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 invention provides a method and apparatus for rinsing an object which has been removed from a chromium plating bath, and which has a source of chromium-containing anions thereon, while preventing the delivery of these anions to the environment. In carrying out the invention, chromium-containing anions are removed from the rinse water by an anion-exchange resin. The resin is periodically regenerated by backwashing it, delivering a dilute alkali metal hydroxide solution to the resin, delivering a more concentrated solution of alkali metal hydroxide to the resin, and by rinsing the resin. Effluent from the backwashing and the initial portion of the regeneration procedure is retained and later delivered to the resin. Effluent which contains a higher concentration of chromate ions, displaced from the resin, is delivered to a concentrated chromate solution storage tank.