When the South Cary Water Reclamation Facility was built in 1988, the nearest residential neighborhood was more than 4 miles away.
Vacant land surrounded the 40-acre plant site in the Town of Cary, North Carolina. The plant sits at an elevation nearly 30 feet below the perimeter tree line. Today, a cul-de-sac in a subdivision — one of several near the site — overlooks the 12.8 mgd advanced tertiary facility.
To accommodate neighbors, facility managers undertook extensive tree plantings and other landscape improvements that made the facility more compatible with what had become a surrounding residential community. By all indications, the neighbors greatly appreciate the changes.
Complaints arise
As the neighborhoods grew closer to the facility by 2004, plant personnel began getting complaints about noise, lights and odor. “We became more proactive in exploring ways to address the complaints,” says Andy Russell, plant manager.
A strategy of planting more trees and shrubs was among the first considerations. The trees that remained on the perimeter after the housing expansion were not enough. A grove of decorative fruit trees, planted during construction as a demonstration for use of the facility’s reclaimed water for irrigation, contributed little to the solution.
Kevin Steed, a certified arborist with the town’s Public Works Division, designed a series of evergreen plantings of loblolly and Virginia pine, cedar, magnolia, arbor vitae, juniper and wax myrtle, along with deciduous trees, such as birch, cypress, holly and Oklahoma redbud. Shrubs like azaleas and boxwood were also included.
The goal in part was to mix the species and vary the heights to change the flow of air and distribute it above grade level. The other intent was to draw neighbors’ eyes in closer to their homes so it diverted their view from the facility.
Nearly 90 4-inch-diameter trees 14 to 16 feet tall were planted along the perimeter nearest to the housing areas. “We would have preferred to use smaller trees because they establish better, but we were looking for an immediate effect and planted rather intensely,” Steed says.
The project also narrowed a portion of a 30-foot-wide service road that provided access to the plant through the neighborhood. The compacted surface was replaced with engineered soil more conducive to plant growth. Reclaimed water for irrigation was distributed to the trees through runs of PVC pipe. Steed expected 25 percent first-year mortality, but after the first winter only about 15 percent of the trees had to be replaced.
Sound and light
Recognizing that plants and trees were not a complete solution for the neighbors’ issues, the plant team also installed aeration diffusion devices and managed process aeration equipment to minimize excess noise. Process pumps, blowers, air piping and tanks were soundproofed with mineral wool insulation and cladding. Silencers were applied to up-blast fan exhaust systems.
Outdoor lighting was changed to eliminate up-beam directional aiming. LED lamps replaced incandescent and fluorescent bulbs. Heavy industrial curtains were installed in the tall biosolids thermal dryer building, which has large windows and high interior lighting.
“We have successfully used landscaping to control some noise and lighting issues, but I’m not sure how much that would have helped odor,” says Russell. “We have relied on unit processes and technology to deal with that issue.”
To more positively control odor, the facility staff covered open structures and collected dirty air into a centralized odor-control system — a biofilter with activated carbon adsorption. They also retrofitted a thermal solids dryer with a multimedia dry scrubber with carbon adsorption. Humid sidestreams are now treated with carbon media point-of-use filter cartridges.
“Feedback from the neighbors about the facility’s efforts has been positive,” Russell says. “We have monthly utility updates that track customer interactions. We’ve seen a big decrease in number of complaints.”
