The Manhattan treatment plant is a 400,000 GPD plant in two trains, containing six 24 x 5.0 Bio-WheelTM. It is able to nitrify and denitrify, with two anoxic basins ahead of the aeration basins. Two conventional flight and scraper clarifiers are used. Three Penn Valley RA S/MLSS pumps are located in a separate pump room. The plant is designed for a future expansion to 0.8 MGD. At this time the effluent limits are 20 mg/L for BOD5 and TSS, however the plant is designed for ultimate limits of 10 mg/L for BOD5, TSS, total Nitrogen and less than 1 mg/L for Phosphorus which may be imposed soon because of its discharge into the Gallatin River.
The plant is of reinforced cast-in-place concrete construction. Each train is 20’ wide by 14’ deep. The general contractor was Johnson-Wilson Construction of Great Falls, Montana. Construction was begun in Spring 2007, with placement of the concrete walls being the first priority.
Following completion of the concrete work, the Bio-Wheelwere installed in the aeration tanks. Note the patented “A-Frames” which suspend the wheels from the top of the concrete walls, so that the wheels may be removed without dewatering the tank or taking the train out of service.
A side-on view of the “A-Frames.” Six 1½” stainless steel bolts hold the frames down to the top of the tank. The trunnion blocks with their UH MW bushings are preassembled in the “A-Frames.”
Each frame is leveled in both directions before the installation of the wheel axle. Notice the lifting eyes on the top angles of the frames.
Each wheel is assembled in the tank. The wheel in the center is awaiting installation of the last six rows of plates.
Three rows of plastic plates are preassembled on the galvanized end plates, ready for installation. Each row is is 8’-4” (2.5 m) in length.
The completed 24 x 5.0 Bio-Wheel are 20’-0” (6 m) wide by 14’-9” (4.5 m) in diameter and contain 31,500 sq. ft. (2930 sq. m.) of fixed film surface area.
The control building, sludge aeration tank and sludge press building were completed in November 2008.
The Bio-Wheelcontrol panel is extremely simple. Each train of three wheels contains a single D.O. probe which is connected through a PLC to the wheels to regulate rotation speed and therefore the amount of oxygen in the mixed liquor.
The control panel contains primarily on-off switches for each wheel, and an operator interface to manually set the speed of each wheel.
On a clear, cold day at the end of November 2007, the wheel installation is completed and the plant is ready for initial start-up. The chains and SEW Eurodrive gearmotors are in place.
Clean water is piped into the bio-tank for checking the operation of the wheels. Note the condensation rising from the “warm” water.
A final check is made as the wheel begins its first rotation. The chain tension is checked and found to be proper as the wheel rotates at 0.45 RPM.
The three Bio-Wheelon the eastern train are in full operation. At this point it is necessary to install the fiberglass covers over the equalization and denitrification tanks.
Notice the RA S/MLSS/WAS pump building in the background adjacent to the clarifiers. The building is heated and is convenient for the operator to check the RA S flow.
For the Manhattan, Montana 400,000 GPD wastewater treatment plant, the Bio-Wheel system was chosen for its modest initial cost and low operating cost. The control system is simple and presents few challenges to the operator. A detailed analysis of the oxygen transfer rate indicates that the combination of the fixed film and activated sludge system is considerably more efficient that an activated sludge process alone, approximating 45% more effective wastewater treatment for the same power consumption.
The Bio-Wheel provides for easy future expansion to 800,000 G PD by adding two additional three-wheel trains and clarifiers. Although the current permit limits do not call for denitrification, the plant has been designed to include this capability.