Author Topic: "Slow Sand" water filtration  (Read 1866 times)

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"Slow Sand" water filtration
« on: February 20, 2011, 01:16:05 PM »
Categories » TEOTWAWKI » "Slow Sand" Water Filtration

"Slow Sand" Water Filtration
Post by irondiopriest on Jan 28, 2010, 4:53pm

I ran across this method of mechanical bio-filtration on a survival website. (Sorry, I don't remember where it was, it was several weeks ago). The site gave schematics and instructions on how to build a "slow sand" filtration device that is capable of creating potable water, even from bacteria-laden surface sources like ponds, runoff, and swamps.

Intrigued, (and mechanically challenged) I set out to find a company that sells these devices prefabricated. I found Blue Future Filters.

See their FAQ's to learn exactly how this works.

Essentially, it is a method of facilitating the microbial activity necessary to consume whatever bacterial matter enters the top layer of the filter by creating the same conditions as a sandy-bed aquifer, and then allowing gravity to move the water through the rest of the filtration process. the claim is the removal of 99.99% of all impurities - drinkable by any standard.

Re: "Slow Sand" Water Filtration
Post by libertasinfinitio on Jan 29, 2010, 7:37am

I think what you're talking about is creating a "natural" filtration system, and I have seen some stuff on that, just cannot recall where. All I remember is alternating layers of sand and different sized rocks and pebbles. Bear on Man vs Wild is great for such ideas! I think the Army Field Manual (available most everywhere) has such a design, and that book is filled with lots of useful stuff and I recommend it as a basic necessity.

Edited to add - I believe it is FM 21-76.
Re: "Slow Sand" Water Filtration
Post by glock32 on Jun 22, 2010, 12:01am

I've been into aquariums (fresh and saltwater) for years, and you incidentally learn a lot about water filtration and purification in that hobby. I use a reverse osmosis filter with deionizing stage to create the tank water. When I first got mine they were found almost exclusively among reef aquarium people, but now you can find them in most home improvement stores. They work by using the pressure of the tap to force water through a membrane that rejects almost everything other than water molecules. A good RO unit with some extra membranes is a good piece of kit to have. I figure you could pretty easily rig up something to pump the water by hand in a SHTF scenario. I believe they make something along those lines for sailors as an emergency tool for turning seawater into freshwater.

They do create a lot of waste water that is laden with all the crap rejected by the membrane, but this waste water just so happens to be excellent for watering plants since it basically has fertilizer in it.
Re: "Slow Sand" Water Filtration
Post by rocketman on Jun 22, 2010, 10:06am

I like the concept, but you'd need a helluva lot of plants to water with the effluent, wouldn't ya?


Re: "Slow Sand" Water Filtration
Post by peachykean on Jan 31, 2011, 4:38pm

On the cable show "The Colony" the survivors construct a filtration system using sand and activated charcoal. First you need a food safe drum or barrel. Make holes in the bottom for water to drip through. Put it on a frame or stand so that there will be room beneath it for a catch basin. Put a layer of small stones or fine gravel in the bottom. Next add a layer of sand, then a layer of activated charcoal. Repeat layers, ending with sand. Leave room on top for a final layer of gravel on top. Pour the water in the top and catch the filtered water in the catch basin. Now the filtered water MUST BE DISINFECTED.

You can boil it, treat it with chemicals ( water purification tabs, bleach, iodine etc. ) or use UV rays to disinfect the filtered water.
An excellent site for FAQs about water can be found at

The SteriPEN company ( ) makes a hand cranked UV purifier for about $100 and also one that uses its own solar charger for about $150 which is small enough to fit in your pocket.

Check out a cheap low tech. build it yourself unit at

Re: "Slow Sand" Water Filtration
Post by johnflorida on Jan 31, 2011, 7:34pm

Worth a look.
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