I saw an emergency filter idea I figured some of you might be interested in

My pleasure.

It would have been nice if they mentioned the results of the variety of trees tested.

I also picture a conversation going on in the department at MIT. "How much is this study going to cost?"

"Well, we have the testing equipment already. If we reuse the materials we can it should cost about $1.00, give or take $.50."

"Uhh, well, we are going to need you to pad that number"
 
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if its going to filter out e.coli, it will get the parasites without much trouble. I would wonder about viruses, but those are not as often a concern, and once the water is clear, a little UV solves that. One thing I've never seen regarding these is any sort of flow rate numbers. I would be thinking that you could create a bowl or cup shape in the field and use that, but generating the head pressure would be difficult, and if its strictly capillary action it would be very slow I'd think. And since you are cutting wood, making some charcoal shouldn't be a much harder step.
 
I thought about the flow as well. Any wood that gave you better flow would provide less filtration. I figure if you had enough tubing to make it worth it you would probably have better options (solar still or others).

The charcoal is a good idea, strange they did not think of that with the study.
 
I think that was just not a focus of the study. I recall from farther back that the idea was researching low cost filter materials, charcoal is good in some ways, poor in others, and has greater value as a fuel in a lot of places. Oddly due to the nature of trees, I don't think that flow rate would affect the filtration, as ideally the water is going cell to cell, as the wood would still be "living" but I'm totally guessing now.
 
This article suggests it was more of a preliminary study and that actual polluted water sources may be more difficult to achieve the same results:
http://www.popularmechanics.com/sci...-can-become-a-backyard-water-filter-16540288/

We're just talking a half-inch to inch piece of branch? That would be pretty simple to carry the tubing and clamp.

As for viruses:
"Xylem filtration won’t fix this by itself, not least because it can’t presently filter waterborne viruses such as hepatitis, rotavirus adenoviruses and so on. But it could have a big impact by removing bacterial and protozoan pathogens such as E coli, salmonella typhi, vibrio cholera and giardia."
http://www.technologyreview.com/view/520706/how-to-build-a-plant-xylem-water-filter/

Flow rate was also a concern, although they used white pine in this study.
 
Here is the more-detailed MIT article
http://news.mit.edu/2014/need-a-water-filter-peel-a-tree-branch-0226

Commentary:
Robert Jackson, an environmental expert at Stanford University, points out that at least as it stands now, the system doesn't do a good enough job at filtering out bacteria. He wrote in an email that filtering out almost all of the nasty bacteria is certainly helpful, "but when you can have hundreds of thousands, even millions, of them in a drop of water, you don't want to rely on something with 99 percent efficiency."

"In a survival or short-term situation this could work," he wrote. "As a longer-term or global solution to the billion people on Earth without access to clean water, call me skeptical."
Click to expand...

MIT said 99.9%. That's "LOG 3"

Sawyer has a filer that does 99.999%

2 log reduction = 99%
3 log reduction = 99.9%
4 log reduction = 99.99%
5 log reduction = 99.999%
6 log reduction = 99.9999%

EPA standards
99.9999% of Bacteria (LOG 6)

99.9% of Protozoa (cysts) (LOG 3)

99.99% of Viruses (LOG 4)
 
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