Montgomery Water Works Econchate Water Pollution Control Facility

1. INTRODUCTION

The Econchate Water Pollution Control Facility (WPCF) serves as a critical infrastructure pillar for the Montgomery Water Works & Sanitary Sewer Board (MWWSSB), managing wastewater treatment for the rapidly expanding eastern sector of Alabama’s capital city. With a permitted design capacity of 24.0 MGD, the facility is one of three major treatment plants operated by the Board, working in conjunction with the Towassa and Catoma plants to serve the metropolitan area.

Situated near Wares Ferry Road, the Econchate facility is strategically positioned to handle flows from residential subdivisions, commercial developments, and light industrial zones that characterize eastern Montgomery. Following significant capital investment over the last decade, the plant has transitioned into a modern activated sludge facility utilizing Ultraviolet (UV) disinfection, reflecting the Board’s commitment to environmental stewardship and strict adherence to the Alabama Department of Environmental Management (ADEM) regulations protecting the Alabama River basin.

2. FACILITY OVERVIEW

A. Service Area & Coverage

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The Econchate WPCF services the Eastern basin of the MWWSSB collection system. This geographic area includes the high-growth corridors of East Montgomery, extending toward the Town of Pike Road. The demographic mix is predominantly residential and commercial, with specific contributors including large retail centers, educational institutions, and healthcare facilities. The collection system feeding Econchate relies on a complex network of gravity mains assisted by strategic lift stations designed to navigate the region’s rolling topography.

B. Operational Capacity

The plant operates with a hydraulic design capacity of 24.0 MGD. While average daily flows (ADF) typically range between 12 and 15 MGD during dry weather, the facility is engineered to handle peak wet weather flows significantly higher due to Inflow and Infiltration (I/I) characteristic of the region’s intense storm events. The facility currently operates at approximately 50-60% of its hydraulic capacity on average, providing a strategic buffer for future development in the eastern expansion zone.

C. Discharge & Compliance

Treated effluent is discharged into Catoma Creek, a major tributary that feeds into the Alabama River. Due to the biological sensitivity of Catoma Creek, the facility operates under strict NPDES limitations regarding Dissolved Oxygen (DO), Ammonia-Nitrogen, and E. coli. The plant has consistently maintained a record of compliance, utilizing advanced aeration control and reliable disinfection methods to mitigate impact on the receiving stream’s aquatic life.

3. TREATMENT PROCESS

The Econchate WPCF utilizes a conventional activated sludge process designed to achieve high-level secondary treatment. The treatment train is configured to maximize BOD and TSS removal while managing nutrient loads.

A. PRELIMINARY TREATMENT

Raw wastewater enters the headworks facility where it undergoes mechanical screening and grit removal.

• Screening: Mechanically cleaned bar screens remove large debris (rags, plastics, wood) to protect downstream pumps and process equipment. Screenings are washed, compacted, and disposed of in landfills.
• Grit Removal: Vortex grit chambers utilize centrifugal force to settle out inorganic solids (sand, gravel, eggshells). This protects the aeration basins from volume loss due to silt accumulation and reduces abrasive wear on sludge pumps.

B. PRIMARY TREATMENT

Flow proceeds to primary clarifiers where gravity settling occurs. These circular tanks reduce the organic load on the biological stage by settling out approximately 60% of Suspended Solids (SS) and 30-35% of Biochemical Oxygen Demand (BOD). Primary sludge is pumped to the solids handling complex, while surface skimmers remove fats, oils, and grease (FOG).

C. SECONDARY TREATMENT

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The biological heart of the facility is the activated sludge system.

• Aeration Basins: The plant utilizes rectangular aeration basins equipped with fine-bubble diffusers. This aeration system provides the oxygen transfer necessary for microorganisms to metabolize the remaining organic matter. The system uses a Plug Flow configuration to prevent short-circuiting.
• Secondary Clarifiers: Mixed liquor flows to large circular secondary clarifiers. Here, the biological floc settles, separating the clear supernatant from the biomass.
• RAS/WAS: A portion of the settled biomass is returned to the head of the aeration basins as Return Activated Sludge (RAS) to maintain the biological population. Excess growth is removed as Waste Activated Sludge (WAS) and sent to solids processing.

D. DISINFECTION

Historically a chlorine gas facility, Econchate was upgraded to Ultraviolet (UV) disinfection.

• Technology: The plant utilizes open-channel, low-pressure, high-intensity UV banks.
• Mechanism: UV light disrupts the DNA of pathogenic organisms (bacteria, viruses), rendering them unable to replicate.
• Benefits: This eliminates the formation of chlorinated disinfection byproducts (DBPs) and removes the safety hazards associated with storing gaseous chlorine and sulfur dioxide (for dechlorination).

E. SOLIDS HANDLING

Solids processing is a critical component of the Econchate operation.

• Digestion: Primary sludge and thickened WAS are stabilized in anaerobic digesters. This process reduces volatile solids, destroys pathogens, and produces methane gas.
• Dewatering: Digested sludge is dewatered using Belt Filter Presses, achieving a cake solid concentration suitable for transport.
• Disposal: The dewatered biosolids are transported to a sanitary landfill for final disposal.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site encompasses substantial acreage off Wares Ferry Road, providing adequate buffer zones from adjacent residential areas. The facility includes a dedicated Administration Building housing the SCADA control room and process control laboratory, maintenance workshops, and a blower building housing the centrifugal blowers for the aeration system.

B. Energy Systems

The facility is a major energy consumer, primarily driven by aeration blowers and influent/effluent pumping. To ensure operational continuity during severe weather events common in Alabama, the site is equipped with industrial-grade standby diesel generators capable of running critical process equipment during grid outages.

C. Odor Control

Odor control is managed primarily through chemical addition at the headworks and proper sludge management. The anaerobic digesters are covered systems, capturing gas and minimizing the release of hydrogen sulfide and mercaptans.

5. RECENT UPGRADES & MAJOR PROJECTS

The MWWSSB has invested heavily in the Econchate facility and its collection system to address aging infrastructure and ensure regulatory compliance.

Upcoming/Ongoing Planning

Current CIP (Capital Improvement Plan) focus for the MWWSSB includes extensive rehabilitation of the collection system feeding Econchate to reduce I/I (Inflow and Infiltration). High I/I rates during storm events dilute the influent and hydraulically stress the secondary clarifiers. Rehabilitation of major trunk lines and lift stations in the eastern basin is ongoing.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Operating under NPDES Permit AL0022713, the facility adheres to strict limits based on the assimilative capacity of Catoma Creek.

• BOD5: Monthly average limits typically set at 15-20 mg/L (seasonally adjusted).
• TSS: Generally capped at 30 mg/L.
• Ammonia (NH3-N): Strict limits during summer months (May-Nov) due to toxicity/oxygen demand concerns in the receiving stream.
• Dissolved Oxygen (DO): Effluent must maintain a minimum DO level (usually > 5.0 mg/L) prior to discharge to prevent oxygen sag in the creek.

B. Compliance History

The Econchate WPCF generally maintains a strong compliance record regarding effluent quality. Challenges, when they arise, are typically hydraulic in nature—associated with extreme wet weather events that can lead to sanitary sewer overflows (SSOs) in the collection system or hydraulic washouts at the plant. The MWWSSB works closely with ADEM to report and mitigate these events.

7. OPERATIONAL EXCELLENCE

A. Staffing

The facility is staffed 24/7 or utilizes remote SCADA monitoring during off-shifts. Operations are led by ADEM-certified Grade IV Wastewater Operators, the highest certification level in the state, supported by maintenance technicians, lab analysts, and electricians.

B. Technology & Monitoring

The plant utilizes a Supervisory Control and Data Acquisition (SCADA) system to monitor tank levels, dissolved oxygen concentrations, pump status, and flow rates in real-time. This allows operators to adjust aeration rates and return sludge flows dynamically to optimize the biological process.

8. CHALLENGES & FUTURE PLANNING

A. Inflow and Infiltration (I/I)

Like many systems in the Southeast, the primary engineering challenge is managing wet weather flows. Groundwater infiltration through aging pipe joints and stormwater inflow lead to peaking factors that stress the hydraulic capacity of the headworks and clarifiers.

B. Nutrient Regulation

While current limits focus on Ammonia, future regulatory trends suggest tighter restrictions on Total Phosphorus and Total Nitrogen. The MWWSSB monitors these trends for future BNR (Biological Nutrient Removal) upgrades that may be required at Econchate.

C. Biosolids Management

Sustainable long-term disposal of biosolids remains a logistical and economic challenge. The Board continually evaluates the cost-benefit of landfilling versus potential land application or composting technologies.

9. COMMUNITY & REGIONAL IMPACT

The Econchate WPCF is the silent engine enabling the growth of East Montgomery. The capacity provided by this facility allows for the development of new housing subdivisions and commercial centers like EastChase. By maintaining high effluent quality, the facility also protects the recreational and ecological value of the Alabama River basin, a vital resource for the state.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The MWWSSB operates a cohesive system. Engineers interested in Econchate should also be aware of:

• Towassa WPCF: Serving the northern/western basins.
• Catoma WPCF: Serving the central and southern basins.
• CT Davidson Water Purification Plant: The primary drinking water facility, ensuring the complete water cycle is managed effectively.

12. FAQ SECTION

Technical Questions

1. What is the hydraulic retention time (HRT) of the aeration basins?
While variable based on flow, typical conventional activated sludge plants aim for an HRT of 4-8 hours. Given the design capacity, Econchate operates within standard engineering parameters for BOD removal.

2. Does Econchate perform biological nutrient removal (BNR)?
The plant is designed primarily for ammonia removal (nitrification) via extended aeration times but does not currently feature a dedicated denitrification (Total Nitrogen removal) or biological phosphorus removal stage.

3. How are grit and screenings handled?
Grit and screenings are washed, compacted, and disposed of in a sanitary landfill to prevent odors and vector attraction.

4. What SCADA system is used?
The MWWSSB utilizes a centralized SCADA architecture, integrating PLCs at the plant level with a central monitoring station for data logging and alarm management.

General Questions

5. Does the plant smell?
The plant utilizes odor control scrubbers and covers on the most odorous processes (anaerobic digestion). While faint odors are inherent to wastewater treatment, the buffer zone and control technologies minimize off-site impact.

6. Where does the water go after treatment?
The highly treated effluent is discharged into Catoma Creek, which eventually flows into the Alabama River, returning water to the natural environment.