Abstract: In the particular embodiment of the invention described in the specification, a liquid to be purified passes first through a screen, a sand trap, a first sedimentation basin, an aeration basin and a second sedimentation basin, and then through a final purification step for chemical admixture and passage upwardly through a particulate filter bed. The particulate filter material is circulated continuously from the bottom of the filter bed through a washing device and the cleaned particulate material is deposited at the top of the filter bed. Sludge collected from the sedimentation basins and the washing device is treated in thickeners and digesters.

Abstract: In the described embodiment of the invention, apparatus is provided for continuous filtration of a suspension or emulsion comprising a tank containing a bed of particulate filtration medium and an inlet arrangement within the filtration bed to introduce the suspension or emulsion. A transport pipe carries dirty filtration medium from the bottom of the tank to a wash device located above the filter bed zone which washes the medium as it passes downward along a washpath. An apertured cone disposed below the wash device distributes the cleaned filtration medium across the top of the filtration bed and an outlet for clarified liquid is positioned above the wash device, which has an inlet above the top of the filtration bed to receive clarified liquid.

Abstract: A suspension or emulsion is filtered by causing the same to flow upwards through a zone of filter medium of particle size forming a filter bed while the filter medium concurrently flows in a downward direction through the filter bed zone. Dirty filter medium at the bottom of the filter bed zone is transported to a wash device located above the filter bed zone and is washed as the dirty medium passes downward along a washpath in the wash device in counter current flow to wash liquid which passes upward though the wash device, whereafter the washed medium is returned to the top of the filter bed zone. A zone of filtrated liquid phase is maintained above the filter bed, and a portion of said filtrated liquid phase is supplied to the wash device as the wash liquid.