PURPOSE: To extremely simply eliminate a problem of the mixing of sludge into a device in an aeration process, a problem of the necessity of secondary equipment or operation for avoiding the problem and a problem of the suction of floated scum and settled sludge during a drain process.
CONSTITUTION: A water gathering port opening and closing device 4 is attached to a water gathering port and a circulation steam is generated in a device by the operation of an underwater pump 12 to generate force which is, in turn, converted to the force driving the water gathering port opening and closing device 4 in an open direction and this force is transmitted to the opening and closing device 4 to open the water gathering port and, further, a changeover valve 6 is operated in connection with the operation of the opening and closing device 4 in an open direction to change over the circulation stream to drain flow through a drain pipe.
SHIMA TOSHIOKI
ONUMA SUSUMU
