Because of the problems noted above, the staff at Eufaula WWTP began to evaluate options to improve WWTP performance via changes in the areation system. One option was to replace the existing aerators with other vertical aerators. A second option was to replace the existing aerators witha diffused aeration system. A third option was to install floating brush rotors maufactured by S&N AIROFLO of Greenwood Mississippi.
Because of the past problems with vertical aerators, WWTP staff was not inclined to install new vertical aerator units. Although diffused aeration is widely used the activated sludge processes, the staff decided not to use diffused areation because of high capital cost. Instead, the decision was made to install floating brush rotors.
BACKGROUND ON FLOATING BRUSH ROTORS
Until the last few years, aeration of activated sludge was typically achieved by diffused aeration systems or vertical aerators. Also, fixed brush rotor aerators were usually used in oxdation ditches. These aeration systems have generally performed well and provided adequate oxygen transfer and mixing. Since 1998, floating brush rotors (FBRs) have become popular choices for oxidation ditches and other types of activated sludge facilities.
Because of the above problems with original fixed rotor designs, floating horizontal aerators have become popular when existing units need to be replaced. FBRs have a very high oxygen transfer rate. FBRs are set at their optimum operating depth to provide maximum oxygen tranfer regardless of the water level in the aeration basin. In addition, FBRs provide excellent mixing of liquor. The Floating Brush Rotors manufactured by S&N AIROFLO of Greenwood, Mississippi, have high pumping rates of about 2100 gpm per horsepower.