Backwashing of V-type filters
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During backwashing of a V-type filter, does the water level drop to the top of the drainage trough or the top of the V-shaped channel? ? ? During the backwashing process, the water inlet valve is closed, but some water still flows into the filter from the permanently open square holes on both sides; it then moves from one side of the V-shaped channel to the other side, thereby cleaning the surface. Then, the drain valve is opened to discharge the water on the surface of the tank through the drain channel until the water level in the filter tank is level with the top of the V-shaped channel. The backwashing process typically involves three steps: air backwashing → simultaneous air and water backwashing → water backwashing.
The water depth above the filter layer is generally greater than 1.2 m, while during backwashing the water level drops to the top of the drainage trough, resulting in a water depth of only 0.5 m.
During backwashing, the liquid levels in the filter beds on both sides drop to the top of the middle drainage channel, and the water in that channel is completely drained through the drainage valve.