As housing developments closed in on the once remote Georgetown Wastewater Treatment Plant, odor control became even more important. Find out how a grit tank cover solved the problem.
The Georgetown Wastewater Treatment Plant (WWTP) located in Ontario, Canada, provides industrial and municipal wastewater treatment for the urban area in the town of Georgetown. The plant treats about 17.5 mld (4.6 mgd). It is sized to accommodate the wastewater treatment needs of a local dairy processing facility, the plant’s largest industrial contributor of wastewater.
The customer needs:
Built in 1960, the Georgetown WWTP was originally located in a remote area. However, in the mid-1990s, houses were developed less than 100 meters from the plant’s property line. Though consultants were hired to conduct dispersion modeling and analyze weather patterns to determine if odors would affect the homes closest to the plant, it didn’t take long before new residents complained about odors.
Although plant management introduced several odor control technologies, including oxidizers, vaporizers, misters, ozone and carbon systems, odor objections continued. The plant wanted to be a good neighbor, so it focused on its grit tanks, which were identified as a significant source of odors.
WWTP staff began investigating different cover options. The tanks have a screw conveyor at the bottom that occasionally must be serviced, so access to tank internals was an important consideration when selecting the cover system.
Geomembrane Technologies Inc. (GTI) was selected to design and fabricate two structurally supported covers for the Georgetown WWTP’s two 2.5m x 10m (8 ft x 33 ft) grit tanks. The retractable covers consist of a high-strength, UV-protected, coated fabric tensioned over a low-profile aluminum arched frame that spans the tank opening. Foul air from below the covers and inside the grit building is withdrawn and treated in a carbon system.
“We can’t chase odors in the wind. A cover makes logical sense. We were convinced that capturing and treating odors was the way to go,” says Wendy Derjugin, plant operations supervisor.
The covers were custom designed to meet specific plant requirements, including: spanning the long dimension of the tanks to allow easier removal of the screw conveyors; the addition of inspection hatches; and accommodation of penetrations for valves, gates, drains and aeration pipes.
The structurally supported covers at the Georgetown WWTP control odors and easily retract, meeting the plant’s access requirements. It takes only one person to easily open the covers for routine inspections.
“Retracting the covers is not labor-intensive. It isn’t the type of equipment that deters people from doing their work because opening the covers is very simple. The covers address this problem area while still allowing us to access equipment. Covering the grit tanks was one of the most effective things we could do to further reduce the potential for odors,” says Derjugin.
The success of the project has plant management convinced it is making continued progress toward addressing odor issues and improving the relationship with nearby residents. The plant is now considering ways to tackle headworks odors.