City Of Tampa Howard F Curren Advanced Wastewater Treatment Plant

1. INTRODUCTION

The Howard F. Curren Advanced Wastewater Treatment Plant (HFCAWTP) serves as the cornerstone of water quality management for the Tampa Bay region. Located on Hooker’s Point, a heavily industrial peninsula extending into Hillsborough Bay, this facility is one of the premier advanced wastewater treatment plants in the southeastern United States. Commissioned in its current advanced configuration in 1979 and named after former Mayor Howard F. Curren, the plant was specifically designed to reverse the ecological decline of Tampa Bay caused by nutrient overloading.

With a permitted capacity of 96 million gallons per day (MGD), the facility employs high-purity oxygen activated sludge processes followed by deep-bed denitrification filters to achieve stringent nutrient removal standards. As the final barrier between the metropolitan wastewater load and the sensitive marine ecosystem of Florida’s largest open-water estuary, the HFCAWTP has been instrumental in the recovery of seagrass beds and marine life in Tampa Bay. Today, managed by the City of Tampa, it stands as a model of Class A biosolids production and nutrient management.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The HFCAWTP services a sprawling urban and suburban footprint covering approximately **217 square miles**. This includes the entirety of the City of Tampa limits and roughly 20% of the wastewater generated in unincorporated Hillsborough County, managed through interlocal agreements. The collection system feeding the plant is massive, comprising over **1,300 miles of gravity sewer**, **150 miles of force main**, and more than **220 pumping stations**. The service area is characterized by a mix of high-density residential zones, the downtown commercial district, and significant heavy industry surrounding the Port of Tampa.

B. Operational Capacity

The facility is permitted for an Annual Average Daily Flow (AADF) of **96 MGD**. Historically, the plant operates at approximately **55% to 65% capacity** (approx. 55-60 MGD), providing significant headroom for future regional growth. However, hydraulic capacity becomes critical during Florida’s intense wet weather events. The plant is designed to handle peak hydraulic flows exceeding **200 MGD** for short durations. The City is currently executing a progressive infrastructure plan to address inflow and infiltration (I/I) in the collection system to maximize this hydraulic efficiency.

C. Discharge & Compliance

Treated effluent is discharged into **Hillsborough Bay** (part of the Tampa Bay estuary) via a deep-water outfall. Because Tampa Bay is a Nitrogen-Limited water body, the HFCAWTP operates under strict **Advanced Wastewater Treatment (AWT)** standards, specifically targeting Total Nitrogen (TN). The facility consistently achieves effluent quality exceeding regulatory requirements, typically discharging water with TN levels well below the permitted 3.0 mg/L threshold, playing a vital role in the Tampa Bay Nitrogen Management Consortium.

3. TREATMENT PROCESS

The Howard F. Curren AWTP utilizes a complex multi-stage process designed specifically for high-efficiency nutrient removal. The treatment train includes preliminary treatment, primary sedimentation, high-purity oxygen activated sludge, secondary clarification, denitrification, and disinfection.

A. PRELIMINARY TREATMENT

Raw influent enters the headworks via large diameter force mains. The facility utilizes **mechanical bar screens** (typically ½-inch to ¾-inch spacing) to remove large debris, rags, and plastics. Following screening, the flow passes through **grit removal chambers** where heavier inorganic solids (sand, gravel, coffee grounds) settle out. Both screenings and grit are washed, compacted, and hauled to a landfill. Odor control at the headworks is aggressive, utilizing chemical scrubbers to mitigate H2S emissions from the long-residence-time collection system.

B. PRIMARY TREATMENT

Wastewater flows into **rectangular primary settling tanks**. Here, the velocity of the water 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). The primary sludge is pumped directly to gravity thickeners.

C. SECONDARY TREATMENT (Carbonaceous Removal & Nitrification)

The heart of the secondary process is the **High-Purity Oxygen (HPO) Activated Sludge system**. Unlike conventional aeration which uses ambient air (21% oxygen), HFCAWTP uses covered aeration basins injected with high-purity oxygen (generated on-site via cryogenic air separation or VPSA).

• **Process Advantage:** The HPO system allows for a higher mixed liquor suspended solids (MLSS) concentration and a smaller physical footprint.
• **Biological Action:** Microorganisms consume the remaining organic matter (BOD) and convert ammonia-nitrogen into nitrate (Nitrification).
• **Clarification:** The mixed liquor flows to **secondary clarifiers**, where the biomass settles out. A portion is returned (RAS) to the HPO tanks, while excess biomass (WAS) is sent to solids handling.

D. ADVANCED TREATMENT (Denitrification)

To meet the strict nitrogen limits of Tampa Bay, the plant employs **Denitrification Filters** (specifically Tetra Denite® deep bed sand filters).

• **Mechanism:** The secondary effluent, which is high in nitrates (NO3), is pumped to these filters.
• **Carbon Source:** Methanol is added as a supplemental carbon source to feed the denitrifying bacteria living in the sand media.
• **Reaction:** These bacteria strip the oxygen molecules from the nitrate, releasing harmless nitrogen gas (N2) into the atmosphere.
• **Filtration:** The sand bed simultaneously filters out remaining suspended solids, producing a crystal-clear effluent.

E. DISINFECTION

The filtered effluent undergoes disinfection using **Chlorine** (sodium hypochlorite or gaseous chlorine) in contact chambers to eliminate pathogens. Before discharge into the bay, **Sulfur Dioxide (SO2)** or sodium bisulfite is added to dechlorinate the water, ensuring no residual chlorine harms marine life in the receiving waters.

F. SOLIDS HANDLING & BIOSOLIDS

Tampa operates a sophisticated biosolids program designed to produce Class A fertilizer:

• **Thickening:** Primary sludge is gravity thickened; Waste Activated Sludge (WAS) is thickened via dissolved air flotation (DAF) or rotary drum thickeners.
• **Digestion:** The combined sludge is stabilized in **anaerobic digesters**. This process reduces volatile solids and produces methane gas.
• **Dewatering:** Digested sludge is dewatered using **belt filter presses**.
• **Heat Drying:** The dewatered cake is processed in a **Heat Drying Facility** (pelletizer). Using heat (often fueled by the plant’s own biogas), the sludge is dried into pathogen-free pellets.
• **Reuse:** The final product is a Class A biosolid marketed as a commercial fertilizer/soil amendment, achieving 100% beneficial reuse.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site occupies over **160 acres** on the industrial Hooker’s Point. The layout is expansive, featuring distinct zones for liquid treatment, solids handling, and administration. The site includes a full-service **NELAC-certified laboratory** that performs daily compliance testing and process control analysis.

B. Energy Systems

The HFCAWTP is a significant energy consumer but employs recovery strategies to offset demand. The anaerobic digesters produce biogas (methane), which is captured and utilized.

• **Biogas Utilization:** The recovered methane is primarily used to fuel the **sludge drying operational furnaces** and/or cogeneration engines (CHP) to produce electricity and heat for the digesters.
• **Standby Power:** The facility maintains massive diesel generators capable of running critical plant functions during hurricane-induced grid failures.

C. Odor Control

Given its proximity to the Port of Tampa, cruise terminals, and the developing Channelside district, odor control is paramount. The plant utilizes a combination of **wet chemical scrubbers** (treating high-intensity odors from headworks and sludge processing) and **carbon adsorption units**. The facility maintains a “good neighbor” policy with strict monitoring of H2S levels at the fence line.

5. RECENT UPGRADES & MAJOR PROJECTS

The City of Tampa is currently in the midst of a **$2.9 billion Progressive Infrastructure Plan (PIP)** for its water and wastewater systems. Several major capital improvements at HFCAWTP have been completed or are underway.

Upcoming/Future Planning (2024-2027):

The City is evaluating the **Tampa Augmentation Project (TAP)** and other water reuse strategies. While TAP (a direct potable reuse concept) has faced regulatory and public review, the drive toward higher-level water reuse remains a long-term strategic goal. Future projects include the rehabilitation of the denitrification filters and further hardening of the facility against storm surge and sea-level rise.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Operating under NPDES Permit **FL0020940**, the facility adheres to “5-5-3-1” AWT standards typical for sensitive Florida estuaries:

• CBOD5: 5.0 mg/L (Annual Average)
• TSS: 5.0 mg/L (Annual Average)
• Total Nitrogen (TN): 3.0 mg/L
• Total Phosphorus (TP): 1.0 mg/L

The plant also adheres to strict fecal coliform and enterococci limits for disinfection.

B. Compliance History

The HFCAWTP maintains a robust compliance record. It has received numerous **Peak Performance Awards** from the National Association of Clean Water Agencies (NACWA), including Gold and Platinum awards for consecutive years of perfect permit compliance. The facility is a key contributor to the recovery of seagrass in Tampa Bay, which reached historic levels in the mid-2010s due to regional nitrogen management.

7. OPERATIONAL EXCELLENCE

Staffing: The facility is staffed 24/7/365 by a team of over 150 professionals, including Florida DEP licensed operators (Class A, B, and C), industrial electricians, mechanics, and laboratory technicians.

Automation: Operations are monitored via a centralized SCADA system. The city has invested in fiber optic networks and cybersecurity measures to protect critical control infrastructure. The plant utilizes real-time nutrient analyzers (ammonia and nitrate probes) to automate blower speeds and methanol dosing, optimizing chemical usage and power consumption.

8. CHALLENGES & FUTURE PLANNING

Current Challenges

Aging Infrastructure: Much of the plant’s concrete and piping dates to the late 1970s. Corrosion control and structural rehabilitation are constant maintenance priorities.

Resilience: Located at sea level on a peninsula, the plant is vulnerable to storm surge. Climate resilience planning involves hardening critical electrical switchgear and elevating backup power systems to withstand Category 3+ hurricane surges.

Future Planning

The City of Tampa’s wastewater master plan focuses on “One Water” solutions. This includes reducing reliance on the Floridan Aquifer by potentially repurposing highly treated effluent for aquifer recharge or river augmentation, rather than discharging it into the bay. Additionally, the **PIP** (Progressive Infrastructure Plan) secures funding for pipe replacement throughout the city to reduce I/I, which directly improves plant efficiency by stabilizing influent concentration.

9. TECHNICAL SPECIFICATIONS SUMMARY

10. FAQ SECTION

Technical Questions

1. What distinguishes the HFCAWTP from conventional secondary plants?
The facility employs a tertiary denitrification step using deep-bed filters and methanol addition to remove nitrogen to levels below 3 mg/L, protecting the sensitive Tampa Bay estuary.

2. Does the plant generate its own oxygen?
Yes. The facility uses on-site oxygen generation (Cryogenic or VPSA) for its High-Purity Oxygen activated sludge tanks, which allows for higher biomass concentrations than conventional aeration.

3. How are biosolids managed?
Tampa converts sludge into Class A fertilizer pellets via anaerobic digestion followed by heat drying. This product is sold commercially, diverting waste from landfills.

4. Is the facility vulnerable to hurricanes?
Located on the coast, the plant has robust emergency protocols, including massive diesel generators and elevated critical infrastructure, though storm surge remains a long-term planning variable.

Public Interest Questions

5. Can the public tour the facility?
Yes, the City of Tampa Wastewater Department offers scheduled tours for educational groups, universities, and professional organizations. Contact the department directly for availability.

6. Does the plant smell?
While wastewater treatment inherently generates odors, HFCAWTP employs extensive chemical scrubbers and carbon filters. Occasional odors may occur, but they are tightly managed to minimize impact on the nearby port and downtown areas.