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February 6, 2026

PDNA Stress Testing Marks Key Milestone at the Nansemond ANRI Facility

The HRSD Nansemond Treatment Plant Advanced Nutrient Reduction Improvements – Phase 2 project recently reached an important milestone with the successful completion of PDNA stress testing on one of the facility’s aeration tanks.

The testing represents the first validation of PDNA system modifications and confirms the facility’s ability to safely manage high-flow conditions.

PDNA stress testing means directing a large volume of flow through a single aeration tank with PDNA modifications installed to confirm the hydraulics work and that the tank openings can handle the flow without failure. The purpose is to evaluate how the system would perform during extreme wet weather events, such as a hurricane, and to confirm the plant would not experience a catastrophic overflow.

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This milestone reflects months of design coordination and in-field modifications by MEB. As the first PDNA-related benchmark on the project, the successful test clears the way for the next phase of work. With the system performing as expected, HRSD has authorized MEB to move forward with modifications on the remaining aeration tanks. These upgrades are essential to achieving substantial completion.

Additional stress testing will take place during start-up to evaluate long-term performance, including how biological growth may impact flow across the PDNA screens over time.

Anna McGrath

Chase Spence, DBIA, CQM-C