| 摘要 |
The sludge water valve for closing the opening communicating with a sludge water discharge channel is disposed in that surface of the side wall of the excess head chamber which is near the solid bed of the filter system and is adapted to open with a hinging movement around a pivot extending substantially at the height of the solid bed along the bottom edge of the valve lid. The discharge rate of the water in the excess head chamber is controlled, and discharge of granular material forming the bed prevented, by the lid being opened stepwise. The top edge of the lid forms a weir edge for the water layer which is immediately above the bed. Consequently, the residual column of the water in the excess head chamber is reduced for the air phase of backwashing.
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