Method for improving biological activity of sludge by using primary sedimentation tank

The invention discloses a method for improving the biological activity of sludge by using a primary sedimentation tank. The method comprises the following steps: discharging all residual sludge of anactivated sludge biological treatment system into inflow ports in the middle and lower parts of the primary sedimentation tank, enabling the residual sludge to present upward flow and rotational flowin the horizontal direction under the action of low-speed propelling or stirring, suspending active components with relatively small specific gravity in the residual sludge, wherein the residual sludge flows upwards along with water flow, flows out from the upper part of the primary sedimentation tank as effluent of a primary sedimentation tank treatment system and is discharged into a subsequentbiological treatment system, and non-active components with relatively large specific gravity in the residual sludge settle towards the bottom of the primary sedimentation tank and are discharged intoa sludge treatment system t