Sanitation District No 1 Dry Creek Wastewater Treatment Plant Northern Kentucky

1. INTRODUCTION

The Dry Creek Wastewater Treatment Plant (DCWWTP) serves as the flagship facility for Sanitation District No. 1 (SD1), the second-largest public sewer utility in Kentucky. Strategically located along the Ohio River in Villa Hills, this facility is the central hub of a regional conveyance system serving Boone, Campbell, and Kenton counties. With a design capacity of 46.5 million gallons per day (MGD), Dry Creek treats the majority of the wastewater generated in Northern Kentucky.

As the primary solids handling facility for the district, Dry Creek is notable for its centralized fluidized bed incineration system, which processes biosolids from both the Dry Creek plant and SD1’s satellite facilities. Operating under the strategic umbrella of the “Clean H2O40” amended consent decree, the facility is currently at the center of significant wet-weather management upgrades designed to mitigate Combined Sewer Overflows (CSOs) and protect the water quality of the Ohio River basin.

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2. FACILITY OVERVIEW

A. Service Area & Coverage

SD1 manages a regional service area covering approximately 220 square miles across Northern Kentucky’s three northernmost counties. The collection system is a hybrid of separate sanitary sewers and aging combined sewers (serving older river cities like Covington and Newport). The Dry Creek facility receives flow from a massive network comprising over 1,600 miles of sanitary sewer lines and 120+ pump stations.

B. Operational Capacity

The plant is designed for an average daily flow of 46.5 MGD. However, due to the prevalence of combined sewers in the collection system, the facility experiences significant hydraulic peaking during precipitation events. The plant’s hydraulic capacity is stressed during wet weather, necessitating the recent construction of upstream equalization (EQ) basins and high-rate transport tunnels (such as the Western Regional Conveyance Tunnel) to modulate flow entering the headworks.

C. Discharge & Compliance

Treated effluent is discharged directly into the Ohio River via a submerged multi-port diffuser outfall. The discharge is regulated under the Kentucky Pollutant Discharge Elimination System (KPDES), administered by the Kentucky Division of Water (KDOW). The facility plays a critical role in regional compliance with the Clean Water Act, specifically regarding the reduction of untreated overflows.

3. TREATMENT PROCESS

The Dry Creek WWTP utilizes an advanced secondary treatment process with specialized solids handling capabilities. The treatment train is designed to handle variable loading associated with combined sewage.

A. Preliminary Treatment

Raw wastewater enters the facility through large-diameter interceptors. The headworks facility utilizes mechanically cleaned bar screens to remove large debris, rags, and plastics. Following screening, flow passes through aerated grit chambers where inorganic solids (sand, gravel, cinders) settle out to prevent abrasion on downstream mechanical equipment. The grit is washed, dewatered, and disposed of in a sanitary landfill.

B. Primary Treatment

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Flow is distributed to rectangular primary clarifiers. These tanks reduce flow velocity, allowing settleable organic 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 50-60% of Total Suspended Solids (TSS) and 30-35% of Biochemical Oxygen Demand (BOD).

C. Secondary Treatment (Vertical Loop Reactors)

The biological heart of the Dry Creek plant consists of Vertical Loop Reactors (VLRs). Unlike conventional plug-flow aeration basins, VLRs function similarly to oxidation ditches but are “flipped” on their side to utilize deep tanks, minimizing the facility’s footprint.

• Configuration: A series of deep, baffled tanks equipped with surface aerators or disk aerators.
• Process: The VLRs maintain a suspension of activated sludge (microorganisms) that consume dissolved organic matter. The system can be operated to achieve nitrification (conversion of ammonia to nitrate) depending on dissolved oxygen control strategies.
• Secondary Clarification: Mixed liquor flows to circular secondary clarifiers where the biological floc settles. Clean water overflows the weirs, while settled biomass is either returned to the VLRs (RAS) or wasted (WAS) to solids handling.

D. Disinfection

Historically a chlorination/dechlorination facility, Dry Creek was converted to Ultraviolet (UV) Disinfection. This upgrade eliminates the safety hazards associated with storing bulk chlorine gas and sulfur dioxide. The effluent passes through channels containing banks of UV lamps, which scramble the DNA of pathogenic organisms, rendering them unable to reproduce. The disinfected effluent is then aerated (cascade aeration) to meet dissolved oxygen permit requirements before discharge to the Ohio River.

F. Solids Handling (Thermal Treatment)

Dry Creek serves as the regional solids processing hub for SD1. Sludge from Dry Creek, as well as imported solids from the Western Regional and Eastern Regional Water Reclamation Plants, is processed here.

• Thickening & Dewatering: Liquid sludge is thickened and then dewatered using high-solids centrifuges to achieve a cake dryness suitable for combustion (typically 20-25% solids).
• Incineration: The dewatered cake is injected into a Fluidized Bed Incinerator. This system uses a bed of hot sand suspended by air jets to rapidly combust organic material at temperatures exceeding 1,400°F.
• Ash Handling: The resulting inert ash is scrubbed from the exhaust stream using advanced air pollution control systems (wet scrubbers/electrostatic precipitators) to meet strict air quality standards before being disposed of at a landfill.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans extensive acreage adjacent to the Ohio River. Key structures include the Administration Building (housing SD1’s central laboratory), the Incinerator Building, Dewatering Complex, and Maintenance garages. The site layout is optimized for the movement of sludge hauling trucks bringing solids from satellite plants.

B. Odor Control

Given the plant’s proximity to residential neighborhoods in Villa Hills, odor control is a primary operational mandate. SD1 utilizes a combination of chemical scrubbers and biological foul air treatment systems covering the headworks, primary clarifiers, and solids handling areas to mitigate nuisance odors.

C. Central Laboratory

The facility houses a NELAP-accredited environmental laboratory. This lab performs compliance testing not only for Dry Creek but for SD1’s entire network of treatment plants and industrial pretreatment program monitoring.

5. RECENT UPGRADES & MAJOR PROJECTS

SD1 is currently executing “Clean H2O40,” a comprehensive infrastructure program driven by an amended consent decree with the EPA and Kentucky Division of Water.

Western Regional Conveyance Tunnel (Completed/Integrated)

• Scope: Construction of a massive deep rock tunnel to store and convey wastewater from the western service area to the Dry Creek plant.
• Impact: The tunnel serves as in-line storage during wet weather, smoothing out peak flows arriving at the plant and significantly reducing SSOs in the collection system.

Pump Station 01 Upgrades

• Scope: Major rehabilitation of the main influent pump station.
• Objective: To increase reliability and pumping capacity to match the peak hydraulic throughput of the treatment plant, ensuring that flow captured by the conveyance system can be lifted into the headworks without bypassing.

Future Planning: Wet Weather Strategy

Upcoming capital improvements focus on further maximizing the treatment of wet weather flows. This includes potential optimization of primary treatment to handle high-flow events (chemically enhanced primary treatment or CEPT concepts) and smart sewer technologies to manage flow distribution across the regional system.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Dry Creek operates under NPDES Permit No. KY0021512. Strict limits are placed on:

• CBOD/TSS: Standard secondary treatment limits (typically 25-30 mg/L monthly average).
• Ammonia-Nitrogen: Seasonal limits to protect aquatic life in the Ohio River.
• E. Coli: Limits apply during the recreation season (May-October).
• Whole Effluent Toxicity (WET): Regular testing to ensure discharge is not toxic to aquatic organisms.

B. Consent Decree Status

SD1 entered into a consent decree in 2007, which was amended in 2019 to extend the compliance deadline to 2040 (hence “Clean H2O40”). The focus is the elimination of sanitary sewer overflows and the significant reduction of combined sewer overflows. Dry Creek’s performance is integral to meeting these regional capture and treatment goals.

7. OPERATIONAL EXCELLENCE

SD1 employs a highly skilled workforce of Class III and IV certified wastewater operators. The utility utilizes a robust SCADA system for real-time monitoring of the plant and remote pump stations. The centralized incineration facility represents a regional approach to solids management, providing economies of scale that reduce the overall cost of treatment for Northern Kentucky ratepayers.

8. CHALLENGES & FUTURE PLANNING

A. Wet Weather Management

The primary engineering challenge remains the management of extreme wet weather flows. The volume of water entering the combined system during heavy rains exceeds the biological treatment capacity. SD1 is employing “gray” infrastructure (tanks, tunnels) and “green” infrastructure (stormwater controls) to manage this volume.

B. Aging Infrastructure

With original components dating back to the late 1970s, asset management is critical. Systematic rehabilitation of concrete tanks, replacement of mechanical aerators, and electrical gear upgrades are ongoing priorities in the Capital Improvement Plan (CIP).

C. Emerging Contaminants

Like all wastewater utilities, SD1 is monitoring regulatory developments regarding PFAS. As a facility that utilizes incineration, the fate of PFAS through the thermal oxidation process is a subject of industry-wide research and future regulatory consideration.

9. TECHNICAL SPECIFICATIONS SUMMARY

10. FAQ SECTION

Technical/Professional Questions

1. What technology is used for aeration at Dry Creek?
The plant uses Vertical Loop Reactors (VLRs), which are deep-tank variations of oxidation ditches, typically equipped with surface mechanical aerators or disc aerators to drive oxygen transfer and mixing.

2. Does Dry Creek accept hauled waste?
Yes, as the regional solids processing hub, Dry Creek accepts dewatered sludge/cake from SD1’s other major facilities (Western Regional and Eastern Regional) for incineration.

3. How are wet weather flows managed?
SD1 utilizes a combination of conveyance tunnels (Western Regional Conveyance Tunnel) and inline storage to equalize flow. Flows exceeding biological capacity may receive primary treatment and disinfection before blending, strictly in accordance with wet weather permit provisions.

4. What is the status of the incineration system?
SD1 operates a Fluidized Bed Incinerator. This technology was chosen for its efficiency in reducing the volume of solids to a sterile ash, minimizing landfill usage.

Public Interest Questions

5. Why does the plant sometimes have an odor?
Wastewater treatment inherently generates odors. However, Dry Creek employs advanced chemical scrubbers and biofilters to capture and neutralize odorous gases. Weather conditions (inversions) can sometimes trap remaining odors near the ground.

6. Is the discharge safe for the Ohio River?
Yes. The effluent is treated to meet strict standards set by the Clean Water Act and the Kentucky Division of Water. It is disinfected to kill bacteria before being released.

7. Who runs the Dry Creek plant?
The plant is owned and operated by Sanitation District No. 1 (SD1), a public utility governed by a Board of Directors appointed by the judges-executive of Boone, Campbell, and Kenton counties.