Stacked Rapid Sand Filtration
The stacked rapid sand filter is a novel self-backwashing filter invented by the AguaClara team. Its unique stacked geometry allows it to use the same flow rate for the filtration and backwash cycles, without the expensive pumps or elevated tanks required to backwash conventional rapid sand filters. In addition, a stacked filtration system requires a much smaller footprint than a conventional filter to treat a given flow rate.
A vertically stacked filtration system meets many of the AguaClara Project constraints. Both normal filtration and backwash operations are gravity driven and require no electricity. In additon, it is an open system. The required construction materials (PVC pipes, sand, concrete, brick, and rebar) are relatively cheap and available in Honduras. Most importantly, stacked rapid sand filtration is proven to consistently lower the effluent to below the US EPA standard of 0.3 NTU.
Current Research
Low Flow Stacked Rapid Sand Filters are an adaptation of rapid sand filters optimized for flows less than 3 L/s that don't require any flow control or backwash.
Further Reading
Proof of Concept Paper
General Filtration
Current Challenges
Past Challenges