Single 55 gallon barrel filter schematic

This page describes the fundamental filter design used in our plant configurations. The single 55 gallon barrel design uses conventional down-flow sand filtration and uses a siphon and clear well to backwash.

Inspiration

Our design was influenced by existing automatic backwash designs, however, this design employs a simpler geometry and incorporates a recycled 55 gallon drum.

Operation

1) Raw water enters 55 gallon drum and passes through sand filter.
2) Filtered water enters screen pipe and flows to clear well.
3) As filter clogs, head loss increases in region "A". This backpressure causes flow to be directed up siphon. The column of water in the siphon rises and eventually passes turn, where flow accelerates, creating a low pressure in region "A". The pressure differential between A and B induces backwash cycle from clear well.
4) Siphon is broken by small pipe exposed to atmosphere, and remaining backwashed water goes to waste. At this point filter has been backwashed and continues operating as normal.

• Interface between sand and effluent pipe has not yet been determined. Possibilities include gravel or screen pipe, respective head losses under investigation