City Of Wichita Wichita Water Pollution Control Plant

1. INTRODUCTION

The City of Wichita Water Pollution Control Plant (WPCP) stands as the largest and most complex wastewater infrastructure asset in the state of Kansas. Serving a regional population of approximately half a million residents, the facility treats an average of 35 to 40 million gallons daily (MGD) before discharging high-quality effluent into the Arkansas River. Operated by the City of Wichita Public Works & Utilities Department, the plant is a critical component of the regional watershed management strategy.

Historically divided into “Plant 1” and “Plant 2,” the facility has recently undergone a transformational consolidation through the Biological Nutrient Removal (BNR) program. This $357 million initiative represents one of the most significant infrastructure investments in Wichita’s history. By transitioning from legacy trickling filter technology to advanced biological nutrient removal, the WPCP has positioned itself as a leader in environmental stewardship, significantly reducing nitrogen and phosphorus loading to the Arkansas River and downstream Mississippi River basin.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The WPCP serves the Wichita metropolitan area, which functions as the industrial and economic hub of South Central Kansas. The collection system spans over 2,000 miles of sanitary sewer mains, managing wastewater from a diverse mix of residential, commercial, and heavy industrial sources (including aerospace manufacturing). The utility also accepts flow from wholesale customers and satellite communities surrounding the city limits, necessitating a robust regional approach to capacity planning.

B. Operational Capacity

Following the completion of recent upgrades, the facility maintains a design average daily flow (ADF) of 54 MGD. However, the plant’s hydraulic design is engineered to handle extreme wet weather events common to the Midwest plains. The peak hydraulic capacity exceeds 160 MGD, utilizing a combination of equalization basins and high-rate treatment bypass protocols (blending) authorized under specific regulatory conditions to prevent sanitary sewer overflows (SSOs). Historical trends indicate steady base flow, with significant diurnal and seasonal peaking factors driven by industrial shift work and precipitation events.

C. Discharge & Compliance

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Treated effluent is discharged into the Arkansas River via a dedicated outfall structure. The discharge is regulated under the Kansas Department of Health and Environment (KDHE) and the U.S. EPA. The river is classified for expected aquatic life and primary contact recreation, driving stringent limitations on E. coli, suspended solids, and increasingly, nutrients. The shift to BNR technology was directly driven by the need to meet new regulatory caps on total nitrogen (TN) and total phosphorus (TP).

3. TREATMENT PROCESS

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it undergoes aggressive physical screening. The facility utilizes multiple mechanically cleaned bar screens to remove large debris, rags, and plastics. Following screening, flow enters vortex grit removal systems designed to settle out inorganic solids (sand, gravel, coffee grounds) to protect downstream pumps and biosolids equipment. The headworks facility is enclosed and equipped with foul air extraction systems routed to chemical scrubbers for odor control.

B. PRIMARY TREATMENT

The flow proceeds to primary clarification. The plant utilizes large circular clarifiers where hydraulic velocity is reduced, allowing settleable organic solids to drop to the bottom as primary sludge, while grease and oils float to the surface for skimming. This stage typically removes 50-60% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD). Primary sludge is pumped directly to the solids handling train.

C. SECONDARY TREATMENT (Biological Nutrient Removal)

The core of the Wichita WPCP is the newly constructed Biological Nutrient Removal (BNR) system. Replacing the legacy trickling filters, the new trains utilize an Activated Sludge process configured for nutrient removal (likely a variation of the A2O or 5-stage Bardenpho process).

• Anaerobic Zones: Promote the growth of Phosphorus Accumulating Organisms (PAOs) for biological phosphorus removal.
• Anoxic Zones: Facilitate denitrification, where bacteria convert nitrates into harmless nitrogen gas.
• Aerobic Zones: Fine bubble diffusion provides oxygen for BOD oxidation and nitrification (conversion of ammonia to nitrate).
• Secondary Clarification: Mixed liquor flows to secondary clarifiers where biomass settles. A portion is returned to the head of the aeration basins (RAS) to maintain biological population, while excess biomass (WAS) is wasted to solids handling.

D. DISINFECTION

Prior to discharge, the clarified effluent undergoes UV Disinfection. The plant utilizes high-intensity, medium-pressure ultraviolet light banks to neutralize pathogens by disrupting their DNA. This system replaces the former chlorination/dechlorination process, eliminating the safety risks associated with storing chlorine gas and preventing the formation of disinfection byproducts in the Arkansas River.

E. SOLIDS HANDLING

Solids management at Wichita WPCP is a complex operation combining primary sludge and waste activated sludge (WAS).

• Thickening: WAS is thickened using gravity belt thickeners or rotary drum thickeners to reduce hydraulic load.
• Anaerobic Digestion: Thickened solids are stabilized in anaerobic digesters. These heated tanks reduce volatile solids, mitigate pathogens, and produce methane gas.
• Dewatering: Digested sludge is dewatered using high-performance centrifuges, producing a cake suitable for land application.
• Disposal: The biosolids are land-applied on agricultural fields, recycling nutrients back into the soil in compliance with EPA Part 503 regulations.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site encompasses a sprawling footprint to accommodate the dual-plant history and the new BNR footprint. The facility includes extensive maintenance shops, a central administration building, and a process control laboratory. The layout is designed with flood protection in mind, given the proximity to the Arkansas River.

B. Energy Systems

Wastewater treatment is energy-intensive, particularly the aeration blowers required for the BNR process. The facility has implemented Variable Frequency Drives (VFDs) on all major pumps and blowers to optimize energy usage. The plant captures biogas (methane) from the anaerobic digesters. Historically used for boiler heating, the system is optimized to offset natural gas purchases for heating digesters and buildings.

C. Odor Control

Odor control is a high priority due to residential encroachment near the plant boundaries. The recent upgrade included significant investments in point-source odor capture at the headworks and solids handling facilities. Technologies deployed include biotrickling filters and activated carbon polishing units to treat hydrogen sulfide and organic odors before releasing air to the atmosphere.

5. RECENT UPGRADES & MAJOR PROJECTS

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The facility operates under NPDES Permit No. KS-0037664. Key parameters include Carbonaceous Biochemical Oxygen Demand (CBOD), Total Suspended Solids (TSS), Ammonia (NH3-N), E. coli, and pH. The new permit cycles place increasing emphasis on nutrient monitoring, specifically Total Nitrogen and Total Phosphorus, to combat eutrophication in downstream water bodies.

B. Compliance History

The Wichita WPCP maintains a strong compliance record. The BNR upgrade was a proactive measure to address upcoming regulatory changes rather than a reaction to consent decrees. The transition to UV disinfection has also ensured consistent compliance with bacteria limits during the recreation season (April-October).

7. OPERATIONAL EXCELLENCE

A. Staffing & Certification

The plant is staffed 24/7/365 by a team of licensed operators, maintenance mechanics, electricians, and instrumentation technicians. KDHE requires high-level certification (Class IV) for shift supervisors and lead operators due to the complexity of the BNR process and the size of the facility.

B. Process Control

The facility utilizes a modern SCADA system that integrates data from thousands of sensors (DO probes, ORP sensors, flow meters). Real-time nutrient analyzers monitor ammonia and nitrate levels in the aeration basins, allowing the automated control system to adjust blower output (air flow) to match biological demand, maximizing efficiency.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

Biosolids Disposal: As with many municipalities, securing long-term, sustainable land application sites for biosolids remains a logistical challenge, particularly during wet weather when fields are inaccessible.

Rate Impacts: While the WIFIA loan reduced costs, the debt service for the $357M upgrade requires careful rate management to remain affordable for Wichita residents.

B. Future Planning

The City maintains a comprehensive Capital Improvement Plan (CIP). Future focus areas include the rehabilitation of large-diameter interceptors feeding the plant and the potential evaluation of water reuse (direct or indirect potable reuse) as drought conditions in the Great Plains become more frequent. The “Water 2060” initiative looks at long-term water sustainability for the region.

9. COMMUNITY & REGIONAL IMPACT

The Wichita WPCP is an economic enabler for the region. By providing reliable industrial wastewater treatment, it supports the local aerospace and manufacturing sectors. Environmentally, the improved effluent quality has a direct positive impact on the Arkansas River ecosystem, supporting fishing and recreational activities in the downtown Wichita corridor. The utility also engages in public education, offering tours to engineering students and community groups to foster understanding of the urban water cycle.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The WPCP relies on a network of 60+ remote lift stations distributed throughout the city’s topography to convey flow to the treatment works. The City also operates the smaller Four Mile Creek Wastewater Treatment Plant, which serves the rapidly growing eastern edge of the city, though the WPCP (Plants 1 & 2) handles the vast majority of the metropolitan load.

12. FAQ SECTION

Technical/Professional Questions:

1. What is the treatment capacity of the Wichita WPCP?
The plant has a design Average Daily Flow (ADF) of 54 MGD and a peak hydraulic capacity exceeding 160 MGD for wet weather events.

2. Does the plant achieve biological nutrient removal?
Yes. Following the 2019-2023 upgrades, the plant utilizes enhanced biological nutrient removal (EBNR) to reduce Total Nitrogen and Total Phosphorus without heavy reliance on chemical precipitation.

3. How are biosolids handled at the facility?
Solids are stabilized via mesophilic anaerobic digestion, dewatered using centrifuges, and land-applied to permitted agricultural sites as Class B biosolids.

4. Who was the design-builder for the BNR project?
The project was delivered by Wichita Water Partners, a joint venture led by Burns & McDonnell and Alberici Constructors.

Public Interest Questions:

5. Does the plant smell?
While wastewater treatment inherently involves odors, the City utilizes advanced chemical scrubbers and biofilters, particularly at the headworks, to capture and treat foul air before it leaves the site.

6. Is the water released into the river clean?
Yes. The effluent meets strict state and federal standards. It is clear, disinfected to kill pathogens, and has low nutrient levels to protect river life.

7. How is the plant funded?
The plant is funded through sewer utility rates paid by residents and businesses. Major capital projects are often financed through low-interest federal (WIFIA) and state (SRF) loans to minimize rate increases.