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• When backwash cycle is initiated, the flow is reversed and the bed is expanded analogous to conventional backwash.

Operation

1)Raw water enters reservoir and passes through Filter. (red arrows)
2)Water passes through sand and exits through inner well screen.
3)Filtered water (green arrows) exits to clear well (not pictured).
4)When backwash cycle (purple arrows) is initiated, sand is expanded and particles exit through screen.
Image Added

Discussion

While the surface area of the filter is increased, the design would be difficult to manufacture. The well screens are expensive and would be difficult to seal. Additionally, headloss across the screens would reduce efficiency.