permaculture

[Belle Starr <belle@seedsave.org>]

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Belle Starr
Cofounder of Seed School
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On Fri, Feb 28, 2014 at 10:01 AM, 
<permaculture-request@lists.ibiblio.org>wrote:

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>    1. MIT Researchers Discover Sapwood is Inexpensive   Water
>       Filtration Method (Lawrence London)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 28 Feb 2014 04:49:32 -0500
> From: Lawrence London <lfljvenaura@gmail.com>
> Subject: [permaculture] MIT Researchers Discover Sapwood is
>         Inexpensive     Water Filtration Method
> To: permaculture <permaculture@lists.ibiblio.org>
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> MIT Researchers Discover Sapwood is Inexpensive Water Filtration Method
>
> http://guardianlv.com/2014/02/mit-researchers-discover-sapwood-is-inexpensive-water-filtration-method/
>
> Sapwood from a tree branch can be used to filter over 99 percent of E.coli
> from drinking water, according to the latest findings by MIT mechanical
> engineers, and this low-cost method of water filtration may prove to be a
> boon to developing countries.
> *How are the water filtration devices made?*
>
> Though likely many types of tree branches can be used to create water
> filtration devices, the MIT researchers used a small segment from a white
> pine tree branch that was an inch long. They peeled the bark off of it, and
> then inserted and fastened it into the end of a plastic tube with the sort
> of metal clamping band used with hoses in cars.
>
> Then, the water polluted with the E.coli is poured into the tube, and the
> water which drips out through the xylem in the chunk of wood has been
> filtered of over 99 percent of the E.coli bacteria ? 99.9 percent, to be
> exact. The chunk of sapwood can be used to filter 4-6 liters of water per
> day, enough for one person.
>
> The MIT mechanical engineers who thought up this ingenious and inexpensive
> method of water filtration published their findings February 26 in PLOS
> One. According to the study?s senior co-author Rohit Karnik, after he
> listened to a talk about how water and sap flows through plants and tree
> branches, he realized that it ?has to pass through these membranes in
> xylem.?
>
>
> In living plants, xylem membranes help transport water and minerals to were
> they?re needed in a plant or tree, and it transports sap in trees. That
> talk gave Karnik the idea to try out a piece of sapwood, and find out if it
> would work as a water filtration method ? and it did work, like a charm.
>
> Though he has some reservations about how the water filtration system will
> handle more heavily polluted water, Rick Andrew, who is the global business
> development director of water systems at the National Sanitation Foundation
> International, has stated that the water filtration devices made with
> sapwood could be a low-tech method to purify water.
>
> Getting easy and inexpensive access to pure water is a major problem in
> many developing countries. Dead and dry wood will not work however; sapwood
> must be used to make the water filtration devices,and plastic tubing and a
> metal clamp needs to be available to make the method work.
>
> Also, it is important to note that while the sapwood is great for filtering
> particles of the E.coli bacteria which are larger than 70 nanometers wide,
> it wasn?t successful at filtering out smaller particles in the 20-nanometer
> range. Since smaller particles can?t be successfully filtered out by the
> white pine sapwood, viruses, which are smaller, can still get through and
> won?t be filtered out.
>
> According to Rohit Karnik, it could well be possible that there are plants
> that would be even better suited as water filtration devices than the white
> pine branches that they used in the study.
>
> Ideally, the wood that?s used should be thin enough it can be easily
> transported, but yet be one you can use for a few days before you?d need to
> throw it away. Karnik added that using sapwood chunks as a part of a water
> filtration device would be ?orders of magnitude cheaper? than the types of
> ?high-end membranes? that are currently available, and also, he reasoned,
> why should a membrane have to be fabricated, when they are cheaply
> available in nature?
>
> The membrane-based water filtration systems are often relatively expensive,
> and some rely on a pump as a necessary part of the device.Others require
> chlorine, which can be expensive, and ? while boiling water can be
> effective ? you need to have enough fuel to be able to boil the water.
>
> The method of using sapwood as a part of a water filtration device is not
> good for filtering a large amount of water for a lot of people at one time,
> but it might prove to be an inexpensive way to filter water for
> individuals.
>
> When mechanical engineers or anyone else attempts to come up with a method
> to filter water, the ideal outcome is that the membrane or other water
> filtration method needs to be able to filter out microbes, but do it while
> maintaining a high flow rate through the filter. Sapwood is perfect to use
> as it satisfies both of these requirements.
>
> Next, the researchers plan to test out the use of other varieties of
> sapwood from different species of trees to determine their relative
> effectiveness as part of a water filtration device. While further
> experimentation is needed to hit upon the very best types of sapwood ? and
> the types that would be the most efficient and most widely available for
> using as water filtration devices in developing countries ? the initial
> findings look like sapwood could potentially be a low-cost method of water
> filtration that eventually be used on a wide-spread basis in developing
> countries.
>
> Written by: Douglas Cobb
>
>
> ------------------------------
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> End of permaculture Digest, Vol 133, Issue 29
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