. The primary treatment stage typically removes 30-40% of BOD and 50-60% of Total Suspended Solids (TSS). The settled primary sludge is pumped directly to the anaerobic digesters.

C. SECONDARY TREATMENT (Hybrid Process)

Dayton utilizes a two-stage biological system:

1. Trickling Filters (Roughing Stage): Primary effluent is distributed over rock-media trickling filters. A zoogleal film (biomass) on the rocks adsorbs and oxidizes organic matter. This stage is energy-efficient and highly resistant to shock loads or toxic upsets, removing a significant portion of the soluble BOD.
2. Activated Sludge (Polishing Stage): Effluent from the trickling filters enters aeration basins. Here, suspended biomass (mixed liquor) is aerated to further oxidize remaining organic matter and convert ammonia to nitrate (nitrification). The basins utilize fine-bubble diffusion for oxygen transfer efficiency.

Following aeration, the mixed liquor flows to secondary clarifiers where the biological solids settle out. A portion is returned to the aeration basins (RAS), and the excess (WAS) is thickened and sent to digestion.

D. TERTIARY TREATMENT

To meet strict effluent limits for the Great Miami River, secondary effluent undergoes tertiary filtration via rapid sand filters. These gravity filters remove remaining fine suspended solids and particulate-bound pollutants (including phosphorus). This step ensures the effluent is polished to near-drinking water clarity, significantly reducing turbidity.

E. DISINFECTION

The filtered effluent is disinfected using liquid sodium hypochlorite (chlorination) to eliminate pathogenic bacteria and viruses. To protect aquatic life in the river, the water is then dechlorinated using sodium bisulfite prior to final discharge. The disinfection season typically runs from May through October per Ohio EPA regulations, though year-round disinfection may be required based on permit cycles.

F. SOLIDS HANDLING

DWRF is a regional hub for solids processing. Primary sludge and thickened waste activated sludge (TWAS) are co-settled or separately pumped to anaerobic digesters.

• Digestion: The facility utilizes mesophilic anaerobic digestion. The digesters reduce volatile solids, minimize pathogens, and generate biogas.
• Dewatering: Digested sludge is dewatered using high-solids centrifuges or belt filter presses (depending on current operational configuration), achieving cake solids of 20-25%.
• Disposal: The Class B biosolids are typically land-applied on agricultural fields as a soil amendment, closing the nutrient loop.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans over 60 acres along the riverbank. It includes distinct zones for headworks, primary treatment, biological towers (trickling filters), aeration basins, and the massive digester complex. The site also houses a fully accredited environmental laboratory that performs daily compliance testing and industrial pretreatment monitoring.

B. Energy Systems & Renewables

Dayton is an industry leader in energy recovery. The anaerobic digesters produce significant volumes of methane-rich biogas.

• Cogeneration: Historically, biogas fueled internal combustion engines to drive blowers and generate electricity.
• RNG Conversion: Recent infrastructure upgrades focus on cleaning biogas to Renewable Natural Gas (RNG) standards for injection into the utility grid or use as vehicle fuel, maximizing the economic value of the waste stream.

C. Odor Control

Given the plant’s proximity to residential zones and the river corridor, odor control is critical. The facility employs chemical scrubbers (wet scrubbers) at the headworks and primary sludge handling areas. Biofilters have also been evaluated for specific solids handling exhaust points.

5. RECENT UPGRADES & MAJOR PROJECTS

The City of Dayton has invested heavily in modernizing the WRF, shifting focus from pure compliance to resource recovery and efficiency.

Phase II Solids Handling & Energy Improvements (2018-2022)

• Project Scope: Comprehensive rehabilitation of the anaerobic digesters, including new mixing systems (linear motion mixers), cover replacements, and gas cleaning equipment.
• Budget: ~$20-30 Million (Estimate based on CIP data)
• Funding: Ohio Water Pollution Control Loan Fund (WPCLF).
• Drivers: Aging infrastructure (some digesters were original to the 1930s/50s) and the opportunity to monetize biogas.
• Technical Highlights: Installation of advanced gas conditioning skids to remove siloxanes and moisture, preparing gas for high-value end uses.
• Results: Increased volatile solids reduction (VSR), increased gas production, and improved system reliability.

Electrical Distribution & Automation Upgrades (2020-Current)

• Project Scope: Replacement of aging high-voltage switchgear and implementation of a new plant-wide SCADA system.
• Drivers: Reliability and risk mitigation against power failures during storm events.
• Technical Highlights: Integration of automated dissolved oxygen (DO) control in aeration basins to reduce blower energy consumption.

Upcoming: Nutrient Removal Optimization (2024-2027 Planning)

• Scope: Evaluation of Biological Nutrient Removal (BNR) capabilities to meet anticipated stricter phosphorus limits for the Gulf of Mexico hypoxia task force goals.
• Expected Technologies: Potential side-stream treatment for centrate (ammonia rich) or chemical precipitation enhancements.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Under NPDES Permit 1PF00000, DWRF is subject to strict limits. Key parameters typically include:

• CBOD5: Monthly average limits often < 10 mg/L (summer).
• TSS: Monthly average limits ~12-15 mg/L.
• Ammonia-Nitrogen: Seasonally variable, often < 1.0 mg/L in summer to protect aquatic toxicity.
• E. coli: seasonal geometric mean limits for recreational contact.

B. Compliance History

The facility maintains a strong compliance record with the Ohio EPA. Occasional challenges have arisen related to wet-weather bypass events, which is common for Midwestern utilities with combined sewers. The City is actively addressing these via Long-Term Control Plans (LTCP) within the collection system to reduce peak flows reaching the plant.

7. OPERATIONAL EXCELLENCE

A. Staffing

The plant is staffed 24/7 by a team of roughly 50-60 personnel, including Class III and Class IV Ohio EPA certified operators, maintenance mechanics, electricians, and laboratory analysts. The complexity of the hybrid treatment process requires high-level operator certification.

B. Technology & Innovation

Dayton has partnered with universities and consultants to pilot high-strength waste (HSW) co-digestion. By accepting fats, oils, and grease (FOG) or food waste into their digesters, they can significantly boost biogas production, turning the plant into a net energy producer.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

Aging Infrastructure: Like many rust-belt cities, the physical structures date back decades. Concrete corrosion in headworks and digesters requires constant rehabilitation.
Wet Weather Flows: Managing the 200 MGD peak hydraulic load without washing out the biological mass in the activated sludge system is a primary operational constraint.

B. Future Planning

The City’s Master Plan focuses on “Water Resource Recovery.” The goal is to transition from a waste disposal facility to a production facility—producing clean water, fertilizer (biosolids), and energy (RNG). Future capital projects will prioritize energy efficiency (blower replacements) and nutrient reduction technologies.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The DWRF relies on a vast network of remote infrastructure, including:

• Regional Pump Stations: Major lift stations pump wastewater from lower elevations and satellite communities to the centralized plant.
• Ottawa Yards: Associated maintenance and storage facilities for collection system operations.
• Lime Reclamation Facility: (Historical note) Dayton operates a separate water supply treatment system that involves lime softening; sludge from water treatment is handled separately from wastewater biosolids.

12. FAQ SECTION

Technical Questions

1. What is the hydraulic retention time (HRT) of the aeration basins?
While variable based on flow, the activated sludge portion operates as a polishing step with shorter detention times (approx. 4-6 hours) compared to conventional activated sludge plants, due to the pretreatment provided by the trickling filters.

2. Does Dayton WRF perform biological nutrient removal (BNR)?
Currently, the plant achieves nitrification (ammonia removal) through the activated sludge process. Total Nitrogen and Phosphorus removal are achieved partially through biological uptake and solids removal, but full BNR configuration is a subject of future planning.

3. How is the biogas utilized?
Biogas is captured from anaerobic digesters. The City has moved toward cleaning this gas for use as Renewable Natural Gas (RNG) or for process heating/power generation, reducing the facility’s carbon footprint.

4. What is the peak flow management strategy?
The plant utilizes flow equalization and the robust nature of the trickling filters to handle wet weather surges. Flows exceeding 72 MGD are treated through the primary and secondary systems up to 200 MGD, ensuring full permit compliance during storm events.

Public Interest Questions

5. Who operates the plant?
The facility is owned and operated by the City of Dayton Department of Water, operating 24 hours a day, 365 days a year.

6. Is the discharged water safe?
Yes. The treated water (effluent) is disinfected and filtered, often cleaner than the river water it enters. It meets all safety standards set by the Ohio EPA for protection of aquatic life and human health.