To provide a lightweight underwater aeration device reduced in trouble and easy in maintenance and control.
The underwater aeration device 10 is equipped with a casing 12 which has an inflow port 20 and an outflow port 12 for water to be treated and in which a flow channel of water to be treated is demarcated, the water sending impeller 26 provided in the casing in a rotatable manner, an air supply pipe 66 for introducing air into the casing, an underwater electromotor 28 for rotationally driving the impeller and the rotational speed control circuit 42 such as an inverter or the like arranged in the underwater electromotor or in the hermetically closed space 44 provided adjacent to the underwater electromotor to control the rotational speed of the underwater electromotor. In this constitution, since the rotational speed of the underwater electromotor is controlled by the rotational speed control circuit reduced in trouble used in place of a gear type speed reducer, the device is made lightweight and can be controlled corresponding to various conditions such as water quality or the like.
TOMITA KIN
ABE TOSHIHIKO
YAMAGUCHI NORIO
UNOZAWA GUMI IRON WORKS