PURPOSE: To permit movement of water in sewage treatments which is intrinsically performed on a pay basis, at the low cost next to free of charge by utilizing pumping-up power stations.

CONSTITUTION: After sewage is conducted from a sewage source 1 to a sewage treatment station 2 and is treated there, it is dropped into an under basin 3 for collection of water. This is pumped up into an upper basin 4 for power generation, from which it is dropped into an under basin 5 for dropping power generation, whereby electric power is generated. This is again returned into the station 2. The sewage is purified by the repetition of such operations cyclically. Upon completion of the purification of water quality, this is separated as clean water 6 and is used. The heads of the water levels of the respective facilities are in order of the basin 4 > the basin 5 > the station 2 > the basin 3. With the basin 5 > the station 2 > the basin 3, just a 10m head suffices.