Tech Brief: Slow Sand Filtration

First used in the U.S. in 1872, slow sand filters are the oldest type of municipal water filtration. Today, they remain a promising filtration method for small systems with low turbidity or algaecontaining source waters. Slow sand filtration does not require pretreatment or extensive operator control—which can be important for a small system operator with several responsibilities.



Yesterday I posted a request for information regarding biosand filters for the Gaza Strip.  I received the following email that is certainly helpful.  I will most certainly contact Comet-Middle East.  

However, from reading the Comet web site they are working solely on the West Bank.  The situation in Gaza is different, more complicated logistically, politically and physically.   Sourcing materials on-site in Gaza is extremely problematic and unfortunately bringing supplies physically from Israel may pose obstacles not easily surmounted.  To that end it would be excellent to try to work with NGOs or civil organizations within the territory itself.  Any ideas or suggestions or contacts will be greatly appreciated.  

Currently we are working on the premise of shipping 20 HydraAid units from the U.S. to Egypt including, initially, the sand and gravel needed for testing and evaluation.  The thinking is to ship them to Egypt and brought in as part of a larger aid mission.   Does this sound practical or feasible?  Again feedback is appreciated.  

Thank you..... your initial response follows ....

I suggest you contact Elad Orian <>.  He is the co-founder and general manager of Comet-Middle East, an Isreali-Palestinian organization working in the "poorest and most marginalized communities in the Occupied Palestinian Territiories".  They recently began installing biosand filters made of 12" PVC pipe.  These are effectively the same as the Hydraid filters made by Triple Quest except that they can be made in-country without the need to import from the US.   

The Hydraid filters bodies are fine, but they are only containers.  The effectiveness of this intemittent slow sand filter technology (biosand filters) is in the filtration sand - not the container.  Proper preparation (sieving and washing) of the filtration sand is critical.  Go to CAWST's website ( to download (free) all the information you will need to prepare and install biosand filters (and how to teach others how to do so).  If you have questions contact 
Yul Tang's picture

I am very interested in older types of water filtration methods. The fact that the filtration uses a biological processes for cleaning the water, and do not need any chemicals or electricity for operation is extremele attractive. I hope to take up on this with some of the council members here in China. Thank you for the insightful tech brief.
Yul Tang