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Issue link: http://wateronline.epubxp.com/i/816402
By Kristina Twigg and Rich Voigt A lexandria Renew Enterprises (AlexRenew) is an advanced water resource recovery facility — previously known as a wastewater treatment plant — that serves the City of Alexandria and parts of Fairfax County, VA. Designed to transform 54 million gallons of wastewater per day on just over 33 acres, AlexRenew is one of the smallest gallon per acre facilities in the nation. Being a good neighbor on a space- constrained urban site within the ecologically sensitive Chesapeake Bay watershed takes ingenuity. In 2016, AlexRenew completed construction on its $160-million State-of-the-Art Nitrogen Upgrade Program (SANUP). This project, nearly 10 years in the making, was designed to protect the Chesapeake Bay by meeting more stringent nutrient limits. SANUP meets these nutrient challenges in a way that conserves space, achieves resource efficiencies, and involves the community. Challenges Prompt Infrastructure Innovation The Chesapeake Bay is the largest estuary in the U.S. It borders Virginia and Maryland, but its watershed spans 64,000 square miles across six states and Washington, D.C. The bay is impaired by nitrogen, phosphorus, and sediment. According to the Chesapeake Bay Program's Bay Barometer released this February, the bay's condition is improving, in part because the region's water resource recovery facilities have met key nutrient reduction milestones 10 years ahead of schedule. Driven by efforts to protect the bay in the late 1990s, AlexRenew initiated a $350-million nutrient upgrade to achieve an effluent limit of 8 mg/L total nitrogen based on permitted flow of 54 million GPD. In 2011, new assessments showed that additional nutrient reductions would be needed to improve the Chesapeake Bay's water quality, necessitating the SANUP program. Starting in 2017, AlexRenew is reducing its effluent total nitrogen concentration to just 3 mg/L, a nitrogen load cap of 493,000 lbs/ year. With SANUP, AlexRenew's total nitrogen discharged to the Chesapeake Bay will be reduced by an additional 20 percent annually. AlexRenew is located in Old Town Alexandria, VA — just outside of Washington, D.C. — a dense urban area along the Potomac River. The site is bounded by a large electrical substation, Interstate 495, a historic cemetery, and commercial and residential development. Just west of the facility's main campus is the South Carlyle site, previously an unregulated landfill and part of the area AlexRenew acquired to expand its facilities. This brownfield with contaminated soils required detailed sampling and analysis. AlexRenew was further challenged by resource protection areas that covered half of the South Carlyle site, as well as the need to create a consistent aesthetic with surrounding development. AlexRenew, in partnership with the consulting firm CH2M (Herndon, VA), developed a technical plan that embraced these various challenges while delivering on the utility's vision to protect the environment, contribute to a vibrant local economy, maintain stable rates, and involve the community. The plan combined three different innovative processes that work together to support AlexRenew's vision and meet its nitrogen reduction target. These include mainstream and sidestream deammonification as well as a nutrient management facility that balances diurnal influent ammonia loading. 22 wateronline.com n Water Innovations Enhanced Nutrient Removal That Saves Resources And Real Estate True to its name, the State-of-the-Art Nitrogen Upgrade Program leverages the latest technology and innovation to clean up the Chesapeake Bay and the environment around our nation's capital. The plan combined three different innovative processes that work together to support AlexRenew's vision and meet its nitrogen reduction target.