With the continuous development of science and technology, "Blower Fan" AC motor speed control technology is widely adopted. Through a new generation of full-controlled electronic components, with the frequency change of AC motor speed way to control the flow of the fan, can significantly reduce the energy of a conventional mechanical regulation of traffic caused by the loss. Energy-saving principle of frequency regulation: shows that, when the rotational speed is reduced by half its original rated speed to traffic conditions corresponding to the point, pressure, shaft power drops to each of the original 1 / 2,1 / 4,1 / 8, which is frequency adjustment method can greatly saving reasons. According to this characteristic frequency regulation, for the waste-water treatment process, the aeration tank remain 5m normal level, requires "Blower Fan" at the outlet pressure constant conditions, a wide range of flow regulation, when large depth adjustment , will make the pressure drop is too large, can not meet the technical requirements. When adjusting the depth is small, it does not reveal its energy-saving advantages, but the apparatus complex, one-time investment increased. Therefore, under this project for an aeration tank to maintain the level of 5m working conditions, "Blower Fan" with frequency adjustment method is clearly inappropriate.