Newport News, VA case study


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The Challenge - Retrofit
The James River Treatment Plant (JRTP) is one of nine major treatment plants operated by the Hampton Roads Sanitation District (HRSD) in southeast Virginia. The JRTP discharges into the James River, a major tributary to the lower Chesapeake Bay. To meet the goals of the James River Waste Load Allocation, the Virginia Department of Environmental Quality issued HRSD a permit for Total Nitrogen (TN) from seven of these plants. HRSD determined meeting the TN mass load would require upgrading the JRTP to produce an annual average TN concentration of 10 mg/l.

The plant is bound by the James River to the west, houses to the north, a park to the east, and a historical farm to the south. Due to these site constraints, additional aeration tanks and clarifiers could not be constructed. HRSD began evaluating IFAS (Integrated Fixed Film Activated Sludge) technologies in order to utilize the existing tank volume.

A major design challenge was to retrofit the existing 200 ft long by 25 ft wide plug flow reactors with pre-anoxic zones for TN removal, an aerobic Hybas zone for BOD removal and nitrification, and a final swing zone to ensure the 1.0 mg/l of ammonia effluent limit.

Plant Overview
The James River Treatment Plant treats an average daily flow of 15.9 MGD. Max Month flows are 20 MGD and peak hour flows are 50 MGD. The existing treatment processes consisted of ¼ inch screens, grit removal, primary clarifiers, nine (9) plug flow aeration tanks with fine bubble diffusers, final clarifiers, and disinfection. Wasted biological solids from the final clarifiers are combined with the primary solids and anaerobically digested. Digested solids are dewatered using centrifuges and the centrate is normally returned to the aeration basins.

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