Puls-A-Clar and Puls-A-Plate clarifiers treat flocculated surface water through a pulsating action of the water. A vacuum chamber and pump system varies the flow into the basin to impart the pulsating action in the sludge bed. Timing of the vacuum and release cycle controls the rate of pulsation. The sludge blanket through which the water passes traps smaller floc particles. Hoppers on the side of the basins collect and discharge sludge.