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 flows to clear well.
3) As filter clogs, head loss increases in region "A". This backpressure causes flow to be directed up siphon. Once the siphon fills backwash can be started.
4)Backwash begins when the operator opens both siphon valves and shuts off raw water inflow.
5)The flow out of the siphon creates a low pressure in top of barrel and flow from clear well expands sand bed and backwashes filter.
6)Backwash is stopped by closing upper valve of siphon and remaining backwashed water stays in column. At this point filter has been backwashed and continues operating as normal; the siphon remains primed.