| 摘要 |
PURPOSE:To conduct washing of filter material efficiently by a simple operation, by providing washing nozzles separately in a horizontal flow portion of a U-shaped tank filled with granular filter material wherein water can be passed downwardly, horizontally, and upwardly so that washing is carried out upwardly in both the downward flow portion and the upward flow portion. CONSTITUTION:Nozzles for washing a downward flow portion A and an upward flow portion C are provided separately in a horizontal flow portion B of a U-shaped tank 13 filled with granular filter material which allows raw water to pass successively through filter material downwardly, horizontally, and upwardly, so that upward washing flow can be applied to the portion A and C. By this system, a filter tank can be wholly and effectively utilized for filtration action and S.S collection quantity can be increased, while frequency of washing of filter material layers can be decreased. Further, filter material of downward flow portion and upward flow portion can be washed separately and under proper conditions, which enables washing of filter material layers in a simple operation smoothly and efficiently.
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