In response to rapid population growth as well as to address the nutrient reduction goals for the Chesapeake Bay established by the Virginia Department of Environmental Quality (VDEQ), the Hampton Roads Sanitation District (HRSD) initiated the York River Treatment Plant (YRTP) Expansion Phase 1 project.

The existing YRTP is a conventional step-feed activated sludge plant and is rated for an average daily design flow of 57 million liters per day (MLD). This project proposes to expand the existing treatment capacity to 114 MLD and to reduce the nutrients discharged to the York River, a tributary for the Chesapeake Bay.

In order to meet the effluent limits set by the VDEQ, a treatment upgrade to limit of technology (LOT) or enhanced nutrient removal (ENR) was required. Malcolm Pirnie worked with HRSD and the VDEQ to develop and evaluate ENR process alternatives to achieve the required effluent limits with the goal of determining the most reliable and cost effective alternative to achieve the aggressive nutrient reduction goals. This paper will highlight the key issues in determining the most desirable treatment process considering both economic and non-economic factors.

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