PURPOSE: To provide the purifying treatment device consisting of a single treatment tank, by which SS, BOD, COD and chromaticity can be eliminated in a high level without providing an primary sedimentation tank in the pre-stage, and also, a service life of an activated charcoal filled filter medium can be maintained extremely long, more remarkably clarified treated water than by a conventional purifying treatment device is obtained, and also, washing can be executed without wasting the treated water.

CONSTITUTION: In a purifying device 1 consisting of a single treatment tank, a sedimenting part, a filling layer B which is provided with a diffuser means in the lower part, and executes filtration by filling a granular filter medium whose void is high, and a filling layer A for treating outflow water of a filling water of the filling layer B by filling activated carbon to which a microorganism adheres are provided in order from the bottom side of the treatment tank through a water feeding member, respectively. Also, this purifying treatment device for organic sewage is provided with a baffle 17 having a foam leading-out part 18 between the filling layer A and the filling layer B, and also, provided with a foam leading-out tube 19 in which one end is opened to the bubbles leading-out part 18, and also, passes through the filling layer A and the other end is opened in a space of the upper part of the treatment tank.