| 摘要 |
Improved open gravity backwash filters have a filter chamber containing a particulate filter bed with drainage space beneath the bed and an effluent channel into which filtered effluent from the drainage space flows at a limited rate during the filter mode of operation. The effluent channel has an outflow weir at a height above the top of the filter bed. There is an influent channel in which the influent liquid level is above the top of the filter bed, a gullet with a floor below the top of the filter bed to receive influent from the influent channel and a waste effluent channel with a floor below the level of the top of the filter bed. During the filtering mode, influent is siphoned from the influent channel into the gullet from where it flows to and through the filter bed. During the backwash mode, filtered effluent is siphoned from the effluent channel into the drainage space to pass upwardly through the filter bed to the gullet and the resulting waste effluent in the gullet is siphoned from the gullet into the waste effluent channel.
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