Suppose that during a new construction project your operators could actually see the spaces where they would be working.

The design process for a new disinfection facility at a clean-water plant in Virginia’s Fairfax County provided that capability. Innovations like that were a key reason the county earned a 2019 Envision Gold Award for Sustainability from the Institute for Sustainable Infrastructure for a UV disinfection facility at the Noman M. Cole Jr. Pollution Control Plant.

The disinfection upgrade is one of many improvements in store for the 50-year-old plant. It can’t all happen at once; engineers, operators and administrators have to pick their battles.

“You can’t upgrade the entire plant all at the same time,” says Laurel Xiao, a capital projects engineer for the Wastewater Design and Construction Division in the county’s Department of Public Works and Environmental Services. “You have to do it stage by stage.” Xiao was the county’s project engineer for the switch from sodium hypochlorite to UV (TrojanUV) for disinfection.  

Collaborative process

The new disinfection system is expected to go online in March. The Envision award was presented when the project was less than half complete because the award was partly based on sustainability in the design process.

One factor was the way the county staff worked with the designers (Hazen and Sawyer PC) and the construction contractor (Ulliman Schutte Construction). Those firms joined with the county staff in a construction-management-at-risk project delivery method that encourages collaboration and teamwork. The method allows early input from the construction manager, and in this case that led to some design improvements and an increase in salvageable material.

Another innovation in design for the UV system was the use of mixed-reality technology. Holographic images of new elements were superimposed on existing spaces to help the design team better understand the work environment being created.

Plant operators and engineers wearing 3D Oculus goggles experienced three-dimensional views of the work spaces before construction. This enabled modifications that could save money or reduce future maintenance. It was the first public works project in the county to use the technology.

“It is a great tool for plant operators to view and provide feedback on the design,” Xiao says. “The 3D images are developed by the design engineer during the design phase so people can view what a building, a piece of equipment, or a piping network looks like before they are constructed.”

Multiple boosts

The change to UV disinfection is expected to improve operations in several ways, including greater safety for workers and the community, reduced labor and maintenance costs, and less use of chemicals. Although the process will require more electricity, the plant’s carbon footprint will be reduced if carbon reductions from chemical manufacture, transportation and storage are counted.

“The old system was more labor intensive. We had to monitor dosages,” Xiao says. “Compared to the new system, it was also expensive to maintain. The old system was outdated. The new one is simpler, safer and more cost-effective.”

Along with the change in disinfection, the upgrade project included filter backwash pumping, a new outfall pipe, pumping for reuse water and advanced plant water with separate disinfection, and various electrical improvements.

Another sustainability boost came from a modification in the hydraulic grade, which eliminated a pump station and offset some of the increased electrical demand from the UV process. New Floway turbine pumps (Trillium Flow Technologies) were also installed to move reuse water to a storage tank, replacing the existing 10-year-old pumps.

Old plant, new processes

The Noman M. Cole facility serves a highly populated area just south of Washington, D.C. It opened in 1970, two years before the Clean Water Act was passed. It was designed for 18 mgd but it has been upgraded numerous times to 67 mgd capacity. Average flow is 40-50 mgd. The plant employs about 100 people.

The tertiary treatment plant uses moving bed biofilm reactor technology for nitrogen removal, with tertiary clarification and filtration for phosphorus removal. Biosolids are dried and incinerated, and the inert ash is taken to a landfill. The plant discharges to Pohick Creek, a tributary to the Potomac River.

The plant produces reuse water for cooling at a power plant and for irrigation at golf course and a ballfield. Advanced plant water is used for in-plant cleaning and other processes.

Fairfax County, with its commitment to continual upgrades at the plant, was honored in August by the National Association of Clean Water Agencies as a Utility of the Future, a program that recognizes facilities that implement technological advancements that improve resource recovery, efficiency and sustainability.