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Technology
Fairfax County discovers many benefits to ultraviolet for wastewater treatment By DANI MESSICK | The Municipal
Fairfax County’s new ultraviolet water treatment facility earned an Envision Gold award for sustainability. The awardwinning Noman M. Cole Jr. Pollution Control Plant is a 67-million-gallon-per-day wastewater treatment plant in Fairfax County, Va., that replaces the old sodium hypochlorite disinfection system. The wastewater treatment plant takes the sewage from the southern half of Fairfax County and reclaims it by removing 99.9% of pathogens. “Disinfection is a dedicated process to remove pathogens and germs, and ultraviolet is EPA approved,” Michael McGarth, plant manager of the Noman M. Cole Jr. Pollution Control Plant, explained. “It uses light to remove microbes, including those that can cause disease.” The change in treatment, from bleach to ultraviolet, is not only more sustainable for the county, but safer for customers and for employees. “Chemicals, added in liquid form, killed the germs,” McGrath said. “Unfortunately, the active ingredient remained and would continue to kill things so we had to add another ingredient, sodium bifluoride.” These chemicals had to be brought in on tankers to the tune of 200 loads per year, or roughly $750,000. “The (old) system required what felt like almost continual adjustment of the chemicals to get the right dose,” McGrath 42 THE MUNICIPAL | JANUARY 2022
Fairfax County, Va., has replaced its old sodium hypochlorite disinfection system for ultraviolet in its Noman M. Cole Jr. Pollution Control Plant. (Photo provided by Fairfax County)
continued. “They’ve got to test every two hours to demonstrate to the Department of Environmental Quality that they’re not distributing too much, so it takes a lot of labor to monitor.” The new system uses an entirely different process. “It does not completely kill the pathogens, but it changes the DNA so they cannot reproduce,” said Capital Improvement Program engineer Sajana Chitrakar. The technology has been used in various communities for drinking water since 1910
but has only been implemented in wastewater since the 1980s. “UV also has the resiliency factor,” Chitrakar continued. “With the chemicals, we had to rely on drivers and availability, and so we have eliminated a portion of that because we don’t need (sodium bifluoride) to reduce the bleach.” It took nearly 10 years from start to finish, McGrath admitted. “Our water flow had to be changed,” he said. “(The project) required us to construct some new concrete tanks and channels in
