The community of Moscow is located in the northeast corner of Pennsylvania, approximately 10 miles southeast of Scranton. The current WWTP consists of an activated sludge system with three oxidation ditches in parallel operation. The total volume of all three ditches is 0.372 million gal per day (mgd), while the average size of each ditch is 180 ft by 24 ft by 6 ft deep.
Previously, two of the ovals were constructed with brush rotor devices for aeration and mixing. The brush rotors system, including bearings and gear reducers, required difficult, expensive and frequent maintenance, coupled with consistent failures. Rotor aerators also cause significant cooling due to their splashing nature and, in cold-weather climates, cause freezing issues. The splashing effect of the rotors decreases water temperatures dramatically, which leads to a decrease in aerobic activity. Rotor covers used to prevent icing issues and to control aerosoling may decrease the oxygen-transfer capabilities of brush rotors by reducing contact of the water with the free-moving ambient air, thus resulting in a reduced standard aeration efficiency.
Ralph DeLeo is the plant superintendent of the MSA and its wastewater treatment facility. “In July 2001, we were researching ways to increase the DO levels in the aeration tanks,” he said. “Following the advice given by the Department of Environmental Protection’s Operator Outreach Program and after another rotor system failure, the authority decided to totally replace the existing system.”