Adjusting the frequency of A/C power effectively controlled the paddlewheel
speed and resulted in significant differences in SOTR performance as tabulated in
Table 5. There was generally an increase in oxygen transfer rate with speed, but
paddlewheel A displayed a most distinct bump when paddling was increased from
76 to 82 rpm. This particular aerator was most efficient paddling at 87 rpm, with
an apparent drop as paddling increased to 103 rpm (50 Hz A/C).