In late 2010, the EPA established the Chesapeake Bay Total Maximum Daily Load, a daily pollution regulation that puts restrictions on the total amount of nitrogen and phosphorus – major sources of nutrient pollution - allowed in the Bay. It is designed to ensure that all pollution control measures needed to restore the Bay and its tidal rivers are secure by 2025.
The effort to turn the tide within the Chesapeake Bay Watershed encompasses water filtration and nutrient removal efforts at over a dozen waterways. More than twenty wastewater treatment plants in the Chesapeake Bay watershed are using the DE NORA TETRA® Denite® technology to meet the stringent National Pollution Discharge Elimination System permit regulations of 3 mg/L Total Nitrogen and 0.3 mg/L Total Phosphorus. The Back River WWTP on the outskirts of Baltimore is the largest denitrification filter in the United States with an average daily flow of 185 million gallons per day (MGD). Back River WWTP is composed of fifty–two 11’-8” wide x 100’-0” long Denite filters arranged in four quadrants. The 81 MGD Patapsco WWTP, under construction, consists of thirty-four 11’-8” wide x 100’-0” long Denite filters.
Other WWTPs using DE NORA TETRA® Denite® technology in the Chesapeake Bay watershed include Arlington County WPCP, WSSC Seneca Creek WWTP, York River WWTP, Cumberland WWTP, H. L. Mooney AWTP, Lebanon WWTP, and Parkway WWTP. The City of Richmond WWTP was a pioneer in the early days of nutrient removal for the Bay, retrofitting their nozzle-bottom filters with robust TETRA underdrains in 1986 to allow for fixed-film denitrification in their tertiary filters.