Wastewater enters through a pipe in the basin center. While the sewage settling in the basin the Sludge sinks to the bottom of the basin and the Scum rises to the surface. The Bridge rotates continuously without a stop by a peripheral driving system. The inner side of the Bridge is fixed to a concrete pillar in the center of the basin by slewing bearing. Sludge scraper sweeps the Sludge into the central sump. The sediment is removed through a pipe which is located at the bottom of the main pit. The scum is swept away by the scum scraper and pushed to the extent of the basin until it reaches the scum box and is flushed by the automatic flushing system through the removal pipe. The scum buffer prevents scum exit through the weirs. The clean water flows through the peripheral weirs and exit through the peripheral effluents canal.