JPS5515658A - Upward channel - Google Patents

Abstract

PURPOSE: To make disintegration of sand layers easy at the back washing and make possible good back washing of filter material by fixing the insert members extending into the sand layers to the body of the apparatus.

CONSTITUTION: Insert members 5 extending up to the lower part of sand layers 2 are fixed to the bottom of the apparatus body. The insert members 5 are of bar- or plate form and in this case they also serve as stays for supporting a filter bed plate 4. Extending the insert members 5 so as to reach at least the lower part of the sand layers suffices. Raw water is supplied from a supply port 6 to the spacing 7 in the lower part of the filter bed, passes through strainers 8 and reaches the filter material layer where it is filtered. At least two pieces of the insert members 5 are provided to obviate distrubing the flow of the raw water and make the disintegration of the sand layers 2 easy at the back washing. When back washing is accomplished by supplying water (air) from the supply port 6, the force lifting the filter material is produced and the friction force between the sand layers 2 and insert members 5 is produced in the sand layers 2 in contact with the insert members 5. The sand layers 2 are disintegrated from the surroundings of the insert members 5 by the shearing forces developed by these forces.

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