To inhibit the generation of hydrogen sulfide without resulting in the large cost increase and enlargement of a facility and without obstructing the smooth flow of sewage in a conveying pipe in a force feed type sewerage facility such as a manhole pumping station.

The manhole pumping station 1 has a return pipe 18 branched from the force feed pipe 13, an on-off valve 19 opening and closing the return pipe 18 and a self-suction type aeration mixer 12. When the shut-down state of a submerged pump 11 continues for a fixed time, the on-off valve 19 for the return pipe 18 is opened, and sewage in the conveying pipe 13 is returned to a pump well 10. The aeration mixer 12 is started, returned sewage is supplied with oxygen and the aeration treatment of sewage is conducted. The operation of the aeration mixer 12 is stopped, the submerged pump 11 is started when the fixed time passes and sewage is force-fed to the force feed pipe 13 again.