Located in southeastern Utah, Moab is a popular resort community that is experiencing a boom in residents and annual visitors. Bordered by the Colorado River and the scenic vistas of the Colorado Plateau, Moab is surrounded by national parks and is a key tourist destination for tens of thousands of travelers from all over the world.
The Moab Water Reclamation Facility (WRF) was initially constructed in the late 1950s to provide primary treatment of domestic wastewater for the Moab area. However, the plant could no longer keep up with the higher flows and loading due to population growth and rising tourism. In addition, with aging infrastructure and a new permit cycle in sight, upgrades to the biological treatment process were necessary to ensure full compliance.
After evaluating several processes, Moab selected the AquaSBR® Sequencing Batch Reactor, a true batch system, due to its many process and mechanical capabilities, including the ability to handle varying flows and loads and retrievable equipment such as diffuser racks, mixers and the decanter from the side of the basin. This allows ease of maintenance without dewatering the basins and taking the system offline.
Economically, the system offered reduced construction and operating costs and provided the lowest cost of ownership over the life of the plant as compared to other treatment processes. The flexibility of the advanced control strategy was also an advantage, which allows for simple modifications to adjust the system to accommodate the loading variations.
In 2018, the City of Moab commissioned the new AquaSBR system, resulting in a revolutionary change for the entire region providing the ability to treat varying loads and flows while producing exceptional effluent quality — well below permit.
“This is the first SBR plant in the state of Utah. The numbers it’s producing have garnered a lot of attention,” Moab WRF supervisor Greg Fosse said.
The AquaSBR system provides several advantages for plant operators, including on-demand process control and ease of maintenance of retrievable components.
“Working at the new plant is much more operator-friendly. Almost everything is automated,” Mark Luddington, Moab WRF assistant operator said.
The plant operates two, single-basin AquaSBR systems in 6-hour cycles. This allows for more water to be treated consistently, with an average daily flow ranging from 1.1 to 1.4 gallons per day.
Where nutrient removal is required, a simple adjustment to the SBR’s operating strategies permits nitrification, denitrification, and biological phosphorus removal. Optimum performance is attained when two or more reactors are utilized in a predetermined sequence of operation.
Design Characteristics
The dual-basin AquaSBR® system at Moab WRF has an average design daily flow of 1.8 MGD (6,814 m3/day). Since start-up, the plant has experienced effluent levels well below permit requirements.
“We’re running at just slightly over 99 percent efficiency on the entire plant on BOD and TSS,” Fosse said. “Our total nitrogen is running between three and four mg/L. We’re pretty much at a point with our effluent discharge quality that we were nominated for Plant of the Year in 2018. We were producing less than minimum reporting limits in less than three months and that’s somewhat unheard of in the industry. WW
