Abstract: A lamella separation apparatus comprising a liquid receiving tank defining an upper sedimentation zone, an intermediate quiescent zone and a lower sludge thickening zone. An outlet trough spans the full length of the tank within the sedimentation zone. An inlet distribution trough spans the full length of the tank and is positioned below the outlet trough. A plurality of lamella plate pack/collector trough assemblies are positioned within the sedimentation zone in transverse orientation with and in communication with the inlet and outlet troughs. The plate pack/collector trough assemblies are individually removable without disturbing the operation of the apparatus. A picket fence sludge thickener rake mechanism is provided in the sludge thickening zone.

Abstract: The rotating backwash isolation hood of a multibed filter is raised and lowered by either hydraulic forces and gravity, or by an improved mechanism employing a pair of pistons and cylinders and a perforated indexing disc, or by both of these arrangements. The force required to lift the hood is reduced by eliminating the effect of the static head of the liquid above the hood. Leakage between the hood and the filter it covers is detected by a pressure differential indicating switch. A floculator may be combined with the multibed filter, and the dirty backwash liquid from the hood may be recirculated into the floculator.