PURPOSE: To restrain generation of hydrogen sulfide by a method wherein the amount of air to be injected into a pressurized sewer pipe is calculated, based on a specified formula using specified values obtained from the measurements made in the pressurized sewer pipe, to make the amount of dissolved oxygen in sewer at the outlet of the pressurized sewer pipe larger than the specified value, and the air in the amount determined by the above- mentioned calculation is injected through the inlet of the pressurized sewer pipe.

CONSTITUTION: A pressurized sewer pipe 3 that sends, by pressure conveyance, sewer sucked with a pump 4 to a manhole 9 and a compressor 7 that injects air into the sewer pipe are provided. The rate of variation per hour of dissolved oxygen DO in the pipe 3 is expressed, by taking the oxygen supply velocity at the inlet of the pipe 3 as Vs and by taking the oxygen consumption velocity in the pipe 3 as Vc, in an equation dDO/dt=Vs-Vc. Then Vs is expressed in the ratio of the amount of air inflow QG at the inlet of the pipe 3 to the amount of sewer flow rate Qt, while the velocity Vc is expressed in the temperature correction value of BOD or COD. By taking the amount of dissolved oxygen at the inlet of the pipe 3 at starting of air injection as DO0, and by taking the amount of dissolved oxygen at the outlet of the pipe 3 after the lapse of time t as DOt, an expression is made in an equation dDO/dt=(DOt-DO0)/t. Then the value of QG is determined so that the value DOt becomes 1.0mg/l or above. Thereby generation of hydrogen sulfide in the pipe can be restrained.