Hampton Roads Sanitation District Nansemond Wastewater Treatment Plant Suffolk

1. INTRODUCTION

The Nansemond Treatment Plant (NTP) serves as a critical infrastructure cornerstone for the Western Tidewater region of Virginia. Operated by the Hampton Roads Sanitation District (HRSD), this 30-MGD facility treats wastewater from the rapidly growing City of Suffolk and surrounding Isle of Wight County. Commissioned in 1983, the plant has evolved from a conventional secondary treatment facility into a biological nutrient removal (BNR) powerhouse, essential for protecting the delicate ecosystem of the Chesapeake Bay.

Beyond its primary treatment function, the Nansemond plant is globally significant as the host site for the SWIFT (Sustainable Water Initiative for Tomorrow) Research Center. This facility represents a paradigm shift in wastewater management, demonstrating advanced water purification technologies to recharge the Potomac Aquifer, mitigate land subsidence, and prevent saltwater intrusion. With its dual role as a regional wastewater workhorse and an innovation hub for water reuse, the Nansemond Treatment Plant sets the standard for modern environmental engineering in the Mid-Atlantic.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The NTP services the “Western Shore” operational area of HRSD’s jurisdiction. This includes the City of Suffolk (one of the largest cities by land area in Virginia), Isle of Wight County, and the Town of Smithfield. The collection system feeding NTP is characterized by a mix of gravity lines and an extensive network of force mains due to the region’s flat topography. As Suffolk continues to experience residential and industrial expansion, the NTP serves a diverse influent base comprising residential flow, food processing wastewater (notably from Smithfield Foods facilities), and light industrial discharge.

B. Operational Capacity

The facility is rated for a design hydraulic capacity of 30 MGD, with a peak hydraulic capacity capable of handling significantly higher wet-weather flows, estimated at approximately 60 MGD. Currently, the plant operates at an average daily flow of approximately 16 to 18 MGD, providing substantial reserve capacity for regional growth. Historical flow trends indicate a steady increase consistent with suburban development in the Suffolk corridor. HRSD utilizes a system-wide approach to capacity, often balancing flows between regional plants via an interconnected interceptor system.

C. Discharge & Compliance

Treated effluent is discharged into the Nansemond River, a tidal tributary of the James River and the lower Chesapeake Bay. The facility operates under a Virginia Pollutant Discharge Elimination System (VPDES) permit administered by the Virginia DEQ. The plant is subject to the stringent requirements of the Chesapeake Bay Total Maximum Daily Load (TMDL), necessitating high-level removal of Nitrogen and Phosphorus. HRSD operates under a “bubble permit” for nutrients, allowing the district to aggregate nutrient loads across its multiple treatment plants, though NTP consistently acts as a high-performing asset within this portfolio.

3. TREATMENT PROCESS

The Nansemond Treatment Plant utilizes a sophisticated multi-stage treatment train designed to achieve Biological Nutrient Removal (BNR). The process reflects HRSD’s proprietary VIP (Virginia Initiative Plant) concept modifications and subsequent upgrades to meet Chesapeake Bay standards.

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it passes through mechanical bar screens to remove large debris, rags, and non-biological solids. Following screening, the flow enters vortex grit removal chambers. These systems utilize centrifugal force to separate heavy inorganic particles (sand, gravel, coffee grounds) from the organic liquid stream. The grit is washed, dewatered, and disposed of in landfills to protect downstream pumps and prevent accumulation in digesters or aeration basins.

B. PRIMARY TREATMENT

The facility utilizes rectangular primary clarifiers. Flow velocity is reduced to allow settleable organic solids to drop to the bottom as primary sludge, while grease and oils float to the surface for skimming. The primary treatment stage typically removes 50-60% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD). Primary sludge is pumped to the solids handling facility.

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

C. SECONDARY TREATMENT (BNR)

The core of the NTP is its 5-Stage Biological Nutrient Removal (BNR) system. This activated sludge process is designed to remove Nitrogen and Phosphorus biologically.

• Anaerobic Zone: Promotes the growth of Phosphorus Accumulating Organisms (PAOs) to facilitate biological phosphorus removal.
• Anoxic Zone: Nitrate-rich internal recycle is mixed with carbon sources to achieve denitrification (conversion of nitrate to nitrogen gas).
• Aerobic Zone: Fine bubble diffusion provides oxygen for nitrification (conversion of ammonia to nitrate) and BOD oxidation.

Following aeration, the mixed liquor flows to secondary clarifiers where the biological floc settles. Return Activated Sludge (RAS) is pumped back to the anaerobic zone, while Waste Activated Sludge (WAS) is removed for processing.

D. TERTIARY TREATMENT

To meet the ultra-low nutrient limits required by the Chesapeake Bay TMDL, NTP employs Deep Bed Denitrification Filters. These gravity filters serve a dual purpose: polishing residual suspended solids and providing a final anoxic environment for denitrification. Methanol or an alternative carbon source is added prior to filtration to drive the conversion of remaining nitrates into nitrogen gas.

E. DISINFECTION

HRSD has transitioned the Nansemond plant to Ultraviolet (UV) Disinfection. The effluent passes through channels containing banks of UV lamps. The UV light penetrates the cell walls of pathogens (bacteria and viruses), disrupting their DNA and preventing reproduction. This method eliminates the need for chlorination and subsequent dechlorination, reducing chemical hazards and preventing the formation of disinfection byproducts (DBPs) in the receiving waters.

F. SOLIDS HANDLING

Primary sludge and WAS are thickened utilizing gravity belt thickeners or rotary drum thickeners. The thickened sludge is stabilized via anaerobic digestion, which reduces volatile solids and produces biogas. HRSD operates a regional solids management plan; typically, dewatered cake from Nansemond is transported to regional processing centers (such as the Atlantic Treatment Plant’s incinerator or composting facilities) rather than final disposal occurring on-site.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The NTP occupies a strategic site near the confluence of the Nansemond and James Rivers. The campus includes the main liquid treatment train, solids handling building, administration/laboratory building, and the distinct SWIFT Research Center. The architecture is industrial-functional, with recent additions (SWIFT) featuring modern educational spaces designed for public tours.

B. Energy Systems

The facility is a significant energy consumer, with aeration blowers and pumping systems acting as the primary loads. HRSD has implemented Variable Frequency Drives (VFDs) on major pumps and blowers to optimize energy usage based on real-time demand. The anaerobic digesters produce biogas (methane), which is captured. While historically flared or used for process heating, HRSD explores cogeneration opportunities to offset electrical grid reliance.

C. Odor Control

Given the plant’s proximity to residential developments and the Nansemond River, odor control is a priority. The headworks and primary clarifiers—the most significant sources of odor—are covered or enclosed. Foul air is extracted and treated through chemical scrubbers (wet scrubbers using hypochlorite/caustic) and biological filters to neutralize hydrogen sulfide and organic mercaptans before release.

5. RECENT UPGRADES & MAJOR PROJECTS

SWIFT Research Center (2016-2018)

Project Budget: ~$25 Million

The most significant recent project at NTP is the construction of the Sustainable Water Initiative for Tomorrow (SWIFT) Research Center. This is a 1.0 MGD advanced water treatment facility built within the plant footprint.

• Technical Highlights: The process takes highly treated secondary effluent and subjects it to an 8-step purification process involving flocculation, ozonation, biologically active filtration (BAF), Granular Activated Carbon (GAC), and UV light.
• Outcome: The resulting water matches drinking water standards and is injected into the Potomac Aquifer via an on-site recharge well. This project served as the pilot for full-scale implementation across the region to combat land subsidence.

Nutrient Removal Optimization (Ongoing)

Project Scope: Continuous upgrades to the aeration control systems, internal recycle pumps, and denitrification filters.

Drivers: Compliance with the Chesapeake Bay Watershed Implementation Plan (WIP) and nutrient credit exchange requirements.

Full-Scale SWIFT Implementation (Upcoming/Planning)

HRSD is currently in the planning and design phases to expand the SWIFT capabilities at Nansemond to treat the full plant flow (up to 30 MGD). This massive capital undertaking will divert the majority of the plant’s effluent from the Nansemond River into the aquifer, effectively eliminating the plant’s nutrient discharge to surface waters.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The NTP operates under a rigorous VPDES permit. Key parameters include:

• Total Nitrogen (TN): Annual average limits driven by the Watershed General Permit (typically < 4.0 mg/L).
• Total Phosphorus (TP): Typically < 0.3 mg/L.
• BOD/TSS: Standard secondary limits (30 mg/L monthly average), though actual performance is often < 5 mg/L.
• Bacteria: Enterococci limits for saltwater discharge.

B. Compliance History

HRSD Nansemond has an exemplary compliance record. The facility consistently achieves Platinum or Gold awards from the National Association of Clean Water Agencies (NACWA) for Peak Performance, indicating years of consecutive operation without permit violations.

7. OPERATIONAL EXCELLENCE

Staffing: The facility is staffed 24/7 by a team of Virginia-licensed wastewater operators (Class I through IV), industrial mechanics, and instrumentation specialists. HRSD maintains a robust internal apprenticeship program to combat industry-wide workforce shortages.

Technology: The plant utilizes a centralized SCADA (Supervisory Control and Data Acquisition) system for real-time monitoring. The SWIFT Research Center is highly automated, utilizing advanced sensors for online monitoring of total organic carbon (TOC) and nitrate to ensure aquifer protection.

8. CHALLENGES & FUTURE PLANNING

A. Climate Resilience

Located in the Hampton Roads region, the Nansemond plant is vulnerable to sea-level rise and storm surge. Future planning includes hardening electrical infrastructure, elevating critical assets, and ensuring outfall hydraulics can overcome higher tidal heads.

B. Aquifer Recharge at Scale

Transitioning the entire 30 MGD flow to SWIFT treatment presents unique operational challenges, including managing brine or backwash streams and ensuring consistent injectability into the aquifer without fouling the recharge wells.

C. Emerging Contaminants

As a leader in water reuse, the facility is at the forefront of monitoring for PFAS (Per- and Polyfluoroalkyl Substances). The GAC contactors in the SWIFT process are specifically optimized to remove these persistent compounds.

10. TECHNICAL SPECIFICATIONS SUMMARY

12. FAQ SECTION

Technical Questions

Q: What is the nutrient removal capability of the Nansemond Plant?
A: The plant utilizes a 5-stage Bardenpho-type process followed by denitrification filters. It consistently achieves Total Nitrogen concentrations below 3.0 mg/L and Total Phosphorus below 0.3 mg/L.

Q: How does the SWIFT process at Nansemond differ from the main treatment train?
A: The main train discharges to the river. The SWIFT train takes secondary effluent and treats it to drinking water standards using ozone and carbon filtration before injecting it into the ground. It does not use Reverse Osmosis, distinguishing it from many other reuse facilities.

Q: Is the Nansemond Plant part of a consent decree?
A: HRSD operates under a regional Federal Consent Decree regarding sanitary sewer overflows (SSOs) and wet weather capacity. The Nansemond plant’s capacity upgrades are part of the district’s long-term plan to satisfy these decree requirements.

General Interest

Q: Does the plant smell?
A: While wastewater treatment naturally generates odors, the Nansemond plant utilizes chemical scrubbers and covered tanks to capture and treat foul air. Occasional odors may occur during maintenance or extreme weather, but they are tightly controlled.

Q: Can I visit the plant?
A: Yes, the SWIFT Research Center at the Nansemond Plant was designed specifically for public education. HRSD offers scheduled tours for schools, civic groups, and industry professionals.